Abstract:

The principle of “less or no damage to the original landform” is emphasized in the design of tunnel portals, while the principle of “designing the tunnel portal in accordance with the construction conditions” is seldom adopted. In some special cases, the cutting scopes of the tunnel portals should be extended to facilitate the tunnel construction, which leads to the change of the original landform. In the paper, comparison and contrast are made between the tunnel portals designed and those built. It is proposed that, when the topography around the tunnel portal is steep and tunnel portal working lot is needed, the cutting and retaining structure of the tunnel portal should be determined in accordance with the construction of the access road. It is emphasized that while the principle of “less or no damage to the original landform” should be followed, the principle of “designing the tunnel portal in accordance with the construction conditions when the topography is steep” should be observed.

Key words: tunnel portal, design principle, access road, steep front slope