Abstract
This research is aimed at investigating the influence of the coal height ratio on the mechanical properties and damage behavior of rock-coal-rock combined samples (RCRCS) under coupled static and dynamic loads. For this purpose, a uniaxial cyclic dynamic loading experiment with four different coal height ratios of RCRCS was conducted. Mechanical properties, failure modes, and wave velocity evolution of RCRCS were analyzed; the process of rock burst under coupled static and dynamic loads in rock-coal-rock combined structure was discussed. The following research results are obtained. (1) The peak strength of RCRCS under static and dynamic load decreases with the increasing coal height ratio as an inverse proportional function. (2) The loading and unloading modulus remains consistent for the same levels of dynamic load; the coal height ratio of 40% may be the limit for the stable value of modulus. (3) The increase of the coal height in RCRCS leads to a gradual increase of the energy release rate; the cracks develop preferentially in coal and then extend to rock sample. The distribution of AE events and damage is consistent with the distribution of passive wave velocity. The research results provide important scientific bases for the guidance of early warning of rock burst.
Highlights
Rock burst is a dynamic disaster in mining engineering with a sudden and violent release of elastic energy accumulated in coal and rock, which poses a significant risk to mine safety [1,2,3]
(1) The peak strength of rock-coal-rock combined samples (RCRCS) under static and dynamic load decreases with the increasing coal height ratio as an inverse proportional function
(2) The loading and unloading modulus remains consistent for the same levels of dynamic load; the coal height ratio of 40% may be the limit for the stable value of modulus
Summary
Rock burst is a dynamic disaster in mining engineering with a sudden and violent release of elastic energy accumulated in coal and rock, which poses a significant risk to mine safety [1,2,3]. The number of coal mines in China with rock burst disasters has been raised from 32 in 1985 to more than 253 in 2019 [4]. Observations showed that the clamping effect of roof-floor surrounding rock on the coal body becomes more significant as the mining depth increases. Rock burst is not caused by a single rock layer or coal seam but by the structural damage of the roof-coalfloor combined system. It is of great significance to investigate the interaction mechanism of static load and dynamic disturbance in the process of rock burst [10,11,12]
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