Research on the “three shells” cooperative support technology of large-section chambers in deep mines

The "three shells" cooperative support technology was proposed herein according to both the large deformation of the rock surrounding large-section chambers in deep mines and the precarious stability of the support structures therein. The development range of the plastic zone in the surrounding rock was controlled by a stress shell to reduce the difficulty of controlling the surrounding rock. Additionally, the residual strength of the rock mass in the plastic zone and the self-bearing capacity of the surrounding rock were improved by a reinforced load-bearing shell. Furthermore, a passive load-bearing shell could restore the triaxial stress state of the surrounding rock on the free surface, reduce the influence of the external environment on the surrounding rock, and reinforce the surrounding rock with the strength of the shell. Reasonable layouts of large-section chambers were determined by analyzing the control effect of the stress shell on the surrounding rock under three kinds of in situ stress fields. The orthogonal test method was applied to reveal the influences of different support parameters in the reinforced loadbearing shell and passive load-bearing shell on the surrounding rock stability. The surrounding rock control effect of the "three shells" collaborative support technology was analyzed through numerical simulation and field monitoring. The results show that the maximum displacement between the roof and floor of the coal preparation chamber in the Xinjulong coal mine was approximately 48 mm, and the maximum displacement between its two sides was approximately 65 mm, indicating that the technology proposed herein could meet the long-term control requirements of the surrounding rock stability for large-section chambers in deep mines.