Soil-water characteristic curve and permeability coefficient prediction model for unsaturated loess considering freeze-thaw and dry-wet

Abstract

The SWCC has played an important role in studying the physical-mechanical behavior and hydraulic property of unsaturated soils. Laboratory experiments of SWCC were performed on unsaturated loess based on filter paper method considering freeze-thaw cycle, coupling of freeze-thaw cycle and dry-wet action. The main results indicate that: (1) With the increase of freeze-thaw cycle or freeze-thaw and dry-wet coupling, the matric suction was logarithmically decreasing and the dry-wet path affected matric suction significantly. There were obvious hysteresis loops between the two SWCC curves of different dry-wet paths, which increased with the increase of water content. (2) The Gardner Model was more appropriate to describe the SWCC, and through measured SWCC from Gardner Model and Childs & Collis-George Model, the prediction model of unsaturated loess permeability coefficient was gained, which had an exponential relationship with matric suction and a power function relationship with volumetric water content, respectively. (3) The vertical distribution model of permeability coefficient under one-dimensional steady state flow was established. The vertical permeability coefficient gradually decreased from groundwater table to ground surface, it decreased first then increased and gradually stabilized with the increase of freeze-thaw cycle at the same depth of soil.