An Investigation of the Contribution of the Pile Base to the Lateral Response of Monopiles in Sand under Static Loading

Large-diameter monopiles with small length to diameter ratios (i.e. short stubby piles) demonstrate a rigid pile response with large movement of the pile base. This base response provides added resistance that is absent in the case of flexible piles. To examine the relative influence of the base resistance, this paper describes results from lateral tests conducted on 457 mm diameter instrumented pipe piles with a length of 1.0 m (i.e. length to diameter ratio of 2.2) at a sand site in Perth, Western Australia. The influence of the base condition on pile lateral behaviour was investigated explicitly by comparing the response of pipe piles with and without the sand plug removed. These tests clearly show that the base makes only a negligible contribution to the piles’ load-deflection response. To verify the general applicability of the conclusion, 3D Finite Element (FE) analyses were performed that first replicated the Perth field tests and then extended the study to typical monopile diameter dimensions of 6, 8 and 10 m. These analyses confirmed the finding of the field tests and further demonstrated that the pile base resistance was not significant for the lateral response of short stubby piles in sand