A CPT-based p-y model for laterally loaded monopiles in sand

Abstract

Large-diameter monopiles are currently the dominant foundation solution for supporting offshore wind turbines (OWTs). Monopiles exhibit a rigid response with significant rotation under lateral load and overturning moment. There is some debate regarding the applicability of p-y models derived from tests on small-diameter slender piles (such as the sand p-y model recommended by the API standard) to monopiles. To address this issue, this study gathered existing field pile load tests and finite element analysis results for large-diameter monopiles in sand and established a database incorporating the CPT results from each testing site. Through a comprehensive analysis of the collected database, a CPT-based p-y model with a modified hyperbolic formulation is proposed. The model has four parameters, which are the initial soil-pile interaction stiffness (k_ini), the ultimate soil resistance (p_u), the stiffness degradation coefficient (m), and the ultimate soil resistance adjustment coefficient (A). All of them are functions of the CPT cone tip resistance (q_c), thus avoiding potential uncertainties with the determination of input soil parameters, such as the peak friction angle, which is necessary for the conventional API p-y model. The model is demonstrated to provide satisfactory performance in predicting the lateral response of monopiles in sand.