1.China Railway Tunnel group Co. Ltd., Luoyang, Henan 471009 China; 2. Yichang-Wanzhou Railway Construction Headquarter of MOR, Enshi, Hubei 445000, China; 3. China Railway Siyuan Survey and Design Group Co., Ltd, Wuhan, Hubei 430063, China
研究结论：隧道洞口发生滑坍除地质原因外，勘察资料不准确和不能及时进行方案完善是设计方面的主要原因，未按设计施工、未及时提出变更、施工方法不当、监控量测不及时是施工方面的主要原因。针对隧道洞口滑坍，应对洞口段进行有效的治理，当软弱不良地层厚度不大于5m 时，可采取加强锚网喷防护；当大于5m、小于10m 时，应采取钢管桩注浆加固；当大于10 m 时，应增设抗滑桩，以取得稳妥的治理效果。同时应及时施做明洞、洞门，以及洞口段的二次衬砌。
Abstract：Research purposes: Yichang-Wanzhou railway has 159 tunnels and 150 tunnel portals. Sloughing had happened to 9 tunnel portals during the construction. The analyses of the cause for the sloughing and its treatment are made for purpose of providing reference to the similar construction.
Research conclusions: The sloughing of the tunnel portal is not only related to the geological reason, but also to the unfaithful reconnaissance and unchanging the design scheme timely. Nowadays the main causes for the sloughing of tunnel portal are that the construction is not conducted according to the design, the construction scheme is not changed timely, the construction method is not suitable and the monitoring is not done on time. For the sloughing of tunnel portal, the following measures should be taken; the anchor bolt and steel gridding and spurt concrete are used if the thickness of the soft rock is less than and equal to Sm, the steel-pipe pile and grouting are adopted if the thickness of the soft rock is 5-10m, and the anti-slide pile should be adopted if the thickness of the soft rock is greater than 10m. At the same time, it is necessary to lay the secondary lining to the tunnel outside and tunnel portal.
2008, Vol. 25 
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