STUDY ON SHEAR CREEP BEHAVIOR OF MUDSTONE AND ITS CORRECTION MODEL OF GANGU FISSURE IN GANSU

Rock shows typical creep property under long-term load, and the mechanical property of fractured mudstone are different from that of intact rock under long-term load. The shear creep test was carried out on the fractured mudstone from the drilled core at Gangu Zhaojiayao landslide in Gansu province, with investigation on the influence of axial compressive stress and the length of prefabricated cracks on the shear creep characteristics of samples. The experimental results show that axial load and crack length have obvious influence on the shear creep characteristics of the samples. The larger the axial compressive stress is, the less the shear creep deformation is. The longer the crack is, the more obvious the shear creep deformation is. When the stress is low, the creep model such as Cvisc model can better reflect the creep mechanical properties of the mudstone; however, in the accelerated creep stage, most of the models can not accurately reflect the nonlinear change of creep curves of the mudstone. The improved Nishihara (K-B) model with less model parameters overcomes the shortcoming that the traditional model cannot describe the nonlinear creep curves, and it can be better applied to engineering soft rock. In the process of shear creep of argillaceous soft rock samples under different loads, the formation of shear failure zone of fractured mudstone is characterized by the combination of gradual and sudden failure. The shear creep mechanical model of mudstone can explain many phenomena of mudstone landslide. The shear creep of the argillaceous soft rock in the potential slip zone of the slope is the intrinsic cause of the landslide.