Optimization Study On The Initial Support Parameters Of The Shallow Depth Of The Road Double-arch Tunnel

The structure style of the double-arch tunnel is quite novel. It is characteristic of a great span, complex construction working procedure and so on. At the same time, it also has the unique merits. Some signs indicate that tunnel will have a rapid development and double-arch tunnel will obtain more applications in our country in the 21st century. However, the study of the double-arch tunnel is far away from mature at present. The design and the construction mainly depend on the project analogy method and have some blindness. Generally, the design is very conservative.This thesis takes the shallow depth part of the K193+260 mileage of the Shenjintang tunnel of the Hurong national skeleton highway as the project background, makes some studies and discussions. The main work and conclusions of the thesis are as below, which are detailed from chapter two to chapter five:(1) The chapter two introduces the project background, including the project design, the tunnel construction and the monitoring measurement, which provides the primitive materials and the comparison object for the later simulation computation.(2) The chapter three details the computation of the excavation and the initial support of the shallow depth part, which unifies the monitoring measurement data on the spot, makes a sure simulation computation for the four steps which get from simplifying the working procedures of the excavation and the support and gains the stresses and the displacements of various steps by using ANSYS killing elements function. The anslysis confirms that the simulation computation is reasonable by comparing the results of the simulation computation with the data of the monitoring measurement and demonstrates that the fourth step is the most dangerous one, but there is much optimization possibility.(3) The chapter four makes a system of the optimization computation for the initial support parameters of the shallow depth part. The object of the optimization computation is the initial support parameters of the left and right holes of the most dangerous step. The process of the optimization computation is devided into two steps. The first step primarily gets the optimization parameters of the initial support and makes the total cost VAL Yuan of the initial support of every m" reduce from original 345.3 Yuan to 124.20 Yuan by using the zero order method. The second step exactly gains the optimization parameters of the initial support and makes the total cost VAL Yuan of the initial support of every m~2 reduce to 123.52 Yuan by using the first order method. The optimization effect is very obvious and reaches the aim of improving the design, using the materials reasonably and reducing the project cost.(4) The chapter five makes the reliability appraisal of the optimization design, which does a probability finite element analysis by using the stochastic finite element theory and obtains the result that the reliability of the optimization design is 99.3746%. The result of the reliability analysis provides enough security for the implementation of the optimization design.