软土地基预制桩施工时桩上浮现象研究

为了研究预制桩施工时桩上浮规律，对温州某工程桩施工时桩上浮现象进行了系统地试验研究。通过检测发现，桩上浮与施工距离、施工顺序密切有关；桩日施工数量越多，桩终压值越高、桩周土质越硬，桩上浮越大；桩不同贯入长度引起的毗邻桩上浮量存在不同，而桩贯入速率对毗邻桩上浮速率影响不大；桩预钻孔、释放孔以及遮帘可以有效减少桩上浮。此外，文中还提出复压值与与单桩竖向承载力特征值、土层特性、桩长度以及桩持力层有关，可根据地区经验取值。

Research on pile floatation in prefabricated pile construction in soft soil foundation

In order to study the rule of pile floatation in prefabricated pile construction, in-situ test for pile floatation in prefabricated pile construction in Wenzhou has been carried out systematically. Test results hold that pile floatation is related to construction distance and construction order. In addition, pile floatation is larger when pile construction quantity per date is more, pile final-pressure value is higher and soil on the periphery of pile is harder. According to test data, it is found that pile floatation is different with different pile penetration length, but the pile penetration speed doesn’t influence on pile floatation speed. What’s more, pile pre-drill hole, release hole as well as barrier can reduce effectively pile floating. Finally, the paper suggests redriving pressure value determination must be based on local experience in relation of the single pile vertical supporting capacity characteristic value, soil characteristics, pile length as well as the pile supporting level.