Mechanical Effects Analysis Of Open Cut Tunnel Structure During Operation Period

With the increasing proportion of open trench tunnel in city traffic system, the health monitoring of the operations of open trench tunnel are paid attention more and more by engineering and academia. In the absence of surrounding rock when composing the stress structure of open trench tunnel, all applied load is borne by the reinforced concrete lining structure, and generating a corresponding internal force effects. Due to the clear force defining characteristics the open trench tunnel have, when carrying out the health warning assessment, the health warning assessment means of the bridge structure can be referenced. By analyzing the internal force affects, stress and deformation effects, to make a judgment on their health status.This paper focus on to provide the basis for tunnel safety assessment and warning indicators relies on Hangzhou Zijingang Tunnel project, based on the measured data come from health monitoring of Zijingang Tunnel, by calculating the internal force of tunnel effect under the condition of traffic load, temperature load and proximity metro shield construction and the action of the ultimate limit state with three-dimensional solid simulation ABAQUS analysis. The main results obtained are as follows:(1) Analysis of measured stress of open trench tunnel in operation period indicate that the temperature strain effect play a leading role in structural strain effects, and the temperature transverse stress effect should be larger than the longitudinal stress effect. And the traffic load strain effect caused by actual traffic in tunnel must be very small.(2) Numerical simulation analysis of influence of traffic load on Zijingang Tunnel indicate that the internal force effect of tunnel structural caused by single vehicle is insensitive, and the transverse stress of tunnel structure caused by lane load reaches 9 percent of the stress when the tunnel was completed, while the longitudinal stress of tunnel structure is small enough to be ignored. So, while under lane load, the transverse stress effect is much larger than the longitudinal stress effect of open trench tunnel frame structure.(3) Numerical simulation analysis of influence of temperature effect on Zijingang Tunnel indicates that the theoretical stress is close to the measured value. And under the action of elevated temperature, the stress of open trench tunnel structure generated in transverse direction will be compressive stress mainly. However, the variation range of stress is much smaller while cooling. So it’s more unfavorable to open trench tunnel in summer.(4) Numerical simulation analysis of influence of line 5 shield tunnel construction on the existing Zijingang Tunnel shows that the "auxiliary driving force reducing-passing slowly" construction mode should be adopted for the subway shield construction while passing through below the Zijingang tunnel.(5) The extreme load pattern in the late stage of open trench tunnel operation is added uniform load on top surface and the uneven settlement at the bottom of structure. Analysis of internal force of Zijingang Tunnel which in the limit state shows that the tunnel framework transfers into mechanism with losing carrying capacity when the uniform pressure load is two times more than it was in the normal state, or when the uneven settlement reaches 0.3m.