Basement

BASEMENT

DCQ3043 CONSTRUCTION TECHNOLOGY 3 TOPIC: BASEMENT

PREPARED BY: MOHD ANUWAR BIN SIMON Mohd Anuwar Simon

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BASEMENT

Mohd Anuwar Simon

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BASEMENT Syllabus Content : 2.1

Understand the construction of basement. 2.1.1 Explain methods of excavation for the construction of deep and huge basement. 2.1.2 Explain usage of waterproofing system in basement construction. 2.1.3 Identify clauses in Uniform Building By-Laws for basement construction. 2.1.4 Describe construction of earthwork support system. 2.1.5 Justify the purpose of earthwork support system.

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BASEMENT Definitions: 1.

2.

INTRODUCTION

A storey with a floor that at some point is more than 1.2m below the highest level of ground adjacent to the outside wall. A storey of a building constructed wholly or partly below ground level exposed to soil, water and/or water vapour pressure.

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BASEMENT Types of Basement: 1.

Semi-basement Single storey with only one, two or three wall fully or partially below ground level.

2.

Residential basement A shallow or semi-basement providing space for storage and/or accommodation, associated with housing.

3.

Shallow basement Not more than one storey wholly below ground level. Mohd Anuwar Simon

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BASEMENT Types of Basement (cont’d):

4.

Deep basement More than one storey wholly below ground level.

5.

Cellar basement Used for storage, heating plant and for purpose other than habitation.

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BASEMENT Basement Requirements:  Primary functional requirements of basement /wall below ground may be summarized as follows: 1. 2. 3. 4.

Structural stability Durability Moisture exclusion Buildability

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Basement Grades:

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 Basements are graded according to BS8102 depending on their specific performance requirements.

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BASEMENT

METHOD OF EXCAVATION FOR THE CONSTRUCTION OF DEEP & HUGE BASEMENT

Classification of Excavation:

Excavation may be classified in the following manner: 1. Shallow excavation – up to 1.5m deep. 2. Medium excavation – 1.5m to 3.0m deep. 3. Deep excavation – over 3.0m deep. Factors that Affect Excavation Work: Method of excavation depends on: 1. Nature of the subsoil - to determine the type of plant or hand tools and the type of earthwork supports. 2. Purpose of the excavation - to determine the sizes, depth and volume of excavation. 3. Presence of ground water - to determine dewatering techniques. 4. Location and surrounding condition - needs permit from local authorities such as JKR, DBKL, etc. and impose certain restrictions and precautions. Mohd Anuwar Simon

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BASEMENT METHOD OF EXCAVATION FOR THE CONSTRUCTION OF DEEP & HUGE BASEMENT Method of Excavation: There are 3 method of excavation for the construction of Deep and Huge Basement that can be used: 1. Excavation with sloping sides / Open excavation. 2. Excavation with temporary support. 3. Excavation with permanent embedded retaining walls to deep basements. Mohd Anuwar Simon

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BASEMENT 1. Excavation with sloping sides / Open excavation  Excavation basement on an open site can be carried out by cutting the perimeter back to the natural angle of repose of the soil.  This method required sufficient site space around for the over excavation and to allow for the creation of a stable slope to sides of the excavation.  No temporary or permanent earth support so saving the cost of excavation but increase in volume of back filling.  Suitable for small scale basement. Mohd Anuwar Simon

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BASEMENT

Excavation with sloping sides / Open Excavation Mohd Anuwar Simon

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BASEMENT 2. Excavation with temporary support  Suitable where the space around the excavation is insufficient for open excavation.  Very economical compare with permanent support such as contiguous piles, secant piles or diaphragm walls.  Temporary support elements such as Steel Sheet Piles, Cross-lot bracing, Rakers and Tiebacks.  Temporary support are placed within the ground around the perimeter of the intended area to be excavated.  When the earth is done excavate, the void will become the basement area.  Permanent basement walls are than constructed and after completion the temporary support is removed. Mohd Anuwar Simon

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BASEMENT Temporary Support Elements:-

Hydraulic vibratory hammer

a) Steel Sheet Pile  Sheet piling is an earth retention and excavation support technique that retains soil, using steel sheet sections with interlocking edges.  The interlocked sheet piles reduced groundwater inflow.  Vibratory hammers are used to install sheet piles. If soils are too hard or dense, an impact hammer can be used to complete the installation. At certain sites where vibrations are a concern, the sheets can be hydraulically pushed into the ground.  Sheet piles are also a sustainable option since recycled steel is used in their construction, and the piles can often be reused. Mohd Anuwar Simon

Interlocking edges

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BASEMENT b) Cross-lot Bracing  Cross-lot bracing using steel sheet piles or I-beam as waler that are driven into the earth.  As the earth is excavated down around the sheeting (waler), tiers of horizontal bracing struts, usually of steel are added to support walers, which are beams that span across the face of the sheeting.  Where the excavation is too wide for cross-lot bracing, sloping rakers are used instead, bearing against heel blocks or other temporary footings.

Mohd Anuwar Simon

Steel sheet pile or I-beam

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Horizontal bracing

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BASEMENT Sheet Pile

Horizontal Bracing Support

A closer view of the cross-lot bracing supporting excavation. Mohd Anuwar Simon

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BASEMENT c) Raker  For very wide excavations, raker bracing is used.  The support for the rakers are installed at the bottom of the excavation.  Construction of the soil support and removal of the remainder of the excavation then begins.  The bottom ends of the rakers are braced against the central part of the building foundation slab.  The excavation was carried to full depth at the center first so that the foundation slab could be placed.  Prior to installation of the rakers, the lower part of the slurry trench concrete wall was supported by an earth berm.  The earth berm remains at the far side of the excavation. Mohd Anuwar Simon

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BASEMENT

A closer view of the rakers supporting excavation.

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BASEMENT d) Tiebacks  To minimize wall movement and ground settlement, tieback anchors are designed to achieve the highest stiffness.  Tieback capacity depends on the vertical and horizontal spacing of anchors and on surcharge conditions.  Typical tieback spacing ranges from 2m to 4m in the vertical, and from 1.5m to 4.5m in the horizontal direction.  First drilling a hole with an auger and then placing a bar (tendon) in the hole, concrete is then poured in the hole and the connection with wall is made.  Different types of augers are used to drill the tieback holes. The choice of the drilling method depends on the soil/rock conditions on the site.  Drilling should be done carefully since inadequate procedures can cause significant soil losses. Mohd Anuwar Simon

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BASEMENT

A closer view of the tiebacks supporting excavation. Mohd Anuwar Simon

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BASEMENT 3. Excavation with permanent embedded retaining walls to deep basement  The construction of deep basement walls can be costly if traditional excavation and construction techniques are used.  Limitation on access to most commercials sites also restrict the possibility of such an approach.  The most common options available for the formation of deep basement wall (permanent embedded retaining walls) are: a) Contiguous piles b) Secant piles c) Diaphragm walls

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BASEMENT

Mohd Anuwar Simon

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BASEMENT a) Contiguous Bored Pile RW

• Piles are installed at centers generally 150mm greater than their diameter therefore leaving gaps in the structural wall where soil is exposed during excavation. • This option is suitable where the retained soil is usually firm to stiff (not generally granular) and where the ground water table is below the level of the maximum excavation. • This is the most economic option and normally the fastest method to construct. Mohd Anuwar Simon

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Contiguous piles for deep basements Mohd Anuwar Simon

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BASEMENT b) Secant Pile RW

• Similar to the contiguous bored pile wall but the gap between piles is filled with an unreinforced cement/bentonite mix (1 to 2N/mm2) for the hard/soft wall and weak concrete (in the order of 10N/mm2) for the hard/firm wall. • Construction is carried out by installing the primary piles (A) and then the secondary piles (B) are formed in reinforced concrete, cutting into the primary piles. • By using this form of construction the ingress of water to any subsequent excavation can be substantially reduced. Mohd Anuwar Simon

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BASEMENT c) Diaphragm Walling  This method need to construct a R.C. retaining wall along the area of work.  The wall is designed to reach very great depth and sequence of work includes: a) Construct a guide wall b) Excavation of the trench using bentonite slurry c) Placement of reinforcements and pumped out bentonite slurry d) Concrete casting

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BASEMENT • The excavation of the deep trenches for segments of the diaphragm wall can be achieved by means of hydraulic grabs, by means of hydro fraise or by means of rotary auguring. • Overlapping holes are drilled to form a wall section as opposed to individual pile holes. • Traditionally, as the spoil is removed from the excavation it is replaced by material called ‘bentonite’ slurry. • This can be used to support the walls of the excavation shaft in order to prevent collapse as the excavation proceeds.

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BASEMENT • Once the excavation of a particular section of walling is complete, a reinforcement cage may be placed into the slurry and concrete placed using a tremie pipe. • Diaphragm walls of 450mm to 1.0m thick can be formed by hydraulic grabs and hydro fraise, whereas thicknesses of up to 1.50m can be achieved using rotary methods. • Diaphragm walls can be constructed to depths of up to 50.00m. • Once the diaphragm walls are placed and completed, the deep excavation work can proceed virtually unobstructed. Mohd Anuwar Simon

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BASEMENT • Some degree of lateral support is normally required to resist the bending stresses that are set up by soil and water pressure as before since a diaphragm wall is not normally intended to act as a pure retaining wall.

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BASEMENT Excavation of panel and installation of rebar cage

Installation of rebar cage and concreting of panel

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BASEMENT Diaphragm wall excavation using clamp shell.

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BASEMENT Waterproofing Work

 Apart from the structural design of basement walls and floor, waterproofing presents the greatest problem in basement construction.  There are 3 types of basement wall structure: 1. Tanked / Membranes 2. Waterproof / Monolithic Structures 3. Drained / Drained Cavities.

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BASEMENT Tanked / Membranes:  Tanked / Tanking / Membranes is a thin material placed either on the external or internal face of a basement wall or floor to provide the resistance to passage of moisture to the inside of the basement.  Membrane material can be applied externally (external tanking) during construction process meanwhile membrane also can be applied to the interior face of the walls after construction (internal tanking).  Membrane materials such as fibre-reinforced bituminous felt, polythene sheet, polyisobutylene plastic, epoxy resin compounds, bituminous compounds and mastic asphalt. Mohd Anuwar Simon

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BASEMENT

Mohd Anuwar Simon

Internal Basement Tanking System DCQ3043 Construction Technology 3

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External Basement Tanking System Mohd Anuwar Simon

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Mastic Asphalt Tanking Asphalt in tanking work is laid in 3 coats to the total thickness of not less than 30mm on horizontal surfaces and not less than 20mm on vertical faces. All internal angles (angle fillet) are reinforced by means of a fillet 50mm on the face, formed in 2 coats. Mohd Anuwar Simon

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BASEMENT Waterproof / Monolithic Structures:  Basement of dense reinforced concrete using impervious aggregates for the wall and floor to form the barrier to water penetration.  Its considered as ‘structurally integrated protection’ where the waterproofing is provided by the structural wall & floor themselves.  Shrinkage cracking can largely be controlled by forming construction joints at regular intervals.  Structural joints normally incorporate water stops made from materials such as neoprene, rubber water bar, PVC etc. Mohd Anuwar Simon

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Rubber Waterstops Mohd Anuwar Simon

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PVC Waterstops Mohd Anuwar Simon

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BASEMENT Drained / Drained Cavities:  Cavity drain structures make allowance for the small amount of water that may pass through the external wall.  The basement is constructed with 2 wall forming a void between the external and internal wall and cavity is formed in the walls around the basement and below the floor.  Traditionally cavities were formed with floor tiles which created void and two separate wall of masonry walling.  Any water that penetrates through the external wall or floor is guided to drainage channels to a sump pit and remove by pumps out of the building. Mohd Anuwar Simon

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BASEMENT

Mohd Anuwar Simon

Traditional Drained Cavities Basement DCQ3043 Construction Technology 3

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BASEMENT In-situ Concrete: Construct the basement using in-situ reinforced concrete and tradition formwork system:  The basement structure can be constructed upon the completion of the excavation with the basement pit properly formed and supported.  Usually this is done in a bottom-up arrangement using in-situ reinforced concrete formed by traditional timber formwork.  However, all the works are to be done in the congested underground environment inside the basement pit with a lot of lateral supporting frame and work in confined space.  Special attention including accurate construction planning and spatial design to allow room for the erection of the formwork as well as for the placing in of the required materials and equipments, safe access etc. should be provided. Mohd Anuwar Simon

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BASEMENT Sequence of Constructing Single Storey Basement

1. Before start of work

2. Prepare perimeter walling

3. Bulk excavation

4. Excavation almost complete

5. Complete excavation work

6. Waterproofing at basement

7. Placing basement flr reinf.

8. Concreting basement floor

9. Concreting wall & column

10. Placing grd flr reinf.

11. Concreting ground floor

12. Finish work

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BASEMENT Sequence of Constructing Huge Basement

1. Driven sheet pile & bulk excavation

2. Excavation, ramming bottom of excavation & bracing earthwork support

3. Lean concrete & horizontal tanking

4. Horizontal tanking

5. Horizontal tanking

6. Load rebar (bar reinforcement)

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7. Reinforcement & waterproofing

8. Reiforcement

9. Concreting

10. Preparing formwork for wall

11. Wall complete

12. Formwork & reinforcement for next level

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13. Constructing the superstructure

14. Ditto

15. Ditto

16. Constructing the superstructure till it gets finished

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BASEMENT CLAUSES IN UNIFORM BUILDING BY-LAWS FOR BASEMENT CONSTRUCTION 72. (1) In the design of basement wall and similar underground structures, provision shall be made for the lateral pressure of adjacent soil due allowance being made for possible surcharge from fixed on moving loads. (2) When a portion, or the whole of the adjacent soil in below a free water surface, computations shall be nased on the weight of the soil diminished by bouyancy plus full hydrostatic pressure. (3) In the design of basement floors and similar structures underground, the upward pressure of water, if any, shall be taken as the full hydrostatic pressure applied over the entire area. (4) The hydrostatic head shall be measured from the underside of Mohd Anuwarthe Simonconstruction. DCQ3043 Construction Technology 3 49

BASEMENT CONSTRUCTION OF EARTHWORK SUPPORT SYSTEM  When applying the principles of permanent embedded retaining walls, two common construction of earthwork support system, there are: 1. Bottom-up Construction 2. Top-down Construction

1. Bottom-up Construction  Figure shown the sequence of operation where the diaphragm walls formed using bentonite.  Retaining walls can from contiguous pile, secant pile and steel sheet pile. Mohd Anuwar Simon

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BASEMENT Bottom-up Construction (cont’d)

 First stage in this process is to form perimeter walls.  This will become the structural walls of the basement.  Bulk excavation then take place to the desired depth (lower level of basement).  The next stage is to form sub-structure such as foundation, column, basement floor up to super-structure as work proceeds.  Advantages using Bottom-up Construction Method are: a) Speed construction b) Save cost c) Stability of the ground around d) Reduce temporary supporting elements

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Sequence of operations for Bottom-up Construction Mohd Anuwar Simon

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BASEMENT Construction of basement using Bottom-up approach  Suitable for basement of small to medium size.

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BASEMENT The overall excavation and lateral support system for a typical large-scale basement construction project (with cut-off wall on the sides, lateral supporting frame and other temporary work stations/platform)

Excavation carried out using excavator and rock breaker within the work pit

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BASEMENT 2. Top-down Construction  Top-down construction attempts to make use of the perimeter elements of the construction works to provide rigidity and bracing against loadings from the ground.  Figure shown the sequence of operations for top-down construction.  First stage the formation of the permanent retaining walls to the perimeter of the basement area.  Retaining walls can from either contiguous pile, secant pile or diaphragm wall. Mohd Anuwar Simon

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BASEMENT Top-down Construction (cont’d)  Next stage is the creation of the foundation that will support the columns of the building structure at internal location.  These columns will provide intermediate support for the floors of the basement and the building superstructure as work proceeds.  In the most cases the foundations to these columns will take the form of CFA piles with columns attached using pile caps or increasingly in the case of steel framed buildings, using the ‘plunge’ method.  Excavation then take place to remove earth from beneath the slab through appropriate holes in the slab.  The process is then repeated until the base slab is reached. Mohd Anuwar Simon

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BASEMENT Construction of basement using Top-down approach.  Suitable for basement of very large size with complex environment.

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BASEMENT Removal of Soil  There will have great amount of excavated soil produced during the process of excavation.  Suitable planning for the removal of the excavated material should be made in advance in order not to cause disruption to work and incur extra costs. Soil removal can be done by the following ways. i. Using manual method, by wheel barrow. ii. Using bucket and lift to ground level by crane. iii. Using hoist rack (opening has to be provided in the basement/excavation pit first). iv. Using gantry crane (opening has to be provided in the basement/excavation pit first). v. Using conveyor belt vi. Using excavating machine to removal spoil, may be in stepped position in case of very deep pit. vii. Using dump truck but access provision has to be provided in advance (such as a temporary ramp or the permanent vehicular access into a basement)

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Remove spoil by steel bucket

Excavating machine to take up spoil from bottom

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Hoisting machine is provided for removing spoil from basement Mohd Anuwar Simon

Using of a gantry crane for spoil removal

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The use of a material hoist for the removal of spoil from the basement interior

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THANK YOU Mohd Anuwar Simon

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BASEMENT References: http://personal.cityu.edu.hk/~bswmwong/contents/ebook/construction_technology/2e.pdf – Excavation & Basement Construction http://www.cv.titech.ac.jp/~courses/atce2/Lesson5.pdf – Excavations and Excavation Supports http://ebooks.narotama.ac.id/files/Deep%20Excavation;%20Theory%20and%20Practice/Chapter%203%20%20Excavation%20Method s%20And%20Lateral%20Supporting%20Systems.pdf – Excavation Methods and Lateral Supporting System http://constructionduniya.blogspot.my/2012/02/top-down-construction.html – Top Down Construction Part 1 http://constructionduniya.blogspot.my/2012/05/structural-members-required-for-top.html – Top Down Construction Part 2 https://www.youtube.com/watch?v=9DBNLAJ-bxk – Video Botton Up Construction https://www.youtube.com/watch?v=vDvyOLD5n5w – Video Top Down Construction https://www.youtube.com/watch?v=jRgxiQSw48U – Video Top Down Construction https://www.youtube.com/watch?v=sboDavo84gc – Video Top Down Construction https://www.youtube.com/watch?v=wUlQyiHfex0 – Diaphragm wall construction https://www.youtube.com/watch?v=li6N6t09J-c – Diaphragm wall construction

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