岩溶区地铁隧道下穿跨河桥梁施工技术研究

以贵阳轨道交通2号线下穿南明河及团坡桥为工程依托,针对岩溶发育区不均匀浅覆土条件下地铁隧道穿越跨河桥梁施工中遇到的抗渗防沉等难题,在遵循浅埋暗挖法十八字方针的基础上进行方案优化。下穿施工前对河床低洼处进行回填,同时增设水平隔水层,初步解决了河水下渗难题。隧道开挖过程中在掌子面进行全断面帷幕注浆及超前管棚支护确保了拱顶的稳定性,采用悬臂掘进机掘进使地层沉降得到控制,二衬混凝土浇筑时采用缺陷预控技术避免了二衬背后出现空洞,同时采用动态监控量测,有效解决了围岩稳定及团坡桥沉降的难题。

Study on Construction Technology of Subway Tunnel Crossing Underneath River Bridge in Karst Area

Based on the project of Guiyang Urban Rail Transit Line 2 crossing underneath Nanming River and Tuanpo Bridge,this paper made an optimization on the scheme on the basis of following the principle of eighteen characters in sallow buried-tunnelling method,for the purpose of solving the anti-seepage and anti-sinking problems encountering in the construction of subway tunnel crossing river bridge under the condition of uneven shallow covering in karst development area.Backfilling the low-lying riverbed of Nanming River and adding a horizontal water-barrier layer were carried out before the construction of undercrossing,which preliminarily solved the problem of river seepage.In the process of tunnel excavation,full-section curtain grouting and advance pipe shed support were conducted on the tunnel face to ensure the stability of the arch roof.The ground subsidence was controlled by using the cantilever roadheader,and the defect pre-control technology was used to avoid the cavity behind the second lining concrete when casting the second lining concrete.At the same time,the problems of stability of surrounding rock and settlement of mass slope bridge were solved effectively by using dynamic monitoring measurement.