A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal def...A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal deformations of the pipe roofs were monitored and the mechanical behaviors of the pipe roofs were analyzed at the test section. A new double-parameter elastic foundation beam model for pipe roof in shallow tunnels was put forward in Wenxiang tunnel. The measured values and the calculation results agreed well with each other,revealing the force-deformation law of big pipe roof in loess tunnel:At about 15 m in front of the excavating face,the pipe roof starts to bear the load;at about 15 m behind the excavating face,the force of the pipe roof tends to be stabilized;the longitudinal deformation of the whole pipe roofs is groove-shaped distribution,and the largest force of pipe roofs is at the excavating face. Simultaneously,the results also indicate that mechanical behaviors of pipe roof closely relate to the location of the excavation face,the footage of the tunnelling cycle and the mechanics parameters of pipe roof and rock. The conclusions can be reference for the design parameter optimization and the construction scheme selection of pipe roofs,and have been verified by the result of numerical analysis software FLAC3Dand deformation monitoring.展开更多
As a major element of the transportation network,tunnels are unavoidably threatened by accidental loads such as vehicle bombs and tank truck explosions.The goal of this research is to explore the dynamic characteristi...As a major element of the transportation network,tunnels are unavoidably threatened by accidental loads such as vehicle bombs and tank truck explosions.The goal of this research is to explore the dynamic characteristics and damage assessment of tunnel structures under contact blast loads.First,three scaled-down reinforced concrete tunnel models were made,and the explosion test and static loading test were carried out successively to evaluate the axial residual bearing capacity,axial displacement and failure mechanism of the tunnel.Secondly,the finite element model is built by utilizing LS-DYNA,and the reliability of the finite element method is confirmed by comparing the data of the explosion test with the static loading test.At the same time,the calculation method for damage coefficient and the classification criteria for damage grade based on axial residual bearing capacity are presented.Then,based on the finite element method,the propagation process of the explosion shock wave in the tunnel and the damage mechanism of the tunnel are investigated.Finally,seven explosion scenarios are developed,the damage degree of these seven tunnels under the blast load is quantitatively analyzed,and further anti-blast design ideas are put forth.The study in this article may give an intended reference for the damage assessment,anti-explosion design and strengthening work of reinforced concrete tunnels.展开更多
By combining the results of laboratory model tests with relevant flow rules, the failure mode of shallow unsymmetrical loading tunnels and the corresponding velocity field were established. According to the principle ...By combining the results of laboratory model tests with relevant flow rules, the failure mode of shallow unsymmetrical loading tunnels and the corresponding velocity field were established. According to the principle of virtual power, the upper bound solution for surrounding rock pressure of shallow unsymmetrical loading tunnel was derived and verified by an example. The results indicate that the calculated results of the derived upper bound method for surrounding rock pressure of shallow unsymmetrical loading tunnels are relatively close to those of the existing "code method" and test results, which means that the proposed method is feasible. The current code method underestimates the unsymmetrical loading feature of surrounding rock pressure of shallow unsymmetrical loading tunnels, so it is unsafe; when the burial depth is less or greater than two times of the tunnel span and the unsymmetrical loading angle is less than 45°, the upper bound method or the average value of the results calculated by the upper bound method and code method respectively, is comparatively reasonable. When the burial depth is greater than two times of the tunnel span and the unsymmetrical loading angle is greater than 45°, the code method is more suitable.展开更多
Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to ...Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to more project,tunnel under-traverse highway,we must decide the controlling standard flexibly,which should base on the pavement service function and the pavement condition.The thesis,based on the pavement evenness and running comfort ability in the view of completing the pavement service function,supposes the longitudinal pavement settlement cross section as a quadratic parabola,and gets the maximal settlement value in the range of longitudinal pavement influence when the tunnel is under-traverse highway perpendicularly.Then the controlling standard is decided.As Wenxiang Tunnel under-traverse Lianhuo Freeway on Zhengzhou-Xi'an Passenger Dedicated Railway Line for an example,the settlement controlling standard is acquired,and we hope it has an direction and reference value to similar tunnel construction.展开更多
基金Major Science and Technology R&D Program of Ministry of Railways(No.2005K001-D(G)-2)
文摘A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal deformations of the pipe roofs were monitored and the mechanical behaviors of the pipe roofs were analyzed at the test section. A new double-parameter elastic foundation beam model for pipe roof in shallow tunnels was put forward in Wenxiang tunnel. The measured values and the calculation results agreed well with each other,revealing the force-deformation law of big pipe roof in loess tunnel:At about 15 m in front of the excavating face,the pipe roof starts to bear the load;at about 15 m behind the excavating face,the force of the pipe roof tends to be stabilized;the longitudinal deformation of the whole pipe roofs is groove-shaped distribution,and the largest force of pipe roofs is at the excavating face. Simultaneously,the results also indicate that mechanical behaviors of pipe roof closely relate to the location of the excavation face,the footage of the tunnelling cycle and the mechanics parameters of pipe roof and rock. The conclusions can be reference for the design parameter optimization and the construction scheme selection of pipe roofs,and have been verified by the result of numerical analysis software FLAC3Dand deformation monitoring.
基金supported by the National Natural Science Foundation of China(Grant No.51678018).
文摘As a major element of the transportation network,tunnels are unavoidably threatened by accidental loads such as vehicle bombs and tank truck explosions.The goal of this research is to explore the dynamic characteristics and damage assessment of tunnel structures under contact blast loads.First,three scaled-down reinforced concrete tunnel models were made,and the explosion test and static loading test were carried out successively to evaluate the axial residual bearing capacity,axial displacement and failure mechanism of the tunnel.Secondly,the finite element model is built by utilizing LS-DYNA,and the reliability of the finite element method is confirmed by comparing the data of the explosion test with the static loading test.At the same time,the calculation method for damage coefficient and the classification criteria for damage grade based on axial residual bearing capacity are presented.Then,based on the finite element method,the propagation process of the explosion shock wave in the tunnel and the damage mechanism of the tunnel are investigated.Finally,seven explosion scenarios are developed,the damage degree of these seven tunnels under the blast load is quantitatively analyzed,and further anti-blast design ideas are put forth.The study in this article may give an intended reference for the damage assessment,anti-explosion design and strengthening work of reinforced concrete tunnels.
基金Project(2014M560652)supported by China Postdoctoral Science FoundationProjects(2011CB013802,2013CB036004)supported by the National Basic Research Program of China
文摘By combining the results of laboratory model tests with relevant flow rules, the failure mode of shallow unsymmetrical loading tunnels and the corresponding velocity field were established. According to the principle of virtual power, the upper bound solution for surrounding rock pressure of shallow unsymmetrical loading tunnel was derived and verified by an example. The results indicate that the calculated results of the derived upper bound method for surrounding rock pressure of shallow unsymmetrical loading tunnels are relatively close to those of the existing "code method" and test results, which means that the proposed method is feasible. The current code method underestimates the unsymmetrical loading feature of surrounding rock pressure of shallow unsymmetrical loading tunnels, so it is unsafe; when the burial depth is less or greater than two times of the tunnel span and the unsymmetrical loading angle is less than 45°, the upper bound method or the average value of the results calculated by the upper bound method and code method respectively, is comparatively reasonable. When the burial depth is greater than two times of the tunnel span and the unsymmetrical loading angle is greater than 45°, the code method is more suitable.
文摘Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to more project,tunnel under-traverse highway,we must decide the controlling standard flexibly,which should base on the pavement service function and the pavement condition.The thesis,based on the pavement evenness and running comfort ability in the view of completing the pavement service function,supposes the longitudinal pavement settlement cross section as a quadratic parabola,and gets the maximal settlement value in the range of longitudinal pavement influence when the tunnel is under-traverse highway perpendicularly.Then the controlling standard is decided.As Wenxiang Tunnel under-traverse Lianhuo Freeway on Zhengzhou-Xi'an Passenger Dedicated Railway Line for an example,the settlement controlling standard is acquired,and we hope it has an direction and reference value to similar tunnel construction.
