All subsoils have different abilities in remaining stable during excavation works. most will assume a natural angle of repose or rest unless given temporary support. the presence of ground water apart from creating difficult working conditions can have an adverse effect on the subsoil's natural angle of repose

Typical  angles of repose:

Excavations cut to a natural angle of repose are called battered: drained clay 45o, wet clay 16o, gravel&dry sand 40o, wet sand 22o

Time factors such as period during which excavation will remain open and the time of year when work is carried out

The need for an assessment of risk with regard to the support of excavations and protection of people within