Prediction of Permeability Coefficient of Unsaturated Loess in Dry-Wet Cycle based on Thermodynamics and Microstructure Evolution Law

Abstract

soil-water characteristic curve describes the relationship between matrix suction and soil saturation (or water content). It affects the shear strength, deformation and seepage behavior of unsaturated soil, and is a very important research content in unsaturated soil mechanics. Based on the internal variable theory of thermodynamics, a soil-water characteristic curve model is proposed, which can comprehensively consider the capillary hysteresis effect and the influence of unsaturated soil volume deformation. Based on the evolution law of microstructure, the moisture distribution in loess under natural humidity was analyzed, and the relationship among pore fractal dimension, unsaturated pore porosity and collapsibility was analyzed by regression analysis. The results show that the larger the pore fractal dimension is, the more complex the pore structure is. The collapsibility coefficient of loess increases with the increase of pore fractal dimension and unsaturated pore porosity, which is the main cause of loess collapsibility. By comparing with the existing test results, it is shown that the model can well predict the change of scanning line of soil in different processes of drying and wetting.