Rock damage control for large-diameter-hole lateral blasting excavation based on charge structure optimization

Abstract Controlling rock damage induced by lateral blasting excavation is a source of concern. In underground mines, large-diameter-hole lateral blasting excavation often causes engineering disasters such as large blocks falling and overall collapse of the remaining rock mass. Because of their high cost and cumbersome operation, conventional contour blasting techniques, such as smooth and presplit blasting, are unsuitable for production boreholes. In this paper, based on the large-diameter-hole lateral blasting excavation of the Shaxi underground mine in China, a field lateral blast test with a single row was initially conducted, and the sonic wave speeds and goaf boundaries were measured to evaluate the damage degree to the remaining rock mass. A numerical model with three rows of boreholes was developed and calibrated against the lateral blast test with a single row. The calibrated numerical model was used to simulate the blasting process. The blast-induced damage characteristics with different charge structures in different rows were investigated, and the optimal charge structure for each row was obtained. The results indicate that the rock damage control effect can be achieved by a reasonable combination of charge structures and number of blasted rows, and it is more satisfactory with an increasing number of blasted rows and a reasonable decrease in the charge coefficient row by row. The rock breaking pattern at Cut X2 shows that most of the boulders are caused by the collapse of the remaining rock mass under the impact of blasting excavation. The ratio of broken rock in Part 4 indicates that the blast impact of the last row plays a dominant role in the damage to the remaining rock mass. Two optimized schemes were applied to the field of large-diameter-borehole lateral blasting, and satisfactory effects were achieved in the blast-induced damage control of the remaining rock mass.