Barrier effect of adjacent deep-buried metro station and its influence on ground settlement induced by foundation pit dewatering

The existing underground structure blocks groundwater seepage (i.e., water-blocking (WB) effect) and restricts surrounding soil movement (i.e., soil-blocking (SB) effect). This leads to differences in the dewatering-induced behaviors of groundwater and strata compared to scenarios without nearby structures. In this study, a typical metro station was chosen as the nearby underground structure that impedes groundwater and soil flow. Three-dimensional hydro-mechanical numerical models were developed based on an actual foundation pit pumping test to analyze the dewatering-induced responses of groundwater and strata under different WB and SB effects. Factors such as the relative location of the metro station to the excavation, the buried depth of the station structure, and the dewatering depth in the model were considered. The results indicate that the presence of a metro station near the excavation site can either aggravate or restrict dewatering-induced ground settlement, depending on the strength of the SB and WB effects. The distance D between the excavation and the metro station determines the relatively strength of the SB and WB effects, thereby influencing whether the ground settlement is aggravated or restricted. On the other hand, the buried depth H of the station only singularly affects the intensity of the WB or SB effect and could not determine which barrier effect plays the dominant role. In practical engineering applications, it is essential to consider both WB and SB effects based on the proximity and buried depth of the adjacent station structure to effectively assess the dewatering-induced behaviors of groundwater and strata.