武汉轨道交通3号线是国内第1条下穿汉江的地铁线路，由于过江区间处于特殊地层条件，遂采用矿山法结合盾构法完成施工。矿山法施工的隧道支护效果对盾构的顺利通过起着关键性作用。为了降低工程风险，减少工程成本，采用FLAC 3D软件进行计算，结合正交试验设计方法，对锚杆长度、锚杆排距和混凝土等级等初期支护参数进行优化分析。结果表明： 1)将正交试验方法引入数值模拟中进行优化设计是可行的，该方法不仅简便，而且能显著减少试验次数； 2)得出各支护参数对隧道变形及造价的影响规律，并最终确定了最优支护参数； 3)验证了最优支护参数的可行性，结论具有一定的理论研究意义和工程应用价值。

No. 3 Line of Wuhan Metro is the first Metro tunnel crossing Hanjiang River in China. Due to the complex geological conditions of the project, “mining method + shield method” are adopted for the tunnel. The effect of the tunnel support installed in mining method has fundamental influence on the successful passing of the shield. In the paper, the parameters of the primary support, including anchor bolt length, anchor bolt row spacing and shotcrete grade, are optimized by means of FLAC 3D calculation and orthogonal experiment, so as to minimize the construction risks and to reduce the construction cost. The results show that: 1) The optimization design by introducing the orthogonal experiment method to the numerical simulation is feasible and convenient, which can reduce the experiment times significantly; 2) The rules of the influence of the support parameters on the tunnel deformation and construction cost are obtained, and the optimum support parameters are determined; 3) The feasibility of the optimum support parameters is verified. The paper can provide theoretical and practical reference for similar projects in the future.