Research on the tunnel invert for under certain particular geological conditions

The tunnel construction can never become a smooth process and will cause lots of troubles without considering the conditions of natural geological rocks. The tunnel between Handan and Shexian on Qing-Lan highway has a standard designation, which has 3 lanes, the maximum width of 16.81m and the maximum height of 11.75m. Benching tunneling method is applied to tunnel excavation in the condition of IV surrounding rock. After extensive studies, the research team found that the rock at the top heading can be graded as level IV, whereas those at and below the bottom heading are just III. This article, using simplifying calculation, numerical simulation and monitoring in site test, is trying to show that if inverted arch is necessary for the construction of the tunnel with complicated geological structure described earlier in the abstract. Finally, the results indicate that inverted arch can be disregarded in large cross sectional 3-lane tunnels.