Definition, principle, characterization and application of mining-induced stress rotation

Mining-induced stress leads to the deformation and failure of surrounding rock. It serves as the premise for support design, determining ground control effectiveness. With the growth in mining intensity and depth, the distribution of mining-induced stress becomes increasingly complex. The frequency of rock instability and dynamic disaster rises, and rock control difficulty increases. To ensure the safe and efficient mining of coal resources, the phenomenon of mining-induced stress rotation was identified by applying field measurement, theoretical analysis, lab experiment and numerical simulation. The scientific definition, mechanical principle, characterization method and its application prospect in mining engineering were systematically clarified. Initially, the ground stress tensor and mining-induced stress increment were obtained by the CSIRO cell, and the calculation method for absolute mining-induced stress was proposed. It revealed the relationship between mining-induced stress tensor matrix and the principal stresses as well as principal directions. The definition of mining-induced stress rotation was then put forward. Based on transformation characteristics of the stress tensor matrix, three mining-induced stress changing modes were determined: principal stress changed while principal direction unchanged (I), principal stress unchanged while principal direction changed (II), and both principal stress and principal direction are changed (III). In-situ data showed that mining-induced stress changing mode belonged to type III, which verified the existence of stress rotation. Subsequently, mechanical principle of stress rotation was investigated, which was attributed to strata movement, stress release and stress concentration. The polar stereographic model was established for mining-induced stress rotation. Three types of rotation trajectory were identified for mining-induced stress. Three-dimensional space rotation problem was simplified into two-dimensional plane problem, enabling quantitative analysis of the rotation amplitude and orientation. Additionally, the relationship between mining-induced stress rotation and surrounding rock stability was explored. Based on the mining-induced stress rotation trajectory, a method for identifying the sensitive zone of rock stability to stress orientation was moreover proposed. The accurate prediction of initiation position and propagation path of failure fractures in the surrounding rock was achieved. Furthermore, five application scenarios of mining-induced stress rotation in underground mining were presented, including the optimization of mining and tunnelling faces, stability analysis of roof structure and support selection, activation prohibition of the fault in deep mining, zonal control of surrounding rock in the panel with large face length, and strong mining pressure control in LTCC with arch-shaped panel. At last, a new surrounding rock control technology was formulated by optimizing stress rotation trajectory. The new method aims to enhance self-bearing capacity of surrounding rock from the source of mining, which provides new idea for surrounding rock control in underground mining.