Field tests on bearing characteristics of DPC pipe piles including effects of end sealing and side grouting

This paper presents the results of field tests performed to investigate the bearing capacity of Drilling with a prestressed concrete (DPC) pipe pile under different end sealing and side grouting conditions. The High Strain Dynamic Testing (HSDT) was conducted to evaluate the bearing characteristics of full-scale DPC pipe piles. Moreover, base resistance theoretical formula considering end sealing effect and shaft resistance theoretical formula considering side grouting effect are presented. The theoretical results were compared with the recommended values of specification for traditional pipe piles and tested values to demonstrate the rationality of theoretical formulas and the superiority of end sealing and side grouting. Furthermore, the effects of sediment under the sealing concrete and grouting conditions on the bearing capacity of a single pile were discussed in detail to reveal the influencing mechanisms of end sealing and side grouting. The result showed that the presented base resistance theoretical formulas can estimate the effect of end sealing on the ultimate base resistance of DPC pipe piles with good accuracy. For 1 m pipe piles, end sealing increases the base resistance by up to 103.5% at most compared to unsealing pipe piles; total shaft resistance of piles with double or multi-pipe grouting is more than 37% higher than the recommended maximum value of traditional pipe piles in the pile foundation specification. In addition, the base resistance was significantly affected by the sediment thickness under the sealing concrete. The hole wall time-dependent deformation caused by drilling and unloading affected the side grouting significantly.