Research progress on chain instability control of surrounding rock for super large section chamber group in deep coal mines

The super large section chamber group is prone to chain instability due to its high stress concentration and large failure range, especially under complex dynamic disturbance in deep coal mines. Its safety and stability have become one of the main bottlenecks restricting the exploitation of deep coal resources. In this paper, the chain instability control of surrounding rock for super large section chamber group in deep coal mines is studied. The main results as follows: firstly, a geomechanical equivalent classification method based on the fuzzy comprehensive clustering method is established. The main influencing factors, such as critical buried depth, cross section, comprehensive compressive strength and integrity coefficient of surrounding rock, are considered. It overcomes the deficiency of traditional division method based on cross section only, and the effective classification of super large section chamber is realized in deep coal mines. Secondly, through comprehensive research methods, such as laboratory tests, theoretical analysis and numerical simulation, the creep constitutive relationship considering compactness coefficient is derived, which is suitable for dynamic and static combined loading conditions. The chain instability mechanism and energy criterion of chamber group are established. On this basis, the deformation and failure evolution of surrounding rock under complex stress environment is revealed. Thirdly, a collaborative control mechanism is proposed. High strength super plastic energy absorbing support materials and new supporting equipment such as high strength tension compression coupling cable have been developed. For long term stability, the progressive reinforcement technology and its design method are established. Fourthly, a monitoring and early warning platform for long term deformation and instability has been built based on comprehensive warning threshold. Finally, in the case study at the Xinjulong Coal Mine, China, the maximum convergence rate of chamber section is about 6.2%, and the range of loosing circle is about 1.0-1.5 m of coal gangue separation chamber group. This research effectively ensures the space safety of coal gangue separation system.