Effects of variable shear rate on residual strength of expansive soils and its engineering enlightenment

The residual strength has a key impact on the deformation and stability of landslides. The whole process of landslide movement often involves the phenomenon of variable shear rates, which is manifested by the acceleration rate and deceleration rate. In order to investigate the effects of the acceleration and deceleration rates on the residual strength of expansive soils, a series of ring shear tests with variable shear rates are conducted to analyze the variation rules of residual strength of expansive soils under different acceleration and deceleration rates, and the role of the effects of the acceleration and deceleration rates of the residual strength at different deformation stages of landslides is discussed. The results show that both the acceleration rate and the deceleration rate have a strengthening effect on the residual strength (positive effects), and the strengthening effects of the acceleration rate on the residual strength are more significant than those of the deceleration rate. The effects of the acceleration and deceleration rates on the residual strength are more significant under the larger normal stress conditions. The effects of the acceleration and deceleration rates on the residual strength are considered to be the result of changes in the state of the shear plane caused by changes of the shear rate, and the soil particles in the shear plane must be readjusted to adapt to the new shear rate conditions under variable shear rate conditions, resulting in changes in the residual strength. During the whole process of landslide movement, the effects of the acceleration and deceleration rates on the residual strength are beneficial for the evolution of landslides towards a deceleration accumulation state.