Experimental Study On Permeability Of Sand-based Cemented Filling Materials

With the improvement of coal resource mining technology in China,filling mining has been widely used as an important mining method to solve the “three unders” mining district and avoid industrial waste such as coal gangue and fly ash occupying cultivated land and polluting the environment.However,for mines that are affected by groundwater,filling mining will destroy the water-retaining layer within the coal mining area and groundwater will flow into the filling region through the cracks in the water-retaining layer,resulting in long-term immersion of the filling body in the groundwater,causing the filling body to be affected by the groundwater for a long time,thereby it affecting the long-term stability of the structure of the filling body.In order to explore the influence law of the permeability of the filling body,improve the water barrier performance of the sand-based cemented filling material and improve the safety of mining,the sand-based cementing filling materials with Aeolian sand as the filling aggregate and some cement and fly ash as the gelling materials is taken as the research object in this paper.the seepage law of sand-based cementing filling materials under the different proportions,different pressure conditions are tested respectively and the influence of various factors on the permeability of sand-based cementing filling materials was studied.Meanwhile the effect of pore size,porosity and surface structure on the permeability of the sand-based cemented filling material is discussed from a microscopic perspective.The main research results of the paper are as follows:(1)The permeability of the sand-based cement filling material under different stress conditions was tested by seepage experiments.The seepage law of the sand-based cement filling material under different axial and confining pressure and the influence of different stresses on the permeability of sand-based cement filling materials are analyzed.(2)According to the test results of the permeability of the sand-based cemented filling materials under different proportions,the seepage law of the sand-based cemented filling materials with different proportions are obtained and the primary and secondary relationships of different factors affecting the permeability of the sand-based cemented filling materials are summarized..(3)the porosity,pore size and surface structure of the sand-based cemented filling material are tested through experiments and the influence of the porosity,the main pore size and the change of the surface structure on the permeability of the sand-based cemented filling material was explained.