Monopiles used as foundations for offshore wind turbines can be installed using different methods including jacking, vibratory driving and impact driving. Significant research efforts have been dedicated to the characterisation of monopile−soil interaction under lateral loading, mainly using p–y curves. There has also been extensive research in quantifying the effect of different installation methods on the axial response using numerical modelling and physical modelling techniques. Little attention has been paid to the effect of the installation method on the subsequent lateral response of a monopile under the in-service condition. In this paper, a purpose-designed apparatus is described that allows in-flight installation using different installation methods followed directly by lateral loading without stopping the centrifuge and thus retaining the installation-induced stress state. Test results from three lateral loading tests are discussed, with the piles either jacked at 1g and Ng or impact driven at Ng into a dry medium dense sand, allowing the effect of the installation method on the initial stiffness and ultimate capacity to be examined. The successfully conducted tests illustrate the capabilities of the new apparatus for centrifuge testing of laterally loaded driven piles.

Monopiles are widely used as the foundation to support offshore wind turbines (OWTs).The response of monopile supported OWTs is strongly affected by the natural frequency of the system relative to the load spectrum, and in turn the natural frequency is governed by the initial stiffness of the foundation. Both fatigue limit state (FLS) and serviceability limit state (SLS) design are also influenced by the foundation stiffness. The stiffness of the foundation during operational loading is a function of the 'initial' soil state postinstallation, which is influenced by the installation effect. This is the first of a pair of companion papers that investigates the effect of different installation methods on the subsequent response of monopile under lateral loading through extensive numerical analysis. The present paper focuses on quantification of the effect of pile installation on the soil states in sand for three different initial relative densities. The numerical model is first validated against purpose-designed centrifuge tests. Subsequent analyses demonstrate how the soil state, including the void ratio and stresses, is altered from in-situ conditions during pile installation, and are markedly different depending on whether the pile is jacked or impact driven. The results presented here and in the companion paper highlight the need to account for the effects of the installation process on the lateral pile response.

Monopiles under in-service conditions are subjected to lateral forces and resultant bending moments from the offshore environment. The subsequent lateral response following installation is significantly influenced by the 'initial' soil state post-installation, which is influenced by the pile installation process as demonstrated in previous numerical studies. To date, there are no technical guidelines established for consideration of installation effects on the design of laterally loaded monopiles. This paper is the second of a pair of companion papers that investigate the effect of different installation methods on subsequent response of monopiles under lateral loading. The paper focuses on the quantification of the effect of pile installation on the initial stiffness and lateral capacity.The numerical model is first validated against purpose-designed centrifuge tests. The analysis confirms that impact-driven piles have significantly higher initial stiffness and lateral capacity than jacked piles and wished-in-place piles. The effect of installation methods on the lateral response is also influenced by the initial soil density, driving distance, pile geometry, stress level, and load eccentricity. The study highlights the importance of considering the effects of the installation process on the subsequent lateral pile response.

This paper evaluates the effect of analysis parameter choices on the stability and efficiency of modelling cone penetration into sand. This very large deformation quasi-static boundary-value problem is modelled here using the arbitrary Lagrangian–Eulerian adaptive mesh technique available within Abaqus/Explicit. The sand response is captured using a hypoplastic constitutive model. It is demonstrated that many choices of analysis parameters lead to spurious results, some of which show clear instability, while other combinations show reasonable stability but over-estimation of the cone resistance. The accuracy of the numerical solution is shown through comparison against centrifuge experimental data for two different relative densities of the sand.