Research On The Mechanics And Optimization Design Of Box Culvert Using Top-Down Construction In Loess Region

Since its lots of advantage, top-down construction has widely been used in underground engineering and municipal engineering. The research on the technology of top-down excavation will prompt the development of pit engineering. Focusing on the characteristic of mechanics and design method of overpass bridge box culvert built with top-down construction technology, firstly, in this paper the construction process was simulated with numerical method, and then the two important design parameter (the depth into the earth and the thickness of wall) of the side wall of box culvert were optimized and adjusted with reiterant calculation and analyse;lastly, the method to determining the design parameters is suggested for other similar projects, and with the method the design production can be optimized enormously. The main results as follows:1) Based on the numerical simulation results, the stress and deformation of supporting structure during the top-down construction had been obtained;and also the principle of the ground deforming of base and surroundings of box culvert had been gotten. The maximum horizontal displacement of supporting structure is smaller than that of the region with soft soil, and it is quite in agreement with the self-stability of loess.2) Based on the optimization of the two parameters of the depth into the soil and the thickness of side wall, the influence of the two parameters on the displacement of wall and on the heave of the base was obtained.3) Focusing on the feature of the supporting structure of rigid body, the method to justify the heave of the pit base and the factorβ,which to reflect the influence on the sidedisplacement of the wall synthetically, had been put forward.4)The method to determine and optimize the design parameters was introduced,which can help for the design of other similar projects, and fulfill the optimization design.