Advancing rate effect on rock and coal failure format in high- intensity mining face

Dynamic failure or even rock burst makes it difficult to keep surrounding rock stay in good control in high intensity mining face. Experimental,theoretical and numerical simulation methods are used in this study to analyze geotechnical material failure feature and strain energy distribution formation in the surrounding rock under intense min- ing activity and,moreover,mechanism of dynamic failure of the surrounding rock is studied. Rock and coal specimens show static failure formation under low loading rate,but it transits into dynamic failure gradually with increase of the loading rate. Geotechnical material belongs to loading rate dependent material which means the stress state may not be subject to the consistent condition. So the rock and coal may present dynamic failure if the loading rate is too high. With increase of the face advancing rate,loading rate of the major principal stress and unloading rate of the minor prin- cipal distributed in the coal seam are rising which may lead to dynamic catastrophe of the surrounding rock. Strain en- ergy density of the coal near the void space is high and the energy dissipated by the main roof at the fracturing time lead to sudden growth of the strain energy density in the coal which make coal spalling show dynamic features. The dis- tance between positions of the peak point of the strain energy in the coal seam before and after the fracture of the main roof is the key area of the surrounding rock control.