隧道洞口设计原则探讨——施工便道引入对隧道洞口设计的影响

目前隧道洞口设计时常常强调贯彻“不破坏或少破坏原始地貌”的原则，很少提到“结合施工条件确定洞口设计方案”的原则，在一些特殊条件下隧道施工需要扩大洞口开挖范围从而造成洞口原始地貌的改变。为了解决目前铁路隧道洞口设计理念与实际施工脱节的问题，对几条铁路隧道洞口设计及实际施工进行了对比分析，提出了为确保铁路施工及运营安全，当隧道洞口地形陡峻且需要开辟洞口工区时应该结合施工便道引入确定洞口的开挖及支挡结构，强调隧道洞口设计不但要贯彻“不破坏或少破坏原始地貌”的原则，在地形陡峻时也要贯彻“结合施工条件确定洞口设计方案”的原则。

Discussion on Tunnel Portal Design Principles: Analysis on Relationship Between Access Road Construction and Tunnel Portal Design

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.