以青岛地铁3号线五四广场站为研究对象，对土岩组合地层地区的吊脚桩设计要点进行研究。通过数模模拟，对土岩组合地层中“吊脚桩”基坑的支护体系变形及内力、“吊脚桩”嵌岩深度与预留岩肩宽度的关系进行了分析，并对有竖向荷载的“吊脚桩”进行了研究。研究表明： 1)随着开挖深度的增加及锚杆的施工，预应力锁脚锚杆对吊脚桩桩底水平位移的控制作用明显。2)随着嵌岩深度和肩岩宽度的增加，吊脚桩桩身最大水平位移呈减小趋势，嵌岩深度取2.0 m，岩肩宽度取1.5 m较为合理。3)由于桩脚嵌入中风化花岗岩，桩顶位移不受竖向荷载控制，仅随开挖深度增加而明显增加；桩身弯矩稍有增大，但变化值极小。

In the paper, the design of the endsuspended piles of the foundation pit of May Fourth Square Station of Line 3 of Qingdao Metro, which is located in soilrock combined strata, is studied. The correlation between the deformation and internal forces of the support system of the foundation pit with endsuspended piles located in soilrock combined strata and the rocksocketed depth and rock shoulder width of the endsuspended piles is analyzed by means of numerical simulation. Furthermore, the displacement and bending moment of the endsuspended piles with vertical load and without vertical load are also studied. Conclusions drawn are as follows: 1) With the increase of the cutting depth and the installation of the rock bolts, the prestressed footlocking rock bolts have obvious effect in the control of the horizontal displacement of the ends of the endsuspended piles; 2) With the increase of the rocksocketed depth and rock shoulder width, the maximum horizontal displacement of the endsuspended piles reduces; It is proper that the rocksocketed depth should be taken as 2.0 m and the rock shoulder width should be taken as 1.5 m; 3) Because the ends of the piles are socketed into the intermediatelyweathered granite, the displacement of the pile top is not controlled by the vertical load, however, it increases obviously as the cutting depth increases; the bending moment of the pile increases slightly, with very small increment. 