Study on gas seepage-stress-damage coupling model in mining coal and rock and its application

摘要

In order to improve effectiveness, safety and economy of protection layer mining, elasto damage constitutive model of coal and rock mass was constructed based on Mole-Coulomb criterion.Using damage variable as transition, coal and rock mass permeability-damage evolution equation was also built.Then, using mining rock mechanics, percolation mechanics and damage mechanics, gas seepage-stress-damage coupling modal of mining coal and rock was constructed.And the elasto plastic damage constitutive model was verified by numerical simulation program through FLAC3D.At last, gas seepage behavior under long distance protective later mining in Gu Qiao Coal Mine was studied through the elasto plastic damage constitutive model.Results showed that under influence of mining, permeability coefficient of protected seam was 1760 times of the original value and gas pressure deduced from 2.8 MPa to 0.6 MPa.Coal and gas outburst hazard was eliminated.Numerical simulation results were basically consistent with actual situation which indicated that the elasto damage constitutive model and gas seepage-stress-damage coupling model can be used to describe coal seam damage and its permeability change.This result has guiding significance on feasibility of protection layer mining, effect pre-evaluation of pressure relief gas extraction in protected seam and optimization of pressure relief gas extraction technology.