Abstract: Hardening soil model is commonly used in geotechnical numerical analyses. In order to study the effect of loading path and drainage condition on the shearing behaviors of undisturbed granite residual soil. Four series of triaxial tests, including the conventional consolidated drained tests, the conventional consolidated undrained tests, the consolidated drained laterally unloading tests and the consolidated undrained laterally unloading tests have been conducted on the undisturbed samples of granite residual soil in Shenzhen. The values of model parameter for different conditions were also calibrated from the test results. It was observed that the specimens first contracted and then dilated in the shearing stage of the conventional triaxial test, but always dilated in the laterally unloading tests. The values of model parameters were closely related to the loading path. The effective internal friction angle measured by the CDLU tests was 20% higher, and the effective cohesion was 46% smaller than those by the CD tests. The reference secant modulus determined from the CDLU tests was 2.9 times, and the unloading-reloading reference secant modulus was 1.8 times those from the CD tests. The values of model parameters were also affected by the drainage conditions. The effective internal friction angle obtained from the CU tests was similar to that from the CD tests, but the effective cohesion obtained from the former was significantly larger than that from the latter. The reference secant modulus determined from the CU tests was twice that from the CD tests, and the unloading-reloading reference secant modulus obtained from the former was 3.8 times that from the latter. Hence, the values of parameters should be determined in accordance with the real loading and drainage conditions for geotechnical numerical analyses.

Key words: hardening soil model, triaxial test, loading path, drainage condition, model parameter