Research On Ground Stress Control Action Of Gas Permeability Of Coal Seam

Analyzing the gas accident in our country’s "the eleven five year plan", coal and gas bursting was a serious threat to safety of coal mine, the main reason was the deep mine mining in recent years, the ground stress increased in deep coal seam, leading to lower permeability of coal seam, gas pressure and content increased, and the creep property of coal increased, the paper expounded the change of ground stress affected the coal permeability, analyzing the feasibility of gas drainage in relieved coal seam.The gas flow in the coal seam influenced by ground stress, considering the darcy seepage of gas was not enough, must be combined with the stress, and combining the permeability with deformation of coal seam, establishing coal seam gas flow coupling equations of the stress-damage-seepage, the paper used RFPA2D-Flow numerical simulation software was based on this constitutive equation.Through the simulation of RFPA software analyzed the strength of coal resisting the ground stress, reaching a conclusion that the bigger homogeneity coefficient, confining stress, the smaller porosity gas pressure and the compressive strength was bigger; the gas flowed in the coal seam reducing the stability of coal, under the action of ground stress reduced coal permeability first, if concentrated stress value more than the strength of coal seam, coal seam would appear macro fracture, leading to ground stress transferring, coal seam relieving and permeability increasing.Through the simulation of RFPA software on gas extraction of drilling in11-2original coal seam of DingJi coal mine, concentrated stress around the drilling resulted in damage of coal body, the concentrated stress moved away from the drilling, as a result the coal body around the drilling relieved, permeability increased; ground stress transferring and coal seam permeability changing had a relationship of cause-result and front-back, therefore, changing the stress state of large-scale coal body around the drilling, ground stress transferred to deeper coal seam, and the permeability of coal seam increased, at the same time, inspecting the results of gas extraction in original coal seam, finding that the gas extraction effect was not ideal in low permeability coal seam, so applying the measure to relieve the coal seam was necessary.Industrial test of long hole blasting to relieve coal seam and draining gas in11-2 coal seam of DingJi coal mine, through comparing the data of gas extraction, gas density and scalar quantity of drill site improved after long hole blasting, proved that ground stress reduced after blasting, the permeability of coal seam increased, and the effect was very well.Figure [49] Table [15] Reference [80]...