Abstract

Direct shear test is one of the important test methods to obtain shear strength index. With the increase of shear displacement, the area of shear plane decreases gradually. According to the normal stress and shear stress, the shear strength line was obtained and the index of shear strength was calculated. However, the phenomenon of shear area decreasing was neglected in the calculation, and the influence of shear area variation was not considered. Based on the change of shear area in the process of shearing, a mathematical model was established, and the formulas for calculating the normal stress and shear stress considering the change of shear area were derived, based on the direct shear test of root–soil complex, the indexes of shear strength were compared and analyzed. The results show that the improved calculation method has a greater effect on the cohesion, and the cohesion obtained was higher than the original calculation method, but it has little effect on the angle of internal friction. The results of this study can be used to evaluate the effect of plant roots on soil strength and to prevent soil erosion and shallow landslide effectively.

摘要

直剪试验是获得剪切强度指标的重要试验方法之一。随着剪切位移的增加，剪切面的面积逐渐减小。根据法向应力和剪应力，得到抗剪强度线，计算抗剪强度指标。但在计算中忽略了剪切面积减小的现象，没有考虑剪切面积变化的影响。基于剪切过程中剪切面积的变化，建立数学模型，并基于根土复合体的直接剪切试验，推导出考虑剪切面积变化的法向应力和剪应力的计算公式。 ,对剪切强度指标进行比较分析。结果表明，改进后的计算方法对粘聚力影响较大，得到的粘聚力高于原计算方法，但对内摩擦角影响不大。本研究结果可用于评价植物根系对土壤强度的影响，有效防止水土流失和浅层滑坡。