The grooving and blasting effect of the drilling and blasting method in roadway tunneling directly affects the blasting cycle efficiency, while the existing studies mostly ignore the influence of mesoscopic defects such as internal joints of rock mass. Based on the PFC (particle flow code) 2D discrete element method, a discrete fracture network (DFN) is introduced to construct a rock mass model with different densities of joints, and the particle expansion method is used to simulate the groove blasting process, and the effects of joint density on crack propagation, energy dissipation and post-explosion block size are systematically analyzed. On this basis, the blast hole layout scheme is optimized, the original 6-hole layout is simplified to a 4-hole diamond-shaped layout, and the 15 ms differential detonation is used to improve the explosive energy utilization rate, and the post-detonation effect is similar to the original scheme. Field tests show that the optimization scheme effectively saves the actual production cost and reduces the drilling workload. The research results emphasize the importance of considering the joint defects of rock mass for the optimization of blasting parameters, and provide a theoretical basis and practical reference for efficient tunneling of rock roadways.

In order to solve the problem of high labour intensity, low work efficiency and poor safety in the drilling of blind shafts using hydraulic rock drills in the Dahongshan Iron Ore Mine, it is proposed to adopt the one-time well-forming technology of blind shaft deep hole blasting. A trenching test was carried out on the test blind patio, and the compensation factor for the area to be blasted was calculated and the trenching hole layout was designed based on the mechanism of rock breaking action and cavity formation theory for undercutting. The detonator was used on site to initiate the detonation and a 3D laser scanner was used to scan the post-detonation cavity to study the variation of its area with depth. The test results show that: after detonation of all the rocks to be blown out of the slot cavity, the cross-section is lotus-shaped, the wellhead area is flat, the wall is clear; after the explosion of the slot depth of 9.64 m, in the near hole 0 ~ 2.5 m, the slot cavity cross-sectional area of more than 0.3 m², in 3 m ~ 8.5 m from the hole between the slot cavity cross-sectional area of 0.2 m² fluctuations, the bottom of the slot cavity cross-sectional area of 0.04 m²; the overall pattern of change in the area of the cavity is from the near orifice to the bottom of the cavity, with the increase in depth of the cavity, the area first gradually decreases, then tends to fluctuate above and below a certain value, and finally decreases rapidly until the bottom of the cavity. This provides reference for the subsequent blasting of the blind shaft in one pass.

In order to study the damage law and failure mode of pegmatite gabbro under cyclic loading, the Split Hopkinson Pressure Bar (SHPB) and PFC3D numerical simulation software were used to carry out cyclic impact tests of pegmatite gabbro at different impact velocities, and the damage characteristics and failure law were analyzed. The results show that: Under low impact velocity, the original cracks of the rock specimen are first compacted and then gradually destroyed with the increase of the number of cycles, and the dynamic compressive strength of the rock specimen increases first and then decreases gradually. With the increase of the number of cycles, the proportion of rock reflection energy and energy consumption density generally show an upward trend, and the proportion of transmission energy generally shows a downward trend. The damage variable of the rock specimen first shows a negative growth and then a steady growth, and the damage variable of the specimen increases rapidly before the macroscopic failure occurs. Under high impact velocity, the rock specimen will be destroyed in each cycle, the dynamic compressive strength of the specimen increases with the increase of the number of cycles, and the damage variable of the specimen also increases with the increase of the number of cycles. The failure process of the specimen under cyclic loading was simulated by PFC3D, and it was found that the rock specimen was always destroyed along the longitudinal plane under cyclic loading.

In view of the problem that mining and crushing of magnetite ore require huge energy consumption, the split Hopkinson pressure bar(SHPB) is used to test and analyze the dynamic mechanical properties and energy dissipation characteristics of magnetite ore during crushing process under different strain rates. Meanwhile, the complete dynamic failure process of the sample is simulated by ANSYS/LS-DYNA software. The results show that the dynamic compressive strength of the magnetite ore samples has a significant strain rate correlation, and increases from 126.77 MPa to 220.62 MPa when the strain rate ranges from 43.94 s^-1 to 147.75 s^-1. Besides, The analysis of energy transfer law shows that the increase trend of reflected energy become more obvious with the increase of incident energy, and the maximum proportion accounts for about 22% of the total incident energy. However, The increase trend of transmission energy become weaker, and the proportion of transmission energy decreases from 78% at low incident energy to 38% at high incident energy. At the same time, the dissipated energy used for specimen crushing increases gradually, which has a linear relationship with the incident energy. The failure mode changes from the splitting failure at low and medium strain rates to crushing failure at a high strain rate. In terms of the crushing scale, most of the fragments at low and medium strain rates are large, while the fragments at high strain rates are small and mostly fine-grained and needle shaped. Numerical simulation results indicate that the initial failure is caused by the "cross" shaped reflected tensile waves on the incident end of the specimen. The results of this study can provide a reference for judging the difficulty of dynamic crushing of magnetite ore and improving the efficiency of rock breaking by impact.