A design method for plastic tube cast-in-place concrete pile considering cavity contraction and its validation

Bearing capacity calculation method and field static load test (SLT) program were carried out simultaneously to study the bearing characteristics of individual Plastic Tube Cast-in-Place Concrete Pile (TC pile), which are increasingly being employed for support of embankments in southeast China. The bearing capacity calculation method considering pile setup (i.e., setup calculation method) was built up according to the cylindrical cavity contraction and horizontal consolidation theories. A series of SLTs on different dates were applied to study the bearing behavior of TC pile and to verify the validity of the established setup calculation method. During TC piles installation, there is about 45% contraction in cylindrical volume due to the extraction of steel casing. Both theoretical and experimental results show that the calculated outcomes considering cylindrical cavity contraction agree well with measured ones. The difference value between them is not more than 12%. On the other hand, if the cylindrical cavity contraction is ignored, the calculated bearing capacities of TC piles are overestimated by 160-300%. The setup of TC pile is mainly due to the increment of pile shaft resistance with time elapsed. Cylindrical cavity contraction accompanied by TC pile installation causes much loss of pile shaft resistance.