海底圆形小断面软土隧道施工技术

厦门翔安隧道服务隧道为类圆形隧道，开挖断面46m2，陆域端存在1000m的全风化土层-全强风化的岩土互层地层，隧道埋深6～40m，全部位于地下水位以下，受厦门地区强降雨的影响，隧道地下水非常丰富，土层遇水即崩解坍塌，就服务隧道在上述地层如何安全快速组织施工进行了论述，结合工程实例，认为采用台阶法（全断面或预留行车平台）施工最有利于小断面圆形隧道的施工、同时得出了该工法合理的初支参数、施工步长、设备配置等，对以后类似隧道施工提供了一定的参考和借鉴。

Construction Technology for Sub-sea Soft Soil Tunnel with Small Cross-section

The service tunnel of Xiang’an sub sea tunnel in Xiamen has near circular cross section. The area of the excavation cross section of the service tunnel is 46m2. In the coastal land portion of the service tunnel, there exists 1000m long alternative ground consisting of fully weathered soil layers and fully heavily weathered rock and soil. The cover of the service tunnel ranges from 6m to 40m. The total length of the service tunnel is located below the ground water level. Due to the influence of the heavy rainfall in Xiamen area, the service tunnel has abundant ground water. The ground of the service tunnel may collapse when water is encountered. In the paper, expatiation is made on the safe and rapid construction of the service tunnel located in the above mentioned ground. Conclusion is made on basis of engineering experience that top heading/bench excavation method, whether the invert part is reserved or not, is favorable for the construction of the circular small cross section tunnels. Furthermore, proper primary reinforcement parameters, construction step lengths and equipment matching are provided for the service tunnel constructed by means of top heading/bench excavation method. The paper can provide reference for similar works in the future.