The Research On Mechanism Of Outburst When The Tunnel Through Gas-containing Fault Zone

China is the most serious country which coal and gas outburst happened frequently in the word,whether in quantity or in scale.It is seriously affecting our economic development and social harmony.Therefore,domestic and foreign experts effort to study and explore this subject unceasingly Aimed at the coal and gas outburst problem of the special geological structure,and combined with ABAQUS three-dimensional numerical simulation technology,this article simulates coal and gas outburst process of the Daping Coal Mine 21 rock down tunnels and analyses the geological parameters which impact the coal and gas outburst.In this paper,main contents and achievements are as follows:1.Combinedwith damage mechanics,this paper derives the porosity,permeability and effective stress principle of the coal contained gas,and associates these variables with the plastic strain of rocks through normalizing all the variables,then establishes the user subroutines for the software's secondary development for coupling the variables in the finite element simulation.2.Relying on the Daping coal mine,this paper sets up three-dimensional finite element model,simulates the process of coal and gas outburst in the special geological conditions with gas pressure.Then a researches on the damage of the cohesive elements at the two interface is done.Through which we arrive at the curve of the rock fissures extend length under the different gas pressure.3.In this paper,I establish the different numerical models of the tunnel excavation with different length,then get the safety thickness of the tunnel excavation from the asymptotic fault plane.As the tunnel excavation close to the fault plane,the propagation of the rock's crack presents a rapid expansion trend,at the same time the gas pressure gradient in rock also increases accordingly,which increases the risk of the coal and gas outburst.The safety thickness of the tunnel simulation should be between 10 to 15m.4.Compared the simulation results with the Daping Coal Mine coal and gas outburst accident,a conclusion can be known that the simulation results and the actual situation are basically consistent.This conclusion can provide guidance for other similar projects and reduce the occurrence of the coal mine.