In this study,the tomography of dynamic stress coefficient(TDSC)was established based on a mechanical model of stress wave propagation in bedding planes and a mathematical model of the stress wave attenuation in rock ...In this study,the tomography of dynamic stress coefficient(TDSC)was established based on a mechanical model of stress wave propagation in bedding planes and a mathematical model of the stress wave attenuation in rock masses.The reliability of the TDSC was verified by a linear bedding plane model and field monitoring.Generally,the TDSC in the dynamic stress propagation of bedding planes increases with the following conditions:(1)the increase of the normal stiffness of the bedding plane,(2)the increase of the incident angle of the stress wave,(3)the decrease of the incident frequency of the stress wave,or(4)the growth of three ratios(the ratios of rock densities,elastic moduli,and the Poisson’s ratios)of rocks on either side of bedding planes.The additional stress weakens TDSC linearly and slowly during the stress wave propagation in bedding planes,and the weakening effect increases with the growth of the three ratios.Besides,the TDSC decreases exponentially in the rock mass as propagation distance increases.In a field case,the TDSC decreases significantly as vertical and horizontal distances increase and its wave range increases as vertical distance increases in the sedimentary rock layers.展开更多
In coal mining, roof collapse and support body failure during entry excavation are a common problem.During excavation, entry positions may be subjected to separation, shear-slip, support body failure,and roof collapse...In coal mining, roof collapse and support body failure during entry excavation are a common problem.During excavation, entry positions may be subjected to separation, shear-slip, support body failure,and roof collapse. Weak coal-rock interfaces allow for shear-slip between layers, causing anchor bolts and cables to fail. Six entry position models are created to evaluate the failure process and determine the best entry position. Results indicate that roof rocks experience bending and shear-slip along the coal-rock interface. Nearby mining activity causes asymmetric deformation of the entry and shear-slip at the roof corners. When anchor cables and bolts in the roof are insufficient to limit separation and shear-slip, support bodies are subjected to tension, shear, and bending. Once the support body fractures,the entry roof experiences progressive deformation resulting in collapse. We determine the optimal entry position in which shear-slip and residual coal are minimized.展开更多
基金This work is supported by the National Natural Science Foundation of China(Nos.51804099 and U1704129)the Focus Research and Special Development for Scientific and Technological Project of Henan Province(No.202102310542)+1 种基金the Fundamental Research Funds for the Central Universities(No.2018ZDPY02ZDPY02)the research fund of State Key Laboratory of Coal Resources and Safe Mining,CUMT(SKLCRSM19KF011).
文摘In this study,the tomography of dynamic stress coefficient(TDSC)was established based on a mechanical model of stress wave propagation in bedding planes and a mathematical model of the stress wave attenuation in rock masses.The reliability of the TDSC was verified by a linear bedding plane model and field monitoring.Generally,the TDSC in the dynamic stress propagation of bedding planes increases with the following conditions:(1)the increase of the normal stiffness of the bedding plane,(2)the increase of the incident angle of the stress wave,(3)the decrease of the incident frequency of the stress wave,or(4)the growth of three ratios(the ratios of rock densities,elastic moduli,and the Poisson’s ratios)of rocks on either side of bedding planes.The additional stress weakens TDSC linearly and slowly during the stress wave propagation in bedding planes,and the weakening effect increases with the growth of the three ratios.Besides,the TDSC decreases exponentially in the rock mass as propagation distance increases.In a field case,the TDSC decreases significantly as vertical and horizontal distances increase and its wave range increases as vertical distance increases in the sedimentary rock layers.
基金supported by the National Natural Science Foundation of China (Nos.51704098,51474209,and 51574227)the Key Project of Science and Technology Research of Henan Education Department of China (No.16A440004)the Natural Science Foundation of Hean Polytechnic University of China (Nos.B20184 and B2018-65)
文摘In coal mining, roof collapse and support body failure during entry excavation are a common problem.During excavation, entry positions may be subjected to separation, shear-slip, support body failure,and roof collapse. Weak coal-rock interfaces allow for shear-slip between layers, causing anchor bolts and cables to fail. Six entry position models are created to evaluate the failure process and determine the best entry position. Results indicate that roof rocks experience bending and shear-slip along the coal-rock interface. Nearby mining activity causes asymmetric deformation of the entry and shear-slip at the roof corners. When anchor cables and bolts in the roof are insufficient to limit separation and shear-slip, support bodies are subjected to tension, shear, and bending. Once the support body fractures,the entry roof experiences progressive deformation resulting in collapse. We determine the optimal entry position in which shear-slip and residual coal are minimized.
