AS 1726:2017
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
AS 1726:2017
Geotechnical site investigations
This Australian Standard® was prepared by Committee CE-015, Site Investigations. It was approved on behalf of the Council of Standards Australia on 7 April 2017. This Standard was published on 2 May 2017.
The following are represented on Committee CE-015:
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Australasian Tunnelling Society Australian Drilling Industry Association Australian Geomechanics Society Austroads Cement Concrete and Aggregates Association Consult Australia CSIRO International Association of Hydrogeologists Australia New Zealand Geotechnical Society University of Newcastle University of Wollongong
This Standard was issued in draft form for comment as DR2 AS 1726:2016. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period.
Keeping Standards up-to-date Australian Standards® are living documents that reflect progress in science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting www.standards.org.au Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at
[email protected], or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.
AS 1726:2017
Australian Standard®
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Geotechnical site investigations
Originated as AS 1726—1978. Previous edition 1993. Fourth edition AS 1726:2017.
COPYRIGHT © Standards Australia Limited All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher, unless otherwise permitted under the Copyright Act 1968. Published by SAI Global Limited under licence from Standards Australia Limited, GPO Box 476, Sydney, NSW 2001, Australia ISBN 978 1 76035 743 6
AS 1726:2017
2
PREFACE This Standard was prepared by the members of the joint Standards Australia/Standards New Zealand Committee CE-015, Site Investigations, to supersede AS 1726—1993. After consultation with stakeholders in both countries, Standards Australia and Standards New Zealand decided to develop this Standard as an Australian Standard only, at this time, rather than a joint Australian/New Zealand Standard. This document may become a joint stand in future revisions. The objective of this Standard is to establish the requirements for the execution of effective geotechnical site investigations and to provide a standardized system for the description and classification of soils and rocks. It addresses spatial and physical characteristics of soil, rock and groundwater, but does not cover the chemical, biological or other environmental aspects of the investigation of contaminated ground. Commentary on the changes from the 1993 edition is set out in Appendix F. Statements expressed in mandatory terms in Notes to Tables are deemed to be requirements of this Standard. Figures provided in this Standard are informative.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The term ‘informative’ has also been used in this Standard to define the application of the appendices to which it applies. An ‘informative’ appendix is only for information and guidance.
3
AS 1726:2017
CONTENTS Page 1
SCOPE ........................................................................................................................ 4
2
EXCLUSIONS ............................................................................................................ 4
3
NORMATIVE REFERENCES ................................................................................... 4
4
DEFINITIONS ............................................................................................................ 4
5
OVERVIEW OF GEOTECHNICAL SITE INVESTIGATIONS ................................ 7 5.1 Process .................................................................................................................. 7 5.2 Geotechnical model ............................................................................................... 9 5.3 Execution of geotechnical site investigation ........................................................ 10 5.4 Initial assessment of site conditions..................................................................... 11 5.5 Fieldwork ............................................................................................................ 11 5.6 Reporting and interpretation ................................................................................ 14 5.7 Review of geotechnical site investigation ............................................................ 15
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
6
SOIL, ROCK AND GROUNDWATER .................................................................... 16 6.1 Soil description and classification ....................................................................... 16 6.2 Rock identification, description and classification............................................... 36 6.3 Surface water and groundwater observations....................................................... 58 6.4 Gases ................................................................................................................... 58
APPENDICES A GEOTECHNICAL SITE INVESTIGATION TECHNIQUES ................................... 59 B LABORATORY EXAMINATION AND TESTING ................................................. 61 C GROUNDWATER CONSIDERATIONS .................................................................. 64 D PROBLEMATIC MATERIALS ................................................................................ 66 E SYMBOLS ................................................................................................................ 69 F COMMENTARY ....................................................................................................... 72 BIBLIOGRAPHY ..................................................................................................................... 74
AS 1726:2017
4
STANDARDS AUSTRALIA Australian Standard Geotechnical site investigations 1 SCOPE This Standard specifies requirements for the execution of geotechnical site investigations and provides a standardized system for the identification, description and classification of soils and rocks. This Standard applies to geotechnical site investigation of natural or filled ground for— (a)
new construction;
(b)
maintenance of existing facilities;
(c)
the evaluation of post construction performance;
(d)
the assessment of failure; and
(e)
broad geotechnical studies.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
NOTE: Commentary on the changes from the 1993 edition is set out in Appendix F.
2 EXCLUSIONS This Standard does not cover the following: (a)
The application of geotechnical site investigation outcomes for geotechnical design.
(b)
The chemical, biological or environmental aspects of the investigation of contaminated ground.
3 NORMATIVE REFERENCES The following normative documents are referenced in this Standard: NOTE: Documents referenced for informative purposes are listed in the Bibliography.
AS 4133 Methods of testing rocks for engineering purposes 4133.4.1 Method 4.1: Rock strength tests—Determination of point load strength index 4133.4.2.1 Method 4.2.1: Rock strength tests—Determination of uniaxial compressive strength of 50 MPa and greater 4 DEFINITIONS For the purpose of this Standard, the definitions below apply. 4.1 Acid sulfate soil Naturally occurring soils, sediments or organic substrates (e.g. peat) that contain sulfide minerals (predominantly pyrite) or their oxidation products. In an undisturbed state where soil is saturated, acid sulfate soils are generally benign. However, if the soils are excavated or exposed to air by a lowering of the groundwater level, the sulfides react with oxygen to form sulfuric acid. NOTE: Refer to Appendix D.
4.2 Carbonate rock A rock containing more than 50% by weight of carbonate compounds (such as calcium carbonate). Standards Australia
www.standards.org.au
5
AS 1726:2017
4.3 Carbonate soil A soil containing more than 50% by weight of carbonate compounds (such as calcium carbonate). 4.4 Cemented soil A soil bound with a cementing substance, such that if remoulded and recompacted to its original density and moisture content, exhibits a significantly lower strength than in its undisturbed condition. 4.5 Classification A system which places a material into one of a limited number of groups on the basis of a defined characteristic or set of characteristics. For example, a soil classification may be based on the grading and plasticity of disturbed samples. 4.6 Cohesive and non-cohesive soils Soils are conveniently divided into two groups based on the ability of a soil mass to hold together. Those capable of holding together are termed ‘cohesive’ and those having no ability, or strength, to hold together by themselves at very low applied total stress levels are termed ‘non-cohesive’.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
4.7 Competent person A person who has, through a combination of training, education and experience, acquired knowledge and skills enabling that person to correctly perform a specified task. 4.8 Consistency The ability of the soil, at specific moisture contents, to resist mechanical stress or manipulation (remoulding). 4.9 Contamination The condition of land or water where any chemical substance or waste has been added as a direct or indirect result of human activity above background level and represents, or potentially represents, an adverse health or environmental impact. Contamination may have an impact on human health during construction or the service life of a structure erected on the site or may have detrimental effects on the environment. NOTE: While this Standard does not address investigation of the presence of contamination or management of such contamination, the possibility of the presence of contamination should be considered during the planning and conduct of geotechnical site investigations.
4.10 Controlled fill Any fill for which engineering properties are controlled during placement. Sometimes referred to as structural or engineered fill. 4.11 Description, soil or rock A statement of the physical characteristics of a sample of soil or rock. 4.12 Desk study A study to collate and review the existing information relevant to the site. 4.13 Dispersive soils Those soils, which by nature of their mineralogy and pore water chemistry, are susceptible to separation in water of individual clay particles. NOTE: Refer to Appendix D.
www.standards.org.au
Standards Australia
AS 1726:2017
6
4.14 Duricrust A cemented zone occurring in weathered rock or soil formed by the mobilization and deposition of minerals. 4.15 Engineered fill Refer to ‘Controlled fill’. 4.16 Fill A volume of material that has been placed by anthropogenic processes. 4.17 Geotechnical Pertaining to the nature, condition and physical properties of the earth’s crust (whether soil or rock and including water and gases therein), which affect its engineering performance. 4.18 Geotechnical model The interpretation of ground conditions in a form useful for engineering design or assessment. It may contain a surface and subsurface model detailing the geological and engineering characteristics of the various materials and groundwater. 4.19 Geotechnical site investigation The process of assessing and evaluating the geotechnical characteristics of a site. Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
4.20 Groundwater Water located beneath the earth’s surface in pore spaces, fractures and voids in soil and rock. 4.21 In situ In the place and condition in which it exists naturally. 4.22 Liquid limit (wL) Moisture content at which the soil passes from the plastic to the liquid state as determined by the liquid limit test. 4.23 May Indicates that a statement is an option. 4.24 Monitoring Recording observations and/or measurements over a period of time. 4.25 Mottled Having areas of two or more colours or shades in a spotted or blotched, irregular configuration. 4.26 Plastic limit (wP) Moisture content at which the soil becomes too dry to be in a plastic condition as determined by the plastic limit test. 4.27 Plasticity index (IP) Numerical difference between the liquid limit and the plastic limit of a soil. 4.28 Project The wider project for which a geotechnical site investigation is carried out. 4.29 Shall Indicates that a statement is mandatory. Standards Australia
www.standards.org.au
7
AS 1726:2017
4.30 Should Indicates that a statement is a recommendation. 4.31 Soil Particulate materials that occur in the ground and can be disaggregated or remoulded by hand in air or water without prior soaking. 4.32 Rock Any aggregate of minerals and/or organic materials that cannot be disaggregated by hand in air or water without prior soaking. 4.33 Uncontrolled fill Materials that have been deposited by anthropogenic processes, which do not meet the definition of ‘controlled fill’. 4.34 Undisturbed sample A term applied to samples obtained using techniques designed to minimize changes in the properties of the sample. 5 OVERVIEW OF GEOTECHNICAL SITE INVESTIGATIONS
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
5.1 Process 5.1.1 General The delivery of geotechnical site investigations should follow an iterative process in which the outcomes of the investigations are reviewed against the purpose for which the investigation is being carried out and further investigations are planned as required. This process is illustrated in Figure 1. Quality assurance and work health and safety programs should be in place during this entire process.
www.standards.org.au
Standards Australia
AS 1726:2017
8
D efin e t h e pur p o se of t h e inve st i g at i o n an d i d e nt i f y t h e s c o p e an d o bj e c t i ve s
A s s e m b l e i nfor m at i o n r e l at i n g to t h e proj e c t
D eve l o p t h e G e ot e c hni c al M o d e l b a se d o n g e o l o g i c al c o n c e pt s, g e ote c h ni c al infor m at i o n an d proje c t infor m at i o n an d ant i c i pate w hat m i g ht b e e n c o u ntere d o n s i te
Plan t h e inve st i g at i o n to ad d r e s s t h e o bj e c t i ve s
Refine the G e ot e c hni c al M o d e l a n d rev i ew t h e inve st i g at i o n outc o m e s ag ain st t h e s c o p e an d o bj e c t i ve s
H ave t h e o bj e c t i ve s b e e n m et an d t h e s c o p e ac hi eve d?
No
Ye s
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Carr y out the g e ote c hni c al i nve s t i g at i o n
R ev i s e o bj e c t i ve s and /or s c o p e and /or investigation methods
C o n clu d e inve s t ig a t ion
FIGURE 1 GEOTECHNICAL INVESTIGATION—OVERVIEW
5.1.2 Project description Geotechnical site investigations are usually carried out in service of a wider activity, such as land development, infrastructure, mining, or assessment of landslide risk. This wider activity is usually referred to as ‘the project’. The entire area that could affect the project or be affected by the project is referred to as ‘the project area’ and the immediate area of the project itself is referred to as ‘the site’. A description of the project, the project area and the site shall be provided.
Standards Australia
www.standards.org.au
9
AS 1726:2017
5.1.3 Purpose of investigation The general purpose of the geotechnical site investigation and its specific investigation objectives within the context of the project shall be clearly defined and documented to the satisfaction of all parties involved. 5.1.4 Scope of work The proposed scope of work shall reflect the investigation objectives and shall be clearly documented. 5.1.5 Staging Geotechnical site investigations are usually carried out in stages, with the number of stages dependent upon the geotechnical complexity of the site. A program of staged investigation should be developed to implement the selected investigation activities. This program should recognize that, during the investigation, conditions may be revealed which were not anticipated or which trigger a need for review of the remainder of the program. For larger or more complex investigations it may be appropriate to include one or more reporting and review stages in order to refine or revise the latter stages of the investigation.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The stages may include the following: (a)
Literature review.
(b)
Site walkover.
(c)
Field investigation staged in order to retrieve data most economically (e.g. carry out cone penetrometer testing first before deciding where to position boreholes with in situ testing and sampling).
(d)
Review after each stage to assess the need to carry out further stages.
(e)
Laboratory testing, staged and optimized for the development of geotechnical design parameters and the soil-groundwater chemistry (e.g. testing to identify acid sulfate soils).
Investigations should be executed in such a way that adequate data are obtained to refine the geotechnical model at the end of each stage, to allow advancement of wider studies or to guide subsequent investigations. Each stage may involve interpretation, analysis and reporting. 5.2 Geotechnical model A geotechnical model shall be developed for every geotechnical site investigation. The level of refinement and model detail will depend on the complexity of the project. In its most basic form the geotechnical model may consist of a simple description of the local geology derived from existing data together with some of the engineering characteristics of the project area. More usually, the geotechnical model would include a geological map and cross-section depicting the strata likely to be encountered and information on the engineering characteristics of the soils and rocks and the groundwater levels. On some large projects, a more sophisticated geotechnical model, based on a large data set and presented as a 3D visualization, may be developed to present the interaction between a large complex structure and a variable soil/rock/groundwater system. The geotechnical model should be based on factors such as the following: (a)
The nature of the project.
(b)
The regional geological and hydrogeological setting.
(c)
The stratigraphic succession, including the presence of significant aquifers.
www.standards.org.au
Standards Australia
AS 1726:2017
10
(d)
Expected groundwater levels.
(e)
The geological structure.
(f)
Geomorphology and surface processes.
(g)
Engineering properties of the soils and rocks encountered.
The geotechnical model shall provide a consistent explanation of the concepts, observations and interpretations associated with the geology, geomorphology, hydrogeology, hydrology and engineering characteristics of the project area that are relevant to the project. The geotechnical model should be used to communicate geotechnical information about the site to all interested parties involved in the project. This information may include: (i)
Past and present surface processes/activities.
(ii)
Types of soil or rock units and their distribution.
(iii) Groundwater levels and groundwater flow directions. (iv)
Preliminary geotechnical characteristics of soil and rock units.
(v)
The types of geological structure and their orientation.
(vi)
Seismic risk.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(vii) Potential occurrence of contaminated ground or groundwater that might be hazardous to people, the environment or the durability of construction materials. (viii) Potential occurrence of hazardous gases. 5.3 Execution of geotechnical site investigation 5.3.1 Health and safety Relevant work health and safety legislation applies to all geotechnical site investigations. Site-specific risk assessment and work method statements should be established. All significant risks associated with the geotechnical site investigation should be assessed, and control measures implemented. 5.3.2 Competency All personnel involved in geotechnical site investigations shall have geotechnical experience, training and qualifications appropriate for their role in the investigation. 5.3.3 Literature review A literature review shall be carried out as part of the geotechnical site investigation. This review should include the assembly of reports, maps and other information pertaining to the site. In selecting relevant information, the site should be considered in terms of its position in the overall landscape and the broader geological setting, prior to the investigation focusing exclusively on the immediate area of the site. Information that can be used to gain an understanding of the site prior to fieldwork includes, but is not limited to, the following: (a)
Geological maps and memoirs of the site.
(b)
Existing geotechnical site investigation reports for the site or nearby sites.
(c)
Topographic or bathymetric information.
(d)
Maps or photographs, which may show topographic features such as swamps or creek lines that have been subsequently obscured by human activities.
(e)
Aerial photographs (vertical and oblique).
(f)
Large scale geological maps.
Standards Australia
www.standards.org.au
11
(g)
Geohazard maps.
(h)
Published soils maps.
(i)
Acid sulfate soil risk maps.
(j)
Maps of vegetation.
(k)
Previous local and anecdotal experience from the area.
(l)
Historical records such as newspaper articles.
(m)
Mine working maps.
(n)
Construction records for the site or nearby projects.
AS 1726:2017
5.4 Initial assessment of site conditions
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
An initial assessment shall be made of the conditions in the area to be investigated, which could be expected to influence the investigation. This may be drawn from site reconnaissance, earlier studies, experience, background reports and published information. This assessment of site conditions influencing the design of the field investigation should include, but not be limited to— (a)
accessibility;
(b)
hazards to health, safety and environment;
(c)
proposed geotechnical model;
(d)
structures or services which could affect or be affected by the investigation;
(e)
groundwater conditions;
(f)
geographical, geomorphological and geological features;
(g)
seismic setting;
(h)
potential for encountering contamination and hazardous gases; and
(i)
regulatory approvals required.
The initial assessment of the site should include an appraisal of the area and volume of ground that would affect or be affected by the project. 5.5 Fieldwork 5.5.1 General Fieldwork should typically include the following: (a)
Mapping of the topography, geology, geomorphology and other relevant features.
(b)
Logging of cuttings or other exposures.
(c)
A program of sub-surface works (such as boreholes, test pits and probe tests such as cone penetration tests).
(d)
Measurements, e.g. recording of groundwater levels and in situ testing.
(e)
Collection of soil, rock and groundwater samples for subsequent testing.
Fieldwork may also involve use of indirect methods, e.g. seismic or resistivity surveys and use of satellite and airborne sensing. All observation locations (especially pits, boreholes and probe tests) shall be surveyed to the required level of accuracy.
www.standards.org.au
Standards Australia
AS 1726:2017
12
5.5.2 Selection of investigation methods The methods to be used for investigation should be selected taking account of— (a)
objectives of the investigation;
(b)
site conditions;
(c)
available equipment;
(d)
cost and time constraints;
(e)
health, safety and environmental considerations; and
(f)
regulatory requirements.
NOTES: 1 A list of some of the available field investigation methods is provided in Appendix A. Laboratory studies may also be required to measure the properties of materials. 2 A list of some of the available laboratory investigation methods is provided in Appendix B. 3 Notes on groundwater considerations are provided in Appendix C.
5.5.3 Data collection and record keeping
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Results from routine field tasks shall be recorded in the field (either electronically or on paper). In addition to the results of the field task, records should reference the project, the date, the location and the person carrying out the work. The records of the results of fieldwork and laboratory testing should be maintained in a form suitable for archival and information transfer. Ideally, this should be in a digital form consistent with standards expected by the client and other professionals contributing to the project. 5.5.4 Sample handling and management 5.5.4.1 Soil Geotechnical site investigation often involves taking soil samples, which may be either disturbed or undisturbed. Project specific procedures for sample handling and labelling, transport and storage, and chain of custody, shall be developed in order to reduce deterioration in sample quality and the potential for errors. All samples shall be clearly labelled and logged with a unique reference number immediately after being taken. Samples suspected of contamination shall be identified on the label. Samples taken for geotechnical purposes should be maintained in a temperature range to avoid freezing or heat damage and wide temperature variations. As soon as practicable after sampling, samples should be stored in airtight bags or containers. Where the intention is to limit disturbance, samples should be coated with wax (preferably microcrystalline) or retained in sealed sample tubes in order to reduce moisture changes during transit to the laboratory. Excess moisture associated with sample collection, such as from drilling fluids, should be removed prior to storage. Soil should be removed from the ends of tube samples to a depth of about 25 mm, and the air gap filled by custom made plugs or molten wax, followed by end caps and adhesive tape. Undisturbed block samples should be cut and trimmed by hand and wrapped in cloth and coated with molten wax. At least three layers of cloth and wax should be applied on each surface. The sealed sample should then be placed into a wooden box with the air gap between the box and sample, filled with packing material. Sample tubes containing soft soil should be transported and stored in a vertical orientation to reduce the potential for sample disturbance, and rough handling should be avoided.
Standards Australia
www.standards.org.au
13
AS 1726:2017
Samples taken for the purpose of testing of the soil chemistry (such as for acid sulfate soil analysis) require special handling, and should be managed in accordance with regulatory guidelines pertaining to the relevant state or territory. 5.5.4.2 Rock Project-specific procedures for core handling and labelling, transport and storage, and chain of custody shall be developed in order to reduce deterioration in core quality and the potential for errors. The same storage temperature control criteria used for soil should be adopted for rock. Measures should be taken to mitigate moisture loss of rock core while working with it in the field. Rock core shall be placed as soon as practicable into a core box in order of increasing depth, left to right, and top to bottom. The core box shall be uniquely identified and labelled with borehole number and core run depths. In order to provide a permanent visual record, all rock core shall be photographed moist under uniform lighting conditions as soon as practicable after placement in core boxes, and prior to sampling or disturbance during logging. Each photograph should include a reference colour chart.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
When core is prone to degradation on drying, the core should be wrapped in plastic film after field logging to reduce changes in moisture content. When core is fragile and may break up in the core box, it should be placed into PVC splits located within the core box. When rock core specimens are sub-sampled from the core tray for laboratory testing, a process for sample handling and management should be developed to reduce the likelihood of damage of the samples during handling and transport. Intervals of core loss or where core is extracted for testing should be marked as such, and in-filled with polystyrene or similar. Where core is observed to have degraded during handling or storage, this shall be noted on logs. 5.5.4.3 Groundwater Groundwater samples may contain dissolved or suspended materials. The method of collection, storage and treatment of samples can affect the results obtained from subsequent laboratory testing. The field procedure used to collect samples shall be recorded and reported, indicating— (a)
time of sampling;
(b)
purging prior to sample collection;
(c)
whether field filtering of the groundwater sample was carried out and if so, the type of filter;
(d)
preservation methods employed after sampling and prior to delivery to a laboratory for testing; and
(e)
quality control and assurance methods employed.
5.5.4.4 Identification and labelling of samples Sample identification shall be shown on sample bags, labels or tags and shall be secure and legible. Where bottles or containers are used to store samples, the identification should be placed on the vessel and also on the lid or cap as required. Each sample retained during the geotechnical site investigation shall be labelled, including a unique identifier. The following details should be included: (a)
Project or job number.
(b)
Date sampled.
(c)
Test pit, borehole, or hand auger hole number.
www.standards.org.au
Standards Australia
AS 1726:2017
14
(d)
Sample location and depth.
(e)
Sample reference number.
(f)
Any other relevant information such as requirements for special handling.
Samples suspected of containing hazardous materials should be labelled and packaged such that those handling the samples from accidental exposure are protected. 5.5.4.5 Storage of samples Prior to and during testing, samples should be stored in designated areas within the laboratory. Samples should be stored in a manner that provides protection from damage, corrosion or contamination that may invalidate test results. All samples should be stored away from direct sunlight and rain. Careless handling of undisturbed samples after they have been received by the laboratory may cause disturbance that could influence test results, potentially leading to serious design and construction consequences. All tube or block samples should therefore be handled by a competent person and stored in an upright position until required for testing, and in a location where they are not likely to be knocked over or dropped.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The potential for disturbance, moisture migration and corrosion within tube samples increases with time. It is therefore important that samples are prepared and tested in a timely manner. When samples are tested more than 30 days after their retrieval, this should be noted on the laboratory data and test results sheet. 5.6 Reporting and interpretation 5.6.1 General A report (or reports) shall be produced that presents the information obtained from the geotechnical site investigations. The report content may include— (a)
factual information and observations;
(b)
interpretations; and
(c)
opinions.
The type of report is dependent on the requirements of the project objectives and shall be as agreed during the planning stage. The various types of geotechnical engineering reports are further explained in Clauses 5.6.2 and 5.6.3. NOTE: A list of graphical symbols that may be useful for reporting purposes is contained in Appendix E.
5.6.2 Geotechnical data report This report documents the procedures employed and the data collected, and despite the fact that soil and rock logging has an interpretive nature attached to it, a geotechnical data report is considered predominantly factual and may also be referred to as a factual report. A geotechnical data report should include but may not be limited to the following information: (a)
Objectives and agreed scope.
(b)
Location and description of the project site and its history.
(c)
Plan showing investigation locations.
(d)
Description of the regional and local geology.
(e)
Records of fieldwork, including methods and results.
(f)
Laboratory testing and summary of results.
Standards Australia
www.standards.org.au
15
AS 1726:2017
5.6.3 Geotechnical interpretive report Interpretation is a continuous process, which should begin in the preliminary stages of data collection and should proceed as information from the ground investigation becomes available. The interpretive report should include but is not limited to the following components: (a)
Reference to the data upon which the interpretation has been made.
(b)
An interpretation of the site geology and the development of the geotechnical model.
(c)
A summary of the geotechnical properties of the ground applicable to the project.
(d)
An engineering interpretation of the implications of the ground conditions for the project.
(e)
An assessment of potential geotechnical risks to the project.
(f)
Recommendations for further work, if relevant.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
In developing geotechnical interpretive reports, there are important aspects to be mindful of, which include the following: (i)
The nature and constraints of the project and proposed development These define how and where structures or facilities will interact with the ground, including the type, degree and period of loading and any site constraints. Possible impacts on the nearby built or natural environment and potential future uses of the site should be considered.
(ii)
The nature and limitations of the geotechnical model The geotechnical model is an interpretation that will change both during the course of the investigations and the development of the overall project, as more information becomes available. Reporting of the geotechnical model should clearly indicate the information on which it is based, the varying reliability of the interpretation and the process whereby an acceptable level of reliability will be achieved.
(iii) The nature and limitation of data Consistency and reliability of data assessed (previous work may have been done by different consultants standards of work and assumptions). Cross-checking and verification to practicable should be undertaken. The limitations of the data collected investigation program should be highlighted.
should be to varying the degree during the
A geotechnical interpretive report may also contain expressions of professional opinion. A professional opinion is dependent on conclusions derived from consideration of relevant available facts, interpretations and analysis and judgement. Since the process involves interpretation and judgement, opinions of professionals may differ, although substantial agreement is expected. 5.7 Review of geotechnical site investigation On completion of a geotechnical site investigation, the findings of the investigation should be reviewed against the objectives of the investigation. Where critical objectives are not adequately achieved, the consequence of this inadequacy should be considered, the risks to the project assessed and recommendations for further investigation developed. Geotechnical project risks identified in the geotechnical interpretive report may be mitigated by review of geotechnical conditions exposed during construction or by monitoring of performance (such as ground movement monitoring or groundwater level monitoring). Recommendations for such review and monitoring should form part of the geotechnical interpretive report. This may include the recommendation for development of a formal risk assessment and risk management plan.
www.standards.org.au
Standards Australia
AS 1726:2017
16
6 SOIL, ROCK AND GROUNDWATER 6.1 Soil description and classification 6.1.1 General The classification system adopted in this Standard differs in a number of important respects from the Unified Soil Classification System (USCS) and AS 1726—1993 and may result in some soils being named and classified differently from USCS and AS 1726—1993. A major difference is the criteria used to distinguish between coarse and fine-grained soils. A behavioural approach has been adopted in this Standard when identifying, naming and classifying soil. However, the boundary defining the change in behaviour between coarse and fine-grained soils is not a precise one. Nevertheless, this boundary has been defined in Clause 6.1.4.2, Table 1 and Figure 2. 6.1.2 Basic approach Description of soil is the process of identifying its components and assessing their relative proportions and behavioural characteristics, observing the condition and structure of the soil and interpreting its origin. Classification of soils involves allocating the soil into different soil groups on the basis of different observable characteristics.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Soil description and classification requires, as a minimum, the identification of the engineering characteristics and properties of the soil through a visual and tactile assessment. Observation and identification of a soil should be carried out in a series of logical steps where the components of the soil are considered and assessed individually. The visual–tactile assessment process may be augmented by laboratory testing. Where laboratory tests are carried out subsequent to visual–tactile assessment, and where these indicate that the visual–tactile assessment was inaccurate, logs and other records of the assessment shall be adjusted if required, and any adjustments made to the logs and other records shall be documented. Soils may be disturbed or undisturbed but if the soil is disturbed there are limits to what can be described. The approach described in this Standard is equally applicable to both natural and artificial soil materials. Although systematic description of the soil composition must be completed before classification can occur, the soil group is usually reported at the beginning of the full description and classification. 6.1.3 Systematic description A soil description should be presented as a series or list of specific terms, separated by semi-colons, generally without these being formed into sentences. A systematic and standardized order of description shall be used. When it is possible, the following characteristics shall be described: (a)
Composition of soil (disturbed or undisturbed state) The description shall include the following: (i)
Soil name (use BLOCK LETTERS).
(ii)
Plasticity, behavioural or particle characteristics of the primary soil component.
(iii) Colour of the soil. (iv)
Secondary soil components’ name(s), estimated proportion(s), plasticity, behavioural or particle characteristics, colour.
(v)
Minor soil component’s name, estimated proportion, behavioural or particle characteristics, colour and, where practical, its plasticity.
The presence of FILL and TOPSOIL shall be indicated at the beginning of the description using BLOCK LETTERS. Standards Australia
www.standards.org.au
17
(b)
AS 1726:2017
Condition of soil The description shall include the following: (i)
Moisture condition (disturbed or undisturbed state).
(ii)
Consistency of fine-grained soils (undisturbed state only).
(iii) Relative density of coarse-grained soils (determined by in situ tests). (c)
Structure of soil In the undisturbed state, the description shall include the following: (i)
Zoning.
(ii)
Defects.
(iii) Cementing. (d)
Origin of soil.
(e)
Additional observations.
NOTE: The order of descriptions given above is recommended.
6.1.4 Composition of soils 6.1.4.1 General Observations of the primary, secondary and minor soil components are used to construct the soil name, which describes the composition of the soil.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
6.1.4.2 Soil components Soils are composed of solid particles, water and gas, sometimes with the inclusion of organic substances. Soil particles are differentiated on the basis of size, according to the definitions in Table 1. TABLE 1 PARTICLE SIZE DEFINITIONS Fraction Oversize
Components
Subdivision
BOULDERS
>200
COBBLES Coarse grained soil
GRAVEL
SAND
Fine grained soil
SILT CLAY
Size* mm
63–200 Coarse
19–63
Medium
6.7–19
Fine
2.36–6.7
Coarse
0.6–2.36
Medium
0.21–0.6
Fine
0.075–0.21 0.002–0.075 6 3 m m) a s c o b b l e s / b o ul d er s or u s e r o c k d e s c r i pt i o n ter m s a s a p pro pr i ate
D o e s t h e s o il reac t (fiz z) w it h d ilute hydro c hl or i c ac i d? YES
NO
Cal c are o u s o r c ar b o n ate s o il ad d t h e a p pro pr i ate prefix fro m Ta b l e 5
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
D o v i s i b l e s o i l p ar t i c l e s (s a n d an d gr ave l) d o m inate — m ake u p m ore t han 6 5% of t h e s o il? YES
NO
C oar se gr ain e d s o il: a m ix ture of s an d an d gr ave l
Fine grained soil
D o e s t h e s o i l h ave a s p o n g y fe e l or fi brou s tex ture, w it h s i g n i f i c ant v i s i b l e o r g an i c m at ter an d an or g ani c o d our ? YES
I s t h e s o i l d ar k c o l o ure d, w i t h an or g ani c o d o ur an d s o m e v i s i b l e o r g a n i c m at ter ?
Is more than 50% of the coarse gr ain e d s o il gr ave l > 2 m m?
YES
NO
NO
NO
YES Organic soil ad d t h e prefix “ O r g ani c ” to t h e s o il nam e
D o e s t h e fin e gr ain e d s o il b e have like a s ilt — i s t h e s o i l d i l at a nt ?
GR AVEL
SAN D
PE AT
YES
NO
SILT
CL AY
NOTES: 1 Gravel, sand, silt and clay are the major components of a soil. They are defined in Table 1. 2 Assessment of component proportions is by dry mass. 3 Dilatancy is assessed on the reaction of wet soil to shaking. Table 7 provides a method of assessment of dilatancy as well as other diagnostic characteristics of silt and clay.
FIGURE 2 PROCESS FOR THE FIELD IDENTIFICATION OF SOIL PRIMARY COMPONENTS www.standards.org.au
Standards Australia
AS 1726:2017
20
6.1.4.4 Soil name The soil name shall be based on the identified components of a soil and their behavioural characteristics. The components of a soil are assessed to be primary, secondary, or minor, on the basis of their significance for the probable engineering characteristics of the soil at any particular moisture content. The primary component of a soil is that component which dominates its engineering behaviour. A secondary component of a soil is any component of a soil which is not the primary component, but which is significant to the engineering properties of the soil. A minor component is present in the soil but is not significant to its engineering properties. 6.1.4.5 Assessment of primary component In the field, the size of grains in the coarse fraction is assessed from a representative portion of the soil, from which any boulders and cobbles have been removed. It may be helpful to examine the soil under air-dried and/or submerged conditions in order to achieve a clear separation between the coarse and fine fractions. In the laboratory, coarse and fine fractions can be separated by wet sieve analysis.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The primary component is chosen to reflect whether the soil is either fundamentally fine or coarse grained. This assessment is made according to whether the total dry mass of coarse fractions exceeds 65% (a coarse soil) or the total dry mass of fine fractions exceeds 35% (a fine soil). If it is a coarse grained soil, the relative proportions of the sand and gravel can be estimated or measured and the primary component identified as SAND if sand exceeds gravel, or GRAVEL if gravel exceeds sand. If it is identified as a fine grained soil, the behaviour shall be assessed to decide if the soil behaves as a silt or a clay and this will indicate primary component and soil name. Where assessed by visual tactile techniques (refer to Tables 7 and 8), a silt is indicated by low dry strength, low wet toughness and dilatancy, whereas a clay is indicated by high dry strength, high wet toughness and plasticity. Where assessed by laboratory testing, clay plots above the A-line and silt below the A-line on the Casagrande chart (refer to Clause 6.1.6 and Figure 5). In borderline cases, the terms silty CLAY or clayey SILT may be used at the discretion of the classifier, noting that there is no specifically defined criterion for their use, and that these descriptions imply only that the materials are borderline between behaving as silts or clays. The presence of cobbles and boulders shall be specifically noted by beginning the description with ‘MIXTURE OF SOIL AND COBBLES/BOULDERS’ with the word order indicating the dominant proportion first and the proportions of cobbles and or boulders described together with an indication of whether they are supported by a matrix of soil or supported by themselves. The remaining soil shall then be described. 6.1.4.6 Assessment of secondary and minor components Any accessory soil components (i.e. those other than the primary component) are deemed to be either secondary or minor components, on the basis of their type and their amount, as determined by their presence on a percentage dry mass basis, according to Table 2. A visual aid to assessing the proportions of coarse particles is provided in Figure 3.
Standards Australia
www.standards.org.au
21
AS 1726:2017
TABLE 2 DESCRIPTIVE TERMS FOR ACCESSORY (SECONDARY AND MINOR) SOIL COMPONENTS In coarse grained soils Designation of components
% Fines 5
Minor
Terminology
Add ‘trace clay/silt’ to description, as applicable
>5, 12 Add ‘with clay/silt’ to description, as applicable
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Secondary
>12
Prefix soil name as ‘silty’ or ‘clayey’, as applicable
5%
% Accessory coarse fraction
In fine grained soils
Terminology
15
Add ‘trace sand/gravel’ to description, as applicable
>15, 30
Add ‘with sand/gravel’ to description, as applicable
>30
12%
Prefix soil name with ‘sandy’ or ‘gravelly’, as applicable
% Sand/ gravel 15
Terminology
Use ‘trace’
>15, 30 Add ‘with sand/gravel’ to description, as applicable >30
Prefix soil name with ‘sandy’ or ‘gravelly’, as applicable
3 5%
FIGURE 3 DIAGRAM OF VARIOUS PERCENTAGES OF GRAINS
6.1.4.7 Assignment of a name The name of a soil is made up of the primary and secondary components. The primary component is included as a noun, written in BLOCK LETTERS on logs, qualified by the secondary components (if present), included as adjectives. Minor fractions are not included in the name, but are included in the description using phrases which include the words ‘trace’ or ‘with’, according to their relative importance, as indicated in Table 2. As an example, consider a soil with 30% plastic fines and 70% coarse fractions, which comprise 10% gravel and 60% sand. The soil is coarse and sand is the primary component. Gravel is a minor component and does not appear in the name. The plastic fines exceed 12% and are a secondary component, so ‘clayey’ is added as an adjective to the word ‘sand’. Hence it would be named ‘Clayey SAND’.
www.standards.org.au
Standards Australia
AS 1726:2017
22
6.1.4.8 Peat soils Organic content of soils can have a significant effect on their geotechnical properties. Colour and odour are the key properties for field identification of organic soils. Organic soils are usually either dark grey or black. Fresh, moist organic soils generally have a mouldy odour which can be intensified by heating. Putrefying, rotten organic components in soil can be recognized by their odour typical of hydrogen sulfide, which can be intensified by pouring dilute hydrochloric acid on the sample. Dry inorganic clays have an earthy odour after being moistened. Organic soils should be named with ‘Organic’ preceding the primary soil name. For example, ‘Organic CLAY’ or ‘Organic SILT’. Peat can be identified in the field by its spongy feel and fibrous texture. Where laboratory tests are available, organic soils and peat may be identified using Table 3. Table 4 provides terms that may be used to describe the degree of decomposition of Peat. TABLE 3 IDENTIFICATION OF ORGANIC SOILS USING LABORATORY TESTS Material
Organic content – % of dry mass
Inorganic soil
25
TABLE 4 DESCRIPTIVE TERMS FOR THE DEGREE OF DECOMPOSITION OF PEAT Term Fibrous
Decomposition Little or none
Remains
Squeeze
Clearly recognizable
Only water No solids
Pseudo-fibrous Moderate
Mixture of fibres and amorphous paste
Turbid water 50% solids
Full
6.1.4.9 Carbonate soils The carbonate content of soils can have a significant effect on their geotechnical properties as soil particles composed of calcium carbonate can have high porosity and low crushing strengths. The carbonate content should be assessed by the application of droplets of dilute hydrochloric acid (10% HCl, see Note to Table 5). Table 5 gives an approximate carbonate content based on the reaction to acid, and provides descriptive terms for carbonate content.
Standards Australia
www.standards.org.au
23
AS 1726:2017
TABLE 5 ASSESSMENT OF CARBONATE CONTENT Term
Reaction to acid
Approximate carbonate content
Non-calcareous
HCl produces no effervescence
Negligible
Calcareous
HCl produces weak or sporadic effervescence
50%
NOTE: 10% hydrochloric acid is made by taking 10 mL of concentrated HCl acid solution (36% HCl) and making it up to 100 mL. This gives 3.6% HCl by mass which is about 1.2 molar.
6.1.4.10 Plasticity and behaviour (fine grained soils) When laboratory tests are available, clay and silt, both alone and in mixtures with coarser material, shall be described according to their plasticity as defined in Table 6. TABLE 6 DESCRIPTIVE TERMS FOR PLASTICITY Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Descriptive term Non-plastic Low plasticity Medium plasticity High plasticity
Range of liquid limit for silt
Range of liquid limit for clay
Not applicable
Not applicable
50
35
Not applicable
>35 and 50
>50
>50
When laboratory tests are not available, plasticity and soil behaviour are assessed in the field using the visual–tactile techniques described in Table 7. These procedures are to be performed on particles less than 0.2 mm in size. For field classification purposes, screening is not intended, simply remove by hand the coarse particles that interfere with the tests. Table 8 gives a guide to typical soil names and plasticity characteristics.
www.standards.org.au
Standards Australia
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
FIELD ASSESSMENT OF FINE GRAINED SOILS Dry strength Mould a pat of soil to the consistency of putty, adding water if necessary. Allow the pat to dry completely by oven, sun or air drying, and then test its strength by breaking and crumbling between the fingers. This strength is a measure of the character and quantity of the colloidal fraction contained in the soil. The dry strength increases with increasing plasticity. High dry strength is characteristic for clays of the CH group. A typical inorganic silt possesses only very low dry strength. Silty fine sands and silts have about the same dry strength, but can be distinguished by feel when powdering the dried specimen. Fine sand feels gritty whereas a typical silt has the smooth feel of flour.
Dilatancy (reaction to shaking)
Toughness (consistency near plastic limit) 3.
Mould a pat of soil to the consistency of putty. If too dry, add water, and if sticky, the specimen should be spread out in a thin layer and allowed to lose some moisture by evaporation. Then, roll a thread of the soil by hand on a smooth surface or between the palms until it is about 3 mm in diameter. The thread is then folded and re-rolled repeatedly. During this manipulation the moisture content is gradually reduced, the specimen stiffens, finally loses its plasticity, and crumbles. When the thread crumbles, the pieces should be lumped together with a kneading action. The plastic limit has been reached, when the soil crumbles at about 3 mm thickness. The tougher the thread near the plastic limit and the stiffer the lump when it finally crumbles, the more potent is the colloidal clay fraction in the soil. Weakness of the thread at the plastic limit and rapid loss of coherence of the lump below the plastic limit indicate either inorganic clay of low plasticity, or materials such as kaolintype clays and organic clays which plot below the A-line. Highly organic clays have a very weak and spongy feel at the plastic limit.
Criteria for describing dilatancy
Criteria for describing toughness
Criteria for describing dry strength
www.standards.org.au
None
The dry specimen crumbles into powder with mere pressure of handling.
None
No visible change in the specimen.
Low
The dry specimen crumbles into powder with some finger pressure.
Slow
Medium
The dry specimen breaks into pieces or crumbles with considerable finger pressure.
Water appears slowly on the surface of the specimen during shaking and does not disappear or disappears slowly upon squeezing.
High
The dry specimen cannot be broken with finger pressure. Specimen will break into pieces between thumb and a hard surface.
Very High
The dry specimen cannot be broken between the thumb and a hard surface.
Rapid
Water appears quickly on the surface of the specimen during shaking and disappears quickly upon squeezing.
Low
Only slight pressure is required to roll the thread near the plastic limit. The thread and the lump are weak and soft.
Medium
Medium pressure is required to roll the thread to near the plastic limit. The thread and the lump have medium stiffness.
High
Considerable pressure is required to roll the thread to near the plastic limit. The thread and the lump have very high stiffness.
24
Prepare a pat of moist soil with a volume of about 10 cm Add enough water, if necessary, to make the soil soft but not sticky. Shake the pat horizontally in the palm of the hand, striking vigorously against the other hand several times. A positive reaction consists of the appearance of water on the surface of the pat which changes to a livery consistency and becomes glossy. When the sample is squeezed between the fingers, the water and gloss disappear from the surface. The pat stiffens, and finally it cracks or crumbles. The rapidity of appearance of water during shaking and its disappearance during squeezing assist in identifying the character of the fines in the soil. Very fine clean sands give the quickest and most distinct reaction whereas a plastic clay has no reaction. Inorganic silt, such as a typical rock flour, shows a relatively rapid reaction.
AS 1726:2017
Standards Australia
TABLE 7
25
AS 1726:2017
TABLE 8 IDENTIFICATION OF FINE GRAINED SOILS BY VISUAL—TACTILE METHODS Soil description
Identification of inorganic fine-grained soils Dry strength
Dilatancy
Toughness and plasticity
None to low
Slow to rapid
Low or thread cannot be formed
Clayey SILT—Clay/silt mixtures of low plasticity
Low to medium
None to slow
Low to medium
Silty CLAY—Silt/clay mixtures of medium plasticity
Medium to high
None to slow
Medium
High to very high
None
High
SILT
High plasticity CLAY
6.1.4.11 Particle characteristics (coarse grained soil) Particle size shall be reported in millimetres or by use of the subdivisions in Table 1.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The spread of sizes represented should be described using one of the following terms (refer to Table 9): (a)
‘Well graded’—having good representation of all particle sizes from the largest to the smallest.
(b)
‘Poorly graded’—with one or more intermediate sizes poorly represented.
(c)
‘Gap graded’—with one or more intermediate sizes absent.
(d)
‘Uniform’—essentially of one size.
The assignment of one of the above terms may be made solely on the basis of visual–tactile examination, or on the basis of laboratory measurements. Where laboratory data are available, a well graded soil is one for which the coefficient of uniformity Cu > 4 and the coefficient of curvature 1 < Cc < 3. Otherwise, the soil is poorly graded. These coefficients
D D where D10 , D30 and D60 are those grain sizes for are given by Cu 60 and Cc 30 D10 D60 D10 which 10%, 30% and 60% of the soil grains are smaller. 2
Where significant, particle shape should be reported as follows: (i)
Equi-dimensional particles: ‘rounded’, ‘sub-rounded’, ‘sub-angular’, or ‘angular’, as shown in Figure 4.
(ii)
Essentially two-dimensional particles with the third dimension small by comparison: ‘flaky’ or ‘platy’.
(iii) Essentially one-dimensional particles with the other two dimensions small by comparison: ‘elongated’. Where significant, particle composition should be described using the rock or mineral name (e.g. quartz sand or carbonate sand).
www.standards.org.au
Standards Australia
AS 1726:2017
26
Rounded
A n g u l ar
Sub-rounded
Su b - a n g u l ar
FIGURE 4 PARTICLE SHAPES
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
6.1.5 Colour The colour of a soil shall be described in the moist condition, using simple terms such as black, white, grey, red, brown, orange, yellow, purple, green, blue, etc. These may be modified as necessary, e.g. by ‘pale’, ‘dark’, or ‘mottled’. Borderline colours may be described as a combination of these colours, e.g. red-brown. Where a soil colour consists of a primary colour with a secondary mottling it shall be described as follows: (Primary colour) mottled (secondary colour), e.g. grey mottled red-brown clay. Where a soil consists of two colours present in roughly equal proportions the colour shall be described as mottled (first colour) and (second colour), e.g. mottled brown and red-brown. A mixture of distinct colours may be described as, for example, mottled red/grey. 6.1.6 Soil classification Soil classification can occur after the soil composition has been described. Soils shall be classified into one of a number of soil groups designated by a two character group symbol. Classification is based on the grading of the coarse particles, and the behaviour and plasticity of the fraction of the material passing the 0.425 mm sieve. This may be assessed by visual–tactile methods or from laboratory tests. Where the classification derived from laboratory tests conflicts with that derived from visual–tactile methods the conflict shall be reported and some or all of the visual–tactile classifications may be modified and, where modified, this shall be documented. The group symbol classifications are given in Tables 9 and 10. Soils are classified to reflect their primary component and significant secondary components. The first classification symbol shall be G, S, M, or C, where the primary components are gravel, sand, silt or clay, respectively. For soils classified as coarse grained soils (S or G), the second symbol reflects either the grading of the coarse fraction, or the presence of clay or silt fines. For soils classified as fine soils (C, M or O), the second symbol reflects the plasticity of the sub 0.425 mm portion of the soil. In cases where laboratory measurements of the Atterberg limits are available, Figure 5 should be used to assist in classifying the fine grained soil. Standards Australia
www.standards.org.au
27
AS 1726:2017
TABLE 9 CLASSIFICATION OF COARSE GRAINED SOILS Major divisions
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Coarse grained soil (more than 65% of soil excluding oversize fraction is greater than 0.075 mm)
GRAVEL (more than half of coarse fraction is larger than 2.36 mm)
SAND (more than half of coarse fraction is smaller than 2.36 mm)
Group symbol
Typical names
Field classification of sand and gravel
Laboratory classification
GW
Gravel and gravel-sand mixtures, little or no fines
Wide range in grain 5% fines size and substantial amounts of all intermediate sizes, not enough fines to bind coarse grains, no dry strength
GP
Gravel and gravel-sand mixtures, little or no fines, uniform gravels
Predominantly one size or range of sizes with some intermediate sizes missing, not enough fines to bind coarse grains, no dry strength
GM
Gravel-silt mixtures and gravel-sand-silt mixtures
‘Dirty’ materials with 12% fines, Fines behave excess of non-plastic fines are as silt fines, zero to medium silty dry strength
GC
Gravel-clay mixtures and gravel-sand-clay mixtures
‘Dirty’ materials with 12% fines, Fines behave excess of plastic fines are as clay fines, medium to high clayey dry strength
SW
Sand and gravel-sand mixtures, little or no fines
Wide range in grain 5% fines size and substantial amounts of all intermediate sizes, not enough fines to bind coarse grains, no dry strength
SP
Sand and gravel-sand mixtures, little or no fines
Predominantly one size or range of sizes with some intermediate sizes missing, not enough fines to bind coarse grains, no dry strength
SM
Sand-silt mixtures
‘Dirty’ materials with 12% fines, excess of non-plastic fines are fines, zero to medium silty dry strength
SC
Sand-clay mixtures
‘Dirty’ materials with 12% fines, excess of plastic fines are fines, medium to high clayey dry strength
5% fines
5% fines
Cu > 4 1 < Cc < 3
Fails to comply with above
Cu > 6 1 < Cc < 3
Fails to comply with above
NA
NOTE: Where the grading is determined from laboratory tests, it is defined by coefficients of curvature C c and uniformity C u derived from the particle size distribution curve, as specified in Clause 6.1.4.11.
For fines contents between 5% and 12%, the soil shall be given a dual classification comprising the two group symbols separated by a dash, e.g. for a gravel with between 5% and 12% silt fines, the classification is GP-GM. Soils that are dominated by boulders, cobbles or peat (Pt) are described separately and are not classified. www.standards.org.au
Standards Australia
AS 1726:2017
28
TABLE 10 CLASSIFICATION OF FINE GRAINED SOILS
Major divisions
Fine grained soils (more than 35% of soil excluding oversize fraction is less than 0.075 mm)
SILT and CLAY (low to medium plasticity, %)
Group symbol
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Highly organic soil
Standards Australia
Typical names
Dry strength
Dilatancy
Laboratory classification
Toughness % < 0.075 mm
ML
Inorganic silt and very fine sand, rock flour, silty or clayey fine sand or silt with low plasticity
None to low
Slow to rapid
Low
Below A line
CL, CI
Inorganic clay of low to medium plasticity, gravelly clay, sandy clay
Medium to high
None to slow
Medium
Above A line
Organic silt
Low to medium
Slow
Low
Below A line
Inorganic silt
Low to medium
None to slow
Low to medium
Below A line
OL SILT and CLAY (high plasticity)
Field classification of silt and clay
MH CH
Inorganic clay of high plasticity
High to very high
None
High
Above A line
OH
Organic clay of medium to high plasticity, organic silt
Medium to high
None to very slow
Low to medium
Below A line
—
—
—
—
Pt
Peat, highly organic soil
www.standards.org.au
29
AS 1726:2017
60
e ) lin - 8 L e (W th 9 0. = U
50
PL ASTICIT Y IN DE X I P, %
IP 40
t
he
CH or O H
IP
=
0.
e 0) lin -2 L (W 73 A
30 CI or OI 20
M H or O H CL or O L
10 CL - M L
M L or O L 0 10
0
20
30
40
50
60
70
80
90
10 0
LIQ UID LIMIT W L , %
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
NOTE: The U line is an approximate upper bound for most natural soils. Data which plot above the U line may represent unusual/problem soil behaviour, or unreliable data and should be considered carefully.
FIGURE 5 MODIFIED CASAGRANDE CHART FOR CLASSIFYING SILTS AND CLAYS ACCORDING TO THEIR BEHAVIOUR
6.1.7 Condition of soil The condition of a soil shall be described. The following terms are used to describe the soil condition: (a)
Moisture condition Where the moisture condition of a coarse grained soil is estimated in the field it should be described by the appearance and feel of the soil using one of the following terms: (i)
Dry (D)
– Non-cohesive and free-running.
(ii) Moist (M) – Soil feels cool, darkened in colour. – Soil tends to stick together. (iii) Wet (W)
– Soil feels cool, darkened in colour. – Soil tends to stick together, free water forms when handling.
The moisture condition of fine grained soils shall be described based on a judgement of the soil’s moisture condition relative to the plastic limit (or liquid limit for soils with high moisture contents), as follows: (A)
‘Moist, dry of plastic limit’ (hard and friable or powdery) (or ‘w < PL’).
(B)
‘Moist, near plastic limit’ (soils can be moulded at a moisture content approximately equal to the plastic limit) (or ‘w ≈ PL’).
(C)
‘Moist, wet of plastic limit’ (soils usually weakened and free water forms on hands when handling) (or ‘w > PL’).
(D)
‘Wet, near liquid limit’ (or ‘w ≈ LL’).
(E)
‘Wet, wet of liquid limit’; (or ‘w > LL’).
www.standards.org.au
Standards Australia
AS 1726:2017
(b)
30
Consistency The consistency of cohesive soils describes the ease with which the soil can be remoulded. Consistency shall be described using the terms in Table 11. Cohesive soils include fine-grained soils, and coarse grained soils with sufficient fine-grained components to induce cohesive behaviour. In the field, the consistency of the soil may be assessed either by tactile means, or by measuring the undrained shear strength by mechanical testing (refer to Table 11). Mechanical determination methods should be carried out in accordance with AS 1289 series. Methods not covered by AS 1289 may also be used provided the method is suitably calibrated. Values of undrained shear strength assessed by field tests for classification purposes may not necessarily be appropriate for use in design. TABLE 11 CONSISTENCY TERMS FOR COHESIVE SOILS Field guide to consistency
Indicative undrained shear strength kPa
Very Soft (VS)
Exudes between the fingers when squeezed in hand
12
Soft (S)
Can be moulded by light finger pressure
>12 and 25
Firm (F)
Can be moulded by strong finger pressure
>25 and 50
Stiff (St)
Cannot be moulded by fingers
>50 and 100
Very Stiff (VSt)
Can be indented by thumb nail
>100 and 200
Hard (H)
Can be indented with difficulty by thumb nail
Friable (Fr)
Can be easily crumbled or broken into small pieces by hand
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Consistency
>200 —
NOTE: Consistency is affected by the moisture content of the soil at the time of measurement.
(c)
Relative density of non-cohesive, coarse grained soils The density of non-cohesive soils is described in terms of density index, as defined in AS 1289.5.6.1. The relative density of coarse grained soils is inherently difficult to assess by visual or tactile means and these techniques should not be used. Relative density assessment should be carried out using a combination of penetration test procedures (standard penetration test, dynamic penetrometer or static cone penetration test, as specified in AS 1289, Methods 6.3.1, 6.3.2, 6.3.3 or 6.5.1) in conjunction with well-established correlations. Alternatively, in situ density tests may be conducted in association with minimum and maximum density tests performed in the laboratory. Table 12 lists descriptive terms applicable to these soils.
Standards Australia
www.standards.org.au
31
AS 1726:2017
TABLE 12 RELATIVE DENSITY OF NON-COHESIVE SOILS Term Very Loose (VL)
Density index % 15
Loose (L)
>15 and 35
Medium Dense (MD)
>35 and 65
Dense (D)
>65 and 85
Very Dense (VD)
>85
NOTE: The moisture content may influence the inferred relative density.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(d)
Cementation Soils or defects within soils may be cemented together by various substances. The following terms should be used to describe cemented soils: (i)
‘Weakly cemented’—the soil may be easily disaggregated by hand in air or water.
(ii)
‘Moderately cemented’—effort is required to disaggregate the soil by hand in air or water.
Where consistent cementation throughout a soil mass is identified as a duricrust, it shall be described in accordance with Clause 6.2 and Table 18. The nature of the cementing agent shall be identified if possible from its appearance, strength, and reaction to acid. 6.1.8 Mass properties of soil If present, the structure of the soil shall be described. The following terms should be used. If alternative descriptions are used, the terms shall be defined: (a)
Zoning Soil in situ or in samples may consist of separate zones differing in colour, grain size or other properties. The patterns of these zones shall be described using the following terms: (i)
‘Layer’, i.e. the zone is continuous across the exposure or sample.
(ii)
‘Lens’, i.e. a discontinuous layer of different material, with lenticular shape.
(iii) ‘Pocket’, i.e. an irregular inclusion of different material. The thickness, orientation and any distinguishing features of the zones shall be described. The boundaries between zones shall be described as gradational or distinct. ‘Interbedded’ or ‘interlaminated’, shall be used if layers of alternating soil types are too thin to describe individually. NOTE: The maximum/mean/minimum thickness of the beds/laminations should be given.
(b)
Defects Defects in soil shall be described using the terms defined in Table 13. NOTE: The approximate dimensions, orientation and spacing of defects should be given.
(c)
Mixed soils ‘Intermixed’ may be used to describe two or more soil types arranged in an irregular manner.
www.standards.org.au
Standards Australia
AS 1726:2017
32
TABLE 13 SOIL DEFECT TYPES
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Term
Definition
Parting
A surface or crack across which the soil has little or no tensile strength. Parallel or sub parallel to layering (e.g. bedding). May be open or closed.
Fissure
A surface or crack across which the soil has little or no tensile strength but which is not parallel or sub parallel to layering. May be open or closed. May include desiccation cracks.
Sheared seam
Zone in clayey soil with roughly parallel near planar, curved or undulating boundaries containing closely spaced, smooth or slickensided, curved intersecting fissures which divide the mass into lenticular or wedge shaped blocks.
Sheared surface
A near planar, curved or undulating smooth, polished or slickensided surface in clayey soil. The polished or slickensided surface indicates that movement (in many cases very little) has occurred along the defect.
Softened zone
A zone in clayey soil, usually adjacent to a defect in which the soil has higher moisture content than elsewhere.
Diagram
S of te n e d zo n e
Tube
Tubular cavity. May occur singly or as one of a large number of separate or interconnected tubes. Walls often coated with clay or strengthened by denser packing of grains. May contain organic matter. Origins include root holes, animal burrows, tunnel erosion.
Tube cast
An infilled tube. The infill may be uncemented or weakly cemented soil or have rock properties.
Infilled seam
Sheet or wall like body of soil substance or mass with roughly planar to irregular near parallel boundaries which cuts through a soil mass. Formed by infilling of open defects.
NOTE: Where practical, the surface of the defects shall be described in terms of shape (planar, stepped, curved, irregular), surface roughness (rough, smooth, polished, slickensided), and coating.
6.1.9 Soil origin The geological origin of the soil shall be interpreted and recorded. Where there is doubt, the terms ‘possibly’ or ‘probably’ shall be used. Soil origin cannot generally be deduced on the basis of material appearance and properties alone; it requires further geological evidence and broader field observation. The geological origin of a soil may be interpreted from an assessment of the geological and geomorphological setting in which it occurs. Soil deposits can be formed in situ from the weathering of parent materials, or formed from the accumulation of soil materials formed elsewhere and transported to their present location. Transported soils may include both natural and anthropogenic materials.
Standards Australia
www.standards.org.au
33
AS 1726:2017
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Useful descriptors of soil origin may include, but are not limited to, the following: (a)
Residual soil Formed directly from in situ weathering of geological formations. These soils no longer retain any visible structure or fabric of the parent soil or rock material.
(b)
Extremely weathered material Formed directly from in situ weathering of geological formations. Although this material is of soil strength it retains the structure and/or fabric of the parent rock material.
(c)
Alluvial soil Deposited by streams and rivers.
(d)
Estuarine soil Deposited in coastal estuaries, and including sediments carried by inflowing rivers and streams, and tidal currents.
(e)
Marine soil Deposited in a marine environment.
(f)
Lacustrine soil Deposited in freshwater lakes.
(g)
Aeolian soil Carried and deposited by wind.
(h)
Colluvial soil Soil and rock debris transported down slopes by gravity, with or without the assistance of flowing water and generally deposited in gullies or at the base of slopes. Colluvium is often used to refer to thicker deposits such as those formed from landslides, whereas the term ‘slopewash’ may be used for thinner and more widespread deposits that accumulate gradually over longer geological timeframes.
(i)
Topsoil Mantle of surface and/or near-surface soil often but not always defined by high levels of organic material, both dead and living. Remnant topsoils are topsoils that have subsequently been buried by other transported soils. Roots of trees may extend significantly into otherwise unaltered soil and the presence of roots is not a sufficient reason for describing a material as topsoil. ‘TOPSOIL’ should be emphasized by the use of BLOCK LETTERS.
(j)
Fill Any material which has been placed by anthropogenic processes described in detail in Clause 6.1.1. ‘FILL’ should be emphasized on logs by the use of BLOCK LETTERS.
Soils should be assigned to a stratigraphic unit. Where there is doubt, the terms ‘possibly’ or ‘probably’ shall be used. 6.1.10 Additional observations Where significant these shall be recorded. Examples include changes in colour over time, odour, hydrocarbon or other contamination, the presence of burrowing animals and delineation of soil horizons. Where there is some doubt as to the representativeness or quality of a sample, this shall be stated. If this affects the overall description, this shall again be reflected in the overall description. If the material is assessed to be not representative, terms such as ‘poor recovery’, ‘non-intact’, ‘recovered as’ or ‘probably’ shall be applied. 6.1.11 Description of fills 6.1.11.1 General Where fill is present, the thickness and composition shall be recorded. The fact that soils have been deposited on a site by other than natural mechanisms may have significant geotechnical and environmental implications. The material shall be identified clearly in the field log as fill, and then described in sufficient detail to record the nature and extent of the particular materials that are present. When describing fill, the word ‘FILL’ shall precede the soil name.
www.standards.org.au
Standards Australia
AS 1726:2017
34
Significant fill materials that may be encountered and should be noted during an investigation are given in Table 14, although this list is not exhaustive. Typical characteristics of fill include— (a)
unusually variable range of colours;
(b)
very distinct changes in soil profile;
(c)
presence of foreign objects such as glass, plastic, slag;
(d)
buried organic matter in some instances; and
(e)
‘cloddiness’ of clay soil indicating previous disturbance by excavation.
Fill placed in accordance with AS 3798 or other controlled method, as demonstrated by construction documentation, may be considered as controlled fill. The presence of controlled fill should be included under ‘additional observations’ (refer to Clause 6.1.10). Fill for which no construction documentation is available shall be considered uncontrolled fill. Wherever possible, descriptions of uncontrolled fill shall follow the system used for other soils as described in Clause 6.1.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
6.1.11.2 Detailed descriptions A list of the main components of uncontrolled fill shall be made in order of decreasing importance. For solid objects, the composition and size shall be given either in millimetres (or metres for larger objects) or using standard soil particle sizes, e.g. ‘15% cobble to boulder sized blocks of reinforced concrete’. For hollow objects, state whether they are empty (and potentially compressible), infilled or crushed. Any putrescible materials shall also be explicitly noted. Additional comment, regarding the structure of the material shall be given. Examples include the following: (a)
The presence of voids.
(b)
If waste is contained in drums or bags.
(c)
If there are discrete layers of materials.
(d)
Any items which could indicate the age of the uncontrolled fill should be identified, such as dates on newspapers, distinctive bottles, or ‘best before’ dates on food and drink packaging.
The terms in Table 14 may be useful in describing organic and artificial materials.
Standards Australia
www.standards.org.au
35
AS 1726:2017
TABLE 14 DESCRIPTIVE TERMS FOR FILL MATERIALS Generalized terms Organic matter
Typical descriptions Fibrous peat Charcoal Wood fragments Roots (greater than 2 mm diameter) Root fibres (less than 2 mm diameter) Night soil Putrescible waste
Artificial materials
Oil, bitumen Masonry Concrete rubble Fibrous plaster, plasterboard Timber pieces, wood shavings, sawdust Iron filings, drums, steel bars, steel scrap
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Bottles, broken glass Leather Slag Chitter, ash, tailings Asbestos, fibre cement Rubber tyres
6.1.12 Problematic soils Some of the more common characteristics of problematic soil include— (a)
volumetric change;
(b)
loss of strength; and
(c)
corrosive potential.
NOTE: Further information about the behaviour of selected problematic soil types is provided in Appendix D.
6.1.13 Examples of soil description and classification To illustrate the application of the provisions of Clause 6.1, the following examples are provided: (a)
For a red-brown, basaltic soil with desiccation cracks, which is assessed as comprising 20% fine to medium, sub-rounded gravel in a very stiff, moist, medium plasticity clayey matrix, an appropriate description would be: CI CLAY with gravel, red-brown, medium plasticity, very stiff; gravel 20%, fine to medium, sub-rounded; moist, with desiccation cracks; residual.
(b)
For a ‘dirty’, grey, medium grained sand encountered on a tidal flat in the Fullerton Cove area, assessed to have 2
Deposited rock type
Low porosity, indurated
CONGLOMERATE (larger rounded grains in a finer matrix) BRECCIA (angular or irregular rock fragments in a finer matrix)
LIMESTONE or DOLOMITE (Note 4) 0.06–2 0.002–0.06
Porous, core can be broken by hand
Ejected from a volcano
CALCIRUDITE AGGLOMERATE (rounded grains in a finer matrix or VOLCANIC BRECCIA (angular fragments in a finer matrix)
SANDSTONE (Notes 1,2)
CALCARENITE TUFF
MUDSTONE (Note 5)
SILTSTONE (Note 5)
CALCISILTITE
silt and clay
mostly silt
Fine grained CALCILUTITE TUFF
2) Medium (0.06–2) Fine (2)
GNEISS—well developed but often widely spaced foliation sometimes with schistose bands
Medium (0.06–2)
SCHIST—well developed foliation with much mica, QUARTZITE—fused quartz grains some micas larger than 2 mm SERPENTINITE—usually a grey and green rock formed by the PHYLLITE—slightly undulose foliation sometimes alteration of mafic igneous rocks spotted. HORNFELS—usually a fine SLATE—well developed planar cleavage grained rock formed by thermal metamorphism
Fine (1000 mm) Surface roughness, shape and waviness.
Standards Australia
www.standards.org.au
49
AS 1726:2017
Although the surface roughness of defects can be described at all scales of observation, the overall shape of the defect surface can usually be observed only at medium and large scale. For example, a defect which appears planar in a 50 mm diameter drill core may be described as curved, undulating or stepped when observed in outcrop where more of the defect is visible. The roughness and shape of defects combine to have a significant effect on their shear strength, which is also affected by large scale features. Where it is necessary to assess the shear strength of a defect, observations should be made at multiple scales. Measurements should be taken as outlined by the following: (i)
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(ii)
Surface roughness At all scales of observation the defect surface roughness shall be described using the following terms: (A)
Very rough Many large surface irregularities (amplitude generally more than 1 mm). Feels like, or coarser than very coarse sand paper.
(B)
Rough Many small surface irregularities (amplitude generally less than 1 mm). Feels like fine to coarse sand paper.
(C)
Smooth Smooth to touch. Few or no surface irregularities.
(D)
Polished Shiny smooth surface.
(E)
Slickensided Grooved or striated surface, usually polished.
Surface shape At the medium scale of observation, description of the roughness of the surface shall be enhanced by description of the shape of the defect surface using the following terms, as illustrated in Figure 7: (A)
Planar The defect does not vary in orientation.
(B)
Curved The defect has a gradual change in orientation.
(C)
Undulating The defect has a wavy surface.
(D)
Stepped The defect has one or more well defined steps.
(E)
Irregular The defect has many sharp changes of orientation.
NOTE: Measurements should be made of the height of steps or irregularities, and the amplitude and wavelength of undulations. Figure 8 shows a generalized guide to measurements at medium scale, which may also be applied to the large scale of observation.
Alternatively, the surface roughness may be characterized by the joint roughness coefficient (JRC) using the profiles provided in Figure 9. (iii) Waviness Where large scale observations are possible, further measurement of the parameters defining defect waviness shall be made. NOTE: See Figure 10. ‘i’ is the angle of the asperities relative to the overall dip angle of the structure. This can be used in conjunction with the angle of friction of the rock surface to assess the shear strength along the defect.
www.standards.org.au
Standards Australia
AS 1726:2017
50
Pl anar
Cur ve d
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
U n d u l at i n g
S te p p e d
Irre g ul ar
10 0 m m
FIGURE 7 DEFECT SHAPES ILLUSTRATED AT MEDIUM SCALE
Standards Australia
www.standards.org.au
51
AS 1726:2017
S tr ai g ht e d g e Wave l e n g t h — m m
As per it y am plitud e — mm
Le n g t h over profil e — m or m m a s a p p li c a b l e
FIGURE 8 MEDIUM TO LARGE SCALE MEASUREMENT OF DEFECT SHAPE
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Typic al roughness profiles for JRC range: 1
0 –2
2
2– 4
3
4–6
4
6–8
5
8 –10
6
10 –12
7
12 –14
8
14 –16
9
16 –18
10
18 – 20
0
5
10 cm
S c al e
This figure is based on: Barton, N and Choubey, V. The Shear Strength of Rock Joints in Theory and Practice. Rock Mechanics. Vol. 10 (1977), pp. 1–54. With permission of Springer. FIGURE 9 ROUGHNESS PROFILES AND CORRESPONDING RANGE OF JRC VALUES ASSOCIATED WITH EACH ONE www.standards.org.au
Standards Australia
AS 1726:2017
52
“ i ” an g l e
“ i ” an g l e O ver all d i p of str u c ture
1–10 m
FIGURE 10 LARGE SCALE MEASUREMENTS OF DEFECT WAVINESS
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
6.2.5.5 Defect coatings and composition of seams Many defects have a surface coating which could affect their shear strength. Description of coating is generally possible for all scales of observation. Coatings shall be described using the following terms: (a)
Clean No visible coating.
(b)
Stained No visible coating but surfaces are discoloured.
(c)
Veneer A visible coating of soil or mineral, too thin to measure; may be patchy.
(d)
Coating A visible coating up to 1 mm thick. Thicker soil material shall be described using defect terms (e.g. infilled seam). Thicker rock strength material shall be described as a vein.
Where possible the mineralogy of the coating shall be identified. The composition of seams shall be described using soil description terms as given in Clause 6.1. 6.2.5.6 Defect spacing, length, openness and thickness Spacing, aperture (openness) and seam thickness and composition shall be described directly in millimetres and metres. In general descriptions, half order of magnitude categories are often useful, e.g. joint spacing typically 100 mm to 300 mm, sheared zones 1 m to 3 m thick. Depending on project requirements and the scale of observation, spacing may be described as the mean spacing within a set of defects, or as the spacing between all defects within the rock mass. Where spacing is measured within a specific set of defects, measurements shall be made perpendicular to the defect set. Defect spacing and length (sometimes called persistence), shall be described directly in millimetres and metres. Where significant, the nature of the defect end condition (i.e. termination) should be recorded in the context of the scale of the exposure. Each end of a defect may— (a)
start and/or end outside the extent of the exposure;
(b)
terminate within rock material; or
(c)
terminate at an intersecting defect set.
Standards Australia
www.standards.org.au
53
AS 1726:2017
6.2.5.7 Block shape Where it is considered significant, block shape should be described using the terms given in Table 23. TABLE 23 BLOCK SHAPE TERMS* Term
Figure
Description
Irregular discontinuities without arrangement into distinct sets, and of small persistence.
Polyhedral blocks
1 1
1
One dominant set of parallel discontinuities (1), for example bedding planes, with other noncontinuous joints; thickness of blocks much less than length or width.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Tabular blocks
1
Prismatic blocks
Two dominant sets of discontinuities (1 and 2), approximately orthogonal and parallel, with a third irregular set; thickness of blocks much less than length or width.
1 2
1
3
2
Equidimensional blocks
Three dominant sets of discontinuities (1, 2 and 3), approximately orthogonal, with occasional irregular joints, giving equidimensional blocks.
1 1
3
2
1
3
3
1
2 2
Rhomboidal blocks 2
Three (or more) dominant, mutually oblique, sets of joints (1, 2 and 3) giving oblique-shaped, equidimensional blocks.
1 3
5 1
Columnar blocks
2 3 4
Several, usually more than three sets of continuous, parallel joints (1, 2, 3, 4, 5) usually crossed by irregular joints; lengths much greater than other dimensions.
* This table has been reproduced from Table 10, ISO 14689-1 Geotechnical investigation and testing— Identification and classification of rock—Part 1: Identification and description. Copyright for these figures remain with ISO.
www.standards.org.au
Standards Australia
AS 1726:2017
54
6.2.6 Stratigraphic unit Rocks should be assigned to a stratigraphic unit. Where there is doubt, the terms ‘possibly’ or ‘probably’ shall be used. 6.2.7 Geological structure After describing the rock material and the defects and observing exposures and/or excavations and/or cores the geological structure of the rock mass should be interpreted and documented. This may include the preparation of borehole logs, maps, sections and/or stereographic projection of defect information to assess the type and distribution of strata, the defect sets and their orientation and the presence of any structures such as dipping strata, folds, faults, and features such as unconformities and weathering profiles. 6.2.8 Examples of rock description and classification
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
To illustrate the application of the provisions of Clause 6.2, the following examples are provided: (a)
ANDESITE, grey-blue, Very High Strength, Slightly Weathered, joint spacing 300 to 3000 mm, vertical columnar joints, sub-horizontal joints with about 5 to 10 m persistence and Extremely Weathered Seams (50 mm of Clayey Sand), columnar joints planar and rough. Triassic Mount Byron Volcanics.
(b)
SANDSTONE, grey, Medium Strength, Slightly Weathered, bedding and joint spacing 20 to 100 mm; interbedded with MUDSTONE, grey green, Very Low Strength, Distinctly Weathered, laminations spaced 10–20 mm. Ordovician Eildon Formation.
6.2.9 Parameters related to core drilling 6.2.9.1 General There are a number of parameters that may be measured during core drilling (of both soil and rock), and which may provide useful investigation data. The measurements that define these parameters should be taken during the drilling process, when drill core is relatively undamaged. 6.2.9.2 Total core recovery Total core recovery (TCR) is defined as:
TCR
Length of core recovered 100% Length of core run
Depth intervals where core is not recovered should be designated ‘No Core’ on drilling records and logs. Where there is doubt about the specific depth interval over which core was not recovered, usual practice is to assign the ‘No Core’ zone to the end of the core run. 6.2.9.3 Defect spacing or fracture index The frequency of defects within drill core should be measured as either— (a)
the spacing between successive defects, or the mean spacing for relatively broken core; or
(b)
the ‘Fracture Index’, which is the number of defects per metre of core.
Under some circumstances it may be useful and practical to record the spacing between defects within specific defect sets. 6.2.9.4 Rock quality designation A measure of defect spacing in drill core is rock quality designation (RQD). NOTE: This measurement was originally developed by Deere et al. (1989) (refer to Bibliography). Standards Australia
www.standards.org.au
55
AS 1726:2017
RQD is expressed as:
RQD =
Length of sound core pieces 100 mm in length 100% Length of core run
Only core lengths of rock strength material delineated by natural defects shall be measured. If the core is broken by handling or by the drilling process, the broken pieces shall be fitted together and counted as one piece. Figure 13 shows the measuring process used to calculate RQD. Length measurements shall be taken along the central axis of the core.
L = 25 0 m m
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
RQD =
25 0 + 19 0 + 20 0 × 10 0% 120 0
L = 0 E x tremely weat hered d o e s n ot m e et s o u n d n e s s r e q u ire m e nt
L = 0 c e ntre lin e p i e c e s < 10 0 m m and ex tremely weat h ere d
L = 19 0 m m
C o r e r u n tot a l l e n g t h = 1. 2 m
= 5 3%
L = 0 < 10 0 m m
M e c hani c al break c ause d by dr illing pro c es s
L = 20 0 m m
L = 0 N o re c over y
FIGURE 13 RQD MEASUREMENT PROCEDURE
www.standards.org.au
Standards Australia
AS 1726:2017
56
RQD should be employed only for core of ‘N’ size or larger (i.e. about 50 mm diameter or greater), as smaller core could bias the results. RQD was originally intended to be measured only over a full core run. There may be valid applications of RQD where it is measured over a specific length, or within specific rock mass units. If such deviations to the original calculation method are made they shall be explained with the reported RQD values. 6.2.10 Classification of the rock mass 6.2.10.1 Weathering grades Where a weathering profile is exposed in an outcrop or an excavation the degree of weathering of the rock mass should be classified using the terms and grades in Table 24. If an alternative rock mass weathering scheme is used it shall be documented. TABLE 24 ROCK MASS WEATHERING GRADES
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Grade
Descriptive term
IA
Fresh; no visible sign of rock material weathering
IB
Fresh except for staining on major defect surfaces
II
Some to all of the rock mass is discoloured by slight weathering
III
Less than 35% of the mass is weathered to a soil
IV
More than 35% of the mass is weathered to a soil with rock present as a discontinuous framework or corestones
V
Virtually all of the rock mass is weathered to a soil but the original mass structure still largely intact
6.2.10.2 Duricrust grades Where a duricrust has developed in a weathering profile and is exposed in outcrop or excavation, the degree of development of the duricrust may be classified. The terms in Table 25 should be used. If alternative duricrust classification schemes are used they shall be documented.
Standards Australia
www.standards.org.au
57
AS 1726:2017
TABLE 25 DURICRUST MASS GRADES Graphic log
Structure term
Grade
Massive or hardspan
DI
More than 90% of the ground consists of duricrust rock material which forms a continuous framework.
DII
Between 50% and 90% of the ground consists of duricrust rock material which forms a continuous framework around soil materials (vuggy) or rock materials (patchy).
DIII
Less than 50% of the ground consists of gravel and cobble sized nodules (rounded or subrounded) or fragments (angular or subangular) of duricrust rock material and it is described as a soil.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Vuggy or patchy
Nodular or fragmental
Description
NOTE: Cavities or vugs within the rockmass should be described in terms of size, frequency and continuity.
6.2.10.3 Rock mass classification schemes Rock mass classification schemes may be used to develop a model of the characteristics of a rock mass. They require the systematic collection of information including the description and classification of rock, soil and water, which is transformed into numerical or ranked information that may be used to support engineering design. A large variety of classification schemes have been developed ranging from simple to complex. All of the schemes are limited in their application. For example, classification schemes that have been developed to predict tunnel support requirements are seldom relevant to slope stability issues and vice versa. Many rock mass classification systems assume that the rock mass is isotropic, which is rarely the case. If a particular rock mass classification scheme is to be adopted for design, the required inputs should be recognized prior to commencing work so that all relevant information is collected during the geotechnical site investigation.
www.standards.org.au
Standards Australia
AS 1726:2017
6.3
58
Surface water and groundwater observations
6.3.1 Surface water Observations shall be made of evidence of surface water flows, seepages, ponding, past flooding and any tidal influences in and around the project site. Where there is evidence of surface water flow, this shall be recorded. Information on past rainfall shall be collected. 6.3.2 Groundwater Movement of groundwater can be inferred from signs indicating discharge zones (such as seeps, vegetation and precipitation of salts) or inflow zones (such as sinkholes or flow into seepage areas) and such areas shall be mapped. Groundwater inflows and outflows encountered during subsurface investigations shall be recorded where feasible. Records of inflow and outflow during borehole drilling shall include the depth and an indication of the magnitude of the flow volume. Groundwater levels encountered during subsurface investigations shall be measured, where feasible, together with the time at which water level measurements are made and additional measurements should be carried out at the beginning and end of each shift.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
The construction method of any piezometers and standpipes shall be recorded. A survey level of the collar of the monitoring well or surveying the level of points of emergence of seepage shall be measured. As groundwater levels can vary with time, multiple and ideally continuous groundwater level measurements should be made. 6.3.3 Groundwater quality Observations of turbidity, colour, temperature, or odour should be made. Groundwater should not be tasted due to the risk of contamination by toxic substances. Strong odour can also be an indication of contamination by volatile substances and protective measures shall be employed where there is any suspicion of a risk to field personnel. Groundwater sampling methods shall be adopted that ensure the representativeness of samples and preserve the integrity of samples. 6.4 Gases Hazardous gases such as methane, carbon dioxide and carbon monoxide, can pose risks for the geotechnical site investigation and project development and may be a health and safety hazard which needs consideration. The possible presence of hazardous gases may be inferred from site history. Where required, procedures for detecting and monitoring these gases shall be implemented. BS 8576:2013 provides guidance on the investigation for hazardous ground gases.
Standards Australia
www.standards.org.au
59
AS 1726:2017
APPENDIX A
GEOTECHNICAL SITE INVESTIGATION TECHNIQUES (Informative) A wide variety of techniques and tests are available for geotechnical site investigations. Listed below are examples of techniques that are commonly considered. Reference should be made to the relevant Australian Standard or other test method for requirements such as sample condition and size. (a)
Geological studies, including: (i)
Regional geological mapping.
(ii)
Geological mapping of excavations and outcrops.
(iii) Geomorphological mapping.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(b)
(iv)
Borehole logging.
(v)
Detailed logging of test pits, excavations and exposures.
Geophysical investigations, including: (i)
Magnetic methods.
(ii)
Seismic methods using refraction, reflection and surface waves.
(iii) Ground penetration radar.
(c)
(d)
(iv)
Electrical resistivity measurement.
(v)
Electromagnetic methods.
(vi)
Geophysical borehole logging, involving seismic, electrical, gravimetric and radiometric logging and sonic testing, and cone penetration testing with the measurement of shear wave velocity and electrical resistivity or conductivity.
Drilling and sampling used to locate specific targets, to determine the vertical profile and lateral variability of the ground, including the groundwater conditions, to collect soil and rock samples, to perform in situ tests to determine mechanical properties of the ground, and for borehole imaging. Common methods include: (i)
Trial pits and trenches.
(ii)
Boring and drilling using rotary core drilling, auger boring and percussion drilling.
In situ probing to enable the assessment of engineering parameters of the ground, including: (i)
Plate bearing test.
(ii)
California bearing ratio.
(iii) Light weight deflectometer. (iv)
Density measurement.
(v)
Standard penetration test.
(vi)
Dynamic penetration tests, such as the dynamic cone penetrometer (refer to AS 1289.6.3.2) or the Perth sand penetrometer (refer to AS 1289.6.3.3).
(vii) Specialized cone penetration tests, such as the static cone, piezo cone, electrical conductivity cone, and seismic cone. www.standards.org.au
Standards Australia
AS 1726:2017
60
(viii) Full flow penetrometers (ball, T-bar and plate). (ix)
Flat dilatometer tests.
(x)
Vane shear test.
(xi)
Pressuremeter test.
(xii) Borehole impression packer. (xiii) Core orientation device. (xiv) Video visual inspection (e.g. borehole periscope, TV, and photography). (e)
In situ methods for obtaining relatively undisturbed samples that enable the evaluation of engineering properties in the laboratory, including block sampling and tube sampling using push-tube and piston samplers.
(f)
In situ rock testing in excavations and galleries, including: (i)
Direct shear tests.
(ii)
Plate bearing test.
(iii) In situ stress measurement. (iv)
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(g)
Point load strength test.
Slope and excavation stability monitoring, including the use of: (i)
Inclinometer.
(ii)
Extensometer.
(iii) Piezometers (e.g. vibrating wire piezometers). (iv)
Surface markers and settlements plates.
(v)
Earth pressure cells.
(vi)
Tilt sensors.
(h)
Blasting tests and vibration monitoring.
(i)
Topographic studies, including satellite and aerial imagery and remote sensing.
(j)
Groundwater studies and sampling, including: (i)
Packer tests.
(ii)
Rising head, constant head and falling head tests.
(iii) Pumping tests. (iv)
Groundwater level measurement.
(v)
Chemical and microbiological water quality.
(vi)
Soil vapour.
(vii) Water sampling with lysimeters.
Standards Australia
www.standards.org.au
61
AS 1726:2017
APPENDIX B
LABORATORY EXAMINATION AND TESTING (Informative) Laboratory testing provides a means of identifying and classifying soil and rock properties. In Table B1, the letter ‘X’ indicates some of the commonly considered laboratory tests. Reference should be made to the relevant Australian Standard or other test method for such requirements as sample condition and size. TABLE B1 LIST OF LABORATORY TESTS
Rock
Aggregates
Recycled masonry and concrete
Pavement materials
Consistency, structure and particle size
X
X
X
X
X
Colour, inclusions, and accessory materials
X
X
X
X
X
Geological description
X
X
X
X
X
Defects and weathering
X
X
X
Moisture content
X
X
X
X
X
Particle size distribution
X
X
X
X
Hydrometer analysis
X
X
X
Liquid limit, plastic limit and linear shrinkage
X
X
X
Emerson class number
X
Pinhole dispersion
X
Hole erosion test
X
In situ density
X
X
X
Particle density
X
X
X
Dry density/moisture relationship
X
Min/max density of cohesionless materials
X
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Test/Examination
Visual examination
Classification
Material density
Aggregate bulk density and unit mass Deformation
Water
Soil
Material type
X
Consolidometer/oedometer
X
Shrink/swell index
X
Soil suction measurement
X
Modulus and Poisson’s ratio
X
X
X
X
X
X
X
X
X (continued)
www.standards.org.au
Standards Australia
AS 1726:2017
62
TABLE B1 (continued)
Pavement materials
X
X
Aggregate crushing value
X
X
Sodium sulfate soundness
X
X
Los Angeles abrasion
X
X
Aggregate polishing value
X
X
Alkali silica reactivity
X
X
Wet/dry strength variation
X
X
X
X
X
X
Soil
Rock
Strength/Durability
Unconfined compression
X
X
Triaxial compression (drained or undrained)
X
X
Direct shear
X
X
Triaxial extension
X
X
Point load strength index
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
California bearing ratio
Organic matter
Chemical tests
X
X
X
X
X
Brazilian indirect tensile strength
X
Slake durability
X
Abrasivity
X
Seismic velocity
X
Porosity/water absorption
X
Cerchar abrasion index
X
Goodrich drillability
X
Cuttability
X
Deval attrition
X X
Aggregates X
Test/Examination
Water
Recycled masonry and concrete
Material type
X
X
X
X
X
X
pH
X
X
Cation exchange capacity
X
X
Anion/cation balance
X
X
Total dissolve solids
X
X
X
Sulfate
X
X
X
X
X
X
Chloride
X
X
X
X
X
X
Organic matter
X
X
X
X
X
X
Acid sulfate
X
X
X
Total salinity and acidity
X
X
Electrical conductivity
X
X (continued)
Standards Australia
www.standards.org.au
63
AS 1726:2017
TABLE B1 (continued)
Mineralogical tests
Hydraulic tests
X
X-ray diffraction
X
Falling head permeability
X
Constant head permeability
X
Triaxial permeability
X
X
X
X
Pavement materials
Recycled masonry and concrete
Water
Aggregates X
X
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Thermal properties
Petrographic analysis
Rock
Test/Examination
Soil
Material type
www.standards.org.au
Standards Australia
AS 1726:2017
64
APPENDIX C
GROUNDWATER CONSIDERATIONS (Informative) Investigation of groundwater in the context of geotechnical site investigation is typically associated with identification of groundwater head distribution, groundwater flow direction, response to rainfall, response to other factors (such as pumping, tidal variation and changing river levels) and hydraulic properties of water bearing soil and rock. Groundwater chemistry can have a significant impact on in-ground infrastructure in contact with groundwater. The presence of iron, manganese and calcium precipitates of hydroxides and carbonates that can clog drainage systems and elevated acidity and elevated chloride or sulfate concentrations can cause durability problems.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Assessment of the presence of contamination as a result of previous site usage can also be important, although this is not addressed in this Standard. An important part of any geotechnical site investigation is the identification of the groundwater level and of any artesian pressures. The variation of groundwater level or pressure over a given period of time may also require evaluation. Reliable information on groundwater levels within the depth proposed for excavations and pile borings and within the zone of influence of foundation pressures is vital to many aspects of foundation design and construction. Changes to groundwater conditions associated with a project have the potential to affect groundwater levels and quality at a distance from the site. This zone of potential influence on groundwater can be much wider than for soil and rock excavation. In addition, groundwater effects may take considerable time to develop or may be relevant only during extreme conditions such as during flooding or high rainfall events. A conceptual groundwater model should be developed as part of the overall geotechnical model where groundwater is a relevant consideration to the investigation. This is a simplified representation of the groundwater system and its behaviour in a form useful to the project. The conceptual model could range from a brief description of the salient features to a detailed presentation incorporating hydrogeological sections illustrating interpreted flow paths, recharge sources and discharge areas. Consideration of potential groundwater impacts associated with a project should occur at each stage of development of the geotechnical site investigation beginning with the desk study. Planning of geotechnical site investigations should include but not be limited to consideration of the following groundwater related factors: (a)
Groundwater levels.
(b)
Groundwater flow directions.
(c)
Hydraulic properties of geological horizons.
(d)
Existing and potential beneficial use of local groundwater.
(e)
Location and type of neighbouring groundwater users.
(f)
Nearby groundwater dependent ecosystems.
(g)
Surface and groundwater bodies within the likely zone of influence.
(h)
Rainfall and groundwater response to rainfall.
(i)
Groundwater chemistry.
Standards Australia
www.standards.org.au
65
Contamination.
(k)
Recharge and discharge processes.
(l)
Site drainage.
(m)
Legislative requirements.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(j)
AS 1726:2017
www.standards.org.au
Standards Australia
AS 1726:2017
66
APPENDIX D
PROBLEMATIC MATERIALS (Informative) A number of different materials may pose particular problems or issues when encountered during geotechnical site investigation or construction. The degree to which a soil or rock may be problematic is a function of— (a)
the nature of the soil (mineralogy, fabric, geotechnical and geochemical properties);
(b)
the geological processes that caused it to be formed; and
(c)
current processes (e.g. weathering, erosion, human activity).
Past and present climate play a major role in the development of soil profiles. Human activity is also an important factor in determining soil behaviour. Site investigation techniques should take these factors into account, and field and laboratory tests carried out to establish the existence and engineering properties of problematic soils.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Some of the more common examples are described briefly below: (i)
Acid generating rocks—naturally occurring rocks that contain an abundance of sulfides mainly in the form of pyrite (FeS2 ). These materials may oxidize to create acids, resulting in acid rock drainage when the acid is dissolved in surface or groundwater. Acid rock drainage occurs naturally within some environments as part of the rock weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities.
(ii)
Acid sulfate soils—naturally occurring soils that contain iron sulfides mainly in the form of pyrite (FeS2 ). The oxidation of pyrite and other sulfides to sulfates can occur during earthworks construction and dewatering, where the soils may be disturbed and exposed to air. While the reactions can be complex the overall result is the conversion of pyrite to iron hydroxides and sulfuric acid, potentially leading to pH values as low as 2 or 3. The effects can pose a significant risk to human health and the environment, in particular groundwater resource contamination by acid, arsenic and heavy metals. Other effects may include ground-heave and the corrosion of buried concrete and steel structures.
(iii) Arid soils—formed when evaporation exceeds rainfall and there is a soil-moisture deficit. The soils may have unusual engineering properties due to extreme desiccation, the presence of precipitated salts, high void ratio, mechanical and chemical weathering, etc. Diurnal temperature changes may cause accelerated disintegration of materials and lithification to occur. (iv)
Collapsible soils—either naturally occurring or formed through human activities. An open metastable structure is a prerequisite and is developed via bonding mechanisms which may include capillary forces (suction) or cementing agents such as clay, sesquioxides, and salts. Collapse may occur when nett stresses due to loading and saturation exceed the yield strength of the bonding materials.
Standards Australia
www.standards.org.au
67
AS 1726:2017
(v)
Degradable rocks—geological materials or formations that in their in situ form may be assigned names or appearances that imply rock-like behaviour. However, once disturbed, some of these materials retain the character of rock, but others may degrade to soil-size particles and exhibit soil-like strength and stiffness. In geological terms, all of the soils and rocks in the earth’s crust are ‘degradable’ in a time frame that is relevant to the long-term performance of engineering projects. Sedimentary rocks constitute the bulk of degradable rocks worldwide, with shale being a prime example, but weathered igneous and metamorphic rocks may also fall into this category.
(vi)
Dispersive soils—soils which, by the nature of their mineralogy and their pore water chemistry, are susceptible to separation of individual clay particles through fine fissures or cracks under seepage flows. The dispersivity of a soil is directly related to its clay mineralogy. Soils with montmorillonite tend to be dispersive, while kaolinite and related minerals (e.g. halloysite) are non-dispersive, and illite is moderately dispersive. The pore water chemistry affects the diffuse double layer geometry and electrical charge. Low electrolyte (pore water) salt concentrations lead to a large diffuse double layer and higher dispersivity (e.g. percolation of a saline soil with fresh water can lead to dispersion). Cation exchange (e.g. Ca++ exchanged for Na+) leads to a smaller double layer and lower dispersivity.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Dispersive soils may be identified from laboratory testing including Emerson class number, pinhole test, and various chemical tests on the soil pore water (e.g. sodium adsorption ratio and exchangeable sodium percentage). (vii) Expansive soils—change in volume in response to changes in moisture content. Changes in moisture content may be induced by seasonal variation or human activity. Such activities can include changes to site drainage, establishment or removal of trees and vegetation, and leakage from tanks or pipes. Shrink-swell behaviour is a function of clay mineralogy and clay content, and the soil-moisture deficit pertaining to the site. (viii) Glacial soils—can vary from sheared basal layers to unsorted mixtures of boulders, gravel, sand, silt and clay. Deposition occurs via a process of pressure and shear beneath the glacier as it advances, and may also be deposited as the ice melts. These processes can lead to spatially very variable soil conditions that contain features that can impact on the mass behaviour thus making the selection of geotechnical design parameters difficult. (ix)
Liquefiable soils—soils capable of undergoing continued deformation at constant low residual stress, or no residual resistance, due to the build-up and maintenance of high pore-water pressures. This behaviour may be due to either static or cyclic stress applications.
(x)
Mudstone—the general name given to fine-grained very low strength sedimentary rocks such as claystone, siltstone and shale that consist of clay and/or silt sized particles that are cemented to form a rock material that often transitions to a hard soil. Depending on their composition and mode of formation, particularly with regard to the clay mineralogy, they may display a range of problematic engineering behaviours such as low strength, poor durability, volume change, and a propensity to slake or disaggregate in water. Such behaviours may be due to the combined effect of natural weathering processes and the impact of engineering works. Mudstones often contain iron oxides and hydroxides, and the iron sulfide mineral pyrite. The pyrite can be problematic due to the generation of acid on oxidation and additional oxides and hydroxides and gypsum (resulting in ground heave).
www.standards.org.au
Standards Australia
AS 1726:2017
(xi)
68
Non-engineered fills—materials that have been placed or deposited by human processes without appropriate treatment. They may consist of natural material (soil/rock) and artificial material such as building waste, domestic waste, mining and quarry waste, and industrial waste. These materials may settle variably, have poor bearing capacity and may undergo significant movements due to causes other than imposed loading. Other problems associated with some wastes include contamination, spontaneous combustion and emission of gas.
(xii) Organic peat soils—highly compressible and exhibit creep behaviour. Other properties include low bulk density and low undrained shear strength. Their engineering behaviour is dependent on their moisture content and organic content and these are the most important index tests. Surcharging is a commonly used technique to manage settlement of roads and structures, with the design criterion usually being to build out sufficient settlement during construction to cover both primary and secondary settlement expected over the design life.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
(xiii) Sensitive soils (clays)—those which lose a portion of their strength and stiffness when remoulded. This is mainly due to reorientation of particles into less favourable positions during the remoulding process. A thixotropic soil is one that regains a portion of its strength with time, usually following some initial mechanical disturbance. (xiv) Soluble geomaterials—such as carbonate soil and rock (limestone and dolomite), gypsum, salt and varieties of these can be dissolved to form cavities leading to ground failure and surface subsidence. Sinkholes (or dolines) commonly occur in the soil cover overlying fissured and cavernous limestone, and can range in size from 1 m to 100 m in diameter and depth. Karst is a term that describes the suite of landforms associated with soluble rocks and karst conditions are probably the most variable encountered and difficult to investigate. (xv) Tropical soils—formed primarily by in situ weathering processes and occur in tropical regions where temperatures and rainfall are high, leading to chemical weathering of primary minerals, and increased penetration of weathering agencies. Weathering is initiated within the joints of the parent rock and gradually penetrates into the rock mass. A common feature of tropical soils is the presence of iron and aluminium oxides (often referred to as sesquioxides), which are released by weathering and are not dissolved hence remaining in situ. These oxides are important because they have an increasing effect on soil stiffness and strength and may provide a curb on soil reactivity. When testing for Atterberg Limits, the clays in certain tropical soils may permanently aggregate under oven and even air drying. This can result in particle size distributions misleadingly indicating sand sized classifications. However, in situ and where protected from desiccation, they would classify as silts or clays. Similarly, such aggregation may also adjust Atterberg Limits to give false classifications, e.g. SILT when the true in situ classification should be CLAY.
Standards Australia
www.standards.org.au
69
AS 1726:2017
APPENDIX E
SYMBOLS (Informative) E1 GEOLOGICAL BOUNDARIES AND STRUCTURES MAPPING SYMBOLS Suggested mapping symbols for geological boundaries and structures are provided in Figure E1. Additional or alternative symbols should be used as necessary.
O b ser ve d g e o l o g i c al b o u n d ar y, p o s it i o n k n ow n O b ser ve d g e o l o g i c al b o u n d ar y, p o s it i o n a p prox im ate ?
?
25
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
25
G e o l o g i c al b o u n d ar y, inter prete d or inferre d
?
B e d d in g
25
Fo li at i o n
25
Cleavag e
A nt i c li n e, F1
J o i nt
S y n c l i n e, F2
Plu n g e of fo l d, or d er an d t y p e in d i c ate d w it h a p pro pr i ate sy m b o l s
25
25
Plun g e of l i n e at i o n on plane
Fault or fault zo n e, s h eare d zo n e
U
U
U
Un c o nfor mit y
FIGURE E1 MAPPING SYMBOLS FOR GEOLOGICAL BOUNDARIES AND STRUCTURES
E2 GEOLOGICAL SOIL AND ROCK MAPPING SYMBOLS Suggested mapping symbols for soils and rocks are provided in Figure E2. Additional or alternative symbols should be used as necessary.
www.standards.org.au
Standards Australia
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
AS 1726:2017
Standards Australia
RO CKS SOILS
SEDIMENTARY
M E TAM ORPHIC
IGNEOUS
B oul d er s an d c o b b l e s
L i m e s to n e
C o ar s e g r a i n e d
C o ar s e g r a i n e d
Gravel
C o n g l o m er ate
Medium grained
Medium grained
Sand
Bre c c ia
Fine grained
Fine grained
Silt
S a n d s to n e
Clay
S i l t s to n e
Weat h ere d profile
Peat
M u d s to n e
D ur i c r u s t
WE ATHERED PROFILES AN D DURICRUSTS
www.standards.org.au
Silty sand
Tu f f
Gy p sum, Ro c ks alt etc.
FIGURE E2 GEOLOGICAL MAPPING SYMBOLS FOR SOILS AND ROCKS
FILL
Fill
70
Coal
NOT E: C omp osit e soi l t y p e s m ay b e sig n i f ie d by c ombi ne d sy mb ol s, e.g.
71
AS 1726:2017
E3 GEOMORPHOLOGICAL MAPPING SYMBOLS Suggested geomorphological mapping symbols are provided in Figure E3. Additional or alternative symbols should be used as necessary.
S h ar p C o n c ave Rounded Break of slo p e S h ar p C o nvex Rounded
10
Clif f
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
S c ar p
S l o p e an g l e of fac et
T T
Te n s i o n c r ac k
Inter m it te nt fl ow
C o nt in u o u s f l ow
O ut fl ow
Infl ow
S t a n d i n g water
Dam p - re e d s
S pr in g
L an d s li d e
Ro c k fall
M u d s li d e
FIGURE E3 GEOMORPHOLOGICAL MAPPING SYMBOLS
www.standards.org.au
Standards Australia
AS 1726:2017
72
APPENDIX F
COMMENTARY (Informative) F1 INDUSTRY SURVEY In 2011, the Australian Geomechanics Society (AGS) issued a survey to its members and stakeholders that considered the possibility of revising AS 1726—1993. The survey comprised a total of 25 questions, 17 pertaining to the technical content of a revised Standard. This edition of the Standard has been informed by the results of that survey. F2 CHANGES FROM PREVIOUS REVISION There are a number of changes and updates in this revision, and details of the most significant changes and additions between the editions of AS 1726 are summarized in Table F1 below. TABLE F1 MAJOR REVISIONS Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Content in AS 1726—1993
Changes in this edition
Comment
General
The main body of the document is The main document now provides normative. There are now six informative requirements for the execution of Appendices. effective geotechnical site investigations and provides a standardized system for the description and classification of soils and rocks.
Appendix A—Description and classification of soils and rocks for geotechnical purposes
Material descriptions, which were informative, are now normative.
The process for describing soils and rock is now largely normative and has been moved to the main body of text.
The boundary defining the change from coarse to fine grained soil was previously set at 50% of soil by weight greater than or finer than 0.075 mm particle size. This assessment is now made according to whether the total dry mass of coarse fractions exceeds 65% (a coarse soil) or the total dry mass of fine fractions exceeds 35% (a fine soil) (refer to Clause 6.1).
In the revised Standard a behavioural approach has been adopted when identifying, naming and classifying soil.
The means of describing carbonate rocks A need for a classification and has been revised and the means of description system for these material describing and classifying duricrusts types was identified. have now been included (refer to Clause 6.1). The description of rock materials, rock defects and rock masses has been significantly revised (refer to Clause 6.2).
A need for a normative classification and description system for rocks and rock masses was identified. (continued)
Standards Australia
www.standards.org.au
73
AS 1726:2017
TABLE F1 (continued)
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Content in AS 1726—1993
Changes in this edition
Comment
Appendix B Field test methods (Informative)
An informative Appendix A lists the most common geotechnical site investigation techniques, replacing the former Appendix B.
Appendix E Commentary
The former informative Appendix mainly The majority of items in the former provided guidance for the execution of Appendix E are now included in the geotechnical site investigations. main body of the Standard, with most now being mandatory.
A3.4 Condition of rock material Table A8
The Uniaxial Compressive Strength augmented by the Point Load Strength Index has been used to classify rock material strength (refer to Clause 6.2.4.1).
—
Table A9 Rock material weathering classification
The terms ‘highly weathered’ (HW) and ‘moderately weathered’ (MW) have been included (Table 17).
—
New addition
A description of geotechnical models and To comply with modern practice the the process to be followed in their development of geotechnical models development have now been introduced was included. (refer to Clause 5.2).
New addition
Guidance in relation to groundwater aspects of geotechnical site investigations is provided.
In the 1993 Standard there was little discussion of groundwater.
New addition
A new clause was added regarding the need to comply with work health and legislation (refer to Clause 5.3.1).
This was in recognition of the current working environment of geotechnical professionals.
New addition
Description of the geological origin of soil is now mandatory (refer to Clause 6.1).
This was included for consistency with the practice of developing a geological model.
www.standards.org.au
Examples of common testing methods have been provided, but the list is not intended to be exhaustive.
Standards Australia
AS 1726:2017
74
BIBLIOGRAPHY Informative referenced documents AS 1289 1289.5.6.1 1289.6.3.1 1289.6.3.2 1289.6.3.3 1289.6.5.1
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
3798
Methods of testing soils for engineering purposes (series) Mehtod 5.6.1: Soil compaction and density tests—Compaction control test— Density index method for a cohesionless material Method 6.3.1: Soil strength and consolidation tests—Determination of the penetration resistance of a soil—Standard penetration test (SPT) Method 6.3.2: Soil strength and consolidation tests—Determination of the penetration resistance of a soil—9 kg dynamic cone penetrometer test Method 6.3.3: Soil strength and consolidation tests—Determination of the penetration resistance of a soil—Perth sand penetrometer test Method 6.5.1: Soil strength and consolidation tests—Determination of the static cone penetration resistance of a soil—Field test using a mechanical and electrical cone or friction-cone penetrometer Guidelines on earthworks for commercial and residential developments
ISO 14689 14689-1 BS 8576
Geotechnical investigation and testing—Identification and classification of rock Part 1: Identification and description Guidance on investigations for ground gas. Permanent gases and Volatile Organic Compounds (VOCs)
Related documents Attention is drawn to the following related documents: 1
Casserly, Ann-Marie. ‘Guidelines for the Preparation of the Ground Report’. Association of Geotechnical and Geoenvironmental Specialists. 26 July 2003.
2
CRIA, ‘Site investigation manual’. Special Publication SP 25. CRIA, London. 1983.
3
Dearman, WR. Engineering Geological Mapping. Butterworth-Heineman. 1991.
4
Deere, DU and Deere, DW. ‘Rock Quality Designation (RQD) After Twenty Years’. Contract Report GL-89-1. Army Corps of Engineers. Washington DC, 1989.
5
Deere, DU, Hendron, AJ Jr. Patton, FD and Cording, EJ. ‘Design of Surface and Near Surface Construction in Rock’, Failure and Breakage of Rock, Fairhurst, C. (Ed.), Soc. of Min. Eng. AIME, New York. 1967. pp. 237–302.
6
Essex, Randall, J. ‘Geotechnical Baseline Reports for Construction: Suggested Guidelines’. American Society of Civil Engineers. 2007.
7
Matula, M. ‘Recommended symbols for engineering geological mapping report by the IAEG Commission on Engineering Geological Mapping’. Bulletin of the International Association of Engineering Geology. Volume 24, Issue 1. December 1981. pp. 227– 234.
Standards Australia
www.standards.org.au
75
AS 1726:2017
Matula, M. ‘Rock and soil description and classification for engineering geological mapping report by the IAEG Commission on Engineering Geological Mapping’.. Bulletin of the International Association of Engineering Geology. Volume 24, Issue 1. December 1981. pp. 235–274.
9
Munsell, AH. ‘A Colour Notation’. Geo. H. Ellis Co. Boston. 1905.
10
Parry, S et al. ‘Engineering Geological Models: An Introduction, IAEG Commission 25’. Bulletin of the Engineering Geology and the Environment. Online publication. 18 February 2014.
11
Ulusay, R (ed.). ‘The ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 2007–2014’. ISRM, Springer. 2015.
12
Ulusay, R and Hudson, JA. ‘The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 1974–2006’. ISRM Turkish National Group, Turkey. April 2007.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
8
www.standards.org.au
Standards Australia
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
AS 1726:2017 76
NOTES
Standards Australia Standards Australia develops Australian Standards® and other documents of public benefit and national interest. These Standards are developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth Government, Standards Australia is recognized as Australia’s peak non-government national standards body. For further information visit www.standards.org.au
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
Australian Standards® Committees of experts from industry, governments, consumers and other relevant sectors prepare Australian Standards. The requirements or recommendations contained in published Standards are a consensus of the views of representative interests and also take account of comments received from other sources. They reflect the latest scientific and industry experience. Australian Standards are kept under continuous review after publication and are updated regularly to take account of changing technology.
International Involvement Standards Australia is responsible for ensuring the Australian viewpoint is considered in the formulation of International Standards and that the latest international experience is incorporated in national Standards. This role is vital in assisting local industry to compete in international markets. Standards Australia represents Australia at both the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).
Sales and Distribution Australian Standards®, Handbooks and other documents developed by Standards Australia are printed and distributed under licence by SAI Global Limited.
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
For information regarding the development of Standards contact: Standards Australia Limited GPO Box 476 Sydney NSW 2001 Phone: 02 9237 6000 Email:
[email protected] Internet: www.standards.org.au
For information regarding the sale and distribution of Standards contact: SAI Global Limited Phone: 13 12 42 Email:
[email protected]
ISBN 978 1 76035 743 6
Accessed by MONASH UNIVERSITY LIBRARY on 23 May 2017 (Document currency not guaranteed when printed)
This page has been left intentionally blank.
