Diaphragm walls, also known as D-walls, are rigid reinforced concrete walls built in the ground. They are built before major excavation can start and are made up of several panels joined together to form a single continuous wall.

The walls are built panel by panel, with each interlocked to ensure they are structurally stable and watertight. Each panel is a massive 6.4m wide, 1.2m thick, and range from 19m to 50m deep into the ground.

There are many advantages to using D-walls over other excavation methods. D-walls are watertight, can be built next to existing structures, and are ideal for deep excavation.