Support Design And Optimization Of Highway Tunnel Based On RMR Rock Classification

To be a big tunnel country, many highway tunnels have been built under complex conditions with rich experience in China. But we bave not formed a creative construction method or improved the tunnel design theory. It is a long way to be a great tunnel country. This paper researches support design optimization of tunnel Mrke with the concept of NATM and RMR surrounding rock classification method based on the North-South highway of the Republic of Montenegro, Eastern Europe which is under construction. By comparison of the similarities and differences of design methods between China and Eastern Europe, this paper provides a reference for China’s enterprises to go abroad for tunnel design and construction, and enriches the design method of highway tunnel at the same time. In this paper, the work and results have been done as follows.(1) By comparison of RMR, Q and BQ, the three common law surrounding rock classification methods and according to the results of previous studies and statistics, using nonlinear fitting comparative analysis as well as the conversion relation between physical mechanics parameters and [BQ] with RMR, we get relationship between RMR and [BQ] and relationship between Q and [BQ]. Finally this provides the basis for tunnel design by comparing the three surrounding rock classification methods.(2) This paper has analysed the basic principle of highway tunnel support design and has revealed the mechanism of excavation, initial support and the second lining support. This paper has used software Midas GTS for the initial support structure calculation and analysis of the preliminary design, analyzed the mechanical characteristics of shotcrete, bolt and steel support structure. This paper has used software Midas Civil for the secondary lining structural calculation of preliminary design and has analysed the characteristics of secondary lining. This paper has used software Unwedge to calculate the stability of three-dimensional wedge, and has set a reasonable tunnel monitoring measurement Program.(3) The calculation results show that the thickness of shotcrete is reasonable. However, the long bolt will make poor construction convenient and it is not easy to achieve the desired effect. The support use less rigidity steel grille in weak tunnel section can not guarantee the safety of the construction, and it will also bring unnecessary losses on the construction schedule, project cost and other aspects. The secondary lining structure is reasonable; there is no need to optimize. For further optimization of the type of steel arch and length of anchors, based on the calculation results we get a good support effect, it also make sense at construction convenience and economics at the same time. In good quality rock passages, the key blocks have a greater impact on the safety of tunnel support, the anchor length of preliminary design and optimization design can through the potential wedge completely and the calculation safety factor did not change, so useing long bolt to increase the stability of the wedge make no sense.