Abstract The performances of a long and deep excavation and underlying collinear existing tunnels in Shenzhen granite residual strata are presented and evaluated. The collinear section for the excavation and tunnel had a length of 3.1 km and the maximum excavation depth was 18.0 m. The excavation was supported with retaining piles, one level of reinforced concrete strut, and 1–3 levels of steel pipe strut. Emphasis is put on the retaining pile displacement, ground surface settlement, and tunnel deformation, correlated with ground conditions, construction activities, excavation geometries, and time-dependent behaviors. An appreciable increase in retaining pile displacement occurred after the end of each soil layer excavation. The ground surface settlements were close to the observations due to metro station excavation with high length to width ratio. In addition, the deformation of the existing tunnel at a certain cross section was governed by the exposure time for the excavation base, base excavated length ahead, and unloading ratio urd (urd = He/C, He was the excavation depth and C was the tunnel cover depth). The upper and lower bounds of the graph of urd plotted against δt/C (δt was the tunnel heave) can be expressed by exponential equations. The observations of this project can provide a reference for cases in similar conditions.

中文翻译：

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深圳花岗岩残土长深开挖共线下伏隧道的观测行为

摘要 介绍并评价了深圳花岗岩残层长深开挖下伏共线既有隧道的性能。开挖与隧道共线段长3.1km，最大开挖深度18.0m。开挖由挡土桩、一层钢筋混凝土支柱和1-3层钢管支柱支撑。重点放在与地面条件、施工活动、开挖几何形状和时间相关的行为相关的挡土桩位移、地表沉降和隧道变形上。在每个土层开挖结束后，挡土桩位移显着增加。由于地铁站开挖高长宽比，地表沉降与观测值接近。此外，既有隧道某一断面的变形受基坑暴露时间、基坑前方开挖长度和卸荷比urd（urd=He/C，He为开挖深度，C为开挖深度）的影响。隧道覆盖深度）。根据 δt/C（δt 是隧道隆起）绘制的 urd 图的上下界可以用指数方程表示。本项目的观察结果可为类似条件下的案例提供参考。他是开挖深度，C 是隧道覆盖深度）。根据 δt/C（δt 是隧道隆起）绘制的 urd 图的上下界可以用指数方程表示。本项目的观察结果可为类似情况下的案例提供参考。他是开挖深度，C 是隧道覆盖深度）。根据 δt/C（δt 是隧道隆起）绘制的 urd 图的上下界可以用指数方程表示。本项目的观察结果可为类似条件下的案例提供参考。