Mechanical response of coal and rock in stope under transient excitation of structure

Dynamic disaster is one of the main disasters in deep coal mining. Revealing the response mechanism is the theoretical basis for solving dynamic disasters of coal-rock of stope. In this paper, the dynamic and static response of coal and rock under the action of structural transient excitation is studied by means of theoretical analysis, physical experiment and field measurement. Results show: The overlying strata is deformed and destroyed after the formation of working face. The spatial structure of overlying strata composed of different strata outside the fracture surface and within the influence range of mining is the internal cause of different mechanical responses of coal and rock in the stope within its influence range. The instability of subsystems such as the fracture of hard strata will cause the transient of spatial structure in the process of mining, which will lead to the occurrence of dynamic mechanical response of coal and rock in the stope and the step change of static mechanical response within its influence range. In the process of dynamic response of coal and rock in the stope, the dynamic load is caused by the vibration of the source area and the transient of the spatial structure. The dissipated energy is composed of two parts: the release of strain energy in the source area and the release of gravitational energy in the spatial structure. Moreover, the dynamic response of coal and rock in the stope is regional, and the dynamic response away from the structural transient region is not obvious. Due to the transient influence of the spatial structure of the overlying strata, the static mechanical response of the coal and rock in the stope is obviously different before and after the transient equilibrium state. Affected by this, the peak point of the abutment pressure on the coal before the working face moves forward, the peak value decreases, and the positive and negative step change zones are formed. Based on the dynamic and static mechanics method, a quantitative calculation method for the superposition of dynamic and static loads of coal and rock in the process of structural transient is established. The maximum dynamic load is about 2 times of the step variable of the static stress, and the peak position of instantaneous maximum abutment pressure on the coal before the working face is located in front of the initial static load. The results have certain theoretical reference value for the research and prevention and control of dynamic disasters in stope.