Experimental study on the normal deformation of joint under dynamic compressions

Understanding the effect of loading rate on the normal deformation characteristics of joints has been an important topic for rock dynamics and rock engineering activities. In this paper, a series of static and quasi-static cyclic compression tests are performed on intact and jointed specimens, to reveal the mechanism of the dynamic normal behaviour of joints. The rate and peak value of the compression loading in each cycle are carefully determined to relate the dynamic normal characteristics of joint to the damage of joint asperities. The effect of loading rate on the normal stress-closure curve in different cycles of loading is analyzed. The results indicate that the loading rate has little or no effect on the normal deformation of joint under compression when the joint behaves in an elastic manner and no damage is caused to joint asperities. And the rate-dependent normal behaviour of joint, on the other hand, is found to be due to the failure of joint asperities, arising from the rate-dependent strength of the material.