Vibration Response And Safety Evaluation Of Large Diameter Urban Railway Tunnel With Running Trains

Combined with the construction and operation of the project,which the large-diameter shield tunnel of the Zhengzhou intercity railway passed through the trunk canal of South-to-North Water Transfer Project.The plane strain model was used to simulate and analyze the variation of the tunnel train vibration response under different influence factors.These influencing factors are single and double train traffic,soil geological changes,train speed,secondary grouting consolidation of surrounding rock,and tunnel depth.When the train is running,the sensitive characteristics of the tunnel vibration response under different influence factors are clarified.The research results provide design reference and basis for tunnel selection.The three-dimensional model simulation was used to analyze the variation of the tunnel train vibration response when the intersection angle between the trunk canal of the South-to-North Water Transfer Project and the underpass tunnel changed.The research results have laid an optimized foundation for determining the intersection angle of the trunk canal and the underpass tunnel.Combined with the concrete fatigue empirical formula,when the train is traveling,the fatigue life of the tunnel lining concrete under different conditions is predicted and comparatively analyzed.When the train is running in the tunnel,the safety of the tunnel is determined.The main results are as follows:?1?Sensitive characteristics of tunnel vibration response under different influence factors when the train is running.When the two trains are running,the stress on the tunnel lining is symmetrical.Compared with a single train,the stress on the unloaded side of the tunnel is greater.When two trains are running,the vertical displacement of the ground surface measurement point is twice that of the former.Under the vibration of the train,the stress change of the lining when considering the secondary grouting consolidation is similar to that without considering the secondary grouting consolidation.It may not be considered in the relevant analysis of tunnel train vibration response.With the increase of the buried depth of the tunnel,the vertical displacement of the ground surface measuring point caused by the train vibration becomes smaller and smaller.Other influence factors have less influence on tunnel dynamic response under train vibration.?2?By analyzing the structural vibration response of the train passing through the tunnel,the internal force variation law of the tunnel is obtained.During the trains running in the tunnel,the maximum values of vertical displacement,vertical acceleration,and circumferential stress were compared for different sections of the lining at different positions within the area of the tunnel length of 100m below the canal.The maximum vertical displacement:right beam>right arch waist>right column>arch bottom>vault.The maximum vertical acceleration:right arch waist,right beam and right column>arch bottom>vault.The vertical displacement and circumferential stress of the measuring points of different sections of the tunnel change little.Under the vibration of the train,the main canal has less influence on the lower tunnel.During the trains running in the tunnel,the maximum vertical displacement value of the measurement point of the canal is-0.42mm,and the maximum vertical acceleration value is 47.59mm/s².The farther the measuring point of the canal is from the lower tunnel,the smaller the vertical displacement is,the smaller the impact of tunnel train vibration on the main canal.When the crossing angle is changed,the maximum vertical displacement of the measuring points at different positions of the different sections of the85°crossing are less than 90°.When the crossing angle is 85°,the circumferential stress of the tunnel arch bottom and the right column is reduced by 0.02MPa?0.03MPa compared with the 90°.The maximum vertical displacement of the measurement point of the canal is0.43 mm,which is 0.1 mm greater than the 90°.The cross angle has little effect on the dynamic response of the tunnel train,but it has a significant effect on the ground dynamic displacement.?3?When the train is running in the tunnel,the influence law of the tunnel lining fatigue life under different conditions is obtained.Compared with single trains,the fatigue life of the tunnel is shorter when two trains are running.When the tunnel passes through uneven geology,the tunnel fatigue life is shorter than normal one.When the surrounding rock grouting consolidation is considered,the stress on the outer vault of the tunnel lining becomes better and the fatigue life of the tunnel becomes longer.In the relevant analysis of the vibration response of the tunnel train,the grouting consolidation of the surrounding rock may not be considered.When the key parts of the tunnel are subjected to circumferential tensile and compressive stress under train vibration,the fatigue life of the concrete using tensile and compression fatigue life prediction formula 4-11 is often the smallest.For the prediction of fatigue life of the tunnel lining concrete when passing single train in this project,the shield tunnel can pass 2.75×10¹⁰ trains,which is much longer than the design life of the tunnel.