厦门海沧海底隧道最大纵坡比选

依托拟建的厦门第2条海底隧道工程--厦门海沧海底隧道，针对处于复杂海域地质条件与下穿城市敏感建筑物群的特长海底隧道最大纵坡问题，展开研究和比选，确定厦门海沧海底隧道的最大设计纵坡。采用国内外调研、工程类比及理论分析等手段，结合国内外有关规范要求，在满足隧道通行能力、行车安全性及最小围岩覆盖厚度的前提下，利用全寿命周期设计理念，通过对不同最大纵坡取值方案的施工风险、施工工期、建设成本、运营成本及车辆运行成本等进行综合论证比较，得到采用35%的最大纵坡施工风险小、经济效应佳的结论。研究重点在于通过全寿命周期成本指标对比选进行量化，研究结果将为海沧海底隧道纵坡的选择提供支持，并为今后类似海底隧道总体设计提供参考。

Selection of Maximum Longitudinal Gradient of Haicang Subsea Tunnel in Xiamen

Haicang tunnel, which is to be built in Xiameng, China, is the second subsea tunnel in Xiameng. The tunnel passes through complex geological conditions under the sea and passes underneath sensitive buildings. In the paper, the possible maximum longitudinal gradients of Haicang tunnel are studied so as to achieve the optimum maximum longitudinal gradient. Similar project cases at home and broad are surveyed, engineering analogy and theoretical analysis are made, the construction risks, construction schedules, construction cost, operation cost and vehicle operation cost of the tunnel under different maximum longitudinal gradients are studied by means of full life cycle design concept, with relevant specifications and standards at home and abroad, the passing capacity of the tunnel, the safety of the vehicle operation and the minimum cover depth considered. It is concluded that 3.5% maximum longitudinal gradient, which can result in low construction risks and optimum economic efficiency, should be adopted for Haicang tunnel. The study result can not only provide support for the selection of the maximum longitudinal gradient of Haicang tunnel, but also can provide reference for the design of similar subsea tunnels in the future.