Study on pressure distribution and damage fractal characteristics of eccentric uncoupled structures

Abstract The eccentric non-coupled explosive loading structure is widely present in engineering rock blasting. The mechanism of its influence on the blasting effect and energy utilization still needs in-depth research. This paper establishes a theoretical model of peak pressure on the borehole wall for the eccentric non-coupled explosive loading structure and uses the ANSYS/LS-DYNA numerical simulation method to study the influence law of different radial non-coupling coefficients K on the damage characteristics of the rock mass. It also quantitatively analyzes the damage spatial distribution characteristics by combining the fractal theory. Finally, the theoretical and numerical analysis results are verified through field tests. The research results show: (1) The pressure distribution on the borehole wall of the eccentric loading structure is significantly asymmetric, and the pressure difference between the coupled side and the non-coupled side increases with the increase in K value; the error between theoretical calculations and numerical simulation results is less than 10%. (2) As the K value increases from 1.6 to 4.0, the damage areas and crack numbers of both loading structures decrease, but the eccentric loading structure always maintains a larger damage range on the coupled side. (3) Based on the fractal theory analysis, when K = 3.4–4.0, the rock mass damage spatial distribution is the most uniform, the standard deviation is the smallest, and the energy utilization efficiency is the highest. (4) The field test verification shows that when K = 3.75, the pre-splitting effect is the best, the half-hole rate reaches 85.7%, the wall surface flatness is controlled within ±5 cm, and compared with traditional methods, the cost is saved by 7% and the efficiency is increased by 45%. The research results provide an important theoretical basis and reference for the engineering application of the eccentric non-coupled loading structure.