The temporary surface surcharge above tunnels is inevitable due to the frequent construction activities along the subway.Although the surcharge was soon removed,the tunnel structure still suffered irreversible deformation,which threatened the safety of subway operation.Previous studies mainly focused on the tunnel deformation caused by the surcharge,while ignored the tunnel deformation during the unloading process after surcharge.The purpose of this experiment was to explore the deformation characteristics of shallow tunnel caused by surface loading-unloading.The scaled tunnel model in this experiment made by 3D Printing technology was based on the shield tunnel with staggered segment without tenon-and-groove.This tunnel model was used for the loading-unloading scale experiment above the shallow-buried tunnel and the loading scale experiment above the normal overburden tunnel in sandy.Then the stress and deformation of shallow tunnel in the loading-unloading process were analyzed,and the difference of stress and deformation between shallow tunnel and normal tunnel during loading were also compared.The experimental data show that the tunnel deformation caused by temporary surface surcharge consists of overall settlement and radial deformation.Some normal performance of the shield tunnel is disrupted due to surcharge,and the resilience of shallow shield tunnel by unloading of the surcharge has a certain hysteresis.The unrecovered offset of the tunnel ring after unloading is the largest at the arch bottom,followed by the arch crown,and the smallest at the arch waist.In addition,the closer to the surcharge center,the more elliptical the ring section is,and arch crown,arch bottom and arch waist are the places where the peak moment occurs.The shallow tunnel is more sensitive to the change of surcharge,which occurs obvious settlement area under the surcharge,while the two ends of the tunnel slightly rise.On the contrary,the differential settlement of the normal tunnel is relatively small,and its settlement curve is relatively smooth.Shallow tunnel is subject to more additional stress,while the affected range is smaller than that of the normal tunnel.These results describe the deformation characteristics of shallow shield tunnel caused by surface loading-unloading,which may provide some theoretical basis for the protection of existing shield tunnel under sudden surface surcharge.
关键词
浅覆土盾构隧道/3D打印/地表临时堆载/卸载回弹/模型试验
Key words
shallow shield tunnel/3D Printing/temporary surface surcharge/unloading resilience/experimentation of physical model
维普
万方数据