Seepage Test And Mass Transfer Analysis Of Fractured Rock Mass

With the accelerating pace of domestic development and construction,more and more major projects and major projects related to international people's livelihood involve seepage mechanics.The mining depth of coal mines is also increasing.More and more mines are harming by water inrush and gas outburst.Therefore,the three axis stress and periodic load in the mine are the most common loading forms of two kinds of rock mass in the mine,and there is a great relationship between the seepage and the external load in the fractured rock mass.So,this paper uses the method of combination of experimental research and theoretical analysis to discuss the variation of the permeability characteristics of fractured rock mass under the conditions of three axis pressure and cyclic loading and unloading.According to the results of experimental and theoretical analysis,a mass transfer model of variable porosity is given in consideration of the transformation of small particles to the skeleton.The numerical calculation software is used to determine the influence of the conversion rate of the two factors on the permeability parameters.The following research results have been obtained:(1)A three-dimensional ensional stress test of the fractured mudstone permeability was conducted by the application of the self-developed crushing rock triaxial seepage test system.The following results were given:the variation of permeability with porosity under various loads;the variation of non-Darcy flow ? factor with porosity;the relationship between the steady-state critical permeability ks and the critical non-Darcy flow ?s during seepage loss and the main conditions for stable seepage loss in the fractured rock mass.(2)Tests of permeability characteristics under conditions of loading and unloading of crushing coal rock were carried out.The effects of cycle times on porosity,permeability and no n-Darcy flow factors were analyzed,and the fitting function of porosity-cycle number during loading and unloading was given;the variation of porosity,permeability and non-Darcy flow factors with the number of cycles was given.(3)On the basis of previous research results and theoretical analysis,a variable porosityseepage mass transfer model was established with the consideration of the conversion of fine particles and skeletons.By application of the theory of seepage mechanics,combirith Forchheimer's empirical formula,the one-dimensional active unsteady-stab page mass transfer kinetics equations are derived concerning the transit between the fine migrating particles and the skeleton.(4)A numerical method was used to solve the seepage mass transfer model with variable porosity concerning the conversion of fine particles and skeletons.The time-dependent curves of porosity,permeability,non-Darcy factor,and percolation velocity at different values of the conversion factor are given,and it can provide theoretical basis for preventing water inrush or coal and gas outburst.With the comparison of previous research results,it is believed that the one-dimensional active unsteady flow mass transfer kinetics equation set up in the paper can be used to describe the seepage behavior of broken rock mass.