Water-Rock-Sand Mixture Flow Theory Of Crushed Rocks And Temporal-spatial Evolution

Because of the shallow,thick and large-scale coal reserves in Western China,high-intensity mining method is adopted in these mining areas.The crushed(caved)zone above coal mine within thin bedrock caused by high-intensity mining often directly connected to the loose sand layer,which will cause water-sand inrush disaster.To illustrate the water-sand inrush and instability failure mechanism in crushed rocks after mining,this paper focuses on the interactions between migration of water-rock(fine particles)-sand mixture fluid and spatial-temporal evolution in crushed rock skeleton void.Theoretical modeling,laboratory test,numerical simulation methods are involved in this study.The results are obtained as follow.(1)The water-rock-sand mixture flow model is established,which including(a)mass concentration,mass conservation,continuity equations of water-rock-sand mixture fluid;(b)constitutive equations that describing fine particle migration released by rock skeleton;(c)non-Darcy(momentum conservation)equation of mixture fluid.Based on this model,the failure characteristics caused by seepage are presented.Numerical solutions to mixture flow model and failure characteristics are gained by Galerkin FEM and FDM.(2)The test system is developed in accordance with the controlling parameters in mixture flow model and the spatial-temporal evolution of seepage field,including(a)cylinder-shaped parameters in material test system determine the controlling parameters of model;(b)according to the inverted trapezoidal-shaped distribution of crushed rocks within roof,the test system for porosity spatial-temporal evolution of crushed rocks is improved.The cone-shaped parameters in seepage field test system tests the temporal evolution of porosity,Aeolian sand outflow rate and final porosity distribution.(3)The mixture flow model is simplified as water-sand and water-rock mixture flow model respectively.The accuracy of the three models is verified through experimental invistigation.The differences of their spatial-temporal evolution of seepage field indicate that: The porosity increase induced by fine particle migration will cause the increase of Aeolian sand outflow rate;the flow resistance of Aeolian sand reduces the fine particle migration.The stress field calculations of the water-rock and water-rock-sand mixture fluid models show that: the flow resistance of Aeolian sand leads to the decrease of shear stress and increase of the instability failure time.(4)The quantitative calculation method of water-sand inrush is obtained in accordance with spatial-temporal evolution of seepage field.The reason for the frequent occurrence of water-sand inrush in Liangshuijing coal mine is analyzed and mixture flow model is adopted in field stimulation.It concludes the effect law of the water-sand inrush and provides the corresponding prevention methods.