LAUSR

To accurately predict coal burst hazards and estimate the failure of coal pillars in underground coal mining systems, it is of great significance to understand the static and dynamic mechanical behavior of rock-coal structures. In experimental scale modeling, rock-coal structures are usually considered as samples (typically φ50 mm × 100 mm) composed of rock or coal components. This work examines the coupled effects of height ratio (a ratio of the height of coal to the height of whole sample) and loading rate on the mechanical interactions of composite samples using granular dynamic models. Results show that: (1) The peak strength of the composite sample decreases with increasing height ratio, while the peak strength increases linearly with loading rate under uniaxial compression. (2) Both the height ratio and loading rate have a significant effect on the micro-cracking in the composite sample. Micro-cracking evolves with strain and this rate increases first slowly and then advances rapidly. (3) Composite samples fail in a progressive manner, and the failure of the coal components controls the collapse of the ensemble sample. Specifically, cracks develop preferentially in the coal and then propagate into the rock.