Study On Prevention And Control Of Complex Dynamic Disasters Of Mine Quake And Rock Burst Under Hard-thick Strata

Mine quakes and other dynamic disasters occur frequently in the mines under hard-thick strata. Strong mine quakes not only induce underground rock burst, but also cause surface building damages and bring psychological "panic" to the residents in the mine region. Mine quakes is gradually evolved into public safety issues from mining safety issues. Most researchers mainly focused on the prevention and control of underground disasters under hard-thick strata without paying much attention on the study on the theory and method of prevention and control of underground rock burst and surface vibration damage. Therefore, this paper has carried out the research on the prevention and control of complex dynamic disasters of mine quakes and rock burst caused by coal mining under hard-thick strata. The main achievements are as follows:(1) The relationship between key strata movement and vertical and horizontal stress evolution was studied, and a prediction model of "mine quake-rock burst" compound dynamic disasters under hard-thick strata was proposed. Based on the movement state of hard-thick strata before-during-after mining in the longwall panel, together with the distribution of overlying strata, the panels were divided into different mining types and the method of estimating static vertical stress and horizontal stress near surrounding rock was obtained. In addition, the model of fracture motion of hard-thick strata was established under these conditions, and the prediction model of "mine quake - rock burst" compound dynamic disasters under hard-and-thick strata was also put forward.(2) The idea of surface "vibration damage boundary" and its evaluation and prediction methods were raised for fracture movement of hard-thick strata. With the case analysis of surface vibration caused by strong mine quakes, this paper introduced the concept of "vibration damage boundary" and set the particle vibration velocity as the main evaluation index of vibration damage. The evaluation method of surface vibration damage induced by mine quakes was initially established. According to the conditions of strong mine quakes induced by hard-thick strata breaking, the prevention and control methods of reducing surface vibration damage were presented as follows:(a) Changing the condition that induces mine earthquake; (b) Reducing the energy released by mine quakes. The methods agree well with in-situ mining practice.(3) The relationship between coal pillar deformation & rock burst instability and surface building protection under hard-thick strata in deep mines was discussed and solutions to coal pillar deformation control under long-term high stress was presented as well. The solutions are as follows:(a) The coal pillar in the strike direction has no rock burst danger; (b) The coal pillar in the strike direction will not fail due to instability caused by long-term strength reduction; (c) The coal pillar in the dip direction deforms evenly so that the ground has no danger of tensile failure. The design formulae of coal pillar width were derived from the established models and the results were verified and applied in a mine in Shandong province, China.(4) This paper also studied the coordination deformation, instability prediction and disaster prevention and control ways of "hard-thick strata-coal pillar" system (small key longwall panel). An analysis of the stress source, form and coordination mechanism of the vertical deformation of coal pillars was analyzed based on the engineering practice of a mine. The stress-strain relationship from the coordination deformation of the "hard-thick strata-coal pillar" system was discussed, and the unstable classification, criterion of "hard-thick strata-coal pillar" system and its impact on the underground dynamic disasters was analyzed.(5) The optimization method of mining design for rock burst prevention and mine quake reduction in the key (stoping) longwall panel under hard-thick strata was proposed. Evaluated by the overall stability and surface building damage induced by mine quakes, this optimization method determined the position of key longwall panel according to the stable evolution of the whole structure of the overlying strata and the motion energy generated from regional stress coordinating to the local longwall panel and stress control. The key longwall panel location and parameters was determined according to the optimization design.The statements and conclusions of this paper are preliminary, and some further improvement and refinement are still in need on the basis of more practice and theoretical analysis, so as to develop more effective theory and methods for solving engineering problems.