In cases where the ground is friable, sandy, or in the presence of groundwater, the self-sinking shoring is used: a 1.25 m pre-trench is dug and the pre-assembled box is lowered into the excavation. During this stage, the workers must not be in the pit. The excavator bucket is used to alternately press on the panels on the two sides of the box. The operation is repeated until the bottom of the pit is reached.

photo Midweight self-sinking MA System