不同接触状态岩石节理的剪切力学性质试验研究

除粗糙度外,节理上、下面壁的接触状态是影响其剪切力学性质的重要因素。采用水泥砂浆制备若干不同形貌的节理,对其上、下面壁沿剪切方向错开不同的位移量、形成不同的接触状态以模拟不同偶合度的节理,在常法向应力条件下进行试验研究。试验结果表明:峰值剪切强度随错开位移量的增加而呈非线性减少,但错开位移对峰值剪切强度的影响随法向应力的增加而减弱;峰值剪切位移随错开位移量的增加逐步变大;剪切刚度随错开位移量的增加逐步减少直至某一恒定值,且在高法向应力下错开位移量对剪切刚度的影响更为明显。采用几种不同的简单函数分析峰值剪切强度与错开位移量之间的关系,在偶合节理峰值剪切强度准则的基础上提出不同接触状态节理的峰值剪切强度准则。与已有的准则相比,新准则采用的描述节理接触状态的参数易于确定且更为客观。

Experimental studies on mechanical behaviour of rock joints with varying matching degrees

Besides surface roughness, the matching degree between the joint upper and lower blocks is another important factor affecting the shear behavior of a rough rock joint. A simplified way, by imposing varying magnitudes of horizontal dislocation along the shear direction between the joint upper and lower blocks, is used to model the different matching degrees of a joint that is made by cement. A large number of direct shear tests are then performed under constant normal stress condition to investigate the shear behavior of rock joints under the varying matching degrees. The experimental observations indicate that with the increase of dislocation, the peak shear strength decreases and has a larger reduction rate under the lower normal stress level. With the increasing dislocation, the peak shear displacement increases, and the shear stiffness decreases and gradually approaches a constant. The influence of dislocation on the shear stiffness is more prominent under a higher applied normal stress. Several simple combinations of roughness parameters and normalized dislocation are used to perform regression analysis, and a new empirical peak shear strength criterion is put forward to capture the peak shear strength degradation of rock joints under different matching degrees. A preliminary comparison between the proposed criterion and the existing criteria is also provided. The new parameters for the proposed criterion can be easily determined in the laboratory.