Microstrecture Characterization And Seepage Numerical Simulation Of Coal Based On Micro CT Technology

Coal is a kind of material with complex and heterogeneous pore structure.The complex pores and fractures with different sizes constitute a complex and diverse microstructure.In the process of mining,there are still many difficulties in the efficient application of coal seam water injection technology.The fine characterization of micro pore and fracture structure is the key basis for efficient engineering practice.And the change of in-situ stress has an important impact on the micro characteristics in the process of mining.Therefore,the study of micro pore and fracture structure of coal body is of great significance for guiding the coal seam water injection.In this paper,the micro CT technology is used to scan the gas fat coal samples,with the help of three-dimensional visualization method to process the image and build a digital model.On the basis of the pore fracture model,the pore network model is established to quantitatively analyze the microstructure parameters such as pore number,throat number,pore radius,throat radius and coordination number of the coal body,and the water injection seepage simulation is carried out to analyze the seepage law of the coal body in the velocity field and pressure field;and the coal matrix model is established to carry out the load loading value in the physical field of solid mechanics simulation,analysis of the coal in the stress state of the micro pore fracture structure damage evolution law.The results show that:(1)In the quantitative statistics of microstructure,the results show that the porosity of each section of the model ranges from 4.05%to 10.23%,the pores are distributed in irregular points,the throat connected between the pores is various,and the pores and throat radius at the fracture are various The maximum pore radius is 12.51 μm and the average pore surface area is 326.6 μm2.(2)In the process of numerical simulation,the pore fracture model of coal body is used for water injection seepage simulation.Along the direction of water seepage,the seepage pressure decreases gradually as a whole.At the fracture location,the pressure distribution of the upper part and the lower part is hierarchical,and the change degree of the fracture location pressure is small;the change of seepage speed and mass flow is more obvious at the fracture location.The coal matrix model is used for stress loading simulation,the model is uniaxial compressed.Under the pressure of 5 MPa,the relative change of the model is more obvious in the upper part of the fracture,and the stress concentration phenomenon occurs in the fracture.0～2 MPa basically has no damage;2～3 MPa is the generation,expansion and connection stage of local damage,in which the damage develops stably;4-5 MPa damage increases rapidly until the damage.For heterogeneous coal samples,numerical simulation has a certain advantage in the study of damage,failure form and mechanism of coal samples.In this paper,the CT 3D reconstruction model is used to study the basic physical characteristics of the coal body,and the numerical simulation is used to analyze the structural characteristics of the coal body in different physical fields.The in-depth study of the coal body provides a theoretical basis for the mine engineering practice.