Matrix compression and multifractal characterization for tectonically deformed coals by Hg porosimetry

Concerning the matrix compression and inter-particle volids, the multifractal characteristics [f(alpha) and D-q] were revealed through LPCO2/N(2)GA (low temperature CO2/N-2 adsorption) and HPMI (high-pressure mercury intrusion) for bituminous TDCs (tectonically deformed coals). The CCs (compression coefficients) increase with the increasing tectonic deformation during brittle deformation stages and decrease for the shear-and ductile deformation coals. The singular index (alpha(0)) transformations demonstrate that the brittle-and shear deformation can promote the PSD (pore size distribution) irregularity. The lower spectral width (alpha(q)-alpha(q+)) for the cataclastic( 0.54-0.58, 0.56 in average), mortar-(0.63-0.64, 0.64 in average), and granulitic coals (0.63-0.64, 0.64 in average) indicates the relatively simple multifractal structures of the PSD. While for the shear-and ductile deformed coals, the multifractal structures are complex with high heterogeneity and significant internal differences within PSD. The left-hand side width (alpha(q)-alpha(0)) and D-0-D-1 (the difference of information dimension to capacity dimension) increase, indicating that the shear-and ductile TDCs have a more clustered distribution in pore volume than brittle TDCs. There exist good positive linear relationships between Dap (adsorption pores' fractal dimension by Sierpinski model) and left-side width D-10-D-0 (R-2 = 0.8741), as well as between D-sp (seepage pores' fractal dimension by Sierpinski model) and right-side width D-0-D-10 (R-2 = 0.831), indicating that the variations of multifractal parameters for q > 0 are attributed to seepage pores' heterogeneity and these for q < 0 are assigned to adsorption-pores' heterogeneity. The D-10-D-0 increases with the increasing deformation intensity, indicating the most complex shapes of the adsorption pores for the ductile TDCs. The D-0-D-10 firstly decreases for the brittle-and shear TDCs then increases for the ductile TDCs.