The document discusses the construction of diaphragm walls. Diaphragm walls are reinforced concrete walls constructed underground using an excavation technique that keeps the trench full of a bentonite slurry. They are commonly used for deep basements and where construction time is limited. The construction process involves excavating trenches in panels, installing stop ends between panels, placing reinforcement cages, and pouring concrete through a tremie pipe to displace the slurry. Proper installation and maintenance of the bentonite slurry is crucial to prevent trench collapse during excavation and concrete placement.

1. Construction of Diaphragm Wall
Presentation by:
Gagan Goswami
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2. Content
Introduction
Application
Category of Diaphragm Wall
Construction Procedure
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3. Introduction
Diaphragm Wall is generally reinforced
concrete wall constructed in the ground using
Underslurry 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 300 and 1200 mm
can be formed in this way up to a depths of 45
meters.
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4. Conceptual sketch showing
the RCC Diaphragm Wall
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5. Diaphragm wall-Application
Commonly used in congested areas
-Can be Installed in close proximity to
existing structure
Practically suited for deep basements
Used in conjunction with “Top Down”
construction technique
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6. Schematic section of Diaphragm
Wall showing typical use
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7. Schematic section of Diaphragm
Wall showing typical use
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8. Schematic section of Diaphragm
Wall showing typical use
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9. Schematic section of Diaphragm
Wall showing typical use
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10. Anchoring of Diaphragm Wall using
Anchor Slab
Anchor Slab
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11. Anchoring of Diaphragm Wall using
Anchor Blocks
Diaphragm Wall
Anchor Bars
Anchor Blocks
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12. Important Conditions
Dictate the use of Diaphragm Wall
Very unstable soil profiles below the water
table
Limited construction time
Where deeper than normal cantilever support
may be required
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13. Positive facades of Diaphragm
Wall
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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14. Negative Facades of
Diaphragm Wall
Not economical for small, shallow Basements
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15. Category of Diaphragm wall
1) In Situ Cement Bentonite Vertical Wall
2) In Situ RCC Vertical Wall
3) Precast RCC Vertical Wall
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16. In Situ Cement Bentonite
Vertical Wall
Provides water tight barrier
Used to prevent seepage/water loss from
Natural reservoir and Dams
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17. In Situ RCC Vertical Wall
Underground Structural element
Used for Retention systems and Permanent
foundation walls
Deep groundwater barriers
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18. Procedure
Diaphragm Wall construction begins with
the trench being excavated in
discontinuous sections or “panels”.
Stop-ends are placed vertically at each end
of primary panel to form joints for
adjacent secondary panel or closing
panels. Panels are usually 4 to 6 meters
long. Stop-ends are used to form the joints
between adjacent panels and a water bar
can be incorporated across these joints.
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19. Construction Method
Secondary Primary Secondary Secondary Secondary Closing Secondary
Construction Joint formed by
Construction Joint
Circular Stopend Pipe
Schematic Diagram Showing Construction Joint between Adjucent Panels
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20. Construction Method
Secondary Primary Secondary Secondary Secondary Closing Secondary
Construction Joint formed by Construction Joint
Flat Stop end
Schematic Diagram Showing Construction Joint between Adjucent Panels
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21. Different Shapes of Diaphragm
Wall Panel
T-Shape Panel L-Shape Panel
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22. Different stages of construction
activities
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23. Diaphragm Wall Construction Site
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24. 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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25. Guide Wall Construction
Guide Wall
is constructed
to fix the
alignment of
Diaphragm Wall
in the field
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26. Guide Wall Construction
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27. Trenching Equipments
Hydraulic Grab
Kelly-mounted or Cable-hung cam buckets
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28. Kelly-mounted Hydraulic Grab
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29. Cable-hung cam bucket
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30. Trenching Process
Trenching usually carried out under
bentonite slurry
Bentonite Slurry – Key component.
-This Slurry acts as shoring to prevent
collapse by hydraulic pressure and
thyrotrophic property.
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31. Bentonite Slurry
Used as a support fluid
The bentonite suspension used in bore holes
is basically a clay of montmorillonite group
having exchangeable sodium cations (Na+).
The action of bentonite in stabilizing the
sides of bore holes is primarily due to the
thixotropic property of bentonite
suspension.
The bentonite suspension when undisturbed
forms a jelly which when agitated becomes a
fluid again.
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32. Functions of Bentonite
In case of granular soils, the bentonite
suspension penetrates into the sides under
positive pressure and after a while forms a
jelly.
The bentonite suspension gets deposited on
the sides of the hole resulting in the
formation of a filter cake in contact with
soil against which the fluid pressure acts.
In case of impervious clay, the bentonite
does not penetrate into the soil, but
deposits only a thin film on the surface of
the hole.
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33. Factors affecting stability
of Trench
Level of the supporting fluid
-Level of the bentonite slurry should be
maintained preferably at least 1.5m above the
ground water level to avoid problem of
instability.
Density and Viscosity of supporting fluid
Loss of shear strength with time
Suction effect during trenching
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34. 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 by
Marsh cone
Swelling index: Swelling index at least 2 times
of dry volume.
pH value : Less than 11.5
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35. Tests and compliance values for support fluid
prepared from bentonite
(as per IS9556-1980)
Property Test method As Before
supplied concret
to the ing
bore
Density Mud balance 1.04- <1.15g/
1.10g/m ml
l
Viscosity Marsh cone 30 - 90
seconds
Shear Shearometer / 1.4 to 10
strength Vane shear N/sq.m
apparatus
pH Digital pH 9.5-12
meter 35

36. Schematic Diagram of
Bentonite Setup
•Storage tanks
Settling Circulation Fresh
T3 T2 T1
Mixer
•Mud
Pump
Diaphragm Wall Construction area
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37. Bentonite Setup
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38. Preparation of Bentonite Slurry
Bentonite slurry made by passing dry powder
through water jet. A conical hopper is used
with bottom nozzle through which water is
pumped under pressure. The bentonite powder
is poured directly from top and when it falls
down the hopper, it gets agitated in the water.
After getting circulated, the mixed bentonite
thus falls in the tank.
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39. Trench Cleaning
Joints of adjacent panels to be cleaned to
obtain watertight bond
Loose materials to be lifted by suitable air
lifting method
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40. Fixing of Stop ends
Stop ends to be fixed at the proper
position keeping it truly vertical
Distance between two Stop ends to be
fixed as per prefixed Panel Layout
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41. Reinforcement Cage
Excavation of panel is followed by placing of
steel reinforcement cage in center of the
panel.
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42. Reinforcement Cage fabrication
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43. Reinforcement Cage shifting
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44. Lowering of reinforcement cage
in the excavated panel
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45. Lowering of reinforcement cage
in the excavated panel
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46. Resting of reinforcement cage
in the excavated panel
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47. Different stages of construction
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48. Placing of Concrete
Placing of concrete having slump 150mm to
190mm by tremmie method
Concrete to be placed through a top metal hopper
and into a rigid leak proof tremmie pipe (2 sets),
sufficiently large enough to permit free flow of
concrete.
Initially there should be a suitable plug at the
bottom of metal hopper, which will not discharge
concrete until sufficient concrete accumulate in
the metal hopper.
concrete displaces the slurry from bottom and
rises in such a manner that mixing of concrete
with slurry does not occurs
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49. Placing Concrete
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50. Placing of Concrete
Pouring shall be continued till it
accumulates in vertical Tremmie pipe up
to top of funnel.
Tremmie pipe shall be raised so as to
release the concrete in a single continuous
flow.
Concrete to be discharged in the trench
without any lateral movement of Tremmie
pipe.
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51. Placing of Concrete
Caution - Bottom end of Tremmie pipe
must remains immersed in concrete.
Operation to be continued till good
concrete reaches 300mm above the
cut-off level of Diaphragm Wall.
This concrete above cut-off shall be
removed when green Chipping of concrete
is not to be permitted.
Length of Tremmie pipe shall be reduced
by removal of Tremmie segment stage by
stage. 51

52. Withdrawal of Stop ends
Withdrawal of Stop ends just after the
Initial setting of concrete.
If retarders are not added, Stop End Pipes
shall be moved up & down not later than
45 minutes from the time of placing of
concrete.
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53. Thank You
If any Query please mail me-
gagangoswami@yahoo.co.in
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