高地应力岩体多孔爆破破岩机制

深部岩体爆破破岩是爆炸荷载与高地应力共同作用的结果。基于一些简化假设，建立了一个高地应力岩体双孔爆破计算模型，采用光滑粒子流体力学-有限元方法耦合数值模拟方法，研究了高地应力作用下炮孔间裂纹的传播及贯通过程，分析了炮孔周围应力场动态演化过程与分布特征。研究结果表明:爆破引起的岩体开裂主要是环向动拉应力所致，地应力对岩体的压缩降低了炮孔周围环向动拉应力、缩短了环向动拉应力的作用时间，因而对爆炸致裂起抑制作用；静水地应力条件下多孔爆破时，垂直于炮孔连线方向传播的爆生裂纹更易受到地应力的抑制；对于高地应力岩体爆破，炮孔间的裂纹扩展长度随地应力水平的提高而减小，裂纹主要沿最大主应力方向扩展，因此沿最大主应力方向布置炮孔、缩短炮孔间距有利于炮孔间裂纹的连接贯通，形成良好的爆破开挖面。

Mechanism of rock fragmentation by multi-hole blasting in highly-stressed rock masses

During blasting in deep rock masses, the rock fragmentation is contributed to the combined effects of blast loading and high in-situ stress. An analysis model based on simplifying assumptions was developed for double-hole blasting in highly-stressed rock masses, and the crack propagation and dynamic stress evolution surrounding the blastholes were studied by using the coupled SPH (smoothed particle hydrodynamics）-FEM（finite element method) method. The results show that the blast-induced rock cracking is mainly caused by the dynamic circumferential tensile stress generated from blast loading. However, in the rock masses subjected to in-situ stress, the dynamic circumferential tensile stress is reduced in magnitude and duration due to the compressive effect of the in-situ stress. Therefore, the in-situ stress plays a role in inhibiting the rock fragmentation caused by blasting. For the case of multi-hole blasting in a hydrostatic in-situ stress field, the crack propagation perpendicular to the connecting line between the adjacent holes is more easily inhibited by the in-situ stress. The length of blast-induced crack growth decreases with an increase in the in-situ stress level. With regard to a non-hydrostatic in-situ stress field, the crack propagation along the direction of the minimum principal in-situ stress is most severely suppressed, and thus the cracks grow preferentially along the maximum principal stress direction. Therefore, arranging the blastholes along the maximum principal stress direction and shortening the spacing between the blastholes will facilitate the crack connections and the formation of excavation surfaces.