Analysis on shaft resistance of the steel pipe prebored and precast piles based on field load-transfer curves and finite element method

Shaft resistance is the major source of bearing capacity and has a critical effect on settlement of prebored and precast pile (PPP). In this paper, the load-transfer behavior and shaft resistance of steel pipe PPP was observed based on real scale pile loading tests. The main focus was on determining the load transfer mechanism and establishing a framework on shaft behavior of steel pipe PPPs. 10 cases of real scale field loading tests were carried out on the fully instrumented steel pipe PPPs, and the load transfer mechanism was observed based on the obtained load-transfer (t-z) curves along the shaft. In addition, the failure surface along the pile shaft was clarified based on the nine small-scale pile loading test results. By analyzing the load-transfer (t-z) curves, it was shown that steel pipe PPP showed two distinctive types of curves related with two different types of failure characteristics – elasto-perfectly plastic and brittle behavior – along the shaft, and this was validated by using intensive finite element analysis. From this, the shaft behavior of the steel pipe PPP can be classified and can be used in analyzing the shaft behavior along the shaft. Moreover, the range and the lower 95% value of the shaft resistance of the steel pipe PPP will be stated for different types of soil the pile is socketed, which can be used as a guideline of PPP design.