Study On Non-darcy Seepage Flow Stress Coupling Of Fractured Rock Mass

Mine water inrush accident is one of the most serious disaster threats in mining production,which seriously threatens the safety of mining production.When the mine water inrush accident occurs,the water inrush intensity is large,the seepage speed is fast,the simple linear Darcy law is no longer applicable,most of them belong to the broken rock mass high-speed non Darcy seepage.The fractured rock mass is often in a complex stress environment.The interaction between stress field and seepage field is a high-speed non Darcy seepage stress coupling problem.The study of this problem has important theoretical significance and engineering value.In this paper,for the non Darcy seepage stress coupling problem of fractured rock mass,by means of the combination of micro mechanism research and macro average law research,physical experiment law research and numerical model calculation research,the following three aspects are studied:the non-linear generation mechanism of fractured rock mass seepage,the seepage experiment of fractured rock mass,the establishment and solution of seepage stress coupling model:(1)The micro model of porous media seepage is established to simulate the free flow of viscous fluid and analyze the transition law from linear to nonlinear seepage state.The transition of seepage from linear to non-linear is a gradual development process.The seepage pressure gradient and flow velocity are in accordance with the linear Darcy equation when the Reynolds number is low,and the non-linear Forchheimer equation when the Reynolds number is high;the larger the porosity is,the smaller the critical pressure gradient of seepage transition is,the more likely the seepage will be non-linear.(2)the permeability of fractured fine sandstone with different pore structure is much higher than that of intact tight rock under high pressure gradient.The seepage state under high pressure gradient conforms to the nonlinear Forchheimer equation.The permeability is greatly affected by pore structure.With the increase of porosity,the non Darcy permeability increases while the non Darcy factor decreases.(3)the high-speed seepage experiment is carried out under different confining pressure conditions to analyze the influence of stress on the permeability of fractured rock mass.The permeability of fractured rock mass is obviously affected by stress.The expression of sum is obtained by defining the sensitive factors of permeability and non Darcy factors.The study of non Darcy seepage stress coupling needs to consider comprehensively the pore structure and stress state of fractured rock mass.(4)the non Darcy seepage stress coupling model is established,and the finite element software felac is used to solve the model.The velocity and pressure gradient of the model are in accordance with the Forchheimer equation,the evolution process of seepage pressure is in accordance with the law of seepage experiment,and the change law of seepage parameters under the action of stress is in accordance with the law of seepage experiment.The interaction between high-speed non Darcy seepage field and stress field is realized,which provides a numerical model for the study of non Darcy seepage stress coupling problem of fractured rock mass.