静压预应力混凝土管桩土塞效应试验研究

对淤泥质黏土互层以及粉土两种土层条件下静压预应力混凝土管桩的土塞效应进行了试验研究。现场及室内试验结果显示，管桩径厚比越大、土层条件越为坚硬则形成的土塞相对高度越大。上硬下软的土层分布易形成闭塞现象，而上软下硬的情况则易导致土塞的滑动。沉桩过程中，管壁端阻与静力触探锥尖阻力具有极为相似的变化规律，两者比值不随土塞高度变化率及沉桩深度的变化而改变。管壁端阻与锥尖阻力的相关性与土层条件密切相关，对于淤泥质黏土和粉土而言，两者比值分别为0.59和0.81。土塞的分层与地基土层分布基本一致，且分层界面为向上凸起的曲面。土塞形成过程中挤密效应是显著的，黏聚力则因扰动的影响有不同程度的降低。直剪试验显示，土塞抗剪强度的时效性是显著的。粉土中预应力混凝土管桩有效土塞高度约为5～6倍桩径，为整个土塞高度的70%；而淤泥质黏土中有效土塞高度大于4倍桩径。试验结果与已有的研究结果较为接近

Research on plugging effect of jacked prestressed concrete pipe pile

The field and laboratory tests are carried out to research the plugging effect of jacked prestressed concrete pipe pile under two different geological conditions.The test show that a higher plug would be caused by the longer pile with thinner wall jacked into stiffer soil.Open-ended pile is prone to a plugged mode when the hard soil is over the soft soil;while the plug is prone to sliding when the soft soil is over the hard soil.The general development of cone tip resistance of cone penetration test(CPT) is...