Numerical simulation of the morphological effect of rock joints in the processes of concentrating elastic strain energy: a direct shear study

Abstract

Rockburst in coalmines is the result of the release of the elastic strain energy (ESE) stored in rock and coal masses. The examination of the elastic strain energy (ESE) along rock joint is important to evaluate the shear strength of rock masses. The morphology of joints and the strength of rock masses are considered as the key factors influencing the distribution of the ESE. In this study, a three-dimensional model is developed to quantify the influence of the morphological effect of rock joint (by varying the amplitude and wavelength of the joint) and different materials (coal or rock) on the distribution of the ESE. The results show that when the wavelength of the joint reaches about 5~20% of the length of the model and the amplitude of joint reaches about 2~10% of the height of the model, a relative high concentration of the ESE was found at the left and right crests, together with a low concentration in the middle crests. For most cases, the maximum ESE generally has a similar order of magnitude (108~109 J) and approximately arched trend for different wave amplitudes for the joints. However, in cases of the flattest joint only reaches about 10−16 J. Regarding the influence of different materials on ESE, the rock-rock system generally has a similar distribution of ESE with the rock-coal system, but the latter one concentrates much more ESE. The coal-rock system has the smallest ESE. This recognition of the highly unbalanced distribution of ESE will certainly help to effectively reduce the potential failure of rocks under the CNL boundary conditions.