Diaphragm Walls

A diaphragm wall could be categories either as a reinforced concrete wall or sheet pile wall. That consists of a vertical concrete reinforced concrete slab fixed in position. It is held in position through the passive and active pressures acting on its lower portion.

A diaphragm wall is constructed through a machine digging a trench in panels of limited length filled along with the bentonite slurry as the digging proceeds to the needed depth. In clays there is no penetration of bentonite slurry within the soil. But in sands and silts, bentonite slurry initially penetrates into the soil and forms a virtually impervious skin of bentonite particles, just a few mm thick, on the sides of the trench. The lateral pressure created through slurry acts on the sides of the short trench panel and avoids its collapse. The required steel reinforcement is lowered into position while excavation is complete. The trench is then filled with concrete through means of a tremie pipe, the displaced slurry being collected for cleaning and further use.

A wall is constructed in on the other hands short panel lengths. While the concrete has developed enough strength, the remaining intermediate panels are excavated and constructed to complete the walls.