大直径泥水盾构微扰动下穿首都机场快轨施工技术研究

Study on Construction Technology of Large Diameter Slurry Shield Tunnelling beneath Beijing Airport Express with Small Disturbance

京沈高铁京冀段望京隧道采用两台Φ10.9 m的大直径泥水盾构下穿北京地铁机场线快轨路基段时,为了满足北京地铁运营公司规定的轨面隆沉值限值要求,通过对盾构下穿时的沉降变形进行模拟分析,设置试验段选取盾构掘进参数,在盾构下穿前对机场快轨路基两侧预埋地面跟踪注浆管进行预注浆加固,使地表呈微隆起状态;在盾构穿越过程中,以全程自动化监测为导向,根据沉降监测数据实时进行地面跟踪补充注浆以主动控制地层沉降速率;隧道内严格控制泥水压力,采取精确控制同步注浆、二次注浆和二次深孔注浆、盾壳外压注克泥效等措施,成功地将机场快轨路基最大沉降值控制在0.68 mm以内,为我国同类地质条件下采用泥水盾构下穿既有城市轨道交通施工提供借鉴。

Wangjing tunnel on Jingji section of Beijing to Shenyang high-speed railway is excavated by two Φ10.9 m slurry shields beneath Beijing airport express on which the train runs at speed of 100 km/h.In order to meet the limit value of ground heaving and settlement specified by Beijing Subway Company,a series of technical measures are taken during tunnelling such as computer simulation of subgrade settlement,setting test section to define shield tunnelling parameters,grouting reinforcement at the two sides of subgrade before tunnelling to produce a little ground heaving;on the basis of full automatic monitoring,supplementary grouting is conducted according to real time monitoring data in order to actively control ground settlement rate;slurry pressure is strictly controlled during tunneling,and the maximum settlement of fast-track subgrade is successfully controlled within 0.86 mm by means of simultaneous grouting,secondary grouting and second deep-hole grouting as well as injection of clay shock outside the shield shell,which sets a record of large diameter slurry shield passing through existing rail track subgrade in China.