Study of plugging of steel H piles, jacked in sand, in a calibration chamber

When predicting the bearing capacity of an H pile, the design engineer is faced with the questions of which perimeter of the pile to consider for lateral resistance, and which base area for tip resistance. These questions derive from the doubt regarding the occurrence of ‘plugging’. The phenomenon, in which soil adheres strongly to the pile, causes failure to occur not at the steel–soil interface but at an enveloping area. There is little experimental data specifically on the plugging of H piles, in which the contribution of shaft and tip loads were properly separated. Different test interpretations by researchers and designers have led to different recommendations for the design of such piles, some considering and others dismissing soil plugging. The research herein described was conducted on instrumented model H piles jacked in fine sand in a large flexible calibration chamber. The results indicate that – even in loose sand – plugging does occur in H piles close to the pile tip and that the tip resistance is an important component of the bearing capacity of such piles.