ABSTRACT

Groundwater will flow under gravity towards drains, ditches, wells, etc. in soils with permeability k>5×10−5 m/s. In fine-grained, less permeable soils, the gravity flow is much reduced, and measures to deal with pore-water pressure and improve flow (e.g. vacuum wells and pre-loading) are required to ensure stability of excavations. Provided the drainage path is controlled, simple gravity drainage is a cost-effective measure which does not always require specialist dewatering design.