Effect of volume changes on soil-water characteristics of unsaturated expansive soil

The effects of deformation on soil-water characteristics of expansive soils were investigated.A series of Soil-Water-Characteristic Curve tests were carried out for the Jingmen compacted expansive soil along the main drying paths.Values of gravimetric water content and volume changes of soil samples at different levels of suction were measured for five different initial void ratio samples.The test results show that the gravimetric water content-suction curves intersect and merge,while the volumetric water content-suction curves display intersections more remarkably.However,the degree of saturation-suction curves do not intersect,indicating that the soil sample of the larger initial void ratio remains the lower degree of saturation under the same suction.These phenomena reflect coupling effects between the soil-water characteristics and the volume change behavior for expansive soils.Based on the test results,three formulas are presented for predicting the gravimetric water content,void ratio and degree of saturation along the main drying paths of the expansive soil,respectively.These formulas rely on the volume-mass relationship and are defined in a unified framework as functions of suction and initial void ratio.Finally,the comparison between the measured and reproduced results validates the presented formulas.