Study Of The Large Deformation And The Construction Methods For Carbonaceous Slate Tunnel

The research in this paper is based on the Xiaopanshan1#tunnel construction project in Jituhui Passenger Railway. The Geological condition of surrounding rock was investigated by field tests, the reasonable construction methods and the key technical parameters of the Rock Mass Plate in the excavation process were analyzed by field monitoring and numerical simulation methods. The main contents and conclusions are as follows.1. In view of the rich diversity and poor stability of the Rock Mass Plate in the surrounding rock in this project, the definitive determination of surrounding rock grading and the properties of the rock mass plate through fields tests is very important. Furthermore, the field tests also afford the fundamental direction for the options of tunnel construction methods.2.The mechanism of large deformation for the tunnel excavation process is expoun ded and analyzed, and the supporting principle of the carbonaceous slate tunnel in the fo rm of inequation is presented3. In the construction process of testing section1in Xiaopanshan Tunnel, the tunnel vault subsidence and horizontal radial convergence was monitored, meanwhile, sensors were put in the representative section in the tunnel, particularly to measure internal forces of the early support of steel arch. According to the results in the constructions sits, utilizing the new construction method, the deformation of surrounding rock was within the scope of permit, and the initial supporting structure was in good condition, so the digging can be carried out as normal.4. Using the FEM software Ansyse to simulate the construction in the tunnel, the method of three stages and seven steps was determined, and the deep-buried condition and shallow-buried condition were also considered. The numerical calculation in different excavation step-length and different initial supporting conditions show that: with the reasonable technical parameters, the method of three stages and seven steps can effectively lessen the settlement of arch crown and convergence, therefore the primary supporting stress can be improved.5. Comparing the data monitored in the construction sites and the results of numerical simulation, the high consistence can be found. With the comprehensive analysis, we can conclude that the effects of changes and adjustments in the excavation method are obvious. They can effectively decrease the deformation of surrounding rocks in the excavation of tunnel as well as improve the stress condition of supporting structure.The research in this paper illustrates that the method of three stages and seven steps with the reasonable technical parameters and initial supporting conditions in the section1in Xiaopanshan Tunnel.