Experimental study of the dynamic driving of steel pipe pile and the mechanism for pile running

Abstract

Large diameter steel pipe piles are widely used in the construction of offshore wind farms. Pile running may take place during the dynamic driving of pile due to its enormous weight. Pile running can cause unsafe construction or even grave losses of life and property, so it is of practical significance to investigate the pile running behavior for the construction of offshore wind farms. In this paper, model tests of dynamic driving of steel pipe piles into soft marine clay were carried out. The vertical displacement and axial strain of the model pile, the skin friction and normal soil pressure on the pile surface, and the pore water pressure around the pile were investigated, based on which the mechanism for pile running was ascertained. It was found that the skin friction and normal soil pressure on the pile surface normally increased accordantly with the driving depth, while the vertical displacement of the model pile by each single hammer blow decreased successively throughout the dynamic driving process. However, in the case of pile running, the vertical displacement by the hammer blow which triggered the pile running was greater than that by the former blow, accompanied by a decrease in the unit skin friction to the pile surface and a continuous increase in the pore water pressure in the soil surrounding the model pile.