To elucidate the dynamics of water seepage within coal matrices during coal seam water injection,this research integrates laboratory experiments with numerical simulations.Experiments were conducted to examine the deformation of coal structures and the evolution of permeability under the dual effects of geostress and pore water pressure coupling.A mathematical model for the evolution of volume deformation under hydraulic coupling was formulated,followed by dynamic numerical simulations of water injection seepage in coal using secondary development with User-Defined Functions(UDF).The findings reveal that porosity changes in the coal rock are jointly influenced by stress and water pressure,with coal rock axial deformation and water pressure distribution showing a progressive decrease from top to bottom.Volume deformation correlates positively with axial load and the magnitude of pore water pressure.Pore water pressure acts as the driving force for the permeation of free wa-ter within pores and fractures,also affecting the coal matrix's mechanical integrity,with increased water pressure facilitating matrix damage.Utilizing UDF to fit the porosity changes against pore water pressure based on perme-ability test results yielded simulations closely aligned with experimental observations,demonstrating minimal discrepancies.This approach,leveraging Fluent for dynamic simulation of fluid-solid coupling experiments,of-fers valuable insights into the seepage behavior of coal.
coal seam water injectionseepageUDFporosityfluid-structure couplingnumerical simulation
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