Numerical Simulation Of Stress Damage And Water Injection Characteristics Of Coal Based On CT Technology

Coal seam water injection is a multi-scale complex project that is coupled by many factors,and usually undergoes a process of exploration from macroscopic phenomena to microscopic mechanisms.From the micro level,the pore fracture characteristics of the coal will directly affect the effect of macroscopic coal seam water injection.At the same time,the deep geological environment such as high ground stress,high ground temperature,high gas and high karst water pressure indirectly affects the flow and propagation of fluids by affecting the evolution of pore fractures during coal formation and the expansion and development of coal pores under mining disturbance.At present,the research on the mechanism of microscopic water injection seepage is still unclear,and the description of the stress effect in the process of water delivery is lacking.Therefore,it is of great significance to study the evolution law of coal and its damage mechanism under the stress-seepage coupling.In order to explore the mechanism of water injection seepage under the microscopic scale,the relationship between coal deformation and water migration is clarified.Firstly,through the CT scanning experiment of the coal samples collected on site,the reconstruction of the microstructure of the coal is completed by using the reconstruction software based on MATLAB language.On this basis,the Mohr-Coulomb constitutive model and the failure failure criterion are used to simulate the stress loading,and the deformation model of the coal is obtained.Finally,the water field and air field structure are added to the deformed structure model.The ALE algorithm with built-in Navier-Stokes equation is used to simulate the seepage of water injection,and the influence of model deformation on the seepage law of water injection is discussed.The research results show that stress concentration is easy to occur around the fracture structure under the action of external force.There are some differences in the stress distribution between pores of different shapes.When the axial strain of the model is 1%,the degree of deformation of the pore and fracture structure is small,resulting in no significant change in the seepage distribution of the coal seam structure.As the displacement load increases,the fracture structure begins to show significant compression deformation.Especially when the axial strain of the model reaches 5%,the fracture structure is basically closed,and the fluid is difficult to reach the middle and rear regions of the model.The permeability change of the pore structure is more complicated,and the change trend of the seepage area gradually increases,and gradually decreases,first decreasing and then increasing.In this paper,the CT-three-dimensional reconstruction model is used to study the stress-seepage coupling effect of the microscopic coal structure,which enriches the existing digital rock physics research methods.