The interval tunnel between the Olympic Sports Center Station and the Century Avenue Station on Lanzhou metro Line 1 crosses under the Yellow River. The setting of an airshaft in the floodplain has to satisfy the requirements of shield maintenance, dismantling, lifting and operation during construction, as well as the requirements of connecting passage ventilation and evacuation function during operation. The shaft is of 33 × 21 m plane size and 45 meters deep, the is constructed in the thick and strong permeable large particles of sand gravel stratum, therefore faces many difficulties and risks. The stresses of retaining structure and inner side wall are analyzed through the implementation of water blocking and water barrier measures, and a composite system of " inner steel concrete diaphragm wall + outer poor concrete diaphragm wall + periphery grouting + precipitation" is put forward, in which the reversely built composite wall structure with suspension water curtain is adopted. Finally, the shaft engineering is completed safely and smoothly, and the result of numerical analysis is in accordance with that of the field tests, the rationality of the analysis is thus verified.%兰州地铁1号线奥体中心站-世纪大道站区间隧道下穿黄河.在黄河岸滩设置中间风井,需满足盾构施工期间的检修、拆解、吊装以及运营期间联络通道和通风防灾、疏散救援等功能需求.风井平面尺寸为33 m×21 m,井深45.5 m,属于巨厚状强透水大颗粒砂卵石地层中的深、大竖井工程,修建难度较大,实施风险较高.通过多种降水、堵水及隔水措施,对风井的围护结构及主体侧墙进行受力分析,提出了"主体结构地下连续墙+外围地下连续墙+地层注浆+区域降水"的组合体系,采用悬挂式隔水帷幕的逆作法复合墙结构型式,工程得以安全顺利实施.现场测试结果与数值分析结果两者基本吻合,验证了分析的合理性.
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