Souterrain The Hague: clogging of groundwater wells above a gel layer during construction of an underground tram station

An injected silicate gel-layer (soft-gel) was used to reduce water inflow into the building pit of the Station Spui in the Souterrain in The Hague. Excessive clogging of wells which hindered dewatering is explained by chemical processes originating from the gel-layer. Chemical and mechanical counter-measures are considered. The final testing, design, installation and performance of a successful dewatering system by means of gravel piles are described.