循环剪切对格栅-土石混合体界面特性的影响

Effect of cyclic shear on interface characteristics of geogrid-soil-gravel mixture

为了研究不同含石量下土石混合体-格栅界面的循环剪切特性,采用循环直剪仪,在不同的竖向应力、剪切位移幅值和剪切频率下进行了单调直剪试验、循环直剪试验和循环后单调直剪试验,探究了5种含石量(0%、25%、50%、75%、100%)、3种剪切位移幅值(1、3、6 mm)和3种剪切频率(0.2、1.0、2.0 Hz)对土石混合体-格栅界面的峰值剪切应力和体变规律的影响。试验结果表明,含石量在0%~75%之间时,随着含石量的增大,土石混合体-格栅界面的循环峰值剪切应力和最大剪切刚度均随之提高,最终竖向位移绝对值和最大阻尼比随之减小;含石量继续增大至100%,土石混合体-格栅界面的最大峰值剪切应力和最大剪切刚度均随之减小,最终竖向位移的绝对值和最大阻尼比随之增大。在同一含石量下,剪切位移幅值和剪切频率越大,界面最大峰值剪切应力和最终竖向位移绝对值也越大。与单调直剪试验相比,循环后单调直剪试验得到的内摩擦角和似黏聚力有所增加,含石量在0%~75%的范围内,内摩擦角和似黏聚力随含石量的增大而线性增加,含石量继续增加至100%,内摩擦角和似黏聚力随之减小。

In order to study the cyclic shear characteristics of soil-rock mixture-geogrid interface under different gravel contents,monotonic direct shear tests,cyclic direct shear tests and post-cyclic monotonic direct shear tests were carried out under different vertical stresses,shear displacement amplitudes and shear frequencies by using cyclic direct shear apparatus.The effects of five gravel contents(0%,25%,50%,75%,100%),three shear displacement amplitudes(1,3,6 mm)and three shear frequencies(0.2,1.0,2.0 Hz)on the peak shear stress and volume change of soil-rock mixture-grid interface were investigated.The test results show that when the gravel content is between 0%and 75%,with the increase of gravel content,the cyclic peak shear stress and maximum shear stiffness of the soil-rock mixture-grid interface increase,and the absolute value of final vertical displacement and the maximum damping ratio decrease.When the gravel content continues to increase to 100%,the maximum peak shear stress and maximum shear stiffness of the soil-rock mixture-grid interface decrease,and the absolute value of final vertical displacement and the maximum damping ratio increase.Under the same gravel content,a great shear displacement amplitude and a high shear frequency lead to a high maximum peak shear stress and the absolute value of final vertical displacement of the interface.Compared with the monotonic direct shear test,the internal friction angle and quasi-cohesive force obtained by the monotonic direct shear test after the cycle increase.In the range of 0%−75%gravel content,the interface friction angle and quasi-cohesive force increase linearly with the increase of gravel content.When the gravel content continues to increase to 100%,the interface friction angle and quasi-cohesive force decrease.