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

Abstract

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.

Keywords

• metro tunnel
• construction waste backfill layer
• stratum deformation
• grouting reinforcement