Study on stress evolution and damage fracture of cut blasting in high in-situ stress roadway

In recent years, the mining state of mineral resources has changed from open air to underground and from shallow to deep. In the drilling and blasting construction of deep rock masses, in-situ stress has a significant impact on the blasting effect. An improved continuum-discontinuum element method (CDEM) considering energy dissipation in the crushing zone under blasting load is used to study the stress evolution process and rupture damage characteristics of ordinary straight hole cut blasting and large empty hole cut blasting under different in-situ stress conditions based on a two-dimensional plane strain model. The numerical results show that the existence of the large empty hole enhances the reflection and stretching effect of the explosion stress wave, weakens the inhibitory effect of the ground stress on the explosion crack expansion, promotes the expansion of the main explosion crack, increases the fractal damage and damage area of the trough blast, and improves the crushing degree of the rock mass of the trough blasting. The bi-directional isobaric in-situ stress has an inhibitory effect on the propagation of blast-induced cracks, especially on the propagation of radial cracks. The larger in-situ stress weakens the interaction of blasting stress waves between holes, and the guiding effect of adjacent holes on the propagation of the main crack is weakened. With the increase of in-situ stress, the fractal dimension and fractal damage of explosion crack decrease gradually on the whole, but the fissure differentiated damage and damage area of large empty hole blasting are significantly greater than the fissure differentiated damage and damage area of ordinary straight hole blasting. It shows that in the high in-situ stress environment, the large empty hole cut blasting can still significantly increase the rock crushing degree and crushing range and improve the blasting effect and crushing efficiency.