Study On Evolution Law Of Bearing Stress Of Steeply Inclined Coal Pillar In Mountain Landform

The long-term stability of steep inclined coal pillar under mountain landform in southwest mining area is conducive to the ecological protection of the surface and mountain.Based on the concept of green mining,aiming at the long-term stability of coal pillar,this paper takes The N2821 working face of Fengchun Coal Mine as the engineering background,adopts research methods such as field investigation,theoretical analysis,numerical simulation and field measurement.The stress distribution law of raw rock,the broken migration law of overburden rock and the evolution law of coal pillar bearing stress are studied deeply.The main conclusions are as follows:The effect of mountain landform on additional stress of coal strata is theoretically analyzed and numerically simulated,and the transfer law of mountain additional stress in coal strata is obtained.According to the topographic contour line of Fengchun coal mine,a three dimensional mountain landform numerical model is established to simulate the influence area of the occurrence of the mountain on the stress distribution of coal strata.The cartesian coordinate system is established and the stress distribution function of raw rock under this condition is obtained.The mechanical model of old roof beam in steeply inclined coal seam under mountain was established,and the mechanical analysis was carried out based on the calculation theory of elastic foundation beam,and the corresponding disturbance curve of old roof beam was obtained combining with the field parameters of Fengchun coal mine.The stress distribution law and the influence of mining parameters on the stress distribution of N2821 working face are obtained by numerical simulation.The results show that the inclined stress of working face is asymmetrical and the plastic zone is shell shape plastic zone.The length of working face has a great influence on the overburden bearing stress,while the dip Angle of coal seam has a great influence on the overburden shear stress.The stress model of steeply inclined coal pillar under the mountain was established,and the necessary conditions for the instability of steeply inclined coal pillar under the mountain were obtained through the stress analysis.The calculation formula for the width of steeply inclined coal pillar under the mountain was obtained combining with the strength formula of coal pillar,and the reasonable size of the coal pillar was 12 m after the relevant parameters of N2821 working face were substituted.Through numerical simulation,the evolution law of bearing stress and the influence of influencing factors on its distribution of the steeply-inclined coal pillar in Fengchun coal mine are obtained.The study shows that the coal pillar in the middle of the goaf is most affected by stress superposition.Due to the short size of the coal pillar,there is almost no elastic core zone in the working face of this section after mining.With the advance of the working face,nearly half of the coal pillars are still intact although some plastic damage occurs under the influence of mining,indicating that the size of the coal pillars determined by theoretical analysis is reasonable.By analyzing and simulating the maximum variation range of each influencing factor,the key factors influencing the bearing stress of steeply-inclined coal pillar under the mountain landform of Fengchun Coal mine are obtained,and the number of mining at multiple working faces that have great influence on the bearing stress of the same steeply-inclined coal pillar is 4.Meet spring through to the coal mine N2821 steep mine pressure measured analysis of fully mechanized working face,the face to the laws of the pressure,the working face advancing stress distribution and stress distribution of coal pillar mining,it is concluded that the laws of the agreement with the theoretical analysis and numerical simulation results,which demonstrates the above theory to determine the size of coal pillar of the rationality.After the field application,the working face has no influence on the mountain surface and village after mining.The research results can provide a certain reference for the design of coal pillar size in the working face of steep inclined coal seam under the mountain in southwest mining area.This thesis has 72 figures,6 tables and 100 references.