在典型的上硬、下软红黏土地层中静压管桩滞留的残余应力对基桩承载特性有较大影响。通过自行设计模型试验设备进行红黏土地层单、群桩静压闭口管桩室内试验，分析3种桩径下静压单、群桩残余应力的变化规律及时间效应。结果表明，静压管桩桩身残余应力沿桩身从上到下先增大后变小，呈折线型分布；对于典型的红黏土上硬、下软地层，桩端持力层位于硬塑层和可塑层时，桩身和桩端残余应力均较小；当管桩压入到基岩持力层后桩端受约束增强，桩身和桩端残余应力明显增大；静压单桩完成后静置初期桩身残余应力时间效应比较明显，减小幅度较大，复压后而后随着休止时间的延长，桩身残余应力呈指数型衰减至一较低稳定值；静载试验时忽略残余应力就将认为整个桩身所受压力偏小，偏大计算中性面以上侧摩阻力7.97%，偏小计算中性面以下侧摩阻力8.33%和桩端阻力2.29%。

Residual stress along piles has a great influence on bearing capacity of pipe pile jacked into red clay with an upper soft layer and a lower harder layer. Using self-developed equipment, indoor model tests are conducted to measure close-end single pipe pile and pile group jacked into layered red clay foundation. The variation of residual stress of single pile and pile group and their time effect with three kinds of diameters are analyzed. The results indicate that the residual stress along pile shaft increases first and then decreases from top of the pile to the bottom. The distribution of residual stress shows a broken line. For a typical red clay foundation with a hard top layer soil and soft lower layer, the residual stresses at pile shaft and pile tip are much smaller when the bearing stratum is hard plastic red clay layer or the plastic layer. However, the residual stress will increase when the piles puncture into better bearing layer. In the early stage of completing jacking single pile, the time effect of residual stress at pile shaft performs significantly. The stress value decreases, and exponentially decays to a lower stable value after the single pile being re-pressed as the rest period keeps going. If residual stress being ignored, the pressure value at pile shaft gotten by static load tests decreases. In this test, more than 7.97% of pile side friction above neutral surface is predicted, while less than 2.29% of pile side friction and 2.29% of pile tip resistance below neutral plane is predicted.