The Simulation Analysis Of Open-excavated Underground Utility Tunnel During Construction Stage

At present,underground utility tunnel are built in the major cities.The construction of underground utility tunnel is conducive to the maintenance and management of all kinds of urban pipelines,saving urban construction space and beautifying the urban landscape.It is the inevitable choice to improve the quality of urban life.With the development of the urbanization,the species and size of urban pipelines are increased.So it is necessary to study the construction of the utility tunnel with the increased size and complex cross section.In this paper,based on a project in Zhongyuan District of Zhengzhou,which is a multi cabin structure underground utility tunnel.ABAQUS was used to made up the integral finite element calculate model consist of soil,supporting structure and the main part of pipeline.To this project the numeric analysis was made to pit excavation and bracing,tunnel construction,pit backfilling.The mechanism and deformation of foundation pit was studied,and the calculated results were compared with the field monitoring data;the deformation and stress change of the main structure of the pipe corridor in the process of pouring and backfilling.and the reliability of the main structure was analyzed.The research results can provide reference for the construction and design of similar projects.Results show that:(1)The numerical calculation results and measured results show good consistency,indicating that the finite element method,the material constitutive model and the calculation parameters are appropriate,the numerical results,to a certain extent,can reflect the deformation regularity of excavation process.(2)The overall deformation of the foundation pit is convex,the soil is raised from the inside to the outside of the pit,the foundation soil is heave and the foundation pit wall is shifted to the outside laterally.In the early stage of foundation pit excavation,the deformation is not obvious.When the three-stage-slope-excavated is in progress,the deformation of the foundation pit is obviously increased.(3)The maximum settlement of the surface is not at the top of the slope.Because of the action of combined bolting and shotcrete system,the anchor beam reinforces the soil of the slope of the foundation pit,so that the settlement near the top of the slope is smaller.(4)In the stage of main body casting,the foundation pit is stable.The location of maximum deformation was in the middle of the mezzanine roof of tunnel which is downward.(5)With the backfill construction of foundation pit,the stress and deformation of the tunnel are gradually increasing.When the backfill height of the foundation pit is greater than the height of the tunnel,the influence of backfill soil on the stress and deformation of the lower part of the tunnel is reduced.(6)Under the control of the concrete strength and deflection of the pipe gallery,the reliability of the pipe gallery structure is within the safe range.