Discrete element study on influence of heterogeneous structure on strength and failure characteristics of coal rock combination

Abstract

The heterogeneous structure in the coal pillar often affects the safety production of the working face. In order to study the influence of heterogeneous structure on the strength and failure evolution characteristics of coal rock combination, a coal rock combination model with randomly distributed heterogeneous structure is established based on discrete element software. Considering that the strength of heterogeneous structure is 25%, 50%, 200% and 400% of coal structure, the strength characteristics, crack development and propagation process of coal rock combination with heterogeneous structure are studied, and its influence mechanism is analyzed. The results show that: the peak strength and elastic modulus of coal rock combination increase with the increase of the strength of heterogeneous structure, and the peak strain decreases with the increase of the strength difference between heterogeneous structure and coal structure. The stress field of coal rock combination is affected by the distribution of heterogeneous structure. The stress concentration area often appears in the area with higher strength in the two types of structures, and takes the junction of the two types of structures as the boundary. During the loading process, micro-cracks first appear in the structures with weak strength, and develop and expand inside the structures with weak attributes. The morphology of through-crack leading to sample failure depends on the distribution characteristics of weak attribute structure.

Keywords

• heterogeneous structure
• coal rock combination
• mechanical properties
• crack propagation
• discrete element method