This section answers the following questions related to the construction of diaphragm walls :
1. Why adopt Diaphragm walls ?
2. When to adopt Diaphragm walls?
3. Where to adopt Diaphragm walls ?
4. How to construct Diaphragm walls ?

For deep excavations (esp. depth > 7.50 m) across soil types, as compared to all types of piles and coffers, Diaphragm walls are :

1. The cheapest to build;

2. The quickest to build;

3. The most rigid;

4. The most water-tight;

5. Require less embedment;

6. The most durable

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WHEN ?

Diaphragm walls are the optimal construction solutions to when the following risks dominate in the project :

1. Ground movement;

2. Liquefaction;

3. High water table;

4. Maximize space utility;

5. Low soil bearing capacity;

6. Mission critical schedule : Top Down construction;

7. Dimensional, alignment and surface finish tolerances;

8. Terrorism and Progressive collapse

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Specifically, the use of Diaphragm walls is most suitable when :

1. Retaining wall surface area > 1500 m2;

2. SPT value of soil >20;

3. Unconfined compressive strength of soil/rock > 30 MPa;

4. No further finishing is planned on the wall surface;

5. Soil types are saturated fines, stiff clays and all types of rock outcrops;

6. Vertical tolerances of 1:400 or better is required.

WHERE ?

Slurry Walls can be categorized into two different types: Structural, and Non-structural.

Structural (Diaphragm Wall) 

For a structural diaphragm wall, slurry is replaced with concrete and some type of reinforcement for resisting structural loads. Structural Diaphragm Walls are used as:

• Deep Basement Walls for buildings, parking garages;

• Permanent Retaining Walls;

• Rigid Earth Retention System for Deep Excavation Support;

• Circular Tunnel Access Shafts;

• Top-Down building construction methods;

• Load Bearing Elements (Barrettes);

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Non Structural (Slurry Wall / Cutoff Wall) 

For a non structural slurry wall, slurry is left in place to self harden or replaced with plastic (or low strength) concrete. Non Structural Slurry Walls are used as:

• Groundwater Cutoff Walls;

• Environmental Cutoff Walls;

• Ground Improvement Systems;

• Contaminant Cutoff Walls;

• Dam and Levee Rehabilitation