独立隧道、小净距隧道和连拱隧道三种隧道设计与施工都要遵循“基本维持围岩原始状态”和“能量最小原理”。只要结构设计合理、科学组织施工，即可基本保持小净距隧道和连拱隧道洞体受力的独立性。连拱隧道优化断面衬砌压力和内力分布基本对称，与分离隧道相接近，是一种合理的连拱隧道构筑方法。

The design and construction of separate tunnels, small netspacing tunnels and doublearch tunnels should follow the principle of trying to maintain the initial state of the surrounding rock mass and the minimum energy principle. If the tunnel structure is rationally designed and the tunnel construction is scientifically organized, the structural forcebearing independence of small netspacing tunnels and doublearch tunnels can be almost maintained. The lining pressures and internal forces of the optimized crosssections of doublearch tunnels are distributed almost symmetrically and are comparable to those of separate tunnels. Doublearch tunnels with optimized crosssections are a reasonable type of doublearch tunnels.