| Along with the coal resources of eastern mining area in China drying up gradually,the focus of coal resource development has transferred to Shanxi,Shaanxi,Inner Mongolia,Ningxia,Gansu and other western provinces.Due to the unique natural geography,geological structure and ecological environment in the west,there are serious geological disasters including a wide range of roof fall and water and sand inrush and the environmental damage such as water and soil erosion caused by the high-intensity mining.So the study on rock mass failure and the regularity of ground pressure behavior under the conditions of the high-intensity mining is urgent and important.It provides the theoretical and field basis for the research on roof instability and disaster control.The thesis aims to study on the law of stratum movement under the conditions of high-intensity mining.The microseismic monitoring system for high-intensity mining was established in working face 11203 of Xiaojihan coal mine.It was obtained that thespace-time evolution characteristics of the microseismic activity and stratum movement,the law of the key stratum breaking and the effect of the mining rate by using quantitative seismology and key strata theory.Considering the microseismic activity effect,the rock mechanics parameters with dynamic characteristics were obtained by using moment tensor inversion.Then,the numerical simulation study on strata breaking under the conditions of the high-intensity mining was done.The main works and achievememts in this thesis are as follows:1.The microseismic monitoring system for high-intensity mining was successfully established in working face 11203 which was the first mining face of Xiaojihan coal mine.The selection and layout of sensor and the composition and installation of the microseismic monitoring system were discussed.It was verified by the artificial blasting test that the accuracy of microseismic monitoring system can meet the requirements of the surrounding rock break monitoring under the conditions of the high-intensity mining.The quantitative calculation of the seismology parameter was realized through the effective and rapid identification of mircoseismic events.It laid the foundation for quantitative analysis of the microseismic space-time distribution.2.The correlation between the number of the microseismic events and the energy release quantity was analyzed by the law of the microseismic space-time distribution.Different precursor characteristics of source parameters were present during the two large energy releases in the process of the working face mining.The stability of rock mass could be judged by the statistical regularity of microseismic parameters.The law of the mine pressure behavior of working face 11203,the law of the' surrounding rock stress and deformation,the distribution characteristics of "Cross three areas" and "Vertical three zones" and the influence range of the stress redistribution were discussed to provide reference for similar mine in mining,supporting and monitoring.3.By using the discrimination method of the key strata,the main key stratum and inferior key strata of working face 11203 were obtained.The inferior key stratum 1 and the inferior key stratum 2 influenced the mine pressure behaior.The breakage laws of the inferior key stratum 1 and the inferior key stratum 2 were obtained by the evolution of the microseismic events during the first weighting and periodic weighting of working face 11203.The variation characteristics of microseismic parameters before the key strata breaking were analyzed,and a method for judging the key strata breaking was put forward based on microseismic parameters.It could also be used as a method of early-warning large-scale rock damage or mine geological disaster.4.Picking up the slow and fast stage of mining,the effect of mining rate on the key strata breaking and surrounding rock failure was obtained by analyzing the results of numerical simulation,the distribution law of microseismic events and the variation characteristics of microseismic parameters.With the increase of mining rate,the failure area induced by mining decreased,the surrounding rock failure occurred to the rear of the working face increased,and the development height of the microseismic events became lower.Thereby the damage of the inferior key stratum 2 reduced and then the mechanism was explained.Microseismic monitoring can be used as a technical means to determine the reasonable mining rate of working face.5.A method of the dynamic characterization of rock mass mechanics parameters was put forward based on the microseismic data of working face 11203.The volumetric joint count of the original crack Jv1I was obtained by field structure plane investigation.The volumetric joint count of the secondary crack Jv2 was obtained by moment tensor inversion.Combining Jv1 and Jv2,the volumetric joint count of rock mass Jv could be got.And then the GSI was quantified by Jv.The rock mass mechanics parameters could be calculated by Hoek-Brown criterion.The rock mass mechanics parameters with dynamic characteristics could be obtained according to the dynamic changes of the microseismic data.The key strata breaking mechanism was studied by numerical simulation of the working face under the conditions of high-intensity mining using the dynamic mechanics parameters based on microseismic data inversion. |
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