Experimental investigation on mechanics properties and failure of coal in Hancheng

The coal in Shanxi Formation of Lower Permian System in Hancheng is a fissured medium of high brittleness and low strength, and its compression strength and failure have a close relationship with the loading conditions and the loading rates. The paper, using rock mechanics method, carried out the research on the mechanical tests through different experimental method for coalbed methane engineering in Hancheng. The experimental results demonstrate that the relation of the loading direction with the direction of the main fracture (cleat) has an important effect on the mechanical properties. When the fracture strike is vertical to loading direction, the compression strength of coal rock is 1.35 times higher than that when the fracture strike is parallel to loading direction. The magnitudes of the elastic modulus and the Poison's ratio, however, are just opposite. When the fracture strike is parallel to loading direction,the elastic modulus of coal rock is 1.66 times higher than that when the fracture strike is vertical to loading direction, and Poison's ratio is about 1.15 times; Under the same experimental conditions, the coal will be more brittle and its strength increases with the loading rate. Thus, the research results may provide some references for recognizing the mechanical properties of fissured coal rock and its applications in engineering.