The study of dynamic fracture mechanism of pre-stressed coal is of great importance to the coal bursts prevention and the coal pillar reinforcement subjected to the dynamic disturbance. In this paper, the effect of pre-static load and dynamic load on the initiation fracture evolution and destruction states of coal were studied using experimental and theoretical approaches. The results show that the coal usually splits into several blocks along the dominant fractures when subjected to the static load. The increase of pre-static load can make the post-peak dynamic stress–strain curve of the specimen gradually transform from type II to type I. The dynamic load plays the same role as that of pre-static load in terms of the effect on the dynamic stress–strain curve, but different in dynamic failure state of the coal. The enhancement of the former will make the dominant fracture expansion and leading the dynamic failure of coal gradually transform from the surface peeling to failure into several large pieces along the dominant fractures, while the increase of the latter will provid increasing kinetic energy to activate the internal fracture expansion of the specimen, and causing the failure state of the specimen transform from the surface peeling to the complete destruction into pieces. For the specimen with the surface peeling failure form, the peeling degree of the specimen depend on both the length of the fracture and the distance of the fracture to the free surface. Based on these results, the dynamic instability mechanism and protection focus of coal pillars under coupled static and dynamic loads were further discussed.

研究预应力煤的动力破裂机理，对防治煤爆和动力扰动下的煤柱加固具有重要意义。本文采用实验和理论方法研究了预静载荷和动载荷对煤的起裂断裂演化和破坏状态的影响。结果表明，煤体在静载荷作用下，通常沿主要裂缝分裂成若干块体。预静载荷的增加可以使试件峰值后动应力-应变曲线由Ⅱ型逐渐转变为Ⅰ型。动态应力-应变曲线，但煤的动态破坏状态不同。前者的增强会使主导裂缝扩展，导致煤体动力破坏逐渐从表面剥落转变为沿主导裂缝的几大块破坏，而后者的增加将提供增加的动能以激活内部试件的断裂扩展，使试件的破坏状态由表面剥落转变为完全破坏成碎片。对于具有表面剥离破坏形式的试件，试件的剥离程度取决于断裂长度和断裂到自由表面的距离。在此基础上，进一步探讨了静动力耦合作用下煤柱的动力失稳机理和保护重点。