Construction of Diaphragm Wall Presentation by: Gagan Goswami 1 - - PowerPoint PPT Presentation

1

Construction of Diaphragm Wall

Presentation by: Gagan Goswami

2

Content

 Introduction  Application  Category of Diaphragm Wall  Construction Procedure

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

• f slurry.

Walls of thickness between 300 and 1200 mm can be formed in this way up to a depths of 45 meters.

4

Conceptual sketch showing the RCC Diaphragm Wall

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

6

Schematic section of Diaphragm Wall showing typical use

7

Schematic section of Diaphragm Wall showing typical use

8

Schematic section of Diaphragm Wall showing typical use

9

Schematic section of Diaphragm Wall showing typical use

10

Anchoring of Diaphragm Wall using Anchor Slab

Anchor Slab

11

Anchoring of Diaphragm Wall using Anchor Blocks

Diaphragm Wall Anchor Bars Anchor Blocks

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

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.

14

Negative Facades of Diaphragm Wall

 Not economical for small, shallow Basements

15

Category of Diaphragm wall

1)

In Situ Cement Bentonite Vertical Wall

2)

In Situ RCC Vertical Wall

3)

Precast RCC Vertical Wall

16

In Situ Cement Bentonite Vertical Wall



Provides water tight barrier



Used to prevent seepage/water loss from Natural reservoir and Dams

17

In Situ RCC Vertical Wall



Underground Structural element



Used for Retention systems and Permanent foundation walls



Deep groundwater barriers

18

Procedure

Diaphragm Wall construction begins with the trench being excavated in discontinuous sections or “panels”. Stop-ends are placed vertically at each end

• f

primary panel to form joints for adjacent secondary panel

• r

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.

19

Construction Method

S e co n d a ry P rim a ry

C

• n

stru ctio n Jo in t fo rm e d b y C ircu la r Sto p e n d P ip e C

• n

stru ctio n Jo in t

S c h e m a tic D ia g ra m S h

• w

in g C

• n

stru c tio n J

• in

t b e tw e e n A d ju c e n t P a n e ls S e co n d a ry S e co n d a ry S e co n d a ry C lo sin g S e co n d a ry

20

Construction Method

P rim a ry

C

• n

stru ctio n Jo in t fo rm e d b y F la t Sto p e n d C

• n

stru ctio n Jo in t

S e co n d a ry S e co n d a ry S e co n d a ry S e co n d a ry C lo sin g S e co n d a ry S c h e m a tic D ia gra m S h

• w

in g C

• n

stru c tio n J

• in

t b e tw e e n A d ju c e n t P a n e ls

21

Different Shapes of Diaphragm Wall Panel

L-Shape Panel T-Shape Panel

22

Different stages of construction activities

23

Diaphragm Wall Construction Site

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

25

Guide Wall Construction

Guide Wall is constructed to fix the alignment of Diaphragm Wall in the field

26

Guide Wall Construction

27

Trenching Equipments



Hydraulic Grab



Kelly-mounted or Cable-hung cam buckets

28

Kelly-mounted Hydraulic Grab

29

Cable-hung cam bucket

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.

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

• f

bentonite suspension.



The bentonite suspension when undisturbed forms a jelly which when agitated becomes a fluid again.

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.

33

Factors affecting stability

• f Trench



Level of the supporting fluid

• Level
• f

the bentonite slurry should be maintained preferably at least 1.5m above the ground water level to avoid problem

• f

instability.



Density and Viscosity of supporting fluid



Loss of shear strength with time



Suction effect during trenching

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

• f dry volume.



pH value : Less than 11.5

35

Tests and compliance values for support fluid prepared from bentonite (as per IS9556-1980)

Property Test method As supplied to the bore Before concreting Density Mud balance 1.04- 1.10g/ml <1.15g/ml Viscosity Marsh cone 30 - 90 seconds Shear strength Shearometer / Vane shear apparatus 1.4 to 10 N/sq.m pH Digital pH meter 9.5-12

36

Schematic Diagram of Bentonite Setup

T1 T2 T3

• Mud

Pump Diaphragm Wall Construction area

• Storage tanks

Fresh Circulation Settling

Mixer

37

Bentonite Setup

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.

39

Trench Cleaning



Joints of adjacent panels to be cleaned to

• btain watertight bond



Loose materials to be lifted by suitable air lifting method

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

41

Reinforcement Cage

Excavation of panel is followed by placing of steel reinforcement cage in center of the panel.

42

Reinforcement Cage fabrication

43

Reinforcement Cage shifting

44

Lowering of reinforcement cage in the excavated panel

45

Resting of reinforcement cage in the excavated panel

46

Different stages of construction

47

Placing of Concrete



Placing

• f

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

48

Placing Concrete

49

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.

50

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

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.

Contact Details

 Gagan Goswami  Cell-+919662506595

Address-

 HERITAGE INFRASPACE INDIA PVT. LTD  F-36,Sukh Shine,  Opposite to Himalaya Mall  Drive In Road, Ahmadabad, Gujarat ,India

E mail- info@diaphragmwallconstruction.com,gagangoswami@yahoo.co.in Website- www.diaphragmwallconstruction.com

52