剪切速率对平直充填节理的剪切力学特性影响研究

Influence of shearing velocity on shear mechanical properties of planar filled joints

不同剪切速率下充填节理的剪切特性对动态荷载作用下工程岩体的安全稳定性有着重要的影响。为了研究剪切速率对充填节理的剪切力学特性的影响,通过花岗岩试块中间充填天然河砂模拟充填节理。采用RMT-150C电伺服试验机进行直接剪切试验,研究了法向压力、剪切速率和充填厚度对充填节理的剪切力学特性的影响。试验结果发现,充填节理的剪切应力-位移曲线属于屈服剪切型,分为弹性阶段、过渡阶段和滑移阶段,无明显峰值强度,在滑移阶段剪切应力继续增加,增加速率与法向压力大小有关。随着剪切速率的增加,充填节理的剪切强度和内摩擦角略有增加。为了考虑充填节理剪切应力-位移关系的非线性变化过程,采用双曲线形式对弹性阶段的应力-位移曲线进行拟合,结果较好,并提出初始剪切刚度和刚度影响系数描述其变形特性。剪切速率和法向压力的增加会大幅度增加初始刚度,充填厚度对两个参数的影响与法向压力有关。对于无起伏度的平直节理,剪切速率和充填厚度对剪切强度影响较小,但对充填节理的变形特性有重要的影响。

The effect of the shearing velocity on filled joints is significant for the safety and stability of engineering rock mass under dynamic loads. To study the effect of the shearing velocity on shear mechanical properties of filled joints, sands were used as the filled material and the granite was used as joint wall. By using the RMT-150C servo-testing system, direct shear tests were conducted on filled joints to investigate the effects of normal stress, shearing velocity and filled thickness on shear mechanical properties. Experimental results show that the shear stress-displacement curve of the filled joint belongs, to the yield shear type, and it can be further divided into three phases： elastic stage, transitional stage and slip stage. At the slip stage, the shear stress continually increased with increasing the shear displacement, and the increase amplitude was related to the normal stress. With the rapid growth of the shear rate, the shear strength and frictional angle increased slightly. The shear stress-displacement curve of the elastic phase was fitted by a hyperbolic form to study its non-linear process and the fitting result turned out to be good. Two new parameters, namely the initial stiffness and stiffness influence coefficient, were defined to describe shear deformation characteristics of the joint. Experimental results show that the initial stiffness increased sharply with increasing the shearing velocity to a high value. As the normal stress increased, the initial stiffness increased linearly, while the stiffness influence coefficient decreased obviously. Moreover, the effects of filled thickness on these two parameters were dependent on the normal stress. For the planar filled joint without roughness, both of the shearing velocity and filling thickness obviously have greater influence on deformation characteristics of the joint than on shear strength.