中文摘要：

针对极小净距交叠隧道受力复杂、爆破不易控制及支护困难等特点，文章以青岛地铁枣李区间隧道交叠段为研究对象，对下行隧道五种不同开挖间距进行数值模拟，分析了下行双线不同间距下地表及拱顶沉降分布特征。结合数值计算及理论分析对不同开挖间距下的围岩稳定性及施工经济性进行研究。结果表明：随着两平行隧道交错开挖间距的增大，隧道上方地表沉降、拱顶沉降和塑性区体积逐渐减小，但与此同时施工工期将会延长，工程支出相应增加，最终通过多指标综合判别确定出隧道左、右线交错开挖间距在25～35m时较为合理。研究成果确保了极小净距交叠隧道施工的安全稳定及经济可行性，可为同类工程建设提供理论依据和实践经验。

英文摘要：

Aimed at addressing the complex force conditions, nels with a minimum clear distance, a numerical simulation is challenges to blasting and support in overlapping tun- carried out for lower tunnel tubes regarding five kinds of excavation spacing. The distribution features of the surface and crown settlements of two lower tunnel tubes for dif- ferent excavation spacings are analyzed based on the Zaoshanlu-Liehun running tunnel project of the Qingdao met- ro, and the stability of the rock mass and construction costs for different excavation spacings are studied by numeri- cal calculations and theoretical analysis. The results show that the surface settlement, vault settlement and volume of the plastic zone will decrease gradually with an increase of the excavation space between the parallel tunnel tubes, along with the extension of construction period and the increasing of expenses; so a reasonable excavation spacing between the left and right tube is 25-35 m determined by the multi-index comprehensive assessment method.