Soil-water and shear strength characteristics of unsaturated red clay

In order to study the unsaturated characteristics of red clay, Geo-experts self-balanced pressure plate meter and ZJ direct shear apparatus were used in experiments to investigate the soil-water and shear strength characteristics of the typical undisturbed and remolded red clays under different dry densities. Based on the experimental results, the physical and mechanical features of unsaturated red clay were discussed. The results show that mineral composition and micro-structural changes may be the major factors accounting for the difference between physical and mechanical properties of the undisturbed and remolded red clay. The soil-water characteristics curve of undisturbed unsaturated red clay show three stages, which has the obvious air-entry values and residual moisture content, while the soil-water characteristics curve of remodeled unsaturated clay presents a semi-parabolic variation. For the undisturbed red clay, the maximum cohesion occurs in a low moisture condition, and the corresponding moisture content is about 5% to 10% larger than the residual moisture content. Thus, in this case, increasing the number of test groups can optimize the test results. For the remolded red clay, the range of the significantly reduced internal friction angle can be determined according to the plastic limit.