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This internationa internationall stand standard ard was devel developed oped in accor accordance dance with inter internatio nationall nally y recog recognize nized d prin principl ciples es on stand standardiz ardization ation established established in the Deci Decision sion on Princ Principles iples for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4767 − 11 (Reapproved 2020)
Standard Test Method for
Consolidated Undrained Triaxial Compression Test for 1
Cohesive Soils This standard is issued under the fixed designation D4767; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript supersc ript epsilon (´) indicates an editori editorial al change since the last revision or reapproval.
test res test result ultss in uni units ts oth other er tha than n SI sha shall ll not be reg regard arded ed as nonconformance with this test method. 1.6.1 The gravitationa gravitationall syst system em of inchinch-pound pound units is used when dealing with inch-pound units. In this system, the pound (lbf) represents a unit of force (weight), while the unit for mass is slugs. The slug unit is not given, unless dynamic (F = ma) calculations are involved. 1.6.2 It is common practice in the engineering/constr engineering/construction uction profession to concurrently use pounds to represent both a unit of mass (lbm) and of force (lbf). This implicitly combines two separate systems of units; that is, the absolute system and the gravitational system. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single standard. stand ard. As stat stated, ed, this stan standard dard incl includes udes the grav gravitat itational ional system of inch-pound units and does not use/present the slug unit for mass. However, the use of balances or scales recording 3 pounds of mass (lbm) or recording density in lbm/ft shall not be regarded as nonconformance with this standard. 1.6.3 1.6 .3 The terms density density and uni unitt wei weight ght are oft often en use used d interchangeably. Density is mass per unit volume whereas unit weight wei ght is for force ce per unit vol volume ume.. In thi thiss sta standa ndard rd den densit sity y is given only in SI units. After the density has been determined, the unit weight is calculated in SI or inch-pound units, or both.
1. Sco Scope pe 1.1 This test method covers the determinatio determination n of strength and stre stress-s ss-strai train n rela relations tionships hips of a cyli cylindri ndrical cal speci specimen men of either an intact, reconstituted, or remolded saturated cohesive soil. Specimens are isotropically consolidated and sheared in compre com pressi ssion on wit withou houtt dra draina inage ge at a con consta stant nt rat ratee of axi axial al deformation (strain controlled). 1.2 This test method provides provides for for the calculation of total and effective stresses, and axial compression by measurement of axial load, axial deformation, and pore-water pressure. 1.3 This test method provides data useful in dete determin rmining ing strength and deformation properties of cohesive soils such as Mohr stre strength ngth envel envelopes opes and Young’ oung’ss modul modulus. us. Gener Generally ally,, three specimens are tested at different effective consolidation stresses to define a strength envelope. 1.4 The determinat determination ion of stre strength ngth envelopes envelopes and the development of relationships to aid in interpreting and evaluating test results are beyond the scope of this test method and must be performed by a qualified, experienced professional. 1.5 All observed observed and calculated calculated values shall conform conform to the guideliness for signi guideline significant ficant digits and round rounding ing esta establis blished hed in Practice D6026 Practice D6026.. 1.5.1 The methods methods used to spec specify ify how data are coll collected ected,, calculated, or rec calculated, record orded ed in thi thiss sta standa ndard rd are regarded regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures dur es use used d do not con consid sider er mat materi erial al var variat iation ion,, pur purpos posee for obtaining the data, special purpose studies or any consideration of en end d us use. e. It is be beyo yond nd th thee sc scop opee of th this is te test st me meth thod od to consider significant digits used in analysis methods for engineering design.
1.7 This standar standard d doe doess not purport purport to add addres resss all of the safety safe ty co conc ncer erns ns,, if an anyy, as asso soci ciat ated ed wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety safety,, health, and environment environmental al practices and determine the applicability of regulatory limitations prior to use. 1.8 This international international standard standard was devel developed oped in accor accor-dance with internationally recognized principles on standardizatio iza tion n est establ ablish ished ed in the Dec Decisi ision on on Pri Princi nciple pless for the Development of International Standar Standards, ds, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trad Tradee (TBT) Committee.
1.6 Units— The The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only and are not considered standard. Reporting of
2. Referenced Documents Documents 2.1 ASTM Standards:2
1 This test method is under the jurisdi jurisdiction ction of ASTM Commit Committee tee D18 on Soil and Rock and is the direct respon responsibility sibility of Subcommittee Subcommittee D18.05 on Strength and Compressibility of Soils. Curren Cur rentt edi edition tion app approv roved ed Apr April il 1, 202 2020. 0. Pub Publish lished ed Apr April il 202 2020. 0. Orig Original inally ly approved approv ed in 1988. Last previous edition approved in 2011 as D476 D4767–1 7–11. 1. DOI: 10.1520/D4767-11R20.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM ASTM Custom Customer er Service at service@
[email protected] astm.org. rg. For Annual Book of ASTM Standards volume Standards volume information, refer to the standard’s Document Summary page on the ASTM ASTM website.
*A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D4767 − 11 (2020) 4.2 In this test method, method, the shear characteris characteristics tics are measured under undrained undrained condi conditions tions and is appl applicabl icablee to field conditions where soils that have been fully consolidated under one set of stresses are subjected to a change in stress without timee for fur tim furthe therr con consol solida idatio tion n to tak takee pla place ce (un (undra drain ined ed condition), and the field stress conditions are similar to those in the test method.
D422 D422 Te Test st Method for Particle-Size Analysis of Soils (WithSoils (With3 drawn 2016) D653 Te D653 Termin rminology ology Relating to Soil Soil,, Rock, and Conta Contained ined Fluids D854 Test Methods for Specific Gravity of Soil Solids by D854 Water Pycnometer D1587/D1587M Practice D1587/D1587M Practice for Thin-Walled Tube Sampling of Fine-Grained Soils for Geotechnical Purposes D2166/D2166M Test D2166/D2166M Test Method for Unconfined Compressive Strength of Cohesive Soil D2216 Test D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass D2435/D2435M Test Meth D2435/D2435M Methods ods for One-D One-Dimen imensiona sionall Consolidation Properties of Soils Using Incremental Loading D2850 Test D2850 Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils D3740 Prac D3740 Practice tice for Mini Minimum mum Requi Requireme rements nts for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction D4220/D4220M Pra D4220/D4220M Practic ctices es for Prese Preserving rving and Tr Transpo ansportin rting g Soil Samples D4318 Test Meth D4318 Methods ods for Liqui Liquid d Limi Limit, t, Plas Plastic tic Limi Limit, t, and Plasticity Index of Soils
NOTE 1—If the strength is required for the case where the soil is not consolidated during testing prior to shear consolidated shear,, refer to Test Method D2850 Method D2850 or or Test Method Method D2166/D2166M. D2166/D2166M.
4.3 Using the pore-water pressure pressure measured during during the test, the shear strength determined determined from this test method can be expressed in terms of effective stress. This shear strength shear strength may be applied to field conditions where full drainage can occur (drain (dr ained ed con condit dition ions) s) or whe where re por poree pre pressu ssures res ind induce uced d by loading can be estimated, and the field stress conditions are similar to those in the test method. 4.4 The shear strength strength determined from from the test expressed expressed in terms of tot terms total al str stress esses es (un (undra draine ined d con condit dition ions) s) or ef effec fectiv tivee stresses (drained conditions) is commonly used in embankment stability analyses, earth pressure calculations, and foundation design. NOTE statements ontest precision bias contained in 2—Notwithstanding this test method. The the precision of this methodand is dependent on the compe competence tence of the personn personnel el performing performing it and the suitability of the equipment and facilities used. Agencies which meet the criteria of Practice D3740 are generally considered capable of competent testing. Users of this test method are cautioned that compliance with Practice D3740 Practice D3740 does does not ensure reliable testing. Reliable testing depends on several factors; Practice D3740 Practice D3740 provides provides a means of evaluating some of those factors.
D4753 Guide for Evaluating, Selecting, and Specifying BalD4753 Guide ances and Standard Masses for Use in Soil, Rock, and Construction Materials Testing D6026 Practice D6026 Practice for Using Significant Digits in Geotechnical Data 3. Terminology 3.1 Definitions— For For standard definitions of common technical terms, refer to Terminology D653 D653..
5. Appar Apparatus atus 5.1 The req requir uireme ements nts for equ equipm ipment ent nee needed ded to per perfor form m satisfactory tests are given in the following sections. See Fig. 1 and and Fig. Fig. 2
3.2 Definitions of Terms Specific to This Standard: 3.2.1 back pre pressu ssure re app applie lied d to the spe specim cimen en pressure— ssure— a pre pore-water to cause air in the pore space to compress and to passs int pas into o sol soluti ution on in the por pore-w e-wate aterr the thereb reby y inc increa reasin sing g the percent saturation of the specimen.
5.2 Axial Loading Device— The The axial loading device shall be a screw jack driven by an electric motor through a geared transmission, a hydraulic loading device, or any other compression device with sufficient capacity and control to provide the rate of axial strain (loading) prescribed in 8.4.2 in 8.4.2.. The rate of
3.2.2 effective consolidation stress— the the difference between the cell pressure and the pore-water pressure prior to shearing the specimen. 3.2.3 failure— a max maximu imum-s m-stre tress ss con condit dition ion or str stress ess at a defined defi ned strain strain for a tes testt spe specim cimen. en. Fai Failur luree is oft often en tak taken en to correspond to the maximum principal stress difference (maximum deviator stress) attained or the principal stress difference (deviator stress) at 15 % axial strain, whichever is obtained first during the performance of a test. Depending on soil behavior and field appli applicatio cation, n, other suitable suitable fail failure ure criteria criteria may be defined defi ned,, suc such h as max maximu imum m ef effec fectiv tivee str stress ess obl obliqu iquity ity,, (σ1 '/ σ3')max, or the principal stress difference (deviator stress) at a selected axial strain other than 15 %.
advance of the loading device shall not deviate by more than 61 % from the selected value. Vibration due to the operation of the loading device shall be sufficiently small to not cause dimensional changes in the specimen or to produce changes in pore-water pressure when the drainage valves are closed. NOTE 3—A loading device may be judged to produce sufficiently small vibrations if there are no visible ripples in a glass of water placed on the loading platform when the device is operating at the speed at which the test is performed.
5.3 Axial Axial Load Load-Me -Measu asurin ring g Dev Device ice— — The T he ax axia iall lo load ad-measuring measurin g devic devicee shall be an elec electroni tronicc load cell, hydr hydraulic aulic load cell, or any other load-measuring device capable of the accuracy prescribed in this paragraph and may be a part of the axial loading device. The axial load-measuring device shall be capable of measuring the axial load to an accuracy of within 1 % of the axial load axial load at failure. If the load-measuring device is located loca ted insi inside de the triaxial compression compression chamber, chamber, it shal shalll be
4. Signi Significanc ficancee and Use 4.1 The shear strength strength of a saturated saturated soil in triaxial triaxial compression depends on the stresses applied, time of consolidation, strain rate, and the stress history experienced by the soil.
insensitive insensit ive to horiz horizonta ontall forc forces es and to the magn magnitude itude of the chamber pressure.
3 Thee las Th lastt app appro roved ved ver versio sion n of th this is hi histo storic rical al sta stand ndard ard is ref refere erenc nced ed on www.astm.org.
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D4767 − 11 (2020)
FIG. 1 Schematic Diagram of a Typical Consolidated Undrained Triaxial Apparatus
FIG. 2 Filter Strip Cage
5.4 Triaxial Triaxial Compression Chamber— The The triaxial chamber shall have a working chamber pressure equal to the sum of the effect ef fective ive conso consolida lidation tion stress and the back pressure. pressure. It shall consist of a top plate and a base plate separated by a cylinder. The cylinder may be constructed of any material capable of withst wit hstand anding ing the app applie lied d pre pressu ssures res.. It is des desira irable ble to use a transparent material or have a cylinder provided with viewing ports so the behavior of the specimen may be observed. The top plate shall have a vent valve such that air can be forced out of
specimen base and to the cap to allow saturation and drainage of the specimen when required. The chamber shall provide a connection to the cap.
the chamber as it is filled. The baseplate shall have an inlet through which to fill the chamber, and inlets leading to the
NOTE 4—The use of two linear ball bushings to guide the piston is recommended to minimize friction and maintain alignment.
5.5 Axial Load Piston— The The piston passing through the top of the chamber and its seal must be designed so the variation in axial load due to friction does not exceed 0.1 % of the axial load at failure and so there is negligible lateral bending of the piston during loading.
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D4767 − 11 (2020) pressure, and record the volume change.
NOTE 5—A minimum piston diameter of 1 ⁄ 6 the specimen diameter has been used successfully in many laboratories to minimize lateral bending.
5.9 Volume Change Measurement Device— The The volume of water entering or leaving the specimen shall be measured with an accur accurac acy y of withi within n 60. 0.05 05 % of the total total volum volumee of the specimen. The volume measuring device is usually a burette connected to the back pressure but may be any other device
5.6 Pressure The cham chamber ber Pressure and Vacuum-Contr acuum-Control ol Devices— The pressure and back pressure control devices shall be capable of applyi app lying ng and control controllin ling g pressure pressuress to wit within hin 62 kPa (0.25 2 lb/in. ) for effective consolidation pressures less than 200 kPa (28 lbf/ lbf/in. in.2) and to within within 61 % for effec effectiv tivee consolid consolidati ation on pressures pres sures greater than 200 kPa. The vacuu vacuum-co m-control ntrol device shall be capable of applying and controlling partial vacuums to within 62 kPa. The devices shall consist of pressure/volume controllers pneumatic pressure regulators, combination pneumaticc pres mati pressure sure and vacuu vacuum m regul regulator ators, s, or any other devi device ce capable of applying and controlling pressures or partial vacuums to the required tolerances. These tests can require a test duration of several day. Therefore, an air/water interface is not recommended for either the chamber pressure or back pressure systems, unless isolated from the specimen and chamber (for example, by long tubing).
meeting the accuracy requirement. The device must be able to withstand the maximum back pressure. 5.10 Deformation Indicator— The The vert vertical ical deformation deformation of the specimen is usually determined usually determined from the travel of the piston acting on the top of the specimen. The piston travel shall be measu me asured red with an acc accura uracy cy of at lea least st 0.2 0.25 5 % of the initial initial specimen height. The deformation indicator shall have a range of at least 15 % of the initial height of the specimen and may be a dia diall ind indica icator tor or oth other er mea measur suring ing dev device ice me meeti eting ng the requirements for accuracy and range. 5.11 Specimen Cap and Base— The The specimen cap and base shall be designed to provide drainage from both ends of the specimen. They shall be constructed of a rigid, noncorrosive, impermeable material, and each shall, except for the drainage provision prov ision,, have a circ circular ular plane surface surface of contact with the porous disks and a circular cross section. It is desirable for the mass of the specimen cap and top porous disk to be as minimal as possible. However, the mass may be as much as 10 % of the axial load at failure. If the mass is greater than 0.5 % of the applied axial load at failure and greater than 50 g, the axial load must be corrected for the mass of the specimen cap and top porous disk. The diameter of the cap and base shall be equal to the initial diameter of the specimen. The specimen base shall be connected to the triaxial compression chamber to prevent late la tera rall mo moti tion on or ti tilt ltin ing, g, an and d th thee sp spec ecim imen en ca cap p sh shal alll be designed desi gned such that eccentricity eccentricity of the pist piston-to on-to-cap -cap conta contact ct relative to the vertical axis of the specimen does not exceed 1.3 mm (0.05 in.). The end of the piston and specimen cap contact area shall be designed so that tilting of the specimen cap during the test is minimal. The cylindrical surface of the specimen base and cap that contacts the membrane to form a seal shall be smooth and free of scratches.
5.7 Pressur Pressuree- and Vacuum acuum-Meas -Measur urement ement Devic Devices— es— The chamber cham ber press pressure-, ure-, back pres pressuresure-,, and vacuu vacuum-me m-measuri asuring ng device dev icess sha shall ll be cap capabl ablee of mea measur suring ing pre pressu ssures res or par partia tiall vacuums to the tolerances given in 5.6 5.6.. They may consist of electronic pressure transducers, or any other device capable of measuring measurin g pres pressures sures,, or part partial ial vacuums to the stated tole tolerrances.. If separate ances separate devic devices es are used to meas measure ure the chamb chamber er pressure pres sure and back pressure, pressure, the devices must be cali calibrat brated ed simultaneously and against the same pressure source. Since the chambe cha mberr and bac back k pre pressu ssure re are the pressure pressuress tak taken en at the mid-height of the specimen, it may be necessary to adjust the calibration of the devices to reflect the hydraulic head of fluids in the chamber and back pressure control systems. 5.8 Pore-Water Pressure-Measurement Device— The The specimen pore-water pressure shall also be measured to the tolerances anc es giv given en in 5.6 5.6.. Durin During g undra undrained ined shear, shear, the pore pore-wate -waterr pressure shall be measured in such a manner that as little water as possible is allowed to go into or out of the specimen. To achiev ach ievee thi thiss req requir uirem ement ent,, a ver very y sti stifff ele electr ctroni onicc pre pressu ssure re transduce tran sducerr or null null-indi -indicatin cating g devic devicee must be used used.. With an electronic pressure transducer the pore-water pressure is read dire directly ctly. . W ith adj a usted null-ind null -indicati ngntain device devic a pres pressure control cont rolthe is contin con tinuou uously sly adjust ed toicating mainta mai in a e con consta stant ntsure level lev el of water/mercury interface in the capillary bore of the device. The pressure required to prevent movement of the water is equal to the pore-water pressure. Both measuring devices shall have a compli com plianc ancee of all the ass assem emble bled d par parts ts of the por pore-w e-wate aterr pressure-measurement system relative to the total volume of the specimen, satisfying the following requirement:
~ ∆ V / V !
/ ∆ u , 3.2 3 1 02 6
m /kN ~ 2
2.2 3 1 02 5
in. /lb! 2
5.12 Porous Discs— Two Two rigid porous disks shall be used to provide drainage at the ends of the specimen. The coefficient of permeability of the disks shall be approximately equal to that −4 −5 of fine sand (1 × 10 cm/s (4 × 10 in./s)). The disks shall be regularl regu larly y clean cleaned ed by ultra ultrasonic sonic or boil boiling ing and brush brushing ing and checked to determine whether they have become clogged. 5.13 Filter-Paper Strips and Disks— Filter-paper Filter-paper strips are used by many laboratories to decrease the time required for testing. Filter-paper disks of a diameter equal to that of the testing. specimen may be placed between the porous disks and specimen to avoid clogging of the porous disks. If filter strips or disks are used, they shall be of a type that does not dissolve in water. The coefficient of permeability of the filter paper shall not be less than 1 × 10 −5 cm/ cm/ss (4 × 10−6 in./s) for a normal 2 pressure of 550 kPa (80 lbf/in. ). To avoid hoop tension, filter stri st rips ps sh shou ould ld co cove verr no mo more re th than an 50 % of th thee sp spec ecim imen en
(1 )
where: ∆V = change change in vol volume ume of the por pore-w e-wate aterr mea measur sureme ement nt 3 3 system due to a pore pressure change, mm (in. ), 3 3 V = total volu volume me of of the the specim specimen, en, mm (in. ), and 2 ∆u = chang changee in pore press pressure, ure, kPa kPa (lbf/in. (lbf/in. ). NOTE 6—To 6—To meet the complia compliance nce requirement, requirement, tubing between the specimen and the measuring device should be short and thick-walled with small bores. Thermoplastic, copper, and stainless steel tubing have been used successfully. successfully. To measu measure re this compli compliance, ance, assemble the triaxi triaxial al cell without with out a spec specime imen. n. The Then, n, ope open n the app approp ropria riate te val valves ves,, incr increas easee the
periphery. peripher y. Filt Filter-s er-strip trip cages have been succe successful ssfully ly used by many laboratories laboratories.. An equat equation ion for corre correcting cting the prin principal cipal 4
D4767 − 11 (2020) or by any other method that will satisfy the requirement for satura sat uratin ting g the spe specim cimen en wit within hin the lim limits its im impos posed ed by the available maximum back pressure and time to perform the test.
stress difference (deviator stress) for the effect of the strength of vertical filter strips is given in 10.4.3.1 10.4.3.1.. NOTE 7—Gra 7—Grade de No No.. 54 Fi Filte lterr Pa Pape perr ha hass be been en fo found und to me meet et th thee permeability and durability requirements.
5.21 Testing Testing Environment Environment— — The The con consol solida idatio tion n and she shear ar portion of the test shall be performed in an environment where temperat temp erature ure fluctu fluctuatio ations ns are less than 64°C (67.2°F 7.2°F)) and and there
5.14 Rubber Membr Membrane— ane— The The rub rubber ber mem membra brane ne use used d to encase the specimen shall provide reliable protection against leakage. Membranes shall be carefully inspected prior to use and if any flaws or pinholes are evident, the membrane shall be discarded disc arded.. To of offer fer mini minimum mum restraint restraint to the spec specimen imen,, the unstretched membrane diameter shall be between 90 and 95 % of tha thatt of the spe specim cimen. en. The mem membra brane ne thi thickn ckness ess shall not exceed 1 % of the diameter of the specimen. The membrane shall sha ll be sea sealed led to the specimen specimen cap and base wit with h rub rubber ber O-rings for which the unstressed inside diameter inside diameter is between 75 and 85 % of the diameter of the cap and base, or by other mean me anss th that at wi will ll pr prov ovid idee a po posi siti tive ve se seal al.. An eq equa uati tion on fo forr correcting the principal stress difference (deviator stress) for the effect of the stiffness of the membrane is given in 10.4.3.2 in 10.4.3.2..
is no direct contact with sunlight. 5.22 Miscellaneous Specimen en tri trimmi mming ng and Miscellaneous Appar Apparatus— atus— Specim carving carv ing tool toolss inclu including ding a wire saw, steel stra straighte ightedge, dge, mite miterr box, vertical trimming lathe, apparatus for preparing reconstituted specimens, membrane and O-ring expander, water content cans, and data sheets shall be provided as required. 6. Test Specimen Preparation 6.1 Specimen Size— Specimens Specimens shall be cylindrical and have a minimum diameter of 33 mm (1.3 in.). The average heightto-ave toaverag ragee dia diame meter ter rat ratio io sha shall ll be bet betwee ween n 2 and 2.5 2.5.. The 1 larges lar gestt par partic ticle le siz sizee sha shall ll be sma smalle llerr tha than n ⁄ 6 the spec specimen imen diameter. If, after completion of a test, it is found based on visual observation that oversize particles are present, indicate this information in the report of test data (11.2.23 (11.2.23). ).
5.15 Valves— Changes Changes in volume due to opening and closing valves may result in inaccurate volume change and pore-water pressure measurements. For this reason, valves in the specimen drainage system shall be of the type that produce minimum
NOTE 10—If oversize particles are found in the specimen after testing, a par particl ticle-s e-size ize analysis analysis may be per perfor formed med on the tested specimen specimen in accordance with Test Method D422 Method D422 to to confirm the visual observation and the results provided with the test report (11.2.4 ( 11.2.4). ).
vo volu lume me ch chan gess du dueeminimum to th thei eirr volume oper op erat atio ion. n. A va valv e ma may y be assumed toange produce change iflve opening or closing clos ing the valve in a clos closed, ed, satur saturated ated pore-water pore-water pres pressure sure system does not induce a pressure change of greater than 0.7 2 kPa (60.1 lbf lbf/in /in.. ). All valves must be be capable of withstanding withstanding applied pressures without leakage.
5.19 Balance— A balance balance or sca scale le con confor formin ming g to the requirements of Specification D4753 Specification D4753 readable readable to four significant digits.
6.2 Intact Specimens— Prepare Prepare intact specimens from large intact sampl intact samples es or from samples samples secu secured red in accor accordanc dancee with Practice D1587/D1587M Practice D1587/D1587M or or other acceptable intact tube sampling procedures. Samples shall be preserved and transported in acc accord ordanc ancee wit with h the practice practicess for Group C sam sample pless in Practices D4220/D4220M Practices D4220/D4220M.. Specimens obtained by tube sampling may be tested without trimming except for cutting the end surfaces plane and perpendicular to the longitudinal axis of the specimen, specimen, provi provided ded soil chara character cteristi istics cs are such that no significant signi ficant dist disturba urbance nce resul results ts from samp sampling ling.. Handl Handlee spec speciimenss car men carefu efully lly to min minim imize ize dis distur turban bance, ce, cha change ngess in cro cross ss section, or change in water content. If compression or any type of notic noticeable eable disturbance disturbance would be cause caused d by the extrusion extrusion device dev ice,, spl split it the sample sample tub tubee len length gthwis wisee or cut the tub tubee in suitable suita ble sections to facil facilitat itatee remo removal val of the specimen with minim min imum um dis distur turban bance. ce. Pre Prepar paree tri trimm mmed ed spe specim cimens ens,, in an environment such as a controlled high-humidity room where soil water cont content ent change is mini minimize mized. d. Where removal removal of pebbles or crumbling resulting from trimming causes voids on the sur surfac facee of the spe specim cimen, en, car carefu efully lly fill the voi voids ds wit with h remolded soil obtained from the trimmings. If the sample can be trimmed with minimal disturbance, a vertical trimming lathe may be used to reduce the specimen to the required diameter. After obtaining the required diameter, place the specimen in a miter box, and cut the specimen to the final height with a wire saw or other suitable device. Trim the surfaces with the steel straightedge. Perform one or more water content determinations on material trimmed from the specimen in accordance with Test Method D2216 Method D2216..
5.20 Water Water Deaeration Device— D evice— The The amount of diss dissolved olved
6.3 Reconsituted Specimens— Soil Soil required for reconstituted
gas (air) in the water used to saturate the specimen shall be decreased by boiling, by heating and spraying into a vacuum,
specimens shall be thoroughly mixed with sufficient water to produce the desired water content. If water is added to the soil,
NOTE 8—Ball valves have been found to provide minimum volumechange characteristics; however, any other type of valve having suitable volume-chang volume -changee chara characterist cteristics ics may be used.
5.16 Specimen-Size Measurement Devices used to Measurement Devices— Devices determ det ermine ine the hei height ght and dia diame meter ter of the spe specim cimen en sha shall ll measure the respective dimensions to four significant digits and shall be constructed such that their use will not disturb/deform the specimen. NOTE 9—Circumf 9—Circumferenti erential al measu measuring ring tapes are recom recommende mended d over calipers for measuring the diameter.
5.17of Sample Extruder— The he sam sample plethe extrud ext ruder er sha shall ll be at capable extruding the soilTcore from sampling tube a unifor uni form m rat ratee in the same dir direct ection ion of tra travel vel as the sample sample entered the tube and with minimum disturbance of the sample. If the soil core is not extruded vertically, care should be taken to avoid bending stresses on the core due to gravity. Conditions at the time of sam sample ple removal removal may dictate dictate the dir direct ection ion of removal, but the principal concern is to minimize the degree of disturbance. 5.18 Timer— A timing device indicating the elapsed testing time to the nearest 1 s shall be used to obtain consolidation data (8.3.3).
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D4767 − 11 (2020) store the material in a covered container for at least 16 h prior to compa compaction ction.. Recon Reconsitu situted ted spec specimen imenss may be prepa prepared red by compacting material in at least six layers using a split mold of circular cross section having dimensions meeting the requirements enumerated in 6.1 6.1.. Specimens may be reconstituted to the desired desired den densit sity y by eit either her:: (1) kne kneadi ading ng or tam tampin ping g eac each h layer until the accumulative mass of the soil placed in the mold is reconsti reconstitut tuted ed to a kno known wn vol volume ume;; or ( 2) by adj adjust usting ing the number of layers, the number of tamps per layer, and the force per tamp. The top of each layer shall be scarified prior to the additi add ition on of ma mater terial ial for the next lay layer er.. The tam tamper per use used d to compact the material shall have a diameter equal to or less than 1 ⁄ 2 the diameter of the mold. After a specimen is formed, with the ends perpe perpendicu ndicular lar to the longitudinal longitudinal axis, remo remove ve the mold and determine the mass and dimensions of the specimen using the devices described in 5.16 5.16 and and 5.19 5.19.. Perform one or more water content determinations on excess material used to prep pr epar aree th thee sp spec ecim imen en in ac acco cord rdan ance ce wi with th Tes estt Me Meth thod od D2216.
thickness of filter disks if they are used) so that the appropriate values may be subtracted from the measurements.
6.4 Deter Determine mine the mass and dime dimensio nsions ns of the spec specimen imen using the devices described in 5.16 5.16 and and 5.19 5.19.. A minimum of three thr ee hei height ght mea measur sureme ements nts (12 (120° 0° apa apart) rt) and at lea least st thr three ee diameter measurements at the quarter points of the height shall be made to determine the average height and diameter of the
7.2.1.5 If filter-paper filter-paper strips strips or a filte filterr-pape -paperr cage are to be used, saturate the paper with water prior to placing it on the specimen. To avoid hoop tension, do not cover more than 50 % of the specimen periphery with vertical strips of filter paper.
specimen. An individual measurement of height or diameter shall not vary from average by more than 5 %.
7.2.2 Dry Mounting Method: 7.2.2.1 7.2 .2.1 Dry the spe specim cimen en dra draina inage ge sys system tem.. Thi Thiss ma may y be accomplished by allowing dry air to flow through the system prior to mounting the specimen. 7.2.2.2 Dry the porous porous disks in an oven and then place the disks dis ks in a des desicc iccato atorr to coo cooll to roo room m tem temper peratu ature re pri prior or to mounting the specimen. 7.2.2.3 Place a dry porous disk on the specimen specimen base and place the specimen on the disk. Next, place a dry porous disk and an d th thee sp spec ecim imen en ca cap p on th thee sp spec ecim imen en.. Ch Chec eck k th that at th thee specimen cap, porous disks, and specimen are centered on the specimen base.
7.2.1 Wet Mounting Method: 7.2.1.1 7.2.1. 1 Fill the specimen specimen drai drainage nage lines and the porepore-water water pressure measurement device with deaired water. 7.2.1.2 7.2.1. 2 Satur Saturate ate the porous disks by boil boiling ing them in water for at least 10 min and allow to cool to room temperature. 7.2.1.3 7.2 .1.3 If filt filterer-pap paper er dis disks ks are to be pla placed ced bet betwee ween n the porous disks and specimen, saturate the paper with water prior to placement. 7.2.1.4 7.2.1. 4 Place a saturated saturated porous disk porous disk on the specimen base and wipe away all free water on the disk. If filter-paper disks are used, placed on the porous disk. Place the specimen on the disk. Next, place another filter-paper disk (if used), porous disk and the specimen cap on top of the specimen. Check that the specimen cap, specimen, filter-paper disks (if used) and porous disks are centered on the specimen base.
7.2.1.6 Proce Proceed ed with with 7.3 7.3..
NOTE 11—It is common for the density or unit weight of the specimen after removal removal from the mold to be less than the value based on the volume of the mold. This occurs as a result of the specimen swelling after removal of the lateral confinement due to the mold.
7. Mount Mounting ing Specimen Specimen 7.1 Preparations— Before Before mou mounti nting ng the spe specim cimen en in the triaxial chamber, make the following preparations: 7.1.1 Inspe Inspect ct the rubber membrane membrane for flaws, pinholes, pinholes, and leaks. 7.1.2 Place the membrane membrane on the memb membrane rane expander expander or, or, if it is to be rolled onto the specimen, roll the membrane on the cap or base. 7.1.3 Check that the porou porouss disks and specimen drainage drainage tubes are not obstructed by passing air or water through the
NOTE 13—If desired, dry filter-paper disks may be placed between the porous disks and specimen.
7.2.2.4 If filter-paper filter-paper strips strips or a filte filterr-pape -paperr cage are to be
appropriate lines. 7.1.4 Attach the pressure-control pressure-control and volume-measurement volume-measurement system and a pore-pressure measurement device to the chamber base.
used, the cage or strips may be held in place by small pieces of tape at the top and bottom. 7.3 Place the rubber membrane membrane around the speci specimen men and seal it at the cap and base with two rubber O-rings or other positive posi tive seal at each end. end. A thin coating coating of silicon silicon grease on the vertical surfaces of the cap and base will aid in sealing the membrane. If filter-paper strips or a filter-paper cage are used, do not apply grease to surfaces in contact with the filter-paper.
7.2 Depen Depending ding on whether the saturation saturation portion portion of the test willl be ini wil initia tiated ted with eit either her a wet or dry drainage drainage system, system, mount the specimen using the appropriate method, as follows in either 7.2.1 either 7.2.1 or or 7.2.2 7.2.2.. The dry mounting method is strongly recommend recom mended ed for spec specimen imenss with initial saturation saturation less than 90 %. The dry mounting method removes air prior to adding backpressure and lowers the backpressure needed to attain an adequate percent saturation.
7.4 Attac Attach h the top drainage line and check check the alignment alignment of the specimen specimen and the spe specim cimen en cap cap.. If the dry mou mounti nting ng method met hod has bee been n use used, d, app apply ly a par partia tiall vac vacuum uum of app approx roxiimately mat ely 35 kPa (5 lbf lbf/in /in.. 2) (no (nott to exc exceed eed the con consol solida idatio tion n stress) to the specimen through the top drainage line prior to checking the alignment. If there is any eccentricity, release the partial vacuum, realign the specimen and cap, and then reapply the partial vacuum. If the wet mounting method has been used,
NOTE 12—It is recommended that the dry mounting method be used for specimens of soils that swell appreciably when in contact with water. If the wet mounting method is used for such soils, it will be necessary to obtain the specimen dimensions after the specimen has been mounted. In such cases, it will be necessary to determine the double thickness of the membrane, the double thickness of the wet filter paper strips (if used), and the combined height of the cap, base, and porous disks (including the
the alignment of the specimen and the specimen cap may be checked and adjusted without the use of a partial vacuum. 6
D4767 − 11 (2020) between betwee n the pore pre pressu ssure re mea measur sured ed at the bottom bottom of the specimen and the pressure at the top of the specimen should be allowed to equalize. When the pore pressure at the bottom of the specimen stabilizes, proceed with back pressuring of the specimen spec imen pore-water pore-water as descr described ibed in 8.2.3.1. 8.2.3.1. To ch chec eck k fo forr equalizat equal ization, ion, close the drainage valves to the specimen and measure the pore pressure change until stable. If the change is less than 5 % of the chamber pressure, the pore pressure may be assumed to be stabilized.
8. Procedur Proceduree 8.1 Prio Priorr to Satu Saturat ration— ion— Afte Afterr asse assembl mbling ing the tri triaxia axiall chamber, perform the following operations: 8.1.1 8. 1.1 Bring Bring th thee ax axia iall lo load ad pi pist ston on in into to co cont ntac actt wi with th th thee specim spe cimen en cap sev severa erall tim times es to per permit mit pro proper per sea seatin ting g and alignment of the piston with the cap. During this procedure, take care not to apply an axial load to the specimen exceeding 0.5 % of the estimated axial load at failure. When the piston is brought broug ht into contact, contact, recor record d the reading of the deformation deformation indicator to three significant digits. 8.1.2 8. 1.2 Fill Fill th thee ch cham ambe berr wi with th th thee ch cham ambe berr li liqu quid id,, be bein ing g carefu car efull to avo avoid id tra trappi pping ng air or lea leavin ving g an air space space in the chamber.
NOTE 14—For saturated clays, percolation may not be necessary and water can be added simultaneously at both top and bottom.
8.2.2 Starting Starting with Init Initiall iallyy Satu Saturated rated Drain Drainage age Syst System— em— After filling the burette connected to the top of the specimen with wit h dea deaire ired d wat water er,, app apply ly a cha chambe mberr pre pressu ssure re of 35 kPa (5 2 lbf/in. ) or less and open the specimen drainage valves. When the por poree pre pressu ssure re at the bot bottom tom of the spe specim cimen en sta stabil bilize izes, s, according to the method described in 8.2.1 in 8.2.1,, or when the burette reading stabilizes, back pressuring of the specimen pore-water may be initiated. 8.2.3 Back-Pressure Saturation— To To saturate the specimen, 4 back pressuring is usually necessary. Fig. necessary. Fig. 3 provides guidance on bac back k pre pressu ssure re req requir uired ed to att attain ain sat satura urati tion. on. Add Additi itiona onall guidance on the back-pressure process is given by Black and Lee5 and Head6 (See (See Note Note 15 on 15 on references).
8.2 Saturation— The The objective of the saturation phase of the testt is to fill all voids in the specime tes specimen n wit with h wat water er without without specimen en or all allowi owing ng the undesirab undes irable le prest prestressi ressing ng of the specim specim spe cimen en to swe swell ll.. Sat Satura uratio tion n is usu usuall ally y acc accomp omplis lished hed by applying back pressure to the specimen pore water to drive air into solution after saturating saturating the system by either: either: (1) applying vacuum to the specimen and dry drainage system (lines, porous disks, pore-pressure device, filter-strips or cage, and disks) and then allowing deaired water to flow through the system and specimen spec imen while maintaini maintaining ng the vacuu vacuum; m; or (2) satu saturati rating ng the draina dra inage ge sys system tem by boi boilin ling g the porous porous dis disks ks in wat water er and allowing water to flow through the system prior to mounting the specimen specimen.. It sho should uld be not noted ed tha thatt pla placin cing g the air int into o solution is a function of both time and pressure. Accordingly, removi rem oving ng as muc much h air as pos possib sible le pri prior or to app applyi lying ng bac back k pressure will decrease the amount of air that will have to be placed into solution and will also decrease the back pressure requir req uired ed for sat satura urati tion. on. In add additi ition, on, air rem remain aining ing in the specim spe cimen en and dra draina inage ge sys system tem jus justt pri prior or to app applyi lying ng bac back k pressure will go into solution much more readily if deaired water is used for saturation. The use of deaired water will also decrease the time and back pressure required for saturation. Many procedures have been developed to accomplish saturation. The following are suggested procedures: 8.2.1 Starting with Initially Dry Drainage System— Increase thee pa th part rtia iall va vacu cuum um ac acti ting ng on to top p of th thee sp spec ecim imen en to th thee
NOTE 15—The 15—The refer references ences presented are for inform informationa ationall purpose purposess only.
8.2.3.1 Applying Applying Back Pr Pressur essure— e— Simultaneously Simultaneously increase the chamber and back pressure in steps with specimen drainage valves opened so that deaired water from the burette connected to th thee to top p an and d bo bott ttom om of th thee sp spec ecim imen en ma may y flo flow w in into to th thee specimen. To avoid undesirable prestressing of the specimen while applying back pressure, the pressures must be applied incrementally with adequate time between increments to permit equalization of pore-water pressure throughout the specimen. The size of each increment may range from 35 kPa (5 2 2 lbf/in. ) up to 140 kPa (20 lbf/in. ), depending on the magnitudee of the des tud desire ired d ef effec fectiv tivee con consol solida idatio tion n str stress ess,, and the percent saturation of the specimen just prior to the addition of the increment. The difference between the chamber pressure
maximum avai maximum available lable vacuu vacuum. m. If the ef effect fective ive cons consolida olidation tion stress under which the strength is to be determined is less than the maximum partial vacuum, apply a lower partial vacuum to the cha chambe mberr. The dif differ ferenc encee bet betwee ween n the par partia tiall vac vacuum uum applied to the specimen and the chamber should never exceed the effective consolidation stress for the test and should not be lesss tha les than n 35 kPa (5 lbf/in. lbf/in.2 ) to al allo low w fo forr flo flow w th thro roug ugh h th thee sample. After approximately 10 min, allow deaired water to percolate from the bottom to the top of the specimen under a 2 14). differential vacuum of less than 20 kPa (3 lbf/in. ) (Note 14). 8.2.1.1 There should always be a positive effective effective stress of 2 at least 13 kPa (2 lbf/in. ) at the bottom of the specimen during this part of the procedure. When water appears in the burette connected to the top of the specimen, close the valve to the bottom of the specimen and fill the burette with deaired water. Next, reduce the vacuum acting on top of the specimen through the bur burett ettee to atm atmosp ospher heric ic pre pressu ssure re whi while le sim simult ultane aneous ously ly
and the bac back k pre pressu ssure re dur during ing bac back k pre pressu ssurin ring g sho should uld not exceed 35 kPa unless it is deemed necessary to control swelling of the specimen during the procedure. The difference between the chamber and back pressure must also remain within 65 % when whe n the pre pressu ssures res are rai raised sed and wit within hin6 2 % wh when en th thee pressures are constant. To check for equalization after application of a back pressure increment or after the full value of back pressure has been applied, close the specimen drainage valves and measure the change in pore-pressure over a 1-min interval. If the change in pore pressure is less than 5 % of the 4 Lowe, J., and Johnson, T. C., “Use of Back Pressure to Increase Degree of Saturation of Triaxial Test Specimens,” Proceedings, Specimens,” Proceedings, ASCE Research Conference Conference on Shear Strength of Cohesive Soils , Boulder, CO, 1960 5 Black, A. W. and Lee, K. L. (1973), “Saturating Laboratory Samples by Back Pressure,” Journal Pressure,” Journal of the Soil Mechanics and Foundation Division, ASCE, Division, ASCE, Vol. 99, No. SM1, Proc. Paper 9484, Jan., pp. 75–93. 6 Head, K. H., (1986), Manual of Soil Laboratory Testing, Volume 3: Effective Stress Tests, Tests, Pentech Press Limited, Graham Lodge, London, United Kingdom, pp. 787–796.
increasin increa sing g the cha chambe mberr pre pressu ssure re by an equ equal al amo amount unt.. Thi Thiss process should be performed slowly such that the difference 7
D4767 − 11 (2020)
FIG. 3 Pressure to Attain Various Degrees of Saturation
differenc differ encee bet betwee ween n the cha chambe mberr pre pressu ssure re and the bac back k
∆σ 3
pressure, another back pressure increment may be added or a measurement may be taken of the pore pressure Parameter B (see 8.2.4 (see 8.2.4)) to determine if saturation is completed. Specimens shalll be conside shal considered red to be be saturate saturated d if the the value value of B is equal equal to or greater greater than 0.95, 0.95, or if B rema remains ins unchan unchanged ged with with additio addition n of back pressure increments.
8.2.4.1 Close the specimen drainage drainage valves, record the pore pressu pre ssure, re, to the nearest nearest 0.7 kPa (0.1 psi psi), ), and increase increase the 2 chamber pressure by 70 kPa (10 lbf/in. ). 8.2.4.2 After approximately approximately 2 min, determine determine and record the maximum value of the induced pore pressure to the nearest 0.7 kPa (0. (0.1 1 psi psi),. ),. For man many y spe specim cimens ens,, the por poree pre pressu ssure re may decrea dec rease se aft after er the imm immedi ediate ate res respon ponse se and the then n inc increa rease se slightly slig htly with time time.. If this occur occurs, s, values values of ∆u shoul should d be plot plotted ted with time and the asymptotic pore pressure used as the change in pore pore press pressure ure.. A lar large ge incre increase ase in in ∆u wit with h time time or value valuess of ∆u greater than ∆σ 3 indicate a leak of chamber fluid into the specim spe cimen. en. Dec Decrea reasin sing g value valuess of ∆u wit with h time time may may indi indicat catee a leak lea k in tha thatt par partt of the por poree pre pressu ssure re mea measur sureme ement nt sys system tem located outside of the chamber. 8.2.4.3 Calcu Calculate late the B-value using Eq using Eq 2. 8.2.4.4 Reapp Reapply ly the same effective effective consolidati consolidation on stre stress ss as existed exis ted prior prior to the B-val -value ue by reducing reducing the chamber chamber pressure pressure by 70 kPa (10 lbf/in. 2) or by alternatively, increasing the back pres pr essu sure re by 70 kPa. kPa. If B is cont contin inui uing ng to in incr crea ease se with with increasing back pressure, continue with back pressure saturation. ti on. If B is equ equal al to or grea greater ter tha than n 0.95 0.95 or or if if a plo plott of of B ver versus sus back pressur pressuree indicates indicates no no further further increas increasee in B with increas increasing ing back pressure, initiate consolidation.
NOTE 16 16—T —The he re rela lati tion onsh ship ipss pre prese sent nted ed in Fi Fig. g. 3 ar aree ba base sed d on th thee assumption that the water used for back pressuring is deaired and that the only source for air to dissolve into the water is air from the test specimen. If air pressure is used to control the back pressure, pressurized air will dissolve into the water, thus reducing the capacity of the water used for back pressure pressure to dissolve air located in the pores of the test specimen. The problem is minimized by using a long (>5 m) tube that is impermeable to air between the air-water interface and test specimen, by separating the back-pressure water from the air by a material or fluid that is relatively impermeable to air, by periodically replacing the back-pressure water with deaired water, or by other means. NOTE 17—Al 17—Although though the the pore pressure pressure Param Parameter eter B is used to determ determine ine adequa adequate te saturation, satura the B als B also o -value a function of soil nt stif stiffness. fness. If the th saturation satura tion of thetion, sample is-value 100 %, %is , the measurement measureme will increa increase see with decreasing soil stiffness. Therefore, when testing soft soil samples, a B-value of 95 % may indicate a saturation less than 100 %. NOTE 18—The 18—The bac back k pre pressur ssuree req require uired d to sat satura urate te a rec reconst onstitut ituted ed specimen may be higher for the wet mounting method than for the dry mounting method and may be as high as 1400 kPa (200 lb/in. 2). NOTE 19—Many laboratories use differential pressure regulators and transducers transd ucers to achiev achievee the requir requirements ements for small differences differences between chamber and back pressure.
8.3 Consolidation— The T he obj object ective ive of th thee con consol solida idatio tion n phase of the test is to allow the specimen phase specimen to reac reach h equil equilibri ibrium um in a drained state at the effective consolidation stress for which a strength determination is required. During consolidation, data is obt obtain ained ed for use in det determ ermini ining ng whe when n con consol solida idatio tion n is complete and for computing a rate of strain to be used for the shear portion portion of the test test.. The consolidation consolidation procedure procedure is as follows: 8.3.1 When the saturation saturation phase of the test is compl completed, eted,
8.2.4 Meas Measur ureme ement nt of the Por Poree Pr Press essur uree Par Parame ameter ter B— Determine Determine the value of the pore pressure Parameter B in accordanc acco rdancee with 8.2.4.1 through 8.2.4.4. 8.2.4.4. The pore pre pressu ssure re Parameter B is defined by the following equation: B 5 ∆ u / ∆σ3
= chang changee in the the chamber chamber pressu pressure. re.
(2 )
where: ∆u = chang changee in the the specimen specimen pore press pressure ure that that occurs occurs as as a result of a drainage change in the chamber pressure valves are closed, and when the specimen drainage specimen
bring the axial load piston into contact with the specimen cap, and record the reading on the deformation indicator to three 8
D4767 − 11 (2020) 8.4 Shear— During During shear, the chamber pressure shall be kept constant consta nt whi while le adv advanc ancing ing the axi axial al loa load d pis piston ton dow downwa nward rd against the specimen cap using controlled axial strain as the loading criterion. Specimen drainage is not permitted during shear. 8.4.1 Prior to Axial Loading— Before Before initiating shear, perform the following: 8.4.1.1 By opening or closing closing the appropriate valves, isolate the specimen specimen so that during shear the spec specimen imen pore-water pore-water pressure will be measured by the pore-pressure measurement device and no drainage will occur. 8.4.1.2 Place the chamber chamber in posit position ion in the axial loading loading device. Be careful to align the axial loading device, the axial load-measuring device, and the triaxial chamber to prevent the application of a lateral force to the piston during shear. 8.4.1.3 8.4 .1.3 Bring the axial load pis piston ton into con contac tactt wit with h the specimen cap to permit proper seating and realignment of the piston pis ton wit with h the cap cap.. Dur During ing thi thiss pro proced cedure ure,, car caree sho should uld be taken not to apply an axial load to the specimen exceeding 0.5 % of th thee es esti tima mate ted d ax axia iall lo load ad at fa fail ilur ure. e. If th thee ax axia iall loadloa d-me meas asur urin ing g dev devic icee is lo locat cated ed out outsi side de of the tr tria iaxi xial al chamber, the chamber pressure will produce an upward force on the piston that will react against the axial loading device. In
significant digits. During this procedure, take care not to apply an axial load to the specimen exceeding 0.5 % of the estimated axial axi al loa load d at fai failur lure. e. Aft After er rec record ording ing the rea readin ding, g, rai raise se the piston a small distance above the specimen cap, and lock the piston in place. 8.3.2 With the speci specimen men drainage valves closed, closed, hold the maxi maximum mum back pressure ure const constant ant and increase ease the chamber cham ber pressure until thepress difference between the incr chamber pressure and the back press pressure ure equal equalss the desir desired ed ef effect fective ive conso consolida lidation tion pressure. pres sure. Consolidatio Consolidation n in stag stages es is requi required red when the final 2 effective consolidation stress is greater than 40 kPa (5.8 lb/in. ) and filter strips for radial drainage are used. The load increment ratio shall not exceed two. 8.3.3 Obtain an initial initial reading on the volume volume change device, device, and, then open appropriate drainage valves so that the specimen may drain from both ends into the volume change device. At increasing intervals of elapsed time (0.1, 0.2, 0.5, 1, 2, 4, 8, 15, and 30 min and at 1, 2, 4, and 8 h, and so forth) observe and record rec ord the vol volume ume cha change nge rea readin dings, gs, and and,, aft after er the 1515-min min reading, record the accompanying deformation indicator readings obtained by carefully bringing the piston in contact with the specimen cap. If volume change and deformation indicator readings are to be plotted against the square root of time, the time intervals at which readings are taken may be adjusted to those that have easily obtained square roots, for example, 0.09, 0.25, 0.49, 1, 4, and 9 min, and so forth. Depending on soil changed d to con conven venien ientt tim timee type ty pe,, ti time me in inte terv rval alss ma may y be change intervals which allow for adequate definition of volume change versus time.
this ca this case se,, st star artt sh shea earr wi with th th thee pi pist ston on sl slig ight htly ly ab abov ovee th thee specimen cap, and before the piston comes into contact with the specimen specimen cap, eit either her ( 1) mea measur suree and record record the initial initial piston friction and upward thrust of the piston produced by the chamber pressure and later correct the measured axial load, or (2) adjust the axial load-measuring device to compensate for thee fr th fric icti tion on an and d th thru rust st.. Th Thee va vari riat atio ion n in th thee ax axia iall lo load ad-measu me asurin ring g dev device ice rea readin ding g sho should uld not exc exceed eed 0.1 % of the estimated failure load when the piston is moving downward prio pr iorr to co cont ntac acti ting ng th thee sp spec ecim imen en ca cap. p. If th thee ax axia iall lo load ad-measuring device is located inside the chamber, it will not be necessary to correct or compensate for the uplift force acting on the axial loading device or for piston friction. However, if an internal load-measuring device of significant flexibility is used in combination with an external deformation indicator, correction of the deformation readings may be necessary. In both cases, record the initial reading on the pore-water pressure measu me asurem rement ent dev device ice to the nea neares restt 0.7 kPa (0. (0.1 1 lbf lbf/in /in.. 2) immediately prior to when the piston contacts the specimen cap and the reading on the deformation indicator to three significant digits when the piston contacts the specimen cap. 8.4.1.4 Check for pore pres pressure sure stabilizati stabilization. on. Recor Record d the 2 pore pressure to the nearest 0.7 kPa (0.1 lbf/in. ). Close the drainage valves to the specimen, and measure the pore pressure chan ch ange ge un unti till st stab able le.. If th thee ch chan ange ge is le less ss th than an 5 % of th thee chamb cha mber er pre pressu ssure, re, the pore pre pressu ssure re may be ass assume umed d to be stabilized. 8.4.2 Axial Axial Loadi Loading— ng— Apply Apply axi axial al loa load d to the specimen specimen using usi ng a rat ratee of axi axial al str strain ain tha thatt wil willl pro produc ducee app approx roxima imate te equali equ alizat zation ion of por poree pre pressu ssures res thr throug oughou houtt the spe specim cimen en at failure. Assuming failure will will occur after 4 %, a suitable rate rate of strain, ε˙ , may be determined from the following equation:
NOTE 20—In cases where significant amounts of fines may be washed from the spe from specim cimen en bec becaus ausee of high initial initial hydr hydrauli aulicc gra gradien dients, ts, it is permissible to gradually increase the chamber pressure to the total desired pressure over a period with the drainage valves open. If this is done, record rec ording ing of dat dataa sho should uld beg begin in imm immedia ediately tely after the tota totall pre pressu ssure re is reached.
8.3.4 8.3 .4 Plo Plott the vol volume ume cha change nge and def deform ormati ation on ind indica icator tor readings versus either the logarithm or square root of elapsed time. Allow consolidation to continue continue for at least one log cycle of time or one overnight period after 100 % primary consolidation has been achieved as determined in accordance with one of the procedures outlined in Test Method D2435/D2435M Method D2435/D2435M.. A marked deviation between the slopes of the volume change and deformation indicator curves toward the end of consolidation based on deformation indicator readings indicates leakage of fluid from the chamber into the specimen, and the test shall be terminated. 8.3.5 Deter Determine mine the time for 50 % prim primary ary consolidatio consolidation, n, t50, in accordance with one of the procedures outlined in Test Method D2435/D2435M Method D2435/D2435M.. If the specimen swells or does not consolidate at the final effective consolidation stress, determine the reason for this behavior and verify that it is not equipment malfunct malf unction. ion. If simi similar lar specimens specimens are bein being g test tested ed at highe higherr final effective consolidation stress and have consolidation data, use the t 50 from these tests. If no other data is available, use a strain stra in rate of 1 % ⁄hr ⁄hr..
9
D4767 − 11 (2020) ε ˙5
4 % / ~ 10 t 50 !
and initial dry unit weight. Calculate Calculate the specimen specimen volum volumee from values measured in 6.4 in 6.4.. Calculate the volume of solids by dividing the dry mass of the specimen by the specific gravity of the solids (Not Notee 22) and dividin dividing g by the den densit sity y of wat water er.. Calculate the void ratio by dividing the volume of voids by the volume of solids where the volume of voids is assumed to be the difference between the specimen volume and the volume of the solids. Calculate dry density by dividing the dry mass of the specimen by the specimen volume.
(3 )
where: t 50 = tim imee va valu luee ob obta tain ineed in 8.3.5.
If, however, it is estimated that failure will occur at a strain value lower than 4 %, a suitable strain rate may be determined using Eq 3 by replacing 4 % with the estimated failure strain. using This rate of strain will provide for determination of accurate effective stress paths in the range necessary to define effective strength envelopes. 8.4.2.1 At a minimum, record load and deformation deformation to three significant digits, and pore-water pressure values to the nearest 2 0.7 kPa (0.1 lbf/in. ), at increments of 0.1 to 1 % strain and, thereafter, at every 1 %. Take sufficient readings to define the stress str ess-st -strai rain n cur curve; ve; hen hence, ce, mor moree fre freque quent nt rea readin dings gs may be requ re quir ired ed in th thee ea earl rly y st stag ages es of th thee te test st an and d as fa fail ilur uree is approa app roache ched. d. Con Contin tinue ue the loa loadin ding g to 15 % str strain ain,, exc except ept loading may be stopped when the principal stress difference (devia (de viator tor str stress ess)) has dro droppe pped d 20 % or whe when n 5 % add additi itiona onall axial strain occurs after a peak in principal stress difference (deviator stress).
NOTE 22—The specific gravity of solids can be determined in accordance with Test Method D854 Method D854 or or it may be assumed based on previous test results.
10.3 Specimen Specimen Pr Propert operties ies After Conso Consolida lidation— tion— Calculate the specimen height and area after consolidation as follows: 10.3.1 Height of specimen specimen after consolidation, consolidation, H c, is determined from the following equation: H c
5 H o 2 ∆ H o
(4 )
where: H o = init initial ial height height of specim specimen, en, mm or cm, cm, and ∆ H o = change in height of specimen at at end of consolidation, consolidation, mm or cm.
NOTE 21—The use of a manually adjusted null-indicating device will require nearly continuous attention to ensure the criterion for undrained shear.
10.3.2 10. 3.2 The The Acro cross ss-se -sect ctio ional nal ar area ea of the spe speci cime men n aft after er consolidation, c, shall be computed using one of the following methods. The choice of the method to be used depends on whether shear data are to be computed as the test is performed (in which case Method A would be used) or on which of the two tw o me meth thod ods, s, in th thee op opin inio ion n of a qu qual alifi ified ed pe pers rson on,, yi yiel eld d specimen conditions considered to be most representative of those after consolidation. Alternatively, the average of the two calculated areas may be appropriate. 10.3.2.1 Method A:
9. Remo Removing ving Specimen Specimen 9.1 When shear is completed, completed, perform the following: following: 9.1.1 9.1 .1 Rem Remove ove the axi axial al loa load d and reduce reduce the chamber chamber and back pressures to zero. 9.1.2 Wi With th the specimen drainage valves remaining closed, closed, quickly remove the specimen from the apparatus so that the specimen will not have time to absorb water from the porous disks. 9.1.3 Remove the rubbe rubberr memb membrane rane (and the filter-paper filter-paper strips str ips or cag cagee fro from m the specime specimen n if the they y wer weree use used), d), and determin dete rminee the water cont content ent of the total specimen in accor accor-dance with the procedure in Test Method D2216 D2216.. (Free water remainin rema ining g on the specimen specimen afte afterr remo removal val of the membrane membrane should be blotted away before obtaining the water content.) In cases where there is insufficient material from trimmings for index property tests, that is, where specimens have the same diameter as the sampling tube, the specimen should be weighed prior pri or to rem removi oving ng mat materi erial al for ind index ex pro proper perty ty tes tests ts and a representative portion of the specimen used to determine its final water content. Prior to placing the specimen (or portion thereof) in the oven to dry, sketch or photograph the specimen showing the mode of failure (shear plane, bulging, or other).
Ac
5
/ H c ~ V o2 ∆ V sat 2 ∆ V c ! /
(5 )
where: 2
2
Ac = consolidat consolidation, ion, cm or m, V o = initial initial volum volumee of spec specimen imen,, cm3 or m,3 ∆V c = chang changee in volum volumee of speci specimen men durin during g consoli consolidatio dation n as indicated by burette readings, cm3 or m,3 and ∆V sat ∆V sat sat
= change change in volume specimen en during during saturatio saturation n as 3 3of specim follows, cm or m : = 3Vo [ ∆H s /Ho ]
where: ∆ H s
= change change in heig height ht of the specimen specimen during during saturation, saturation, mm, cm, or m.
10.3.2.2 Method B:
10. Calculations
Ac 5 ~ V wf 1 V s ! / H H c
10.1 Calculations are are only shown using SI units. Other units units are permissible, provided the appropriate unit conversions are used to maintain consistency of units throughout the calculations. See 1.6.1 See 1.6.1 – 1.6.3 for additional comments on the use of inch-pound units. Measurements and calculations shall contain a minimum of three significant digits.
(6 )
where: volume of water water (based on final final water content) content),, V wf wf = final volume 3 3 cm or m, and 3 3 V s = volu volume me of solid solids, s, cm or m, as follows: V s = w s /(G s pw) where:
10.2 Initial Specimen Properties— Using Using the dry mass of the
s w specimen mass, , g, G s = = spec specimen specific ific gravit grdry avity ymass of solids, so lids, and and
total specimen, calculate and record the initial water content, volume of solids, initial void ratio, initial percent saturation, 10
D4767 − 11 (2020) where:
density ty of water water at 20 °C, °C, 0.9982 0.9982 g/cm.3 pw = densi
∆(σ 1 − σ 3 ) fp
10.3.3 Usi 10.3.3 Using ng the cal calcul culate ated d dim dimens ension ionss of the spe specim cimen en after consolidation, and assuming that the water content after consolidation is the same as the final water content, calculate the consolidated void ratio and percent saturation. NOTE 23—The specimen will absorb water from the porous disks and drainage lines during the time it is being removed from the apparatus. When Whe n this ef effec fectt is sign signific ificant ant,, Met Method hod A will yie yield ld mor moree rea reason sonable able values. NOTE 24— In this test method, method, the equation equationss are written written suc such h that compression compre ssion and consoli consolidation dation are conside considered red positive positive..
P fp
Ac
(2) For va valu lues es of ax axia iall st stra rain in of 2 % or le less ss,, us usee th thee following equation to compute the correction:
10.4 Shear Data: 10.4.1 Calculate the axial strain, ε 1, for a given applied axial load as follows: ε 1 5 ∆ H / H c
K fp
~
(7 )
NOTE 26—For 26—For filterfilter-paper paper generally used in triaxia triaxiall testing testing,, K fp is approximately 0.00019 kN/mm or 0.19 kN/m (1.1 lbf/in.).
10.4.3.2 Correction for Rubber Membrane— Use Use the following equation to correct the principal stress difference (deviator stress) for the effect of the rubber membrane if the error in principal stress difference (deviator stress) due to the strength of the membrane exceeds 5 %:
(8 )
~
∆(σ 1 − σ 3 ) m
D c
E m
t m
ε1
= measured measured principal principal stre stress ss dif differe ference nce or devi deviator ator 2 stress, kN/m = kPa, = give given n appli applied ed axial load (cor (correcte rected d for upli uplift ft and piston friction if required as obtained in 10.4.3.1 10.4.3.1), ), kN, and = corr correspon esponding ding cros cross-se s-section ctional al area area,, cm2 or m.2
~
A c ! fp 5 K fp P fp / A
= membra membrane ne cor correc rectio tion n to be sub subtra tracte cted d fro from m the measured principal stress difference (de2 viator stress), kN/m = kPa, =
=4 A / π 5
diameter of specimen after consolidation, mm or cm, = Young’s Young’s modulus for the membrane material, 2 kN/m = kPa = thickness thickness of the memb membrane, rane, mm or cm, and = axial stra strain in (dec (decimal imal form form). ).
(1) The Young’s Young’s modulus of the membrane material may be determined by hanging a 15-mm (0.5-in.) circumferential strip of membrane using a thin rod, placing another rod through the bottom of the hanging membrane, and measuring the force per unit strain obtained by stretching the membrane. The modulus value may be computed using the following equation:
10.4.3.1 Correcti For vert vertical ical Correction on for Filt Filter-Pa er-Paper per Stri Strips— ps— For filterfilt er-pap paper er str strips ips whi which ch ext extend end ove overr the tot total al len length gth of the specimen, apply a filter-paper strip correction to the computed values of the principal stress difference (deviator stress), if the error in principal stress difference (deviator stress) due to the strength of the filter-paper strips exceeds 5 %. (1) For values values of axia axiall strain above 2 %, use the following following equation to compute the correction: ∆ σ 1 2 σ3
(9 )
σ 1 − σ 3
A
(12)
c
where:
P
where:
10.4.3 Calculate Calculate the meas measured ured princ principal ipal stre stress ss dif differe ference nce (deviator stress), σ1 − σ 3, fo forr a gi give ven n ap appl plie ied d ax axia iall lo load ad as follows:
!m 5 ~ 4 E mt mε ! / D c
∆ σ 1 2 σ 3
NOTE 25—The cross-sectional area computed in this manner is based on the ass assumpt umption ion that the spe specim cimen en def deform ormss as a righ rightt cir circula cularr cyl cylinde inderr during shear. shear. In cases where there is localiz localized ed bulging, it may be possible to det determ ermine ine mor moree acc accura urate te val values ues for the are areaa bas based ed on spe specim cimen en dimension measurements obtained after shear.
P / A
(11)
limiting ting axial axial strain strain decimal decimal format format,, and 50 = limi axial strain strain (decimal (decimal format) format) for the given given axial load, load, ε1 = axial and an d ot othe herr te term rmss ar aree th thee sa same me as th thos osee de defin fined ed in subparagraph (1) of 10.4.3.1.
where: Ac = averag averagee cro crossss-sec sectio tional nal are areaa of the spe specim cimen en aft after er 2 2 consolidation, cm or m, and axiall strain strain (decimal (decimal format) format) for for the given given axial load. load. ε1 = axia
σ1 2 σ 3 5
1
where:
10.4.2 Calcul 10.4.2 Calculate ate the cross-s cross-sect ection ional al area, area, A, for a giv given en applied axial load as follows:
! fp 5 50ε K fpP fp / Ac
∆ σ1 2 σ3
where: ∆ H = chan change ge in he heig ight ht of sp spec ecim imen en du duri ring ng lo load adin ing g as determined from deformation indicator readings, mm or cm, and H c = heig height ht of specime specimen n after after consolidat consolidation, ion, mm or or cm.
A 5 Ac / ~ 1 2 ε 1!
= filter-pape filter-paperr correction correction to be subtr subtracted acted from the measured principal stress difference (de2 viator stress), kN/m = kPa, = loa load d car carri ried ed by filt filterer-pap paper er str strips ips per uni unitt length leng th of perim perimeter eter cover covered ed by filte filter-pap r-paper er,, kN/mm or kN/m (See Note 26), = perimeter perimeter cover covered ed by filte filter-pap r-paper er,, mm or m, and = cr cros osss-se sect ctio iona nall area area of of spec specim imen en aft after er 2 2 consolidation, cm or m.
/ A m! / ~ ∆ L / L ! E m 5 ~F /
(13)
where: 2
E m = Young’s modulus modulus of the membrane membrane material, material, kN/m = kPa (See Note 27) F = forc forcee applied applied to to stretch stretch the membr membrane, ane, N or kN, kN, L = unstr unstretche etched d length length of of the memb membrane rane,, mm or or cm, cm, ∆ L = cha change nge in leng length th of of the the membr membrane ane due to the the forc force, e, F , mm or cm, and
(10)
11
D4767 − 11 (2020) areaa of the memb membran ranee = 2 t m W s , mm 2 or cm.2 Am = are
σ 3 f 5 σ 3 f 2 ∆ u f , '
'
~
σ1 5 σ 1 2 σ
where:
f
10.4.3.3 Corrected Principal Stress Difference— This This value is as follows: 2 σ3
P
! c 5 A 2 ~ σ
1
!ƒ p 2 ~ σ
2 σ3
1
2 σ3
!m
3 f
(2 0) (21)
10.8 Mohr Stress Circles— If If desired, construct Mohr stress circles at failure based on total and effective stresses on an arithmetic plot with shear stress as ordinate and normal stress as abscissa using the same scales. See Fig. See Fig. 4. 4. The circle based on total stresses is drawn with a radius of one half the principal stress difference (deviator stress) at failure with its center at a value equal to one half the sum of the major and minor total principal prin cipal stresses. stresses. The Mohr stress circ circle le based on ef effecti fective ve stresses is drawn in a similar manner except that its center is at a value equal to one half the sum of the major and minor effective principal stresses.
NOTE 27—A typical value of E E m for latex membranes is 1400 kPa (200 lbf/in.). NOTE 28—The corrections for filter-paper strips and membranes are based on simplified assumptions concerning their behavior during shear. Their actual behavior is complex, and there is not a consensus on more exact corrections.
1
!cf 1 σ
'
where ∆u f is the induced pore-water pressure at failure.
t m = thickness thickness of the memb membrane, rane, mm mm or cm, cm, and width th of cir circum cumfer ferent ential ial strip strip of mem membra brane, ne, 15 mm W s = wid (0.5 in.).
~σ
3
and
(14)
where:
11. Report: Test Test Data Sheet(s)/Form( Sheet(s)/Form(s) s)
(σ 1 – σ 3 )c = corrected principal principal stress stress difference difference or deviator stress, kN/m2 = kPa,
11.1 The met method hodolo ology gy use used d to spe specif cify y how data are recorded on the data sheet(s)/form(s), as given below, is covered in 1.5.1 in 1.5.1..
'
10.4.4 Calculate the effective effective minor principal stress, stress, σ 3 for a given applied axial load as follows: '
σ 3 5 σ 3 2 ∆u
11.2 11 .2 Recor Record d as a mini minimum mum the foll following owing general general infor informamation (data): 11.2 1.2.1 .1 Identi Identifica ficatio tion n dat dataa and vis visual ual des descri cripti ption on of specimen, including soil classification and whether the specimen is intact, reconstituted, or otherwise prepared, 11.2.2 Values of plastic limit and liquid limit, if determined in accordance with Test Method D4318 D4318,, 11.2.3 Value of specific gravity of solids and notation if the value was determined in accordance with Test Method D854 Method D854 or or assumed, 11.2.4 11 .2.4 Parti Particlecle-size size anal analysis, ysis, if dete determin rmined, ed, in accor accordance dance with Test Method D422 Method D422,, 11.2.5 11 .2.5 Initi Initial al specimen dry unit weight, void rati ratio, o, water content, and percent saturation, (specify if the water content specimen was obtained from cuttings or the entire specimen),
(15)
where: σ 3' = effective effective minor principal principal stress at the given given axial load, kPa, minorr principa principall stress stress at the the given given axial axial load, load, kPa, and σ 3 = mino ∆u = ind induce uced d por pore-w e-wate aterr pre pressu ssure re at the given given axi axial al load (tot (t otal al po pore re-wa -wate terr pr pres essur suree mi minu nuss th thee to tota tall bac back k pressure), kPa. 10.5 Prin Principal cipal Stress Stress Dif Differe ference nce (Devi (Deviator ator Str Stress) ess) and Induced Por Pore-W e-Water ater Pr Pressur essuree vers versus us Strai Strain n Curve Curves— s— Prepare Prepare graphss showi graph showing ng relat relationsh ionships ips betwe between en princ principal ipal stre stress ss dif differfer(deviator stress) and indu induced ced porepore-water water pressure with ence (deviator axiall stra axia strain, in, plot plotting ting deviator stress and indu induced ced porepore-wate waterr pressure as ordinates and axial strain as abscissa. Select the principal stress difference (deviator stress) and axial strain at failure in accordance with 3.2.3 3.2.3..
NOTE 29—The 29—The specifi specificc gravity determined determined in accord accordance ance with Test Method D854 is required for calculation of the saturation. An assumed specific gravity may be used provided it is noted in the test report that an assumed value was used.
10.6 p' − q Diagram— Prepare Prepare a graph showing the relationship shi p betw between een p' and and q, plotting q as as ordinate ordinate and p' as abscis abscissa sa using the same scale. The values of p' and and q fo forr a gi give ven n axi axial al load may be computed as follows: p ' 5
~~ σ
1
2 σ
! c 1 2 σ ! '
3
2 q5
~ σ
1
3
2 σ3
2
5
!c
~σ
' 1
1σ
' 3
!
2
11.2.6 Initi 11.2.6 Initial al heig height ht and diameter diameter of spec specimen, imen, 11.2.7 Method followed for specimen specimen saturation (that (that is, dry or wet method), 11.2.8 Total back pressure, pressure, 11. 1.2. 2.9 9 The po pore re pr pres essu sure re Pa Para rame mete terr B at th thee en end d of saturation, 11.2.10 Effe Effective ctive consolidation stress, 11.2.11 Tim Timee to 50 % primary consolidation, consolidation, 11.2.12 Specimen dry unit weight, void ratio, ratio, water content, and percent saturation after consolidation, 11.2.13 11 .2.13 Speci Specimen men cross cross-sec -section tional al area afte afterr cons consolida olidation tion and method used for determination, 11.2.14 Failure criterion criterion used, 11.2.15 The value of the principal stress difference difference (deviator stress) at failure and the values of the effective minor and major principal stresses at failure, (indicate when values have been corrected for effects due to membrane or filter strips, or both),
(16) (17)
where: corrected principal principal stre stress ss dif differen ference ce (devi (deviator ator (σ 1 − σ 3 )c = corrected stress), kPa, and σ ' ' 3 = effective effective mino minorr prin principal cipal stre stress, ss, kPa. 10.7 Dete Determin rminee the major and mino minorr prin principal cipal stresses stresses at failure based on total stresses, σ 1 f and σ3 f respectively, and on effecti ef fective ve stre stresses, sses, σ'1 f and σ'3 f respectively, as follows: σ 3 f 5
effective consol oliida dati tio on st strress ss,, , ~ ! σ 1 f 5 σ 1 2 σ 3 cf 1 σ3 f
( 18) (19)
11.2.16 Axial strain 11.2.16 strain at failure, failure, perce percent, nt, 11.2.17 11 .2.17 Rate of strain, percent percent per minu minute, te, 12
D4767 − 11 (2020)
FIG. 4 Const Constructi ruction on of Mohr Stres Stress s Circle
11.2.18 .2.18 Princ Principal ipal stress dif differen ference ce (devi (deviator ator stress) and in11 duced pore-water pore-water pressure versus axial stra strain in curv curves es as described in 10.5 in 10.5,, 11.2.19 11 .2.19 The p' − q diagram as described in 10.6 10.6,, 11.2 1.2.20 .20 Moh Mohrr str stress ess cir circle cless bas based ed on tot total al and ef effec fectiv tivee stresses, (optional), 11.2.21 11 .2.21 Slope of angl anglee of the fail failure ure surface (optional (optional), ), 11.2.22 11 .2.22 Failu Failure re sketch or photo photograph graph of the specimen, specimen, and 11.2.23 11 .2.23 Remar Remarks ks and notations notations regarding regarding any unusual conditions diti ons such as slic slickensi kensides, des, stra stratific tification ation,, shell shells, s, pebbl pebbles, es, roots, and so forth, or other information necessary to properly interpret inte rpret the resu results lts obtai obtained, ned, incl including uding any depa departure rturess from the procedure outlined.
either not feasible or too costly at this time to have ten or more labora lab orator tories ies par partic ticipa ipate te in a rou roundnd-rob robin in tes testin ting g pro progra gram. m. Subcommittee D18.05 is seeking any data from users of this test method that might be used to make a limited statement on precision. 12.2 Bias— There There is no accepted reference value for this test method, therefore, bias cannot be determined. 13. Keyw Keywords ords 13.1 back press pressure ure satu saturati ration; on; cohe cohesive sive soil; consolidated consolidated undrained strength; strain-controlled loading; stress-strain relationships; total and effective stresses
12. Prec Precision ision and Bias Bias 12.1 Precision— Test Test data on precision is not presented due to the nature of the soil materials tested by this procedure. It is
13
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