Physical Properties Of Brittle Deformation Series Tectonically Defromed Coal And Quantitative Characterization Of Its Structure

The main research contents of this paper are physical properties and structure quantitative characterization of brittle deformation series tectonically deformed coals(TDCs).Based on the geological features of Suxian mining area,the macro-micro structure,pore structure,permeability and adsorption properties of the samples were analyzed by means of mercury intrusion experiment,liquid nitrogen adsorption experiment,permeability test and isothermal adsorption experiment.Parameters of fissure structure and pore structure were extracted and clustered.The fuzzy comprehensive evaluation method was used to construct the quantitative identification model of brittle sequence TDCs based on pore indexs and fissure indexs,the results of the test were tested.Main achievements and knowledge of the paper are as follows.(1)Macro and micro structure characteristics of brittle series TDCs and their differences are discussed.The primary structure coal is complete hard with original structure clearly visible,the cracks are mostly smooth primary fissures;Cataclastic coal shows as certain size of fragments with multiple directions smooth fracture development;Schistose structure coal is broken as tabular and schistose,the bedding fissure develop foremostly and there will be some cleavage characteristics;Mortar coal break into fragments of different sizes,there often develop multiple groups of joints in different directions,coal mass will be cut into different sizes by the intersection of cracks;Granulitic coal crush into small pieces or crushed powder,directional particle flow characteristics is visible,there develop large mount of fine fissures where fracture gathered,whose extension are unstable.(2)Pore and fissure structure characteristics and its control of adsorption and seepage were profound analyzed.With the increase of the coal mass deformation degree,the total pore volume,porosity,BET area and BJH cumulative pore volume of brittle series TDCs are increasing,the specific surface area changes little.The primary structure coal is dominated by the semi-open shape primary hole,with the increase of the deformation,the hysteresis loop and the liquid nitrogen hysteresis loop are becoming more and more obvious.The semi-open hole is gradually transformed into open hole or bottle hole.The adsorption amount of TDCs increases with the increase of adsorption pressure,but the increase rate decreases.Adsorption capacity of the brittle series TDCs is slightly larger than that of the primary structure coal,but the difference between is very small.The pore and fissure structure has a significant control effect on permeability,under the same stress condition,permeability increases with the degree of deformation.With the increase of the effective stress,the permeability is decreasing exponentially,and the permeability damage rate increases logarithmically with the increase of the effective stress.(3)Statistical method and fractal theory were used to characterize pore and fissure structure of brittle series TDCs,cluster analysis was performed meanwhile.With the increase of deformation degree,the fractal dimension,the total length of the fissure,the fissure area and the fractal dimension of the fissile sequence tend to increase,the fissure opening degree tends to decrease.Fracture density and fissure length are clustering in the first and second categories;fissure area,clustering effect of capacity fractal dimension D1 and fissure opening degree is not obvious.The Menger fractal dimension D2 is mainly in the range of 2.87-3.48,with the increase of coal deformation,D2 is increasing,and the cluster analysis shows that the samples are mainly concentrated in the first and the second categories.The FHH model fractal dimension D3 is between 2.23 and 2.82,with the increase of coal deformation,D3 has no obvious trend.D3 is mainly concentrated in the second cluster and the third cluster.Fissure density,fracture total length and D2 play a dominant role in the determination of brittle sequence tectonic coal types,and the remaining parameters have little effect on the identification results.(4)The comprehensive evaluation index system was established based on fracture density(M),fissure length(L),fissure opening(W),fissure area(A),fractal dimension fractal dimension(D1)and pore fractal dimension(D2),fuzzy comprehensive evaluation model of the pore-fissure index was constructed,and the quantitative characterization of brittle sequence TDC classification was realized.