We built a three-dimensional model to simulate the disturbance of the stress field near the reverse fault in Zhaziao, Leyi Township owing to hydraulic fracturing. The pore pressure, and shear and normal stresses durin...We built a three-dimensional model to simulate the disturbance of the stress field near the reverse fault in Zhaziao, Leyi Township owing to hydraulic fracturing. The pore pressure, and shear and normal stresses during fracturing are analyzed in detail. Input rock mechanics parameters are taken from laboratory test data of shale samples from the study area. The simulation results suggest that after 16 hours of fluid injection, the pore-pressure variation can activate the reverse fault, i.e., we observe reverse slip, and the shear stress and displacement on the fault plane increase with time. The biggest stress–strain change occurs after one hour of fluid injection and the yield point appears about 0.5 h after injection. To observe the stress evolution in each section, the normal displacement on the boundary is constrained and the fault plane is set as nonpermeable. Thus, the sliding is limited and the shear displacement is only in the scale of millimeters, and the calculated magnitude of the induced earthquakes is between Mw-3.5 and Mw-0.2. The simulation results suggest that fluid water injection results in inhomogeneous fracturing. The main ruptured areas are around the injection positions, whereas the extent of rupturing and cracks in other areas are relatively small. Nevertheless, nonnegligible fault activation is recorded. Sensitivity analysis of the key parameters suggests that the pore pressure is most sensitive to the maximum unbalanced force and the internal friction angle strongly affects the fault slip. Finally, the comparison between the effective normal stress and the maximum and minimum principal stresses on the fault plane explains the fault instability, i.e., the Mohr circle moves towards the left with decreasing radius reduces and intersects the critical slip envelope, and causes the fault to slip.展开更多
Dynamic disasters,such as rock burst due to the breaking of large area stiff roof strata,are known to occur in the hard rock strata of coal mines.In this paper,mechanical models of the fracturing processes of thick ha...Dynamic disasters,such as rock burst due to the breaking of large area stiff roof strata,are known to occur in the hard rock strata of coal mines.In this paper,mechanical models of the fracturing processes of thick hard rock strata were established based on the thick plate theory and numerical simulations.The results demonstrated that,based on the fracture characteristics of the thick hard rock strata,four fracture models could be analyzed in detail,and the corresponding theoretical failure criteria were determined in detail.In addition,the influence of weak interlayer position on the fracture models and ground pressure of rock strata is deeply analyzed,and six numerical simulation schemes have been implemented.The results showed that the working face pressure caused by the independent movement of the lower layer is relatively low.The different fracture type of the thick hard rock strata had different demands on the working resistance of the hydraulic powered supports.The working resistance of the hydraulic powered supports required by the stratified movements was lower than that of the non-stratified movements.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41604050 and 41774192)
文摘We built a three-dimensional model to simulate the disturbance of the stress field near the reverse fault in Zhaziao, Leyi Township owing to hydraulic fracturing. The pore pressure, and shear and normal stresses during fracturing are analyzed in detail. Input rock mechanics parameters are taken from laboratory test data of shale samples from the study area. The simulation results suggest that after 16 hours of fluid injection, the pore-pressure variation can activate the reverse fault, i.e., we observe reverse slip, and the shear stress and displacement on the fault plane increase with time. The biggest stress–strain change occurs after one hour of fluid injection and the yield point appears about 0.5 h after injection. To observe the stress evolution in each section, the normal displacement on the boundary is constrained and the fault plane is set as nonpermeable. Thus, the sliding is limited and the shear displacement is only in the scale of millimeters, and the calculated magnitude of the induced earthquakes is between Mw-3.5 and Mw-0.2. The simulation results suggest that fluid water injection results in inhomogeneous fracturing. The main ruptured areas are around the injection positions, whereas the extent of rupturing and cracks in other areas are relatively small. Nevertheless, nonnegligible fault activation is recorded. Sensitivity analysis of the key parameters suggests that the pore pressure is most sensitive to the maximum unbalanced force and the internal friction angle strongly affects the fault slip. Finally, the comparison between the effective normal stress and the maximum and minimum principal stresses on the fault plane explains the fault instability, i.e., the Mohr circle moves towards the left with decreasing radius reduces and intersects the critical slip envelope, and causes the fault to slip.
基金the Beijing Outstanding Young Scientist Program of China(No.BJJWZYJH01201911413037)projects(Nos.41877257 and 51622404)supported by National Natural Science Foundation of China+1 种基金Shaanxi Coal Group Key Project of China(No.2018SMHKJ-A-J-03)the Fundamental Research Funds for the Central Universities of China(No.2021YJSLJ23)。
文摘Dynamic disasters,such as rock burst due to the breaking of large area stiff roof strata,are known to occur in the hard rock strata of coal mines.In this paper,mechanical models of the fracturing processes of thick hard rock strata were established based on the thick plate theory and numerical simulations.The results demonstrated that,based on the fracture characteristics of the thick hard rock strata,four fracture models could be analyzed in detail,and the corresponding theoretical failure criteria were determined in detail.In addition,the influence of weak interlayer position on the fracture models and ground pressure of rock strata is deeply analyzed,and six numerical simulation schemes have been implemented.The results showed that the working face pressure caused by the independent movement of the lower layer is relatively low.The different fracture type of the thick hard rock strata had different demands on the working resistance of the hydraulic powered supports.The working resistance of the hydraulic powered supports required by the stratified movements was lower than that of the non-stratified movements.
