Study Of The Hydraulic Flushing Boreholes Reasonable Amount Of Coal Extraction Considering The Time Effect

In the development of the coal industry,domestic and foreign scholars have invented a variety of hydraulic pressure relief measures,such as hydraulic punching,coal seam water injection,hydraulic fracturing,and achieved good application effect,but the mechanism of gas extraction under the creep of coal is lacking in-depth study in those technical measures.Based on the experimental method of laboratory parameter test,numerical simulation and field investigation,the paper discusses the gas extraction effect considering coal creep,the following research:(1)Based on the Burgers viscoelastic model,the visco-elasto-plastic creep model of Cvisc coal is constructed and deduce the constitutive equation of creep segment of Cvisc,The results show that the Cvisc creep model can be complete and accurate describe the whole creep process of coal.(2)In the laboratory,the coal samples collected in the field were tested under different axial compression creep parameters.The experimental data show that the instantaneous strain accounts is the main part of the total deformation.When the stress level is high,the specimen usually enters the accelerated creep stage until it is destroyed.The four creep parameters in the model are slightly different under different stress and show regular changes.(3)Based on FLAC3 D finite element numerical simulation software,the Cvisc visco-elastic-plastic creep model is constructed.The simulation results show that the pore size is increasing and the logarithmic function increases with the amount of coal and the amount of coal after creep stabilization,and when the amount of coal is 1.15 t / m and 0.77 t / m,the creep stability Safety Requirements for Safety Work in Mining Face.(4)Considering the variation law of porosity and permeability in coal seam under creep deformation,the mathematical model of hydraulic drainage with different expansion is constructed.The simulation results show that with the increase amount of coal,the effective extraction radius and the plastic zone around the hole Showed the trend of logarithmic function growth.(5)To study the relationship between the amount of coal and the creep deformation law of the coal body around the hole.Combining with the field drilling in Xuehu coal mine,Take the effect of penetrating the hydraulic reinforcement and the safe operation requirements in mining roadwaypenetrate as a consideration,to determine the reasonable amount of coal expansion for Xuehu coal deposit state is 1.15 t / m.