广州市珠江新城区旅客自动输送系统土建二标盾构左右线2次成功下穿运营中的地铁一号线隧道，垂直距离最近处2.342m。介绍盾构下穿处地铁一号线的地质条件、工程特点、难点以及盾构施工引起地面和建筑物沉降的机理，重点阐述在未对地铁一号线进行加固保护的情况下穿越施工中所采取的主要措施，包括盾构设备的全面检修，掘进施工中对推力、压力、出碴量的精确控制，及时的同步注浆和二次注浆，适时的监控量测等，这些措施有力的保证了地铁一号线的安全。

The twin tubes of a shieldbored tunnel cross underneath the operating No.1 line of Guangzhou Metro successfully, with the minimum vertical distance between the twin tubes and the operating Metro tunnel being 2.342m. In the paper, the geological conditions, the features and difficulty of the project and the mechanisms of the ground surface settlement and building settlement caused by shield boring are presented. The measures taking during the boring of the tunnel under the condition of no preconsolidation of No.1 Metro line, which includes full inspection and repairing of the shield equipment, accurate control of the thrust force, pressure and muck discharging rate during boring, timely simultaneous grouting and secondary grouting and timely monitoring measurement, are expatiated. For the sake of these measures, the safety of No.1 Metro line is guaranteed.