Study On Gas Creep-seepage Law Of Coal Seam With Soft And Low Permeability

It is an specially complex and dynamic solid-gas coupling process of the gas flow in coal seams,and the process is the result of gas flow field and coal deformation field.And a large number of factors made a great deal of influences to this process.Creep is the main form of the coal-rock mass rheological property,the creep damage and instability of the loaded coal-rock mass with the increase of time is caused by the creep characteristics.This paper takes the loaded briquette coal specimen which containing gas as the research object.And based on the structure model of pore-fissure media,with the help of the laboratory simulations and theoretical analysis this paper systematically analyzed the core structure,fracture structure of coal and the seepage characteristics and solid-gas coupling effect of coal containing gas.This article assumes that the gas flow field is constituted by the adsorbed gas diffusion in coal matrix and the free state gas Seepage in coal mass fracture.And Gas seepage in coal mass fracture comply with Darcy's law.This paper primarily combining laboratory simulation experiments and theoretical analysis research methods,taking the RLW-S500 G creep testing machine and gas adsorption-desorption-seepage experiment system as platform to carry out creep-seepage tests of coal samples containing gas under different gas pressures and confining pressures.Which is aimed to research the creep-seepage laws and creep instability phenomenon of loaded raw coal samples with containing gas.The main conclusions can be seen from this paper as the following:The microstructure characteristics of coal containing gas study.The classification and genesis of the core structure,fracture structure of coal containing gas were systematically summarized.And combined with the box counting dimension in fractal theory,comprehensively consider varied factories influencing the internal structure of coal,the mathematical model of porosity of coal containing gas was established.And the absorption characteristic,desorption characteristic and transformation characteristic were studied.In the experimental process of creep-seepage tests of coals containing gas,the results show that with the increase of axial press the permeability of coal contain gas firstly decreases and then be steady.The permeability of coal gradually increases when the coal containing gas entering a non-steady-state creep stage,and it will be the maximum when the coal damages.With the increase of confining press,the coal become more tight,and the change regulations of permeability of coal contain gas are similar to the process of axial press.Pore-pressure in the inner of coal will increase with the increase of gas pressure,and the permeability will slowly decrease at first and then it will slowly increase.There is a inflection point between the permeability curve and gas pressure curve,and this is a typical phenomenon called slippage effect.Based on the failure processes during the creep process of coal containing gas,this paper establishes and verifies the creep model and damage evolution equation of coal containing gas combined with existing creep model and theory of creep-seepage.And this creep model can effectively express the creep process of coals containing gas under three dimensional stress state.Combined with the technology and method of gas drainage in daily production of Daping mining and Gaocheng mining.The fifth chapter will put forward rationalization proposals in order to optimize parameters for gas extraction of gas containing coal based on the previous content.