钢筋混凝土环形围檩在黄土地区小尺寸深基坑中的应用

Application of circular reinforced concrete purlins in the small‑size deep foundation pit in the loess area

为解决周边环境条件异常复杂、无锚索施工空间、紧邻对变形异常敏感的多层建筑物的自重湿陷性黄土地区开挖尺寸小深度大的顶管工作井的难题,以西安市东郊某直径10.0 m,深度24.50 m的深基坑为代表,采用钢筋混凝土环形围檩替代传统的内支撑来抵抗土压力,既不影响狭窄空间的土方开挖,又很好的控制了围护结构的变形,保护了周边环境的安全。数例工程实践表明,在直径小于12 m,深度不大于25 m的圆形深基坑中,采用钢筋混凝土环形围檩体系,支护费用低、围护结构变形很小、周边环境安全可靠、土体中无锚杆(索)残留,对邻近地下空间后期开发利用无影响。项目的顺利实施为自重湿陷性黄土地区类似深基坑开挖提供了一种解决问题的思路,具有一定的借鉴意义。

In the case of a typical circular deep foundation pit with a diameter of 10.0m and a depth of 24.50m in the eastern suburb of Xi’an,in order to solve the difficulties in excavating a pipe jacking well with a small size and a large depth in the loess area collapsible under overburden pressure,including the extremely complex surrounding environment,close proximity of the working well to multi‑storey buildings which are extremely sensitive to deformation,no anchor cable construction space,the circular reinforced concrete was used to resist the earth pressure instead of the traditional inner support,which not only eliminated disturbance on the excavation in the narrow space,but also controlled the deformation of the enclosure structure and protected the safety of the surrounding environment.Several engineering practices show that in a circular deep foundation pit with a diameter of less than 12m and a depth of no more than 25m,the designed system has low cost,small deformation with the enclosure structure,safe and reliable surrounding environment,no anchor rod(cable)remaining in the soil,and no impact on the later development and utilization of the adjacent underground space,which provides reference for excavating similar deep foundation pits in the loess area collapsible under overburden pressure.