近年来，常出现在深基坑开挖支护中的吊脚桩存在一定的安全隐患。为此，以青岛地铁某长条形基坑为载体，对上软下硬地质条件下遇到的吊脚桩问题展开研究。首先，根据地质条件及周边工程概况，给出基坑开挖及支护思路和方案；然后，结合支护方案采用弹性抗力法和等效被动土压力法分别对上部桩撑（锚）体系和下部岩石边坡稳定性进行分析计算。实际应用结果表明： 1）青岛地区上部土层适合采用桩+支撑，下部岩石边坡采用锚喷支护的组合支护方案； 2）直壁开挖的岩石边坡中，微型钢管桩具有超前支护、预裂及减振作用； 3）推荐算法适合于吊脚桩支护体系的设计。

Recently suspended piles always exist in deep foundation pits, which could cause potential safety risks. In this paper, the “suspended piles” of a stripshaped foundation pit of Qingdao Metro located in hardsoft heterogeneous ground is studied. First, excavation and support scheme is proposed for the project on basis of the geological conditions and the surrounding environment; Secondly, the stability of the upper pilestrut bracing system and the lower rock slope of the foundation pit is analyzed by means of elastic resistance method and equivalent passive earth pressure method. The practice shows that: 1) In Qingdao, the “pilestrut ” support system is suitable for the upper soil strata, and the bolting and shotcreting support system is suitable for the lower rock slope; 2) The micro steel pipe piles adopted in the cutting of the vertical rock slopes of the foundation pit play the role of advance support, presplitting and vibration reduction; 3) The calculation method proposed is suitable for the design of the suspended pile support system. 