Numerical analysis of hard rock blasting unloading effects in high in situ stress fields

Abstract

Blasting in high in situ stress fields is different from blasting at the earth’s surface because of the dynamic unloading effect in the former. In order to study the coupling of dynamic loading and dynamic unloading in the blasting process, the explicit finite element method and explicit-implicit finite element method are employed respectively to investigate the influence of high stress on blasting effects. The results show that the stress and strain change rules of the two methods are clearly different. The stress and strain change rates calculated by the explicit-implicit algorithm simulation are greater than the results simulated by the explicit finite algorithm. The radius of the blasting cavity calculated by the explicit-implicit finite element method is 0.015 m larger than that of the explicit finite element method. Based on the results of the explicit finite element method, a theoretical model is also established, which helps to clarify the effects of high in situ stress unloading when blasting in a high in situ stress field. The model shows that the maximum tensile radial displacement caused by high in situ stress dynamic unloading at the edge of the blasting cavity is 0.12 mm, and the dynamic unloading radial tensile effect can lead to rock failure. This research illustrates that high stress has a considerable influence on the blasting process and on rock-breaking effects. According to the findings, certain blasting engineering design suggestions are made.