Abstract:With respect to more and more shallow embedded tunnel constructed beneath existing subway tunnel,the effects of shallow embedded tunnel construction on existing subway tunnel are discussed;and some key control techniques used successfully in Chongwenmen station of Beijing metro line No.5 constructed beneath existing tunnel of metro line No.2 are presented. A comprehensive survey of the existing subway tunnel has been performed before the tunnel construction. Based on the survey results,the deformation control indexes and their allowable values are identified in the light of theoretical analyses and similar engineer experiences. The finite element method combined with experience and judgment is recommended to predict the effects of tunneling on the existing subway. The more suitable excavation construction methods and auxiliary measures such as big steel pipes,face grouting reinforcement and compensation grouting are selected by various comparison analyses. On the basis of numerical analyses and similar engineer experiences,the allowable value of the main deformation control index is controlled according to construction steps. A system of remote real-time monitoring is used to monitor dynamic responses of the existing subway;and the measured data were back analyzed immediately. When abnormal issues are found,protective measures are adopted in time to ensure safety running of the existing subway. For example,control compaction grouting is adopted to heave up the existing tunnel structures in the case,and the maximum upheaval of the existing tunnel reaches 16 mm.