LAUSR

Abstract Mechanical properties of coal are key factors that influence coal mining and methane extraction. Considering the difficulties in obtaining the mechanical properties of the tectonic coal and some intact coal, uniaxial compression tests were conducted on both types of coal particles in the size range of 0.2–4.0 mm. The force-displacement curves, effective elastic moduli and tensile strengths of the intact and tectonic coal particles were obtained. The power functions were used to describe the distributions of the effective elastic moduli and tensile strengths with the diameters of both coal particles. Statistical distributions of the effective elastic modulus and tensile strength for each coal sample with different particle size intervals were also plotted using a logistic function. The test results revealed that the intact coal shows obvious brittleness, whereas the tectonic coal has a smaller brittleness. The obtained effective elastic modulus and tensile strength of the intact coal are 2.72–4.57 and 2.86–6.35 times those of the tectonic coal, respectively, with particle diameters of 0.2–4.0 mm. The characteristics of low strength and large deformation of the tectonic coal would result in greater difficulty of methane extraction and increased risk during coal mining. Some considerations on the structural model of the tectonic coal and measures to enhance the methane extraction efficiency and reduce the risk of mining were also analyzed.