循环剪切荷载作用下含二阶起伏体模拟岩石节理力学特性研究

利用人工材料浇注含二阶起伏体的模拟岩石节理试样,进行常法向荷载循环剪切试验,研究节理剪切力学特性在循环剪切过程中的劣化规律。试验结果表明:二阶起伏体对节理循环剪切力学特性有重要影响,剪切强度、剪切刚度、剪胀角随剪切循环次数增大而衰减,衰减趋势随着二阶起伏度的增大而加快;法向应力、二阶起伏度较大时,二阶起伏体对剪切力学特性的影响主要体现在第1轮剪切循环中,在随后的剪切循环中影响不明显;法向应力、二阶起伏度较小时,二阶起伏体的影响在前几轮循环剪切过程中均有较清晰的体现。基于Hertz接触力学理论,提出了节理面微凸体球面接触细观模型,揭示了节理循环剪切宏观试验现象的力学机制。

Study of mechanical characteristics of simulated rock joints with second-order asperity under cyclic shear loading

Simulated rock joint samples with second-order asperity are made of artificial material. A series of constant normal load (CNL) cyclic shear tests are carried out to study the deterioration law of shear mechanical characteristics during process of cyclic shearing. Based on the experimental results，it can be found that the second-order asperity has an important influence on the shear mechanical properties of joint samples under cyclic shear loading. The shear strength, shear stiffness and dilatancy angle decrease with an increase of shear cycles, and decay more quickly with an increase of second-order asperity height. The influence of second-order asperity on the shear mechanical properties is mainly reflected in the first shear cycle with higher height of second-order asperity under higher level of normal stress, and it has no obvious effect on subsequent shear cycles. On the other hand, the influence is reflected more clearly during the begging of the shear cycles to the joints with smaller height of second-order asperity under lower level of normal stress. Finally, based on the theory of Hertz contact mechanics, a spherical contact microscopic model of asperity on the joint surface is proposed; and the mechanisms of macroscopic phenomenon during cyclic shear tests are revealed by the model.