Lowering water level in an excavation for a multi-family residential building in urban development

The paper concerns lowering water level in excavations for residential buildings in a dense urban development. The construction and protection of excavation walls as well as the methods of lowering the water level and its impact on the surroundings were discussed. An excavation dewatering system is presented on the example of a multi-family residential building with one underground floor, built in dense urban development. The excavation executed in the sandy subsoil below the groundwater level and encased with walls made of steel sheet piles was analysed. Two concepts of lowering the water level in the excavation were considered: the first with use of a wellpoint system, the second with use of a well with pumps. The conducted calculations showed that when using a wellpoint system to lower the water level in the excavation for analysed multi-family residential building, a system consisting of 260 wellpoints with a spacing of 1.0 m should be made. The efficiency of a single wellpoint is 12.25 m3•d–1, and the efficiency of the entire installation is 3,185.69 m3•d–1. When draining the wells, a system consisting of 9 wells should be made, with a unit capacity of 375.58 m3•d–1 and efficiency of the total installation 3,380.22 m³•d⁻¹.