Study on wetting-induced collapsibility of loess at tight sandstone gas well station in Lüliang

Mercury intrusion porosimetry (MIP) and scanning election microscopy (SEM) tests are conducted on undisturbed and collapsed loess samples from the tight sandstone gas well station site in Lüliang. By comparing the test results before and after wetting-induced collapse, significant changes in pore size distribution and particle morphology are observed, leading to variations in the hydraulic and mechanical properties of unsaturated soil mechanics principles and the microstructural changes during wetting, this study attributes the abrupt strength reduction of site loess during collapse primarily to the loss of matric suction upon water immersion. With prolonged wetting, the bridging effect within aggregated clay particles gradually diminishes, and chemical cementing agents (e.g., calcium oxide and organic matter) dissolve over time. Using factor analysis, the correlations among various physical indexes of loess are investigated, and a multiple regression equation is proposed to rapidly predict the collapsibility coefficient using void ration, degree of saturation, and water content, based on the cumulative variance contribution rate. The model predictions agree well with experimental data, providing a convenient toll for rapid prediction in engineering practice.