Two-way Eight-lane Highway Tunnel Support In The Small Spacing The Maximum Reaction Analysis And Support Parameters Optimization Study

The eight lanes bidirectional tunnel has been normally built, so as to accommodate the increase busy traffic nowadays. Thereby brought many difficulties for the construction and design which assembles the one of large-span tunnel and the close-distance tunnel. Firstly, the large-span tunnel has a higher demand for support than the traditional tunnel due to the span-ratio augmented by clearance requirement. Secondly, for small-distance tunnel, the stability of the former tunnel will be significantly impacted by the later excavated tunnel and the shared rock between the neighboring tunnels needs to be particularly consolidated. While the research on this field is still in its infancy, there is no delicate design criterion refer to.Based on the limit analysis upper bound law and the example of Niutou Mount highway tunnel with large-span and small-distance, the paper will study on the construction mechanics and support parameter of the closely build tunnels with small distance between by the large infinite difference software and theoretical and numerical computation. The study mainly includes:1. Discuss the minimum upper boundary solution of the support counter-force of the circular bi-tunnel parallel build in linear elastic medium by the limit analysis upper bound law, and study the relevant parameters by Matlab.2. Research on how to improve the way of distribution of the anchor support. The norm has given guidance on the inter-distance of anchor, under different rock level, in three lanes tunnel. In order to extend the guidance to four lanes tunnel, the paper has done a comparison for the rectangle and quincuncial arrangement of anchors within a set of latitude and longitude distances, then given the optimal result serving as a reference to the practical engineering.3. Analyze the stability of the surrounding rock by several support style combined by excavation, anchor, shotcrete and lining. Study on different way of consolidating the rock in middle of the closely built tunnels, and find out the best way of consolidation for different conditions.4. Simply analyze the monitor data obtained from the Niutou Mount tunnel project, and compare it with the computation result, which can used as a verification for the calculation method in the paper.