盾构近距离下穿既有车站设计难点及对策

北京地铁8号线区间盾构近距离下穿既有2号线地铁车站，且净距<2.3 m，在北京尚属首创。针对盾构穿越中遇到的下穿运营车站、隧道与既有车站竖向间距小及围护资料不详等困难，通过对矿山法、盾构法、盾构法和暗挖法相结合等方案比选，最终选择了盾构法下穿既有线的设计方案。为了预测穿越施工对既有线的影响，对特级风险源进行了现状检测和安全评估，并针对施工中遇到的难点通过对探测导洞、盾构管片与钢环复合结构设计及采取相关技术措施，最终实现了成功穿越，保障了既有地铁线的安全运营。

Design Difficulties and Countermeasures for Shied Boring Closely Underneath Existing Metro Station

The running tunnel fl＇om Andelibeijie Station to Guloudajie Station on Line 8 of Beijing Metro crosses closely underneath existing Gulou Station on Line 2 of Beijing Metro, with 2.3 m net elearance. Comparison and contrast is made among mining method, shield boring method and ＂mining ＋ shield boring＂ method, and shield boring method is seleeted to build lhe running tunnel. The condition of the special risk sources is investigated and the safety thereof is estimated, so as to predict the influenee of shield boring on the existing Metro station. Survey gallery, composite tunnel sttalcture consisting of concrete segment rings and steel rings and other technical measures are taken for the running tunnel. In the end, the shieht erosses the Metro station successfully and the safe operation of the existing Metro station is guaranteed.