建筑垃圾回填层地铁隧道暗挖法施工地层变形特性分析

Stratum Deformation Characteristics Analysis of Underground-excavated Metro Tunnel in Construction Waste Backfill Layer

[目的]地铁隧道工程穿越杂填土地层施工的案例越来越多。杂填土地层具有孔隙率高、强度低及易变形等特点,导致地铁隧道穿越杂填土地层时的地面沉降机理不清,需要对其地层变形特性进行深入分析。[方法]以北京地铁16号线看丹站—榆树庄站区间暗挖地铁隧道工程为依托,在简述了该区间工程概况的基础上,阐述了监测断面(选取了3个典型断面)及监测点的布置方案。对3个断面上各测点的监测数据进行分析,形成了各断面的地面沉降时程曲线及沉降速率时程曲线。进一步计算了5个地层损失率取值下断面一的沉降槽曲线,并将断面一实测地面沉降槽曲线与3条理论计算沉降槽曲线进行对比,进而得到建筑垃圾回填层地铁隧道暗挖法施工地层变形的特性。[结果及结论]杂填土易发生湿陷沉降,在地铁施工干扰下地层发生整体沉降,进而导致地层变形呈现出沉降量大、沉降槽宽等特点。当隧道全断面处于杂填土范围内时,地层受隧道开挖的扰动程度被放大,此时采取仰拱下方注浆加固是控制地层沉降的有效措施。

[Objective]There are more and more cases of metro tunnel engineering crossing through miscellaneous fill strata featured by high porosity,low strength,and easy deformation,resulting in unclear land subsidence mechanism of the above metro tunnel construction,an in-depth analysis on the deformation characteristics of this strata is required.[Method]Leveraging the underground-excavated metro tunnel project at Kandan Sta.to Yushuzhuang Sta.interval on Beijing Subway Line 16,and based on an introductive description of the interval engineering,a layout scheme of monitoring profiles(three typical profiles are selected)and monitoring points is elaborated.The monitored data at each measuring point on the three profiles are analyzed,forming the land subsidence time-history curve and the subsidence rate time-history curve for each profile.The subsidence trough curves of profile I under five values of formation loss rate are calculated,and the field-measured land subsidence trough curves of profile I are compared with three theoretically calculated subsidence trough curves.In turn,the characteristics of construction stratum deformation of underground-excavated metro tunnel in construction waste backfill layer are obtained.[Result&Conclusion]The miscellaneous fill is prone to collapsible subsidence,and the stratum can undergo overall subsidence under the disturbance of metro construction,further resulting in stratum deformation characterized by larger subsidence amount and wide subsidence trough.When the tunnel full-profile is within the range of miscellaneous fill,the disturbance degree of stratum by tunnel excavation is amplified,at which point grouting reinforcement under inverted arch is an effective measure to control land subsidence.