Mechanism of the piping phenomenon in a granite residual soil foundation pit

In the construction of a subway foundation pit in a granite stratum, soil gushing in the foundation pit and a large settlement of the surrounding strata can occur. To explore the mechanism and treatment methods, in this study, seepage tests and numerical simulations of the granite residual soil were conducted. The results showed that the main reason for foundation settlement was that the residual soil pipes weakened under a large hydraulic slope. According to the research conclusion, a method of controlled pumping of foundation pits was proposed, and subsequent construction achieved good results.