Research On Voids’ Fractal Characteristics And Permeability Of Typical Strata In North China Coal Field

On the basis of full investigation, drawing lessons from Hydrodynamics and Fractal theory, a mathematical model has been established, which is correlation model between the fractal characteristics of microscopic voids and macroscopic permeability of typical strata in North China coal field. The theoretical model under different scales was verified by indoor laboratory experiments and data from field test. The research objects are from three typical mining area(Kailuan, Inner Mongolia, Henan) four coal mines. Obtaining field data by means of drilling core, the polished sections for SEM and the small-diameter core samples for permeability determination have been gotten through processing.Small-scale analysis: The voids’ fractal dimensions under micro-scale are counted and analyzed by numerical image processing technology and Fractal theory. The fractal characteristics of voids are explored. The permeability related to the fractal dimension D is calculated. Two efficient SEM image processing and information extracting technology have been formed, which is MATLAB method and Photoshop + image-Pro-Plus + Excel method.Meso-scale analysis: The permeability k of cylindrical rock sample(diameter 2.5cm,longer than 5cm) was measured by HLB series constant fluid pump;Large-scale analysis: The permeability coefficient K was obtained by pumping and dewatering test.On this basis, the relevance between different permeability from different scales has been researched. The feasibility from microscopic features of voids to get to the macroscopic permeability has been studied.The theoretical assumptions and technical route will be verified by applying to the typical strata from Hebei, Henan and Inner Mongolia. The final effect of sandstone application is better than limestone. It is clear that in the large-scale hydrogeological applications, the accuracy is difficult to guarantee because of geology, engineering, and other factors, even if the mathematical model of permeability is established under different scales.