Abstract:

The exit portal section of Jiahuoyan tunnel on ShanghaiChengdu expressway is located in complex geological conditions under unsymmetrical loading. In order to ensure the construction safety of the exit portal section, retaining walls are built on the external side of the tunnel to relieve the unsymmetrical loading, pilot tunnel is built to create working face and enlarging excavation is made from the opposite direction to achieve the standard crosssection of the tunnel. In this way, the requirements of quality, safety and environment protection are satisfied.

Key words: Jiahuoyan tunnel, unsymmetrical loading, exit portal section, pilot tunnel, enlarging excavation