Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacem...Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacement field of the existing tunnel line and the contact channel with different net distances and horizontal angles are analyzed by ANSYS finite element software and field measurement method.The obtained results indicate that during the freezing period,the temperature drops at different measuring holes are almost the same.The temperature near the bottom freezing tube drops faster than that far from the tube.It is found that the bilateral freezing technique improves the formation of the freezing wall in the intersection area.In this case,the intersection time of the cross-section is 7 days faster than that of the adjacent ordinary section.The change curve of the displacement of the surface uplift in different freezing periods with the distance from the center of the channel is“M”shaped.The maximum uplift displacement at 12 m from channel center is 25 mm.The vertical displacement of the measuring point located above the central axis of the connecting channel is large.The farther the point from the central axis,the smaller the corresponding vertical displacement.When the horizontal angle between the existing tunnel and the connecting channel is less than 60,the existing vertical displacement of the tunnel changes rapidly with the horizontal angle,reaching 0.17 mm/.Meanwhile,when the net distance is less than 6.1 m,the change rate of the vertical displacement of the tunnel is up to 2.4 mm/m.展开更多
An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. ...An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. The opening and relative dislocation of the longitudinal joints can be calculated using Dirac delta functions. Compared with other approaches, our method yields results that are consistent with centrifugation test data. The effects of the stiffness reduction at the longitudinal joints (α and β), the shearing stiffness of the Timoshenko beam GA, and different additional pressure profiles on the responses of the shield tunnel are investigated. The results indicate that our proposed method is suitable for simulating the discontinuous mechanical behaviors of existing shield tunnels with longitudinal joints. The deformation and internal forces decrease as α, β, and GA increase. The bending moment and shear force are discontinuous despite slight discontinuities in the deflection, opening, and dislocation. The deflection curve is consistent with the additional pressure profile. Extensive opening, dislocation, and internal forces are induced at the location of mutation pressures. In addition, the joints allow rigid structures to behave flexibly in general, as well as allow flexible structures to exhibit locally rigid characteristics. Owing to the discontinuous characteristics, the internal forces and their abrupt changes at vulnerable sections must be monitored to ensure the structural safety of existing shield tunnels.展开更多
Tunnel excavation below existing tunnels produces ultimate and serviceability problems to the existing tunnels.The behaviours of induced stresses on the existing tunnels haven’t yet been fully recognized.In this stud...Tunnel excavation below existing tunnels produces ultimate and serviceability problems to the existing tunnels.The behaviours of induced stresses on the existing tunnels haven’t yet been fully recognized.In this study,a centrifuge model test was adopted to investigate the effects of new tunnelling on two existing overlying tunnels.One existing tunnel model simulated a prototype composite lining tunnel and the other simulated a prototype segmental lining tunnel.The volume loss produced by new tunnel excavation was modelled by an in-flight actuator system.The surface settlements,the existing tunnels settlements,the soil pressures on existing tunnels,the bending movements of existing tunnels,and the joint behaviours of existing tunnels were monitored.The volume of surface settlement trough was much smaller than the soil volume moving into the tunnel,due to the heave of the tunnel bottom and the dilation of sand during shearing.The maximum settlement of the segmental lining model was larger than that of the composite lining model as the equivalent bending stiffness of the composite lining model was larger than that of the former.Due to new tunnel excavation,the soil pressures on different positions of the existing tunnel behaved differently,and the bending movements of the existing tunnels decreased.Moreover,the joint deformation of existing tunnel caused by new tunnel excavation could be classified into three types:(1)translation,(2)rotation,and(3)combination of both.展开更多
This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numeric...This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numerical modelling to predict tunnel deformation before construction.Then,a targeted protection scheme was developed according to the obtained numerical results.The full construction period field monitoring scheme can monitor tunnel responses during construction.Subsequently,the safety of the tunnel structures was evaluated according to the monitoring results,and the evolution of tunnel deformations was analysed.The analytical results can help to clarify the influence characteristics of different construction stages,verify the effect of the proposed protection scheme,and determine the disturbance mechanism of short-distance pile construction.According to the results,the tunnel deformation mainly occurred during pile construction and river channel excavation,and the tunnel vertical displacement and convergence were mainly affected by the construction.The anti-floating scheme of the partition excavation and casting effectively controlled the tunnel heave with an alarm value of approximately 6 mm.The penetration of the short-distance casing resulted in a tunnel deformation.The main construction influence area of the casing pile was within 6D(D is the pile diameter).展开更多
基金This research was supported by the project of Natural Science Foundation of Fujian Province(No.2022J01925)supported by the project of the Fuzhou Science and Technology Plan Project(2021-P-047)supported by the Open Project Program Foundation of Engineering Research Center of underground mine construction,Ministry of Education(Anhui University of Science and Technology)(No.JYBGCZX2021104).
文摘Based on the engineering background of the contact channel between Shangyang and Gushan of Fuzhou Metro Line 2 undercrossing the existing tunnel line,the freezing temperature field of the contact channel,the displacement field of the existing tunnel line and the contact channel with different net distances and horizontal angles are analyzed by ANSYS finite element software and field measurement method.The obtained results indicate that during the freezing period,the temperature drops at different measuring holes are almost the same.The temperature near the bottom freezing tube drops faster than that far from the tube.It is found that the bilateral freezing technique improves the formation of the freezing wall in the intersection area.In this case,the intersection time of the cross-section is 7 days faster than that of the adjacent ordinary section.The change curve of the displacement of the surface uplift in different freezing periods with the distance from the center of the channel is“M”shaped.The maximum uplift displacement at 12 m from channel center is 25 mm.The vertical displacement of the measuring point located above the central axis of the connecting channel is large.The farther the point from the central axis,the smaller the corresponding vertical displacement.When the horizontal angle between the existing tunnel and the connecting channel is less than 60,the existing vertical displacement of the tunnel changes rapidly with the horizontal angle,reaching 0.17 mm/.Meanwhile,when the net distance is less than 6.1 m,the change rate of the vertical displacement of the tunnel is up to 2.4 mm/m.
基金supported by the National Natural Science Foundation of China(Grant No.52108363)Postdoctoral Science Foundation of China(No.2021M700654)+2 种基金Fundamental Research Funds for the Central Universities(No.3132022175)Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University(No.TUL2022-01)Liaoning Revitalization Talents Program(No.XLYC1905015).
文摘An analytical model is proposed to estimate the discontinuous mechanical behavior of an existing shield tunnel above a new tunnel. The existing shield tunnel is regarded as a Timoshenko beam with longitudinal joints. The opening and relative dislocation of the longitudinal joints can be calculated using Dirac delta functions. Compared with other approaches, our method yields results that are consistent with centrifugation test data. The effects of the stiffness reduction at the longitudinal joints (α and β), the shearing stiffness of the Timoshenko beam GA, and different additional pressure profiles on the responses of the shield tunnel are investigated. The results indicate that our proposed method is suitable for simulating the discontinuous mechanical behaviors of existing shield tunnels with longitudinal joints. The deformation and internal forces decrease as α, β, and GA increase. The bending moment and shear force are discontinuous despite slight discontinuities in the deflection, opening, and dislocation. The deflection curve is consistent with the additional pressure profile. Extensive opening, dislocation, and internal forces are induced at the location of mutation pressures. In addition, the joints allow rigid structures to behave flexibly in general, as well as allow flexible structures to exhibit locally rigid characteristics. Owing to the discontinuous characteristics, the internal forces and their abrupt changes at vulnerable sections must be monitored to ensure the structural safety of existing shield tunnels.
基金the financial support by the Key Project of High-speed Rail Joint Fund of National Natural Science Foundation of China(Grant No.U1934210)the Natural Science Foundation of Beijing(Grant No.8202037)+1 种基金the National Natural Science Foundation of China(Grant No.52108363)the China Postdoctoral Science Foundation(Grant No.2021M700654).
文摘Tunnel excavation below existing tunnels produces ultimate and serviceability problems to the existing tunnels.The behaviours of induced stresses on the existing tunnels haven’t yet been fully recognized.In this study,a centrifuge model test was adopted to investigate the effects of new tunnelling on two existing overlying tunnels.One existing tunnel model simulated a prototype composite lining tunnel and the other simulated a prototype segmental lining tunnel.The volume loss produced by new tunnel excavation was modelled by an in-flight actuator system.The surface settlements,the existing tunnels settlements,the soil pressures on existing tunnels,the bending movements of existing tunnels,and the joint behaviours of existing tunnels were monitored.The volume of surface settlement trough was much smaller than the soil volume moving into the tunnel,due to the heave of the tunnel bottom and the dilation of sand during shearing.The maximum settlement of the segmental lining model was larger than that of the composite lining model as the equivalent bending stiffness of the composite lining model was larger than that of the former.Due to new tunnel excavation,the soil pressures on different positions of the existing tunnel behaved differently,and the bending movements of the existing tunnels decreased.Moreover,the joint deformation of existing tunnel caused by new tunnel excavation could be classified into three types:(1)translation,(2)rotation,and(3)combination of both.
基金supported by the National Natural Science Foundation of China(Grant No.52078129).
文摘This study presents the construction of a river channel and a bridge adjacent to existing metro tunnels in Changzhou.The influence of simultaneous construction on these existing tunnels was investigated via 3D numerical modelling to predict tunnel deformation before construction.Then,a targeted protection scheme was developed according to the obtained numerical results.The full construction period field monitoring scheme can monitor tunnel responses during construction.Subsequently,the safety of the tunnel structures was evaluated according to the monitoring results,and the evolution of tunnel deformations was analysed.The analytical results can help to clarify the influence characteristics of different construction stages,verify the effect of the proposed protection scheme,and determine the disturbance mechanism of short-distance pile construction.According to the results,the tunnel deformation mainly occurred during pile construction and river channel excavation,and the tunnel vertical displacement and convergence were mainly affected by the construction.The anti-floating scheme of the partition excavation and casting effectively controlled the tunnel heave with an alarm value of approximately 6 mm.The penetration of the short-distance casing resulted in a tunnel deformation.The main construction influence area of the casing pile was within 6D(D is the pile diameter).