为减少小净距重叠隧道爆破开挖对结构及中夹岩的不利影响，以重庆轨道交通6号线大龙山站—花卉园站区间重叠隧道(长约500 m)爆破开挖为依托，首先结合工程实际情况及相关施工经验，说明重叠段总体施工方案优选为“先上洞后下洞”的开挖方法，但需根据净距大小采用不同的施工措施；然后通过理论计算论证了上下间距较小时爆破开挖不能保证结构安全，需要采用减震爆破及非爆破的开挖技术，才能保证中厚层状岩最小净距重叠隧道“先上洞后下洞”开挖方法的实现。实施效果证明： 对于中夹岩厚度小于3.5 m的最小净距地段（长约25 m），可先行开挖上洞上台阶，预留下台阶，并待后行下洞减震爆破通过后，再采用非爆破开挖预留的上洞下台阶，以完全消除爆破开挖对最小净距中夹岩的影响，确保了最小净距段结构及施工安全。

DalongshanHuahuiyuan running tunnel on Line 6 of Chongqing Metro has a 500 mlong closelyspaced stacked tunnel section, which is located in mediumthick layered rocks. The blasting excavation of the stacked tunnel may have adverse impact on the tunnel structure, as well as on the rocks between the twin tunnel tubes. It is proposed that the upper tunnel tube should be excavated before the lower tunnel tube and that countermeasures should be taken according to the thickness of the rocks between the twin tunnel tubes. Theoretical calculations made shows that, for the twin tunnel tube section with thin rocks between the tunnel tubes, vibrationreducing blasting technology and nonblasting excavation technology should be adopted so as to ensure the safety of the tunnel structure. For the 25 mlong twin tunnel tube section with less than 3.5 mthick rock between the tunnel tubes, the top heading of the upper tunnel tube should be excavated, while the bench of the upper tunnel tube should be reserved; Then the lower tunnel tube is excavated by blasting means before the bench of the upper tunnel tube is excavated by nonblasting means, so as to minimize the adverse effect on the rocks between the twin tunnel tubes and, in the end, to ensure the safety of the tunnel structure and the tunneling activity.