The stability analysis of a deep buried tunnel subjected to dynamic disturbance is an important issue.In this study,the transient response has been obtained by establishing a water-rich tunnel model considering excava...The stability analysis of a deep buried tunnel subjected to dynamic disturbance is an important issue.In this study,the transient response has been obtained by establishing a water-rich tunnel model considering excavation damage zone(EDZ).Based on Biot’s two-phase dynamic theory and wave function expansion method,the analytical solution of dynamic response around the water-rich tunnel containing EDZ subjected to P wave is derived.Moreover,Fourier transform and Duhamel’s integral technique is introduced to calculate the transient response,and the equivalent blasting curve is adopted to input excitation function.The dimensionless parameters thickness N and shear modulus ratio lare defined to characterize the degree of damage in the surrounding rock,investigating the influencing factors,such as the parameters and the incident source frequencies.The results indicate that the dynamic stress concentration factor(DSCF)gradually decreases as the dimensionless parameters increase.Additionally,it is observed that the DSCF is more sensitive to changes in the thickness parameter N.Finally,the influence of the waveform parameters has been taken into account in the analysis of transient response,and the stress state and transfer process in each time stage of the EDZ are analyzed.This study establishes a theoretical foundation for comprehending the mechanical behavior and support design considerations associated with a deep-buried water-rich tunnel containing EDZ.展开更多
Overbreak and underbreak are the crucial problems during the blasting excavation of underground tunnels owing to their effects on the construction costs and operational safety.A critical challenge facing overbreak and...Overbreak and underbreak are the crucial problems during the blasting excavation of underground tunnels owing to their effects on the construction costs and operational safety.A critical challenge facing overbreak and underbreak control is the difficulty in developing guidelines with respect to various and complex engineering conditions.In this study,a series of field measurements of overbreak and underbreak using the Focus^(S)150 laser scanner were performed in a deep roadway of the Kaiyang phosphate mine,China.The distri-bution and extent of the overbreak and underbreak surrounding the roadway contour were accurately analyzed in accordance with the collected point cloud data.Subsequently,a simplified three-dimensional model was established to simulate the blasting excavation of pre-stressed roadway using the explicit dynamic analysis code LS-DYNA.A comparison of numerical and measurement results revealed that the proposed model was a reliable tool to simulate the overbreak and underbreak induced by blasting excavation.Thereafter,the influ-ences of uncontrollable geological factors such as in situ stress conditions and controllable blasting factors including contour hole spac-ing(S),charge concentration(b)and decoupled coefficient(f)as well as stemming were further numerically investigated.The simulation results indicated that the lateral pressure coefficient significantly affected the distribution pattern of the overbreak and underbreak,while the stress magnitude contributed to their extents.Moreover,a comparison of the simulation findings and the field measurement data indicated that the minimal extents of the overbreak and underbreak corresponding the optimal contour blasting results were obtained at S=0.70 m,b=0.9 kg/m and f=2.5,respectively.Furthermore,the contour blastholes stemmed with sand created smaller damage to the periphery rock mass of roadway and enhanced the utilization efficiency of explosive energy.The research findings of this study pro-vide important implications for similar blasting excavation projects.展开更多
This study investigated the impact of a non-causative fault on the dynamic response of a nearby lined tunnel under the incidence of plane SV waves using the indirect boundary element method.The effects of several crit...This study investigated the impact of a non-causative fault on the dynamic response of a nearby lined tunnel under the incidence of plane SV waves using the indirect boundary element method.The effects of several critical parameters,such as the incident frequency,the inclination degree of the fault,the distance between the fault and the tunnel on the hoop stress of the lined inner and outer walls,were explored intensively.The numerical results indicated that the non-causative fault could significantly change the hoop stress distribution of inner and outer surfaces of the tunnels.In general,for the vertically incident seismic waves,when the tunnel was located in the foot wall(under the fault),the hoop stress within the tunnel was significantly greater than that of the tunnels in the non-fault half space,with an amplification factor of up to 117%.The amplification effect became more pronounced as the fault dip angle increased.However,when the tunnel was located in the hanging wall(above the fault),the non-causative fault could produce a significant shielding effect on the dynamic response of the tunnel under high frequency wave incidence,with the reduction of hoop stress being up to 81%.For lowfrequency waves,though,the fault could lead to an increase of the hoop stress of the tunnel of up to 152%.The research results will provide a reference for the seismic design and safety protection of underground structures in non-causative fault sites.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12072376 and 52274105).
文摘The stability analysis of a deep buried tunnel subjected to dynamic disturbance is an important issue.In this study,the transient response has been obtained by establishing a water-rich tunnel model considering excavation damage zone(EDZ).Based on Biot’s two-phase dynamic theory and wave function expansion method,the analytical solution of dynamic response around the water-rich tunnel containing EDZ subjected to P wave is derived.Moreover,Fourier transform and Duhamel’s integral technique is introduced to calculate the transient response,and the equivalent blasting curve is adopted to input excitation function.The dimensionless parameters thickness N and shear modulus ratio lare defined to characterize the degree of damage in the surrounding rock,investigating the influencing factors,such as the parameters and the incident source frequencies.The results indicate that the dynamic stress concentration factor(DSCF)gradually decreases as the dimensionless parameters increase.Additionally,it is observed that the DSCF is more sensitive to changes in the thickness parameter N.Finally,the influence of the waveform parameters has been taken into account in the analysis of transient response,and the stress state and transfer process in each time stage of the EDZ are analyzed.This study establishes a theoretical foundation for comprehending the mechanical behavior and support design considerations associated with a deep-buried water-rich tunnel containing EDZ.
基金the National Natural Science Foundation of China(Grant Nos.11772357,12072376)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2021XQLH053).
文摘Overbreak and underbreak are the crucial problems during the blasting excavation of underground tunnels owing to their effects on the construction costs and operational safety.A critical challenge facing overbreak and underbreak control is the difficulty in developing guidelines with respect to various and complex engineering conditions.In this study,a series of field measurements of overbreak and underbreak using the Focus^(S)150 laser scanner were performed in a deep roadway of the Kaiyang phosphate mine,China.The distri-bution and extent of the overbreak and underbreak surrounding the roadway contour were accurately analyzed in accordance with the collected point cloud data.Subsequently,a simplified three-dimensional model was established to simulate the blasting excavation of pre-stressed roadway using the explicit dynamic analysis code LS-DYNA.A comparison of numerical and measurement results revealed that the proposed model was a reliable tool to simulate the overbreak and underbreak induced by blasting excavation.Thereafter,the influ-ences of uncontrollable geological factors such as in situ stress conditions and controllable blasting factors including contour hole spac-ing(S),charge concentration(b)and decoupled coefficient(f)as well as stemming were further numerically investigated.The simulation results indicated that the lateral pressure coefficient significantly affected the distribution pattern of the overbreak and underbreak,while the stress magnitude contributed to their extents.Moreover,a comparison of the simulation findings and the field measurement data indicated that the minimal extents of the overbreak and underbreak corresponding the optimal contour blasting results were obtained at S=0.70 m,b=0.9 kg/m and f=2.5,respectively.Furthermore,the contour blastholes stemmed with sand created smaller damage to the periphery rock mass of roadway and enhanced the utilization efficiency of explosive energy.The research findings of this study pro-vide important implications for similar blasting excavation projects.
基金supported by the National Natural Science Foundation of China(Grant Nos.51878434,51878108)Natural Science Foundation of Tianjin(Grant No.18JCZDJC 39200)Program of Tianjin Science and Technology Plan(Grant No.18ZXGDGX00050).
文摘This study investigated the impact of a non-causative fault on the dynamic response of a nearby lined tunnel under the incidence of plane SV waves using the indirect boundary element method.The effects of several critical parameters,such as the incident frequency,the inclination degree of the fault,the distance between the fault and the tunnel on the hoop stress of the lined inner and outer walls,were explored intensively.The numerical results indicated that the non-causative fault could significantly change the hoop stress distribution of inner and outer surfaces of the tunnels.In general,for the vertically incident seismic waves,when the tunnel was located in the foot wall(under the fault),the hoop stress within the tunnel was significantly greater than that of the tunnels in the non-fault half space,with an amplification factor of up to 117%.The amplification effect became more pronounced as the fault dip angle increased.However,when the tunnel was located in the hanging wall(above the fault),the non-causative fault could produce a significant shielding effect on the dynamic response of the tunnel under high frequency wave incidence,with the reduction of hoop stress being up to 81%.For lowfrequency waves,though,the fault could lead to an increase of the hoop stress of the tunnel of up to 152%.The research results will provide a reference for the seismic design and safety protection of underground structures in non-causative fault sites.
