In order to ensure the safety of tunnel construction, a tunnel collapse risk assessment model was established based on catastrophe theory. The surrounding rock grade, groundwater, tunnel depth, angle of unsymmetrical pressure, geological exploration, excavation span, construction technology and construction management were selected as the indexes for the risk assessment of the mountain tunnel collapse through analyzing nearly 300 cases of tunnel collapse. All the evaluation indexes can be divided into three categories i.e., geological factors, survey and design factors, and construction factors. The quantitative analysis and the criteria of indexes were determined. Exemplification of Hongyansi Tunnel was evaluated by the catastrophe theory. The evaluation result obtained from the proposed method agrees well with practical situation. In the process of construction, an active precautions are not considered by the construction unit. Meanwhile, Heavy rains have fallen on Hongyansi Tunnel. They are important reasons for causing collapse disaster. On the spot, using leading conduit and pipe-shed to deal with the tunnel collapse in arch is successful. Fundamental and method disposing tunnel collapse have been stated in this paper and marked effect is obtained in the engineering practice.%为确保隧道施工安全，基于突变理论建立隧道塌方风险评价的突变理论模型。基于我国近300例隧道塌方资料的分析，结合隧道的地质因素、勘察设计因素以及施工因素，选取围岩级别、地下水、偏压、埋深、地质勘查、开挖跨度、施工技术水平和施工管理水平这8个主要因素作为山岭隧道塌方风险评价指标，并对这8个评价指标分别进行定量描述；在对红岩寺隧道孕险环境及风险诱因分析基础之上，运用突变理论模型对红岩寺隧道进行塌方风险评价。研究结果表明：结果与实际施工情况一致；但由于施工单位未采取积极的风险规避及控制措施，且连续强降雨，导致发生“关门”式塌方灾害；针对发生的“关门”式塌方采用超前小导管与管棚相结合的注浆法处治方案，施工中遵循了“先加固、防扩展、后处理、稳通过”的处理原则，成功完成塌方段治理，且效果显著。
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