Research status and evaluation of theoretical calculation of plastic zone boundary for hole surrounding rock

In underground mining engineering, there are roadways, openings, various mining chamber spaces, artificial boreholes and natural caves, etc.The failure and stability of their surrounding rock can be unified into the study of rock mass mechanics around the hole in the infinite underground space. Combined with the engineering conditions of underground coal mines, the theoretical formula under hydrostatic pressure condition and the boundary equation of plastic zone under non-uniform stress field were studied by using the method of comparative analysis between theoretical calculation and numerical simulation. The mechanical model, the derivation principle, the derivation process and the calculation accuracy of the theoretical calculation were analyzed in detail, and its applicability was evaluated and analyzed. The results show that the derivation process of theoretical formula under hydrostatic pressure is rigorous and the calculation accuracy is high. It is suitable for the calculation of plastic zone range of surrounding rock under hydrostatic pressure, approximate hydrostatic pressure and low deviator stress conditions, but not under high deviator stress conditions. The derivation process of the plastic zone boundary equation in non-uniform stress field was simplified, and it was an approximate solution. The approximate solution has some errors in accuracy compared with the numerical simulation results, but it can well reflect the plastic zone evolution law of the surrounding rock in the non-uniform stress field. It has important guiding significance for studying the failure law and disaster-causing mechanism of the surrounding rock in the underground high deviating stress field. Based on the analysis and evaluation of the existing theory for calculating the plastic zone boundary of surrounding rock, the advantages and disadvantages of different theoretical methods and applicable conditions are clarified, which is of great practical significance for the rational application of theory to guide engineering practice.