STUDY ON THE UNLOADING CREEP CHARACTERISTICS OF LOESS AND THE MECHANISM OF TYPICAL EXCAVATED LOESS LANDSLIDE

Excavation unloading is one of the main inducing factors of loess landslides. In order to deeply study the unloading creep characteristics of loess and the mechanism of excavated loess landslides, we selected the typical excavation loess landslide—the loess of Shangzhuang landslide in Yulin City as the research object and carried out a series of triaxial unloading creep tests of loess. We analyzed the influence of unloading on the creep characteristics of loess and revealed the mechanism of excavation-type loess landslide based on the experimental results and numerical simulation methods. The greater the unloading stress level of the sample, the greater the creep deformation of the sample and the longer it takes for the sample to reach a stable creep state. The larger the initial consolidation stress is, the smaller the proportion of the unloading value of the specimen's creep failure to the confining pressure is. We obtained the long-term strength of the sample by the isochronous curve method and calculated the long-term cohesion and long-term internal friction angle of the loess in the study area. In addition, we introduced the long-term strength loss rate and analyzed the law of instantaneous strength and long-term strength. Numerical simulation results show that a strain concentration area is formed at the toe of the excavation slope. The displacement of the slope gradually increases from top to bottom. Compared with the unexcavated condition, the unloading stress in the soil after excavation increases significantly, which leads to the increase of the creep deformation of the slope body, and finally causes the slope body to slip. The research results can provide theoretical support for landslide prevention.