A series of dynamic behavior tests on Nanjing flake-shaped fine sand were performed by using the WFI cyclic triaxial apparatus made in England. The dynamic behaviors of Nanjing flake-shaped fine sand under different s...A series of dynamic behavior tests on Nanjing flake-shaped fine sand were performed by using the WFI cyclic triaxial apparatus made in England. The dynamic behaviors of Nanjing flake-shaped fine sand under different static deviator stress levels and cyclic stress ratios were studied. Through comparing the effective stress path under cyclic loading with static loading, the processes of liquefaction of saturated Nanjing flake-shaped fine sand with development of dynamic pore-water pressure, including the initial compact state, compression state and dilative state, were investigated. The variation of the shear stiffness with the number of cycles and cyclic strain was investigated by analyzing the secant shear modulus in each unload-reload loop of dynamic stress-strain relationship. And by means of the exponential function, the empirical equations of the relationship between secant shear modulus Gsec, shear modulus ratio Gsec/Gmax and cyclic strain ε were established based on series of test results. The results show that according to different combinations of static deviator stress and cyclic stress, two kinds of failure patterns with deviator stress reversal or no deviator stress reversal are observed in the samples tested in this series, including cyclic mobility and the failure of accumulation residual strain. In addition, the degradation of dynamic shear modulus is due to the development of vibration pore-water pressure and it is observed that the shear modulus reduces with the progressive number of cycles.展开更多
The traditional research considers that the effective range of forced local ventilation in single head tunnel is the horizontal distance from the jet exit section to the rotary section, but there is a low wind speed a...The traditional research considers that the effective range of forced local ventilation in single head tunnel is the horizontal distance from the jet exit section to the rotary section, but there is a low wind speed area at the end of the range which can not completely and effectively release toxic and harmful gases. In this area, due to the small jet energy, there is no way to effectively remove the toxic and harmful gases produced in the driving process, which seriously affects the safety of the mine.?Therefore, the reasonable definition of the effective range of the forced local ventilation of the single head tunnel can not only improve the theory of the local ventilation of the mine, but also prevent the accumulation of gas and ensure the life safety of the employees. In this paper, the definition of effective range of local ventilation in single head heading face is put forward, and the rationality of the definition of effective range is verified by numerical simulation. On the basis of reasonable definition of effective range, the relationship between wind speed and effective range under different ventilation modes is studied by numerical simulation. The results show that when the wind speed at the outlet of the air duct is less than 20 m/s, the effective range changes rapidly with the outlet wind speed, and after more than 20 m/s, the effect of wind speed on the effective range is gradually weakened. Under the same exit wind speed, the effective range of parallel and coplanar air inlet is much greater than that of single air inlet.展开更多
基金Project (2007CB714200) supported by National Basic Research Program of ChinaProject (90715018) supported by Key Research Project of National Natural Science Foundation of China
文摘A series of dynamic behavior tests on Nanjing flake-shaped fine sand were performed by using the WFI cyclic triaxial apparatus made in England. The dynamic behaviors of Nanjing flake-shaped fine sand under different static deviator stress levels and cyclic stress ratios were studied. Through comparing the effective stress path under cyclic loading with static loading, the processes of liquefaction of saturated Nanjing flake-shaped fine sand with development of dynamic pore-water pressure, including the initial compact state, compression state and dilative state, were investigated. The variation of the shear stiffness with the number of cycles and cyclic strain was investigated by analyzing the secant shear modulus in each unload-reload loop of dynamic stress-strain relationship. And by means of the exponential function, the empirical equations of the relationship between secant shear modulus Gsec, shear modulus ratio Gsec/Gmax and cyclic strain ε were established based on series of test results. The results show that according to different combinations of static deviator stress and cyclic stress, two kinds of failure patterns with deviator stress reversal or no deviator stress reversal are observed in the samples tested in this series, including cyclic mobility and the failure of accumulation residual strain. In addition, the degradation of dynamic shear modulus is due to the development of vibration pore-water pressure and it is observed that the shear modulus reduces with the progressive number of cycles.
文摘The traditional research considers that the effective range of forced local ventilation in single head tunnel is the horizontal distance from the jet exit section to the rotary section, but there is a low wind speed area at the end of the range which can not completely and effectively release toxic and harmful gases. In this area, due to the small jet energy, there is no way to effectively remove the toxic and harmful gases produced in the driving process, which seriously affects the safety of the mine.?Therefore, the reasonable definition of the effective range of the forced local ventilation of the single head tunnel can not only improve the theory of the local ventilation of the mine, but also prevent the accumulation of gas and ensure the life safety of the employees. In this paper, the definition of effective range of local ventilation in single head heading face is put forward, and the rationality of the definition of effective range is verified by numerical simulation. On the basis of reasonable definition of effective range, the relationship between wind speed and effective range under different ventilation modes is studied by numerical simulation. The results show that when the wind speed at the outlet of the air duct is less than 20 m/s, the effective range changes rapidly with the outlet wind speed, and after more than 20 m/s, the effect of wind speed on the effective range is gradually weakened. Under the same exit wind speed, the effective range of parallel and coplanar air inlet is much greater than that of single air inlet.
