Stress-Path Dependent Behavior of Cohesionless Soil

The strains induced in cohesionless soil by changes in stress vary considerably depending on stress level (defined as a stress ratio), confining pressure, and on whether the changes in stress involve primary loading, unloading, or reloading. The nature of stress-path dependency, the principles that govern deformations in cohesionless soil, and prediction of soil response for a variety of stress-paths have been investigated. Based on the results of triaxial tests it was found that except for the maximum previous stress level experienced, the stress history has little influence on the behavior of cohesionless soil. However, for stress-paths involving unloading or reloading, stress-path does have an influence on the strains, and the stress-path with the higher average stress level produces the larger strains. An elastoplastic stress-strain theory was used to calculate the strains for the stress-paths investigated and generally good agreement between calculated and measured strains was obtained. It is shown that the plastic deformations in cohesionless soil can be determined from the state of stress, the increment in stress level, and the increment in total work.