| With the condition of a large population and lack of resource, the resource per capita of our country is much less than the developed countries. In order to maintain a sustainable development and create a harmonious society, it is important to conserve resources. Nowadays, with the rapid development of the subway industry, the consumption of building materials has increased steadily. It needs to be considered to optimize the design of subway construction to ensure the security of the premise, and to cut the project cost. The current mainstream metro tunnel project is designed to use analogy preliminary design to meet a certain threshold, then to check support parameters as the second design. This approach analogy design has an inevitable blindness. Currently, the safety factor of metro tunnel design is generally too high and did not take the advantage of surrounding rocks to support, and the rock support parameter can be obviously optimized.This paper relies on the construction of the first phase of the M3 Qingdao Metro Line project. It is based on the measurement results of the construction site of supporting parameters mechanics experimental and the theoretical analysis of tunnel support, and the research method is FLAC3 D numerical calculation combined with orthogonal test method. The purpose of this paper is to optimize the surrounding rock support parameters of the main sections of the M3 line. The main work and conclusions of this paper are as follows:Firstly, based on the data of the M3 Qingdao Metro Line project and combined with the supporting theoretical analysis, this paper carried out a mechanical experiment on the tunnel support parameters, by studying the rock pressure, bolt stress, steel arch support stress and deformation of mechanical behavior in the early construction process. The results showed that: within the steps construction impact of superimposed distance test section <14m is monitoring measurement values; and because each measured value is small, so optimizing the proposed support parameter is feasible.Secondly, the tunnel construction process is divided into four phases: the advance support stage, the current excavation stage, the current support stage and the pre-excavation support stage. Considering the characteristics of construction process,that is "first by force, after excavation then support ", the actual construction process of subway tunnel existed surrounding rock unloading effects. Then this paper uses theFLAC3 D calculating software to simulate the construction process by comparing the simulation results with the field test results of the specific mechanical class IV surrounding rocks, construction method, the depth of excavation and other footage.The results show that: in the current excavation stage, vault settlement value is being controlled in 5mm(rock stress release rate of about 45%) to support, and the calculate results of the simulation are accordant to the field monitoring data, and it proves the correctness of the model parameter selection. The scope of the working face forward impact distance <4m, backward affect distance <14m; consider supporting role effect when unloading effect on retaining structure will not consider the effect of 60% when unloading.Finally, this paper adopts the numerical model test and orthogonal test method to evaluate the security of each program by using the security indicators, and the key elements are: the initial layer of shotcrete, bolt length, bolt spacing, steel arch spacing,thickness of small catheter equivalent. With a cost-effective evaluation to evaluate the comprehensive performance of each program, the optimization support parameters are:Shotcrete layer thickness of 150 mm, anchor length of 3.0m, bolt spacing of 1.5m,steel grid spacing of 1.25 m, equivalent to a small lead small pipe thickness of 150 mm.The cost of supporting parameters material per meter decreases about ?1092.64 than the original design, cutting off 21% total costs. |
PDF Full Text Request