| Utility tunnel in the layout of a variety of municipal pipelines generally choose multiple section form.Most of the existing utility tunnels are equipped with the construction of the axillary angle,in order to facilitate the production of prefabricated components and on-site assembly construction the new monolithic precast concrete utility tunnel generally do not use axillary angle.This paper takes the actual utility tunnel project in this city as the research object,in this paper,a static load test is carried out on the segmental model of the utility tunnel without axillary angle and monolithic precast concrete utility tunnel,and the mechanical properties of the crack development,failure mechanism,ultimate bearing capacity and failure form of the utility tunnel without axillary angle are studied.Through the finite element software ATENA,the nonlinear analysis of the utility tunnel is carried out to study the structure performance of the utility tunnel under the actual uniform load loading mode,the axillary angle and the reinforcement form of monolithic precast concrete utility tunnel.The main purpose of this paper is to study whether the utility tunnel without axillary angle meets the specifications of our country,and compare with the utility tunnel with axillary angle,whether it can have the same structural performance as the utility tunnel with axillary angle.In addition,the structural performance of monolithic precast concrete utility tunnel and cast-in-place utility tunnel with axillary angle is compared,which provides a reference for the utility tunnel project without axillary angle.The utility tunnel without axillary angle test and the monolithic precast concrete utility tunnel test results show that: the loading and changing process of two specimens were similar,and all experienced the four stages of elasticity,cracking,stiffness degeneration and destruction,and the final damage of two specimens was shear failure;and the structure design control condition of the utility tunnel was the maximum crack width,And compared with the structural load design value and quasi-permanent value,there is sufficient security surplus.The three experiments model of cast-in-place utility tunnel without axillary angle model,monolithic precast concrete utility tunnel and the cast-in-place utility tunnel with axillary angle model are used as examples.by comparing the calculation results of the calculation formulae of shear capacity of different countries(USA,UK,Australia,Europe and China),we find the calculation results of the shear bearing capacity of the roof of the utility tunnel in our country design code named Code for Design of Concrete Structure(GB50010-2010)are not safe.ATENA finite element models of cast-in-place utility tunnel without axillary angle model and cast-in-place utility tunnel with axillary angle model are established.The simulation results agree well with the experimental results It is proved that ATENA software can simulate the fracture distribution,failure form,ultimate bearing capacity and so on,and the ATENA software can be used in the finite element analysis of the structure of the utility tunnel in scientific research and practical engineering.By comparing the finite element model under the action of the uniform load and the experiment and the finite element model under the action of the concentrated load,it is found that the change of load mode will not change the ultimate failure shape of the utility tunnel structure,and the fracture distribution is very close,and the test results under the concentrated load can provide a reference for the utility tunnel project under the actual uniformly distributed load.The influence of the axillary angle on the mechanical properties of the utility tunnel is studied by ATENA finite element analysis.A non-axillary angle finite element model with the same reinforcement as the model with axillary angle,a model increasing the longitudinal rib(no axillary angle)and a model increasing the longitudinal rib and rib in the bottom of the roof(no axillary angle)are established,the analysis results show that: under the crack width control,the axillary angle can reduce the stress of the steel bar to some extent,However,by suitably increasing the longitudinal ribs of the roof,the structural performance of the tunnel without axillary angle is comparable to that of the tunnel with axillary angle.A finite element model with reinforcement form of monolithic precast concrete utility tunnel is established for the integral model of test assembly(the material is the same as finite element model with axillary angle).The analysis results show that the structural performance of the monolithic precast concrete utility tunnel model is equivalent to that of the model with axillary angle,and the structural truss reinforcing bars increase the shear bearing capacity of the structure to some extent and constrain the development of the cracks. |
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