暗挖地铁车站下穿既有地铁隧道施工控制

Construction Control of a Newly-Built Subway Station Undercrossing the Existing Subway Tunnel

以北京地铁5号线崇文门暗挖车站下穿既有地铁隧道施工为背景,探讨采用柱洞法结合超前管幕施工的控制技术。施工前对既有地铁轨道和隧道结构进行加固。根据现状评估数据制订既有地铁隧道结构沉降控制标准,并制定各施工步序的沉降控制值。监测结果表明:既有地铁隧道结构变形缝处沉降量最大,是施工控制的重点部位;超前管幕起到了防塌作用,但其自身施工引起既有地铁隧道结构沉降9.52mm,选用时应慎重;侧洞管幕施工完成时,变形缝处隧道结构累计沉降量超限,且道床与隧道间发生严重脱离。采用抬升注浆和充填注浆分别对既有地铁隧道结构累计沉降量超限及道床与隧道间脱离进行处理,最终将既有地铁隧道结构沉降量控制在16.75 mm以内,道床与隧道间脱离区域被有效填充,确保了施工期间既有地铁线路的安全运营。

Based on the case of Chongwenmen Station which is a newly-built subway station in line 5 of Beijing subway crossing through the bottom of the existing subway tunnel, the construction control techniques of pioneer heading-column combining with pipe roof are discussed. Before construction, the existing subway track and tunnel structures were reinforced, and the overall allowable settlement values of the existing subway tunnel were identified by evaluation data. The respective allowable settlement value of the existing subway tunnel in each key construction step was assigned. Monitoring data show that the deformation joint of the existing subway tunnel has the maximal settlement, which is the key part for construction control. Pipe roof can avoid the collapse of the strata but the construction of itself can bring a settlement of 9.52 mm in the existing subway tunnel, so it should be used carefully. After finishing the pipe roof above the side tunnels of the newly built subway station, the total settlement of the existing subway tunnel deformation joint overran the allowed value and the track bed disjoined the tunnel structure badly. Lifting grouting and filling grouting were used respectively to treat the overmuch settlement and the disjoined part. Finally, the settlement of the existing subway tunnel was controlled within 16. 75 mm, and the disjoined part between the existing subway track bed and tunnel was reliably filled. With these control measures, the existing subway line was operated safely during construction.