Experimental Investigation And Theoretical Analysis Of Assembled Integral Utility Tunnel

As an intensive and sustainable installation method of pipelines,utility tunnel can effectively avoid the frequent city road excavations and prolong the service lives of pipelines.At present,cast-in-site utility tunnel and precast utility tunnel are the main structures,but their excavated volume and backfill are high.Composite structure has the dual advantages of cast-in-site structure and precast structure,so it is used in utility tunnel in this paper.Assembled integral utility tunnel are presented,and the mechanical property of the joint is studied.The precast structure of the new utility tunnel can support foundation pit to avoid large excavation.Major achievements of the dissertation are as follows:(1)According to Chinese Codes,assembled integral utility tunnel is designed.The tube element with overhanging plate is precast.The joint is combined with overhanging plate and cast-in-site concrete.The joint is designed to ensure the bearing capacity and waterproof performance.The design method of the assembled integral utility tunnel with integral precast tube element is presented.In usage stage,the integral utility tunnel is calculated.In construction stage,the precast u-shaped overhanging plate is checked.(2)According to a utility tunnel project,the cast-in-site utility tunnel,precast utility tunnel and assembled integral utility tunnel are designed.Through economic analysis and comparison of these three types of utility tunnels,it can be found that the assembled integral utility tunnel is with lowest cost.Compared with cast-in-site utility tunnel,its cost can be reduced by 22%.(3)The bending test is designed to reserch the flexural behavior of the joint of the assembled integral utility tunnel.The failure pattern,bending bearing capacity,load-deflection curves and strain changes are analyzed firstly.Although the flexural behavior of assembled integral slab is poorer than the cast-in-site concrete slab,it still has ductility and can meet the requirement of bearing capacity to some extend.(4)The experiment is simulated by the finite element software ABAQUS.The flexural behavior at elastic stage is simulated accurately,but the plastic change can’t be simulated exactly.Through the parametric study,the following conclusion is drawn:Improving the concrete strength grade,reducing the gap width and lowerring the overhanging plate’s thickness can increase the flexural behavior of assembled integral slab.(5)According to the experimental phenomenon and the finite element analysis results at elastic stage,the assembled integral slab is converted into equivalent slab with varying sections to calculate flexural bearing capacity and deflection.The calculation results are in good agreement with the test.The error rates are less than 15%.