Numerical Simulation Analysis Of Stress And Deformation In Excavation Of Large Section Tunnel

Subway construction is the focus of Chinese urban underground space development in the Twentieth Century.However,because of design errors,incorrect construction and so on,accidents are increasing,and has brought huge losses to the people and the country.Therefore,studying the stress of subway structure members is an important part of urban subway construction design.At the same time,a huge project also need enormous cost and investment,therefore,on the premise of safety,making full use of structure strength,speeding up the construction progress and reducing costs become very important.This dissertation studied the effect of different geological conditions to mechanical properties of the tunnel structure and environment,further studied the response of structure on the construction process,discussed the influence factors of performance,construction progress improvement and cost reduction by the original model comparison and single out the reasonable project.This dissertation set up 3D finite element model by ABAQUS,and simulated the construction process of a tunnel with large section.The results showed that on the construction process,middle hole excavation played a major effect on ground settlement,accounted for about 70%,side hole excavation only accounted for about 30%,so after the excavation,the support should close loop as soon as possible to reduce settlement.The total settlement of the settlement caused by excavation is about 61%.In the process of removing temporary supports and making secondary linings,it's about 39%.In the aspect of the internal forces of structure,on the construction process,the initial lining of arch feet and side wall,secondary lining of arch feet were relatively weak in the process of construction site,easily damaged.The simulation of different geological conditions indicated that the worse geological conditions were,the greater the force of the linings was,the more dangerous the structure was.Therefore,it could reduce the construction difficulty and cost according to the different geological by choosing different structure form or material.After calculation by the original model,it did the original model comparison.With controlling variable method,initial lining thickness,the concrete strength of secondary lining and the distance of removing support were studied.Through the analysis,it pointed that reducing the initial lining thickness could make the stress of the initial lining and secondary lining increasing,and make ground settlement greater,Reducing the concrete strength of secondary lining,increasing the distance of removing support respectively could make ground settlement greater and sedimentation speed quicker.According to the variable effects on all aspects of the model,supposed that the initial lining thickness was 200mm,the concrete strength of secondary lining was C25,the distance of removing support was 9m.The results of the simulation were within the specification range,tunnel construction met the safety requirements,and could save about a lot of cement,and accelerated the construction progress.