A Non-Darcy Flow Model For Water Inrush Through Broken Rock Mass And Its Engineering Application

Water inrush is one of the most serious disasters that threaten the safe production of underground mines in China.Water inrush generally flooded mine in a short time,which cannot only cause heavy economic losses and grievous casualties for mines,but also give serious impact on the water resource environment of the mine and surrounding area.Therefore,it is of great theoretical and practical significance to study the seepage problem of water inrush for the identification of flow mechanisms,prediction of inflow and prevention of inrush disasters.Water outburst through fault and collapse column,post-peak and caving rock masses by mining can be considered as water inrushes through broken rock mass.The relationship between the velocity and pressure gradient is nonlinearity.The Darcy’s law cannot model the seepage mechanism or predict inflow of water inrush accurately in the engineering practice.This paper focuses on the seepage problem of water inrush through broken rock mass under the erosion effect.Laboratory experiment,theoretical modeling and numerical simulation are used to study the non-Darcy seepage mechanism of broken rock mass.The main works and achievements are presented as follows:1.The pore structure of broken rock mass will change with small particles migration.Based on the essence of structural evolution,a simplified mesoscopic numerical model of porous medium is established.Water-flow through the pore spaces of porous media is governed by the incompressible Navier-Stokes equation,which is calculated by COMSOL.Thus,the relationship between pressure gradient and velocity at the macro-level is related to the fluid flow mechanism at the meso-level.It is clearly that the non-Darcy seepage in broken rock mass is the macro-responses of the development of fluid inertia at the macro-level.2.14 groups broken rock mass specimens with different porosity are made.The steady seepage method is adopted to carry out the non-Darcy seepage experiments using a high-velocity seepage system for porous media,which is self-developed by Northeastern University.The formula of inverse function is recommended to describe the relationship between the non-Darcy factor and square root of the permeability.The equation with few parameters satisfies the dimensional consistency principle and it is convenient for engineering applicability.3.For the non-Darcy seepage behavior of broken rock mass under erosion effect,a mixed fluid non-Darcy seepage model is established based on the theory of continuum mechanics.In this model,water and the fluidized particle are treated as one-phase mixed fluid in the process of seepage through broken rock mass.The model can reflect the interaction of the evolution of broken rock mass structure,the high-velocity seepage and the filling particles flow.Additionally,the numerical solution of the model is realized by FELAC software.The evolution laws of broken rock mass structure,fluid media and seepage field under seepage erosion are obtained by numerical simulations.4.Uniformity of dynamics system of the three flow fields is one of the significant characteristics of the water inrush through broken rock mass induced by seepage erosion.The three flow fields include Darcy flow in aquifer,Forchheimer flow in broken rock mass channel and Navier-Stokes flow in roadway.Taking this characteristic into account,a non-Darcy seepage model of water inrush through broken rock mass is built.The model establishes the connection of aquifer and the roadway through broken rock mass.Moreover,the whole dynamic process simulation of water inrush under seepage erosion is realized by FELAC software.5.Taken the water inrush through fault X1 in Zhongguan iron mine as an example,the whole process of water inrush through fault is simulated based on the proposed non-Darcy seepage model.Then the evolution of the fault structure and seepage field is analyzed.Finally,the non-Darcy seepage mechanism of the water inrush through the fault induced by the seepage erosion is revealed.It can be a reference for the studies of non-Darcy seepage problem in other similar mines.