| The Jiangcang mining area of the Muli coal field in Qinghai is located on the northern edge of the Qinghai-Tibet Plateau,and the surface of the mining area is generally distributed with thick layers of permafrost.Compared with ordinary rock formations,the integrity of permafrost layers is very good,which has a significant impact on mining safety and surface damage characteristics during coal seam mining.Because the mechanical strength of frozen soil changes with temperature,it is of great significance to consider the influence of the temperature of the frozen soil layer on further revealing the breaking and breaking laws of the permafrost layer overlying the coal minin g process.This paper takes the first mining area of Nangmut Coal Mine in Jiangcang mining area as the specific engineering background,and uses physical experiments,numerical simulations,and theoretical analysis to study and analyze the breaking rules of permafrost overlying large-deep angle coal seams.Through the uniaxial compression test,the compressive strength and tensile strength of the remolded frozen soil specimens at different temperatures were tested,and the quantitative relationship between the temperature and the frozen soil strength was obtained.The FLAC3D software was used to simulate the excavation of the first mining face.During the excavation process,the stress distribution,migration law and plastic zone distribution of the permafrost layer were analyzed.The simulation results show that under the influence of mining,the stress distribution of the frozen soil layer does not change much,the whole frozen soil layer sinks about 2m,and the displacement difference due to asynchronous movement within the soil body,the temperature change has a significant effect on the displacement of the frozen soil,frozen soil Significant plastic failure occurred on both sides of the layer;on the basis of theoretical analysis and numerical simulation,a mechanical model was established to analyze and calculate the striking breaking step of the long-wall mining frozen soil strata,and the calculation formula of the frost breaking step of the frozen soil was obtained.The initial breaking step distance of the permafrost layer overlying the mining area is less than or equal to 88m,and the periodic breaking step distance is less than or equal to 11m.The research in this paper reveals the breaking law of long-wall mining overlying permafrost when temperature changes,which provides a theoretical basis and supplement for well mining and related research under similar conditions,and also has an important reference for the safe and efficient mining of coal mines in the mining area.value. |
