Abstract: Along with increase of design of underground structures with large size, the difficulties of deep foundation pit excavation and dewatering are increased. In the 2×1000MW aircooled unit of Huadian Ningxia Lingwu Power Generation Company Limited project phase II, the depth of the foundation pit of wagon tipper room is about -16.00m. In the foundation pit dewatering construction for this area, the annular tube well dewatering technology was adopted. After the implementation of the dewatering construction, the ground water level is lowered obviously; and the consolidation of the soil body of excavated foundation pit was favorable and can satisfy the design requirement. The implementation of this technology provides some experiences for structure foundation pit dewatering in soft soil area with larger pit depth, rich ground water and higher ground water level.

Key words: soft soil, foundation pit of structures, simple hydrology test, ground water level, multi-stage dewatering, tubular well