Large Section Of The Parallel Three-hole Tunnel Construction And Mechanical Characteristics

In order to meet the increasing traffic demand, small spacing tunnel of three holes with large section seems be of great demand. However, owning to its particularity and infrequence, the interaction among tunnels is fairly serious, several key problems during the design and construction need to be solved urgently. As a result, it is necessary to analyze the construction mechanical characteristics of this type tunnel.Based on the Hanfushan three holes large section small spacing tunnel as an example, this paper focus on the construction technology and mechanical characteristics of three-parallel-tunnel with large section and small spacing, with the methord of theoretical analysis, numerical simulation and measurements at the scene.In this thesis, the main content are followed:1. The research carrying out in the domestic and abroad on the small-distance tunnels is summarized. Using 2D Finite Difference Method, the mechanical characteristics of surrounding rock of the three-parallel-tunnel with large section and small spacing and the two-way paralle tunnel are analyzed and compared for different rock conditions and tunnel spacing. The design and construction of the three-parallel-tunnel with large section and small spacing should focus on the middle hole's state and stability of middle rock pillars.2. Considering the characteristics of Hanfushan Tunnel, three holes tunnel construction sequence, liner construction order, tunnel construction method and tunnel longitudinal spacing are analyzed and compared, by adopting the three-dimensional numerical means. The partial results of numerical analysis and the results of the measurement are comparatively analyzed, and the optimum construction schemes are put, meanwhile, the mechanical characteristics and laws of the three tunnels are analyzed.3. According to the code for design on tunnel of railway, and taking account of the effect of three tunnels excavated on the distribution of rock pressure, an analysis method of rock pressure and loads mode for three parallel tunnels with large section and small spacing is proposed. And then, the calculation methods are established for shallow unbiased and shallow biased tunnel respectively.