地铁出入口加深改造基坑稳定性分析

On Stability of Deepened and Transformed Foundation Pit at Subway Entrance

目前地铁出入口明挖基坑多采用围护桩+钢支撑的支护型式,围护桩设计嵌固深度一般不小于基坑开挖深度的1/3,方能确保基坑开挖安全。对因地铁出入口下沉改造导致围护桩嵌固深度不够的情况,本文通过基坑稳定的分析与计算,分析基坑稳定与围护桩嵌固深度的关系曲线,并结合现场实际条件,提出经济、合理的补救方案。结果表明,旋喷地层加固方案取得良好效果,在一定程度上弥补围护桩嵌固深度不够的缺陷,使结构变形在规范允许范围之内。此外,分段施工对基坑开挖安全十分重要,可以采用增加临时支撑体系或锚索等方式来增加基坑整体稳定性。

Currently, the foundation pit at the subway entrance is mostly constructed by adopting the supporting form of connecting supporting piles and steel timbering. And the designed embedment depth of supporting piles is normally not less than one third of excavation depth of the foundation pit, so as to guarantee the excavation safety of foundation pits. As for the situation insufficient embedment depth of supporting files caused by subsiding of subway entrance, this paper gives an analysis of the relation curve between stability of foundation pit and embedment depth of supporting files through analysm ana calculauon of stability of foundation pit, and brings forward an economic and reasonable remediation, in connection with the real on-site situation. The result shows that jet strata reinforcement method acquires favorable effects and this method fills up the deficiency of insufficient embedment depth of supporting piles, limiting the structure distortion within the permitted range. Besides, section construction is especially necessary for the safety of excavation. And temporary supporting system or anchor line can be added to improve the overall stability of the foundation pit.