| Through the systematic analysis of the geological engineering properties of the tunnel, various factors affecting the stability of surrounding rock, deformation and failure characteristics, using 3D finite difference calculation software FLAC3D main do the pebble soil layer mountain tunnel portal construction mechanics and technology research; By the theoretical analysis and numerical simulation, the different construction methods are compared, and researching the related calculation methods for improving the new construction method.(1).Through summarizing the research status of tunnel portal section construction at home and abroad, mainly includes in terrible topography and geological conditions, the mountain tunnel entrance section excavation method and the auxiliary construction methods commonly used. Bolt, sprayed concrete and steel supports flexible support can be used to control the deformation after the excavation on the basis of ensure the safety of construction. In construction process, temporary inverted arch in the bottom of the tunnel, long tubular shanty grout injection and foot bolt lock method can be used to achieve the purpose of control the deformation of tunnel in the special section. Combining with the tunnel portal common problems, we can choose a reasonable excavation method and the auxiliary method to ensure the safety of the tunnel into the hole.(2).By finite difference software for sandy pebble stratum tunnel with seven steps three steps construction to carry on the numerical simulation. In view of the three-bench seven-step method can’t effectively reduce the deformation of the surrounding rock, the new three-bench step method for the excavation is put forward. Using a great shed advance support, radial anchor reinforcement of surrounding rock bolt, hollow glass fiber reinforcement measures. According to the calculation of the deformation of the surrounding rock and supporting structure in the results to evaluate the new method. |
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