Diaphragm Wall Presentation
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1 Construction of Diaphragm Wall Presentation by: Gagan Goswami
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Diaphragm Wall is generally reinforced concrete wall constructed in the ground using Under slurry technique which was developed in Europe.The technique involves excavating a narrow trench that is kept full of an engineered fluid of slurry.Walls of thickness between 600 and 1200 mm can be formed in this way up to a depths of 45 meters.
Transcript of Diaphragm Wall Presentation
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Construction of Diaphragm Wall
Presentation by:
Gagan Goswami
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Content
Introduction
Application
Category of Diaphragm Wall
Construction Procedure
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IntroductionDiaphragm Wall is generally reinforcedconcrete wall constructed in the ground usingUnderslurry technique which was developed inEurope.
The technique involves excavating a narrowtrench that is kept full of an engineered fluidof slurry.
Walls of thickness between 300 and 1200 mmcan be formed in this way up to a depths of 45meters.
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Conceptual sketch showingthe RCC Diaphragm Wall
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Diaphragm wall-Application Commonly used in congested areas
-Can be Installed in close proximity toexisting structure
Practically suited for deep basements Used in conjunction with “Top Down”
construction technique
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Schematic section of DiaphragmWall showing typical use
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Schematic section of DiaphragmWall showing typical use
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Schematic section of DiaphragmWall showing typical use
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Schematic section of DiaphragmWall showing typical use
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Anchoring of Diaphragm Wall usingAnchor Slab
Anchor Slab
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Anchoring of Diaphragm Wall usingAnchor Blocks
Diaphragm Wall
Anchor Bars
Anchor Blocks
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Important ConditionsDictate the use of Diaphragm Wall
Very unstable soil profiles below the watertable
Limited construction time Where deeper than normal cantilever support
may be required
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Positive facades of DiaphragmWall
Can be Installed to considerable depth Formation of walls with substantial thickness Flexible system in plan layout Easily incorporated into Permanent works Designable to carry vertical loads Construction time of Basement can be lowered
considerably. Economic and Positive solution for large deep
basement in saturated and unstable soil profiles. Can be used for seepage control in Dams. Noise levels limited to engine noise only. No vibration during installation.
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Negative Facades ofDiaphragm Wall
Not economical for small, shallow Basements
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Category of Diaphragm wall
1) In Situ Cement Bentonite Vertical Wall2) In Situ RCC Vertical Wall3) Precast RCC Vertical Wall
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In Situ Cement BentoniteVertical Wall
Provides water tight barrier Used to prevent seepage/water loss from
Natural reservoir and Dams
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In Situ RCC Vertical Wall
Underground Structural element Used for Retention systems and Permanent
foundation walls Deep groundwater barriers
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Procedure
Diaphragm Wall construction begins withthe trench being excavated indiscontinuous sections or “panels”.Stop-ends are placed vertically at each endof primary panel to form joints foradjacent secondary panel or closingpanels. Panels are usually 4 to 6 meterslong. Stop-ends are used to form the jointsbetween adjacent panels and a water barcan be incorporated across these joints.
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Construction Method
Secondary Primary
Construction Joint formed byCircular Stopend Pipe
Construction Joint
Schematic Diagram Showing Construction Joint between Adjucent Panels
Secondary Secondary Secondary Closing Secondary
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Construction Method
Primary
Construction Joint formed byFlat Stop end
Construction Joint
Secondary Secondary Secondary Secondary Closing Secondary
Schematic Diagram Showing Construction Joint between Adjucent Panels
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Different Shapes of DiaphragmWall Panel
L-Shape PanelT-Shape Panel
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Different stages of constructionactivities
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Diaphragm Wall Construction Site
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Construction Procedure
Stage-1: Fixing of Alignment Stage-2: Guide wall Construction Stage-3: Trenching Stage-4: Trench Cleaning Stage-5: Stop ends fixing Stage-6: Reinforcement Cage lowering Stage-7: Placing of Concrete Stage-8: Withdrawal of Stop ends
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Guide Wall Construction
Guide Wallis constructed
to fix thealignment of
Diaphragm Wallin the field
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Guide Wall Construction
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Trenching Equipments
Hydraulic Grab Kelly-mounted or Cable-hung cam buckets
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Kelly-mounted Hydraulic Grab
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Cable-hung cam bucket
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Trenching Process
Trenching usually carried out underbentonite slurry
Bentonite Slurry – Key component.-This Slurry acts as shoring to preventcollapse by hydraulic pressure andthyrotrophic property.
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Bentonite Slurry
Used as a support fluid The bentonite suspension used in bore holes
is basically a clay of montmorillonite grouphaving exchangeable sodium cations (Na+).
The action of bentonite in stabilizing thesides of bore holes is primarily due to thethixotropic property of bentonitesuspension.
The bentonite suspension when undisturbedforms a jelly which when agitated becomes afluid again.
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Functions of Bentonite
In case of granular soils, the bentonitesuspension penetrates into the sides underpositive pressure and after a while forms ajelly.
The bentonite suspension gets deposited onthe sides of the hole resulting in theformation of a filter cake in contact withsoil against which the fluid pressure acts.
In case of impervious clay, the bentonitedoes not penetrate into the soil, butdeposits only a thin film on the surface ofthe hole.
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Factors affecting stabilityof Trench
Level of the supporting fluid-Level of the bentonite slurry should bemaintained preferably at least 1.5m above theground water level to avoid problem ofinstability.
Density and Viscosity of supporting fluid Loss of shear strength with time Suction effect during trenching
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Specification of Bentonite(as per IS:2911-Part1:Sec2) Liquid limit : 300 to 450 % (in accordance
with IS:2720-part V )
Sand content : Less than 7 %
Density: 1.12
Marsh viscosity : About 37 second, tested byMarsh cone
Swelling index: Swelling index at least 2 timesof dry volume.
pH value : Less than 11.5
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Tests and compliance values for support fluidprepared from bentonite
(as per IS9556-1980)Property Test method As supplied
to the boreBefore
concreting
Density Mud balance 1.04-1.10g/ml
<1.15g/ml
Viscosity Marsh cone 30 - 90seconds
Shearstrength
Shearometer /Vane shearapparatus
1.4 to 10N/sq.m
pH Digital pH meter 9.5-12
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Schematic Diagram ofBentonite Setup
T1T2T3
•MudPump
Diaphragm Wall Construction area
•Storage tanks
FreshCirculationSettling
Mixer
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Bentonite Setup
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Preparation of Bentonite Slurry
Bentonite slurry made by passing dry powderthrough water jet. A conical hopper is usedwith bottom nozzle through which water ispumped under pressure. The bentonite powderis poured directly from top and when it fallsdown the hopper, it gets agitated in the water.After getting circulated, the mixed bentonitethus falls in the tank.
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Trench Cleaning
Joints of adjacent panels to be cleaned toobtain watertight bond
Loose materials to be lifted by suitable airlifting method
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Fixing of Stop ends
Stop ends to be fixed at the properposition keeping it truly vertical
Distance between two Stop ends to befixed as per prefixed Panel Layout
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Reinforcement Cage
Excavation of panel is followed by placing ofsteel reinforcement cage in center of thepanel.
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Reinforcement Cage fabrication
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Reinforcement Cage shifting
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Lowering of reinforcement cagein the excavated panel
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Resting of reinforcement cagein the excavated panel
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Different stages of construction
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Placing of Concrete
Placing of concrete having slump 150mm to190mm by tremmie method
Concrete to be placed through a top metal hopperand into a rigid leak proof tremmie pipe (2 sets),sufficiently large enough to permit free flow ofconcrete.
Initially there should be a suitable plug at thebottom of metal hopper, which will not dischargeconcrete until sufficient concrete accumulate inthe metal hopper.
concrete displaces the slurry from bottom andrises in such a manner that mixing of concretewith slurry does not occurs
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Placing Concrete
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Placing of Concrete
Pouring shall be continued till itaccumulates in vertical Tremmie pipe upto top of funnel.
Tremmie pipe shall be raised so as torelease the concrete in a single continuousflow.
Concrete to be discharged in the trenchwithout any lateral movement of Tremmiepipe.
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Placing of Concrete
Caution - Bottom end of Tremmie pipemust remains immersed in concrete.
Operation to be continued till goodconcrete reaches 300mm above thecut-off level of Diaphragm Wall.
This concrete above cut-off shall beremoved when green Chipping of concreteis not to be permitted.
Length of Tremmie pipe shall be reducedby removal of Tremmie segment stage bystage.
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Withdrawal of Stop ends
Withdrawal of Stop ends just after theInitial setting of concrete.
If retarders are not added, Stop End Pipesshall be moved up & down not later than45 minutes from the time of placing ofconcrete.
Contact Details
Gagan Goswami Cell-+919662506595Address- HERITAGE INFRASPACE INDIA PVT. LTD F-36,Sukh Shine, Opposite to Himalaya Mall Drive In Road, Ahmadabad, Gujarat ,India
E mail- [email protected],[email protected]
Website- www.diaphragmwallconstruction.com
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