Considering the changes in unsaturated soil saturation after pipeline leakage: A modified Terzaghi model

Pipeline leakage leads to the saturation and weakening of the surrounding soil, increasing the pressure exerted by the overlying soil on underground engineering structures and posing a serious threat. Therefore, it is necessary to thoroughly understand the influence of pipeline leakage on the overlying soil pressure. Based on the saturation distribution within different diffusion ranges, an analysis model for pressure in loose soil under the influence of pipeline leakage was presented. Considering the variation in the matric suction of the unsaturated soil, the soil pressure can be modeled based on the incomplete arch effect. The influence of the relevant parameters on the overlying soil pressure was analyzed, and the accuracy and rationality of the modified model were verified using a trapdoor test. These findings indicate that the modified model can accurately estimate the soil pressure caused by a pipeline leakage. The overlying soil pressure is directly proportional to the diffusion distance, tunnel width, and slip surface inclination angle and inversely proportional to the relative deformation. The rate of change was mainly influenced by the parameters affecting the soil arching effect. The modified model presented in this study can be used to directly calculate the overlying soil pressure affected by pipeline leakage. This calculation is based on the known physical and mechanical parameters of unsaturated soil, pipeline leakage range, and relative deformation of the tunnel, thus providing a theoretical basis for the design of structures under urban pipelines.