Research On The Damage Mechanical Characteristics And Permeability Evolution Law Of Coal Rock Under Hydraulic Couplin

In the engineering activities of coal mine resources exploitation,gas is the main factor causing coal and gas outburst accidents,and permeability is an important parameter to judge gas emission.With the continuous advancement of the mining face,the stress environment of coal in front of the working face changes obviously,which leads to coal damage under the disturbance of mining.In the underground environment,coal are in a complex environment where stress,water and gas are coupled with each other,and the evolution law of permeability is more complicated.The essential attribute of coal damage under external load is the process that energy dissipation causes coal to gradually lose its bearing capacity,and the sudden release of elastic strain energy is transformed into the power of damage,creating external conditions for coal and gas outburst.Therefore,it is of great significance to analyze the influence of water and stress on coal damage,and study the permeability characteristics and energy evolution law in the process of coal damage evolution to scientifically guide coal mine safety mining operations.In this paper,the test samples were taken from No.3 coal seam of Zhaozhuang Mine and Sihe Mine in Jincheng,Shanxi Province.Triaxial compression mechanical test and seepage test were carried out under different water content conditions by triaxial servo seepage device.By combining experimental research with theoretical analysis,the mechanical characteristics and seepage characteristics of coal in the process of hydraulic coupling were deeply studied,and the models of coal damage-seepage and damage-energy coupling were established.The main research progress is as follows:1)Triaxial compression seepage test and effective stress seepage test of coal with different water contents are carried out,and the damage mechanics and seepage characteristics of coal with different water contents are discussed respectively.The change of mechanical strength of coal in the process of whole stress-strain is studied,and the influence law of water on coal mechanics and seepage characteristics is revealed.2)The overall damage evolution equation of coal deformation and failure process under hydraulic coupling is put forward.Based on the research of coal damage mechanics and permeability characteristics,the damage constitutive model of coal under the action of water and stress and the damage seepage model of elastic-plastic deformation of coal in different stages are established.The rationality of the established model is verified by experiments,which can represent the dynamic mechanical law and gas migration characteristics under the disturbance of coal mining.3)Analyze the energy evolution law of coal damage process under the influence of water and stress,and the energy accumulation,transformation and release of coal show periodic changes at different deformation and failure stages.The unit of coal are divided into two parts: pore and skeleton.Based on statistical damage mechanics,the damage constitutive model under the influence of pore change is established from the angle of energy dissipation.The influence of pre-peak and post-peak brittleness parameters on the brittleness degree of coal is quantitatively analyzed by energy parameters,and the mutual feedback relationship between the overall damage and energy dissipation of coal in the process of triaxial compression mechanics is further revealed.