Experimental and numerical study on water and sand leakage of foundation pit in water-rich sandy soil with different grain size distribution

In the area of water-rich sandy soil, the disaster of water and sand leakage (WSL) is easy to occur in foundation pit engineering, which leads to disaster such as surface collapse. Grain size and composition affect the disaster degree of WSL. In order to study the WSL in foundation pit of water-rich sandy soil with different grain size distribution, three groups of samples with different grain size distribution are prepared according to the median particle size (d50). A visual experimental device is designed to simulate the process of WSL after defect appears at the water-stop curtain and DEM-CFD coupling method is used to simulate the experimental process to explore the influence of different grain size distribution on time, morphology and process of WSL. Results show that: (1) The WSL process of foundation pit can be divided into three stages: the extension period, the stabilization period and the mutation period. (2) As the content of coarse particles increases, the sandy soil is more likely to form soil arch. (3) In terms of the WSL erosion range, Soil A with mostly coarse particles < Soil B with uniform particles < Soil C with mostly fine particles.