Research on Structural Evolution and Microseismic Response Characteristics of Overlying Strata during Repeated Mining of Steeply Inclined and Extra Thick Coal Seams

Abstract

Repeated mining is the main factor that leads to development, propagation, and eventual deformation of the overlying strata fissures in the steeply inclined and extra thick coal seams (SIETCS). The evolution of the overlying strata structure is closely related to microseismic events in a mine. As the mining depth increases, the evolution rules of the overlying strata structure become more complicated and can easily induce dynamic disaster accidents. To solve these problems, this paper established a physical similarity simulation model. Microseismic monitoring equipment was used to study the relationship between the evolution of the overlying strata structure and the energy-frequency of microseismic events. On the basis of the principle of quantitative seismology, the response relationship between the overlying strata structure and the microseisms at different mining stages was compared and analyzed from a quantitative perspective. The characteristics of cumulative apparent volume, energy index, and microseismic b value were used to reveal the precursor characteristics of overburden instability and failure. The results showed that due to the occurrence characteristics of coal seam, the distribution characteristics of rock stratum stress, and the effects of mining disturbances, the energy accumulation-release period after instability failure of the overlying strata induced by shallow mining was longer than the energy accumulation-release period induced by deep mining. And the deep coal and rock mass had a periodic “balance-instability-rebalance-instability again” dynamic evolution process under the disturbance of repeated mining. In the working face mining, the slope of the accumulative apparent volume ΣVA curve suddenly increased, and the energy index EI gradually decreased at the late peak period, which indicated the deformation and failure of overburden. However, the b value of the microseismic event presented the precursory characteristics of rock stratum fracture that gradually increased and then changed drastically.

Microseismic energy distribution and impact risk analysis of complex heterogeneous spatial evolution of extra-thick layered strata

“…In terms of microseismic research on working face mining in complex heterogeneous space, Xingping Lai et al [16][17] revealed the loss of overlying rock through the characteristics of microseismic "energyfrequency" distribution, cumulative apparent volume, energy index and microseismic b value. Precursor characteristics of stability failure.…”

Mechanical Behavior Characteristics and Energy Evolution Law of Coal Samples under the Influence of Loading Rate—A Case Study of Deep Mining in Wudong Coal Mine

“…Steeply inclined thick coal seams are widely distributed in China, with large dip angles and complex geological structures. This makes the mining of steeply inclined thick coal seams a technical problem in mining that has long plagued the development of China's coal industry [1][2][3][4][5][6][7][8][9]. Therefore, in order to meet the safety and high-efficiency production of steeply inclined thick coal seam entering deep mining, it is urgent to carry out mechanical test research on coal samples affected by mining depth in order to better understand the energy accumulation and its evolution law in the process of mining stress increase under the influence of mining depth.…”

Coupling Analysis of Water Injection Softening-Precursor Information Prediction of Coal-Rock Mass Based on Energy Conduction

“…The essence of rockburst is the differential distribution of energy caused by mining disturbance and the inevitable result of the dynamic adjustment in the process of quantitative change [12][13]. The existing energy priming theory shows [14][15][16][17] that the formation of rockburst is often highly correlated with the dynamic-static combination.…”