北京地铁五号线崇文门车站从既有环线地铁之下穿过，车站拱顶上缘距既有线底板下缘只有1.98m，以大管棚作为超前支护。本文介绍了大管棚施工的主要技术措施和控制地层沉降的方法，分析管棚的变形机理，对实测变形值和计算值进行了比较。

Chongwenmen Metro station of No.5 line of Beijing Metro crosses underneath the existing Metro line, with the distance between the vault of Chongwenmen Metro station and the soleplate of the existing Metro line being only 1.98m. Piperoofs consisting of huge steel pipes are installed as advance reinforcement. The paper introduces the major technologic measures of the construction of the piperoofs and the ground settlement control methods, analyses the distortion mechanisms of the piperoofs and compares the measured distortion values with the calculated values.