Centrifuge Model Testing of Loess Landslides Induced by Excavation in Northwest China

Abstract

Excavation leads to unloading rebound and stress redistribution in the soil of a slope near the excavation face. The process of reequilibrium of the stress is followed by large deformation or even failure of the slope. In this study, the excavation-induced Yangya landslide was selected as a geological prototype. From reduced triaxial compression (RTC) tests, the characteristics of deformation and the mechanical response of unloading soil were analyzed, which were related to the instability and response mechanism of a loess slope under unloading. Furthermore, a geotechnical centrifuge was used to simulate the deformation and failure process under the condition of excavation at the slope toe. The deformation characteristics before and after the slope toe excavation and the response characteristics of the earth pressure inside the slope were studied. The results show that after excavation of the slope toe, local collapse occurs near the excavation surface. The displacement, the potential slip surface, and the tensile cracks of the slope develop progressively from the front edge to the trailing edge of the slope. Moreover, the failure of a loess slope induced by excavation is dependent on the change of pressure unloading ratio; when the confining pressure unloading ratio reaches a critical level, the shear strength decreases sharply. Differences also exist in the critical unloading confining pressure ratio between shallow and deep failures in excavation-induced landslides. Therefore, the scope of the unloading effect of the excavation on the slope directly determines the scale of the landslide. After excavation, stress relaxation clearly occurs within the slope, and the unloading effect is more obvious near the excavation surface. The excavation mainly affects the front and middle parts of the slope and has little or no effect on the rear part of the slope. The deformation and failure mechanisms of the loess slope induced by excavation are characteristic of a typical progressive retreat failure mode landslide.