Abstract
With the increased mining depth, the dynamic disaster of rock burst in coal mines has become increasingly prominent, and the impact tendency of coal and rock mass in deep coal seam mining is a necessary condition for the occurrence of rock burst and an important index to measure the failure of coal and rock mass. Laboratory tests and numerical tests were used to study the impact tendency of coal and roof strata, including the deformation characteristics, failure characteristics, and bending energy index of the coal and rock mass of different sizes, the failure law and energy evolution characteristics of tlhe coal and rock mass under the same size, and the unloading characteristics of the coal and rock mass under the same size and different confining pressures. The results are shown as follows: (1) The rock roof was determined to have a weak impact tendency through the mechanical test. (2) With the increased size, the microcracks in the rock samples increased correspondingly, and the increased meso‐defect leading to the increased heterogeneity was an essential reason for the size effect. The strength of the rock mass decreased with the increased specimen size. The larger the specimen size was, the lower the bending energy index was. (3) Triaxial loading and unloading were tested for the same size under different surrounding rocks. Under the same loading conditions, with the increased confining pressure, the strength and bending energy index of rock mass increased correspondingly, and the failure of rock mass transformed from tensile to shear failure. The failure form and strength characteristic of rock under the unloading condition are different from those under the loading condition. The failure degree was intense, with a high bending energy index. Compared with the loading situation, the impact tendency caused by unloading was higher, and the dynamic impact disaster was more likely to occur.
Highlights
Rock burst, a common dynamic disaster often accompanied with sudden, quick, and violent ejection of coal or rock during the exploitation of the coal seams, often happens in complex ways under special conditions, even without warning signs [1, 2]
(2) With the increased size, the microcracks in the rock samples increased correspondingly, and the increased meso-defect leading to the increased heterogeneity was an essential reason for the size effect. e strength of the rock mass decreased with the increased specimen size. e larger the specimen size was, the lower the bending energy index was
Under the same loading conditions, with the increased confining pressure, the strength and bending energy index of rock mass increased correspondingly, and the failure of rock mass transformed from tensile to shear failure. e failure form and strength characteristic of rock under the unloading condition are different from those under the loading condition. e failure degree was intense, with a high bending energy index
Summary
A common dynamic disaster often accompanied with sudden, quick, and violent ejection of coal or rock during the exploitation of the coal seams, often happens in complex ways under special conditions, even without warning signs [1, 2]. Such a failure characteristic poses a great threat to the safety and efficiency of mining [3, 4]. Based on theoretical analysis and experimental measurement, Yao et al [16] classified the impact tendency indexes of coal samples by taking surplus energy and peak damage factor as a judgment basis. E data basis is provided, which has a useful reference for preventing the impact tendency of the coal seam roof
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call