Research On Non-Darcy Flow Seepage Characteristics Of Grade Coal Blending Rock Based On The Fractal Theory

The permeability of the fractured rock mass is many times higher than that of the intact rock mass,so the disaster caused by the penetration mostly happens in the area of broken coal rock.However,due to the different water conditions in the underground engineering,the fractal size of the fractured rock mass under different humidity is greatly different,which affects the porosity of the fractured rock mass and changes its non-Darcy seepage characteristics.Therefore,it is of great theoretical significance to study the non-Darcy seepage characteristics of different graded broken coal rocks for safe underground production.In the paper,in consideration of characteristics of broken coal rock particles accords with the fractal theory distribution,the fractal geometry theory is combined with the physical parameters of the fractured coal-rock porous medium,by analyzing the compaction deformation of different graded broken coal rock samples and the variation law of particle size fractal dimension and porosity,to establish the relationship between axial displacement and axial stress of broken coal rock porous medium under different gradation and infer the relationship between the granular fractal dimension and porosity,as well as it between the fractal dimension and axial stress.Using the DNS200 electronic universal testing machine,the mechanical properties of similar materials in standard coal samples under different humidity were tested to analyze the compressive strength,elastic modulus,stress,strain and the degree of fracture development under axial stress.Studies have shown that the standard sample decreases its compressive strength by about 22.70%and the modulus of elasticity is reduced by about 25.65%with each 15%increase in humidity.The DDL600 electronic universal testing machine was used to test the fractal dimension of the fractal dimension of crushed coal samples with different humidity and different grades,which is going to analyze the variation of fractal dimension and compressive modulus with axial stress on condition of this environment.And Based on fractal theory,the seepage characteristics of different graded fractured coalmass under axial stress and the influence of particle size fractal dimension on permeability characteristics were analyzed,The results show that when the fractal dimension is less than 2.4,the variation of the permeability of the broken coal is larger.When the fractal dimension is less than 2.4,the seepage tends to zero.and the theoretical model of axial stress and fracture-like seepage fractal was established.In this paper,by studying the particle size fractal dimension of fractured coal rock porous media,porosity and the variation law of permeability,theory of particle size fractal seepage has been enriched,which provided theoretical basis for non-Darcy seepage problems in the field of mining,groundwater geological engineering and so on.