Abstract:

In case highways in mountainous areas are routed along rivers and/or along mountain sides, some of the tunnel portals are located in asymmetricalloaded conditions, which results in great difficulties to the construction of the portal sections. The scheme of halfburied portal section in extremely asymmetricallyloaded conditions is proposed and studied, with the portal section of a highway tunnel as an example. The stress conditions of the surrounding rock mass and the reinforcement structure are analyzed by FEM and the key points of the halfburied portal section scheme are summarized, which provides theoretical support for the execution of the works. So far the construction of the tunnel portal section has been successfully completed and no engineering diseases have occurred. The paper can be served as reference for similar projects in the future.

Key words: tunnel, asymmetrical loaded portal, half buried, portal section scheme, numerical simulation