Static and Dynamic Behavior of Hydro-Collapsible Soils

摘要

Collapsible soils, whether engineered or naturally occurring, may exist in seismic zones. This study focuses on the evaluation of the shear strength and volume change of collapsible soils subjected to static and dynamic shear loading under a range of confining pressures and wetting conditions which ranged from "as-prepared" to soaked to backpressure saturated. Tests are conducted on reconstituted samples simulating compacted engineered fill and natural density samples. Prior to shear loading (whether static or dynamic), triaxial response-to-wetting tests are performed under soaked or backpressure saturated conditions. Volumetric strains are measured using an image processing technique and the results are compared with those obtained from a one-dimensional test. A series of consolidated-undrained triaxial tests are performed to evaluate undrained shear strength after wetting, and correlations between undrained shear strength and degree of saturation are obtained. A series of stress-controlled cyclic triaxial tests are performed to evaluate the dynamic shear strength after wetting. Trends for the development of axial strain with the progression of loading cycles are dependent on wetting conditions (degree of saturation/matric suction). Furthermore, the cyclic stress ratio at failure is correlated with degree of saturation and charts for the evaluation of dynamic settlement of the test soils are developed. Finally, post-cyclic static shear strengths are determined by conducting a series of undrained static shear triaxial tests on selected samples following the application of cyclic load.