This paper concerns the impact of an operating metro train on the structure of a shield tunnel lining and its soft foundation. An elastoplastic 3D dynamic finite difference model was established by using the FLAC3D nu...This paper concerns the impact of an operating metro train on the structure of a shield tunnel lining and its soft foundation. An elastoplastic 3D dynamic finite difference model was established by using the FLAC3D numerical soft- ware. By fully considering the joints, the A-B-K segments and the soft stratum, the dynamic response of the shield tunnel buried in thick, soft soil under the vibrating load induced by a metro train was numerically simulated. The simulation result, for which the joint was considered, was compared with the result when the joint was not considered. The results show that an operating metro train induces a significant dynamic response in the structure of the lining of the shield tunnel and its soft foundation. The severe dynamic response zones of the lining structure are largely distributed in the range of the lower half of the segment-ring and the nearer to the bottom of the segment-ring, the more severe the response. Of two horizontally symmetric, corresponding places on the segment lining, the one near the joint is more severe in its dynamic response than that of the one far from the joint; the nearer the zone of the foundation soil to the lower half of the seg- ment-ring, the more severe the dynamic response. The maximum shear strain of the foundation soil takes place near the joint between two normal segments at the bottom. The dynamic response influenced by joints is more severe than the response not influenced by joints, showing that the non-joint assumption is somewhat impractical.展开更多
The transient pressures induced by trains passing through a tunnel and their impact on the structural safety of the tunnel lining were numerically analyzed.The results show that the pressure change increases rapidly a...The transient pressures induced by trains passing through a tunnel and their impact on the structural safety of the tunnel lining were numerically analyzed.The results show that the pressure change increases rapidly along the tunnel length,and the maximum value is observed at around 200 m from the entrance,while the maximum pressure amplitude is detected at 250 m from the entrance when two trains meeting in a double-track tunnel.The maximum peak pressure on the tunnel induced by a train passing through a 70 m^(2) single-track tunnel,100 m^(2) double-track tunnel and two trains meeting in the 100 m^(2) double-track tunnel at 350 km/h,are−4544 Pa,−3137 Pa and−5909 Pa,respectively.The aerodynamic pressure induced axial forces acting on the tunnel lining are only 8%,5%and 9%,respectively,of those generated by the earth pressure.It seems that the aerodynamic loads exert little underlying influence on the static strength safety of the tunnel lining providing that the existing cracks and defects are not considered.展开更多
Excavation and lining are two main important tasks in tunnel construction. Conventional sequential operations may not be appropriate due to time limit for a project and the high cost of construction. The authors devel...Excavation and lining are two main important tasks in tunnel construction. Conventional sequential operations may not be appropriate due to time limit for a project and the high cost of construction. The authors developed a new mode of tunnel construction that excavation and lining can be operated simultaneously. The new mode of tunnel construction has been successfully applied to Dahuofang Water Conveyance Project in Liaoning Province. This paper makes a comparison of Main Beam TBMs and Double Shield TBMs used in Dahuofang Water Conveyance Project, and the features of Full-ring Inner-through Lining Shutter Jumbo which solves the problem of interference between excavation and lining.展开更多
文摘This paper concerns the impact of an operating metro train on the structure of a shield tunnel lining and its soft foundation. An elastoplastic 3D dynamic finite difference model was established by using the FLAC3D numerical soft- ware. By fully considering the joints, the A-B-K segments and the soft stratum, the dynamic response of the shield tunnel buried in thick, soft soil under the vibrating load induced by a metro train was numerically simulated. The simulation result, for which the joint was considered, was compared with the result when the joint was not considered. The results show that an operating metro train induces a significant dynamic response in the structure of the lining of the shield tunnel and its soft foundation. The severe dynamic response zones of the lining structure are largely distributed in the range of the lower half of the segment-ring and the nearer to the bottom of the segment-ring, the more severe the response. Of two horizontally symmetric, corresponding places on the segment lining, the one near the joint is more severe in its dynamic response than that of the one far from the joint; the nearer the zone of the foundation soil to the lower half of the seg- ment-ring, the more severe the dynamic response. The maximum shear strain of the foundation soil takes place near the joint between two normal segments at the bottom. The dynamic response influenced by joints is more severe than the response not influenced by joints, showing that the non-joint assumption is somewhat impractical.
基金Project(51975591)supported by the National Natural Science Foundation of ChinaProject(P2018J003)supported by the Technology Research and Development Program of China Railway。
文摘The transient pressures induced by trains passing through a tunnel and their impact on the structural safety of the tunnel lining were numerically analyzed.The results show that the pressure change increases rapidly along the tunnel length,and the maximum value is observed at around 200 m from the entrance,while the maximum pressure amplitude is detected at 250 m from the entrance when two trains meeting in a double-track tunnel.The maximum peak pressure on the tunnel induced by a train passing through a 70 m^(2) single-track tunnel,100 m^(2) double-track tunnel and two trains meeting in the 100 m^(2) double-track tunnel at 350 km/h,are−4544 Pa,−3137 Pa and−5909 Pa,respectively.The aerodynamic pressure induced axial forces acting on the tunnel lining are only 8%,5%and 9%,respectively,of those generated by the earth pressure.It seems that the aerodynamic loads exert little underlying influence on the static strength safety of the tunnel lining providing that the existing cracks and defects are not considered.
文摘Excavation and lining are two main important tasks in tunnel construction. Conventional sequential operations may not be appropriate due to time limit for a project and the high cost of construction. The authors developed a new mode of tunnel construction that excavation and lining can be operated simultaneously. The new mode of tunnel construction has been successfully applied to Dahuofang Water Conveyance Project in Liaoning Province. This paper makes a comparison of Main Beam TBMs and Double Shield TBMs used in Dahuofang Water Conveyance Project, and the features of Full-ring Inner-through Lining Shutter Jumbo which solves the problem of interference between excavation and lining.
