Experimental Study On Fluid-Solid Coupling Seepage Stability Of Broken Coal And Rock

With the increase of coal mining depth,more and more mines are facing the threat of dynamic disasters such as water inrush or coal and gas outburst.The occurrence of such dynamic disasters are closely related to the seepage of water and gas in broken coal and rock.Therefore,the study on the rule of fluid-solid coupling seepage of broken coal and rock becomes the basic problem of water inrush or coal and gas outburst disasters prevention and control.In this paper,we studied the rule of fluid-solid coupling seepage of broken coal and rock by using methods involving experiments,theoretical analysis and numerical simulation,and obtained the following research results:(1)The seepage test of broken coal and rock under step loading is carried out,and the variation law of porosity with time under axial load is given.The parameter Dv describing the degree of decrease of seepage velocity is defined,and the relationship between the parameter and the effective stress is given.The permeability parameters and creep parameters of the broken coal and rock samples with different particle sizes are obtained.(2)The seepage characteristics of broken coal and rock under triaxial stress are tested by using the self-developed triaxial permeability test system.The results show that the seepage law of broken coal and rock under triaxial stress is in accordance with the Forchheimer equation;The relationship between seepage velocity and effective stress is deduced;The variation law of confining pressure and permeability of broken coal and rock is obtained,i.e.the exponential foinula k = aeb?3 is described.The specific effects of porosity on the permeability of broken coal and rock under triaxial stress is analyzed.(3)Based on the experimental results and theoretical analysis,the dynamic model of fluid-solid coupling seepage of broken coal and rock mass is established.The model is simplified by decoupling method,and the total equilibrium state of the seepage system is obtained.The critical pressure gradient of seepage failure of broken coal and rock is obtained,which can provide reference for the prevention of dynamic disaster such as water inrush or coal and gas outburst.(4)The numerical simulation method is used to solve the hydrodynamic model of the broken coal and rock.The variation of a series parameters,including the pore pressure,porosity,permeability,non-Darcy flow ? factor etc.,in the numerical simulation results,are analyzed.The dynamic model of fluid-solid coupling seepage can be used to describe the seepage behavior of broken coal and rock.