西安地铁隧道穿越饱和软黄土地段的地表沉降监测

Ground settlement monitoring above Xi'an Metro tunnel through the saturated soft loess

以西安地铁一号线朝阳门站—康复路站区段饱和软黄土地铁隧道为研究对象,通过施工期现场地表沉降变形监测,分析了在饱和软黄土特殊地层条件下隧道浅埋暗挖法施工引起的该区段地表沉降变形规律以及地表沉降槽分布特征。结果表明:在饱和软黄土隧道开挖时,随着掌子面的推进,隧道顶地表沉降可分为沉降微小阶段、沉降显著发展阶段、沉降缓慢阶段和沉降稳定阶段;单线隧道开挖后的最大地表沉降量为18.89mm,双线隧道开挖后的最大地表沉降量为36.4mm;已开挖隧道对围岩土体的扰动作用使得后开挖隧道的地表沉降发展较大;双线隧道的地表沉降槽宽度接近单线隧道沉降槽宽度的2倍,因此可以将其近似为单线隧道地表沉降槽宽度与双线隧道轴线中点距离之和;单线隧道开挖后地表沉降槽宽度为8.4～9.3m,双线隧道开挖后地表沉降槽宽度为16.2～17.5m;隧道开挖施工的沉降槽宽度参数为0.435～0.467,单线隧道开挖后的地层损失率为0.765%～1.324%,双线隧道开挖后的地层损失率为1.231%～2.200%。

The tunnel through the saturated soft loess from Chaoyangmen Station to Kangfulu Station in Line 1 of Xi＇an Metro was taken as example; based on the local ground settlement deformation monitoring during the construction, the discipline of ground settlement deformation caused by the tunnel construction with shallow tunneling method under the special condition of saturated soft loess and the distribution of settling vessel were analyzed. The results showed that the ground settlement above the tunnel could be divided into little settlement, significant fast settlement, slow settlement and stable settlement stages when the excavation face went forward continuously, and the tunnel with saturated soft loess was excavated; the maximum settlement was 18.89 mm after single tunnel excavated and 36.4 mm after double tunnels excavated; the ground settlement of tunnel excavated secondly was large because of the disturbance of the tunnel excavated firstly to wall rock; the width of ground settling vessel of double tunnels was approximately twice of single tunnel, so the width of ground settling vessel of double tunnels approximated the sum of the width of ground settling vessel of single tunnel and the distance of axes midpoints between the double tunnels; the widths of ground settling vessel were 8.4-9.3 m after single tunnel excavated and 16.2-17.5 m after double tunnels excavated; the parameters of width of ground settling vessel were 0. 435-0. 467 after tunnel excavated, loss ratios of stratum were 0. 765%-1. 324% after single tunnel excavated and 1. 231%-2. 200% after double tunnels excavated.