暗挖地铁隧道下穿既有线高架区间影响分析

Influence analysis on underground excavation of subway tunnels undercrossing elevated section of existing lines

以北京地铁12号线大蓟区间下穿13号线高架区间为背景,在风险保护设计的基础上,完成了暗挖地铁隧道下穿地铁高架区间三维计算模型的建立,对比分析了不加固、仅洞外加固、洞外加固+桥桩底部加固三种工况下13号线高架区间结构竖向位移、水平位移、差异沉降变化特征,并将计算结果与实测结果进行了对比分析。研究表明:穿越施工显著影响范围约为4倍暗挖地铁隧道跨度;双线间既有结构受叠加施工影响大于双线外结构,是施工监测的关键位置;后施工隧道两侧承台差异沉降大于先施工隧道两侧承台差异沉降;现场监测结果反映了合理的暗挖隧道设计和洞内外风险控制措施是既有地铁线路保护的基础。

Taking the background of the section from Dazhongsi Station to Jimenqiao Station of Beijing Metro Line 12 undercrossing elevated section of Beijing Metro Line 13,a 3D calculation model was been built for the underground excavation of subway tunnel undercrossing elevated section based on the risk protection design.The change characteristics of vertical displacement,horizontal displacement and differential settlement of the elevated section structure of Beijing Metro Line 13 under three reinforcement working conditions were compared and analyzed,including non-reinforcement,outside tunnel reinforcement and outside tunnel reinforcement with bridge pile bottom reinforcement.The calculated results were compared with the measured results.The research shows that the significant impact range of the undercrossing construction is about 4 times the span of the underground excavation subway tunnel;the existing structure between the double lines is more affected by the superposition construction than the structure outside the double line,which is a key position for construction monitoring;the differential settlement of the caps on both sides of the tunnel after construction is greater than the differential settlement of the caps on both sides of the previously constructed tunnel;the on-site monitoring results reflect that reasonable underground excavation tunnel design and risk control measures inside and outside the tunnel are the basis for the protection of existing subway lines.