Study On Permeability Characteristics And Micromechanism Of The Lower-group Coal Floor Rock

With the shallow coal resources depletion in North China coalfield, the region of the lower-group coal bearing confined-aquifer threat is increasing. For the sake of safety, it must be well aware of the formation mechanism of aquifer and water-resisting layer. Taking the lower-group coal floor rock as the research object, on the basis of the traditional geology and modern mineral analysis technology to analyse the characteristics of lithology, through the indoor experiment and the similar experiments and theoretical analysis to research micro pore structure characteristics of coal floor rock and its effect on the permeability, from the micro perspective to analyse the mechanism of karst aquifer and characteristics carbonate rocks, it achieves the following innovations.(1) Using the method of pressure solution to prepare the continuous changes microstructure of samples, analyzing the influence of microstructure on the permeability, it gets the relationship of pore throat diameter of the pore ratio and permeability of argillaceous limestone and sandstone respectively, the results show that the relationship of the pore ratio and permeability is positive, and different rocks show different patterns.(2) According to the experimental results, the equations of pore throat diameter and permeability are established. Basing statistics results of the pore throat in the casting slice, the spatial distribution of the pore throat is not pure random variables but random field, and infiltration model is established under considering spatial variation of the pore throat.(3) Analyzing threshold cast thin section of rock using of image processing technology, getting the physical model of micro entity permeability, and influence of the pore throat diameter and the osmotic pressure gradient on rock permeability through the Comsol finite element simulation, the results show that it is the function relationship of micro pore throat diameter and pressure power.(4) The soluble strength of the rock composition controls dissolution rate and microstructure controls morphology of rock erosion, the strongly soluble limestone composition and weak permeability and the unhomogeneous distribution pore throat are the main cause of corrosion concentrated force strongly, which are the main reason for the limestone developed into strong karst aquifer. The relatively poor soluble dolomite composition and the homogeneous distribution pore throat, which are main reason for developing uniform equivalent corrosion and the formation of the honeycomb caves.(5)Through the laboratory permeability test and impermeability test, it verifies the accu racy of the equation of the proportion of different pore throat diameter of the pores and permea bility, and the accuracy of the relationship between anti-pressure strength and diameters of pore throat. Based on the relationship, it gets the cause of carbonate rock which have waterproof f unction is mainly the diameter of the pore throat which is less than 1μm.