During the construction of a new tunnel overcrossing existing tunnels at close proximity, the existing tunnels should be protected by protective structures and/or ground improvement measures. However, the construction of these structures and ground improvement may cause movement or deformation to the existing tunnels, potentially jeopardizing their operational safety, particularly under soft soil and sensitive ground conditions. This study presents the results of a year-long field monitoring program focusing on the movement of two underlying subway tunnels during different construction phases of an overcrossing cut-and-cover tunnel. Protective structures/measures for the existing subway tunnels included the construction of H-pile walls, deep soil mixing, cast-in-situ bored piles, and staged excavation for the new tunnel. In terms of construction-induced movement to the existing subway tunnels, it was found that the construction of H-pile walls induced the largest vertical settlement, the deep soil mixing operations induced the largest horizontal displacements, and the staged excavation induced the largest uplift. Although the maximum horizontal displacement at the springline of a subway tunnel near the center of the construction area slightly exceeded the alarm value, the implemented protective structures/measures were effective in reducing the total horizontal and vertical displacements of the existing tunnels.

在修建与邻近现有隧道交叉的新隧道时，应采用防护结构和/或地面改良措施来保护现有隧道。然而，这些结构的建设和地面改良可能会导致现有隧道的移动或变形，可能危及其运营安全，特别是在软土和敏感的地面条件下。本研究介绍了为期一年的现场监测计划的结果，重点关注跨越明挖回填隧道的不同施工阶段期间两条地下地铁隧道的移动。现有地铁隧道的防护结构/措施包括H型桩墙、深层土拌和、钻孔灌注桩、新隧道分段开挖等。从施工引起的现有地铁隧道位移来看，H桩墙施工引起的竖向沉降最大，深层土拌和作业引起的水平位移最大，分段开挖引起的隆起最大。尽管施工区中心附近某地铁隧道弹线处最大水平位移略超警戒值，但所实施的防护结构/措施有效减少了既有隧道的水平和竖向总位移。