为预防改扩建隧道施工发生安全事故，提高改扩建隧道施工安全风险控制能力，以新建后祠隧道坍塌风险事件为例，进行施工安全风险评估。根据现有研究成果和工程实际情况，建立改扩建隧道施工安全指标体系，利用物元可拓模型确定各指标关联度、利用熵权法计算指标的权重，分别对风险发生的可能性和风险严重程度进行综合评价，最后利用风险矩阵法判别风险等级。将该评价方法应用于新建后祠隧道施工风险评估中，结果表明： 基于可拓理论和风险矩阵的评估方法对改扩建隧道施工安全风险评估具有一定的适用性。

In order to avoid the serious safety accidents induced by tunnel rehabilitation/enlargement and improve the safety risk control capacity, the safety risk assessment of collapse of Houci Tunnel is carried out. The safety index system of tunnel rehabilitation/enlargement is established according to the existing research results and the actual situation of the project; and then the correlation degree of each index is determined by matterelement extension model, the entropy weight method is used to calculate the index weight; finally, the probability of the risk and risk severity are evaluated respectively, and the risk grade is identified by the risk matrix. The safety risk assessment method is applied to Houci Tunnel, and the applicable results show that the abovementioned method is feasible for safety risk assessment of tunnel rehabilitation/enlargement.