富水砂层中地铁隧道施工降水现场试验研究

Field Dewatering Test for Metro Tunnelling in a Water-Rich Sand Stratum

  • 摘要: 在富水砂层地区修建地铁,降水是施工的关键。文章在总结分析青岛地区含大量粘粒的砂层这一特殊地层的物理力学性质基础上,以河西站—河东站区间典型断面为背景,布设试验断面,对降水效果及对周边环境影响进行了研究。研究结果表明,通过管井降水可基本将水位降至边墙至仰拱位置,但在土岩组合面,降水困难;水位降低3.57~4.73 m,失水引起的沉降约为-5.58~-10.72 mm;地表最终累计沉降为-24.93~-75.72 mm,降水引起沉降约占总沉降的14.15%~24.65%;降水引起建筑物沉降约-5.1~-2.1 mm,建筑物累计沉降为-18.37~-7.25 mm,降水引起建筑物沉降约占总沉降的17.40%~29.05%,降水对周边环境影响不大;相比非降水施工,利用管井降水后采用小导管加固,在秋冬少雨季节,施工效率明显提高,但在多雨季节,施工容易造成地层大范围下沉,需提高地层加固强度。同时,采用FLAC3D数值模拟软件对降水效果进行计算,计算结果与现场试验基本相符。

     

    Abstract: Considering that dewatering is essential for metro construction in water-rich sand strata, and using a typical section of the running tunnel from Hexi Station to Hedong Station as an example, the dewatering effect and its influence on the surrounding environment were researched in a test section in Qingdao based on an analysis of the physical and mechanical properties of the sand stratum, which had a high number of clay particles. The results show that groundwater can be lowered to a level between the invert and sidewall under normal conditions by tube well dewatering, but this will be difficult in a combined rock and soil stratum; lowering the water level of 3.57~4.73 m may cause ground settlement of-5.58~ -10.72 mm; the total ground settlements are -24.93~-75.72 mm, of which the settlement induced by dewatering is 14.15%~24.65%; the total building settlements are -18.37~-7.25 m, of which the settlement induced by dewatering is 17.40%~29.05% (about -5.1~-2.1 mm), showing that dewatering has little effect on the surrounding environment. Compared to construction with no dewatering, adopting tube well dewatering and condulet reinforcement can improve construction efficiency in dry seasons such as autumn and winter while it may induce a wide range of settlements in rainy seasons, which necessitates enhanced reinforcement strength of the stratum. The dewatering effect was also calculated by FLAC3D software, indicating that the calculated results agree well with the tested ones.

     

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