Precipitation method for excavation of foundation pit at collapsible loess region

The invention discloses a precipitation method for the excavation of a foundation pit at a collapsible loess region, which concretely comprises the following steps that: a hanging type waterproof curtain (6) is constructed at a water-containing soil layer (2) of a field area after the construction of an enclosure structure (7) of a foundation pit (8) at the field area, which is to be excavated, is finished; afterwards, a precipitation well (9) is arranged in the foundation pit (8); and meanwhile, a recharge well (5) is arranged between the foundation pit (8) and a peripheral building (4). In the process of excavation of the foundation pit, the water level is lowered to a designed elevation by using the precipitation well (9). Meanwhile, the operation of recharge is carried out by utilizing the recharge well (5). The technical scheme provided by the invention not only can meet the requirement of precipitation in the excavation of a foundation pit at a collapsible loess region but also can be used for preventing the overlarge sedimentation of a soil mass at the periphery of the foundation pit, which is caused by precipitation, better protecting the safety of a building at the periphery of the foundation pit, farthest saving water resources and lowering the engineering cost.