为解决富水砂层超小净距叠线隧道盾构安全掘进的技术难题，依托郑州地铁3号线太康路—二七广场站区间隧道，针对有限场地条件、富水粉细砂层、超小净距和二次沉降叠加等问题，提出叠线隧道施工的安全控制技术。1）采用水平“板式”冻结壁进行冻结加固和短钢套筒始发技术，提高端头土体稳固性，降低始发渗漏水风险； 2）通过先在下部隧道对中夹层注浆、上部隧道掘进后再进行中夹层补注浆，确保中夹层强度满足要求，以有效减小二次沉降； 3）合理控制盾构掘进参数，加强同步注浆，加强隧道洞内外监控量测； 4）上部隧道掘进时在下部隧道采用滚轮台车进行支撑，跟随上部隧道盾构掘进同步移动台车，确保提供持续的支撑力； 5）通过分析下部隧道掘进及上部隧道叠加掘进施工时的监测数据，结果表明地面沉降、管线沉降及洞内变形的最大值分别为1474、244、314 mm，实现了控制地面、管线及洞内变形均在安全范围内，取得了良好效果。

To guarantee the safe shield tunneling of overlapping tunnel with ultrasmall clear distance in waterrich sandy stratum, a case study is conducted on the tunnel between Taikang road station to Erqi square station of Zhengzhou metro line No. 3. Then, the safety control techniques for overlapping tunnel are proposed according to complex and severe conditions such as the limited site conditions, waterrich siltyfine sandy stratum, ultrasmall clear distance, and the superposition of secondary settlement. The results show the following: (1) The horizontal platetype freezing wall for freezing reinforcement and short steel sleeve launching technology are adopted to improve the stability of the end soil and to reduce the risk of water leakage of shield launching. (2) To ensure strength of the soil layer and reduce the secondary settlement, the middle layer in the lower tunnel is grouted first, and the middle layer in the upper tunnel is grouted after tunneling. (3) Shield driving parameters are reasonably controlled, and synchronous grouting and monitoring inside and outside the tunnel are strengthened. (4) The lower tunnel is supported by roller trolley when tunneling in the upper tunnel, and the trolley is moved synchronously with the upper tunnel shield tunneling to ensure the continuous support force. (5) The analytical results of monitoring data of the tunneling of the lower tunnel and the superimposed tunneling of the upper tunnel show that the maximum ground settlement, pipeline settlement, and tunnel deformation are 14.74 mm, 2.44 mm and 3.14 mm respectively, which can control the ground, pipeline, and tunnel deformation within the safe range and achieve good results.