Numerical analysis of internal erosion during negative pressure penetration of suction caisson foundations

Suction caissons are initially installed into the seabed through self-weight penetration, after which pumping is applied to generate suction within the caisson to facilitate further installation; however, the seepage induced by suction can cause internal erosion, thereby altering the soil permeability characteristics. This study develops a finite element model for internal erosion to simulate the coupled seepage-erosion process, with the model's validity verified through comparison with experimental data from soil column tests. A finite element model of suction caisson installation is finally established, and the results show that: (1) Internal erosion can alleviate the concentration of high hydraulic gradients within the caisson, manifested by the average hydraulic gradient along the inner caisson wall decreasing rapidly with time during the initial stage before stabilizing; (2) The porosity distribution shows that erosion predominantly occurs in the region inside the caisson, particularly at the caisson skirt tip, where the differential erosion of soil inside and outside the caisson leads to a redistribution of the seepage field and a reduction in local hydraulic gradients along the caisson wall.