浅埋洞口段黄土公路隧道施工变形性状现场测试研究

以某黄土公路隧道工程为依托，借助现场测试方法研究浅埋洞口段黄土公路隧道地表沉降、拱顶下沉和周边收敛时态分布规律，并结合实测数据建立隧道施工变形统计分析预测模型。研究结果表明:（1）黄土隧道施工变形呈现显著的时间和空间效应，其时态分布曲线符合指数函数型发展规律；（2）地表沉降随时间呈增长趋势，约60 d后逐渐趋于稳定，其最大值（w_max）的统计变化范围为（?30.78～?105.20）mm；（3）横向地表沉降曲线分布呈凹槽形，沉降槽宽度约（3～5）倍隧道跨度（B），且隧道开挖引起的地层损失率为0.74%～3.08%；（4）拱顶下沉与周边收敛时态曲线可分为线性增长、持续变形和平稳发展3个阶段，且线性增长阶段占总变形量的60%以上；（5）v_max的统计值变化范围为（?17.1～?201.1）mm，其95%置信区间为?51.53，?65.11]，u_max的统计值变化范围为（?12.1～?122.0）mm，其95%置信区间为?35.08，?43.39]，建议V级围岩黄土隧道预留变形量取值范围为（?100～?150）mm；（6）拱顶下沉与周边收敛速率时态曲线呈先急剧增加后逐渐衰减趋势，最终稳定后的拱顶下沉速率（Δv）和周边收敛速率（Δu）依次为（?0.05～?0.80）mm/d和（?0.02～?0.60）mm/d。

Field test on the construction deformation characteristics for a loess highway tunnel at the shallow portal section

Based on a loess highway tunnel project, the temporal distribution rules of ground settlement, vault settlement and peripheral convergence for the loess highway tunnel at shallow portal section are studied with the field test method, and the statistical analysis predictive model for the loess tunnel construction deformation is established combining with the actual measurement data. The results show that (1) the construction deformation of the loess tunnel presents significant time and spatial effects, and the temporal distribution curve can be expressed by an exponential function. (2) The ground settlement shows the growth movement with time, approaching stability after about 60 days, and the maximum ground settlement, w_max, ranges from ?30.78 to ?105.20 mm. (3) The transverse ground settlement curve is of the trough shape, the width of trough is around 3?5 times that of B, and the ground loss rate caused by tunnel excavation ranges from 0.74% to 3.08%. (4) The vault settlement and peripheral convergence experiences successively three stages: linear growth stage, continuous deformation stage and steady development stage, and the deformation of linear growth stage accounts for more than 60% of total deformation. (5) The maximum vault settlement, v_max, ranges from ?17.1 to ?201.1 mm, and its variance estimation for sampling is ?51.53, ?65.11] based on the 95% confidence interval. The maximum peripheral convergence, u_max, ranges from ?12.1 to ?122.0 mm, and its variance estimation for sampling is ?35.08, ?43.39] based on the 95% confidence interval. It is suggested that the reasonable reserved deformation values of grade Ⅴ surrounding rock loess tunnel range from ?100 to ?150 mm. (6) The rate curves of vault settlement and peripheral convergence increase first, and then decreases sharply with time. The steady displacement rate of vault settlement (Δv) and peripheral convergence (Δu) ranges from 0.05 to 0.80 mm/d and from 0.02 to 0.60 mm/d, respectively.