Effects of Monopile Installation on Subsequent Lateral Response in Sand. II: Lateral Loading

Abstract

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.

Effects of Monopile Installation on Subsequent Lateral Response in Sand. I: Pile Installation

“…The findings highlight the differences between the original in situ soil state and that at the end of pile installation. These differences will have an important influence on the inservice lateral pile response as discussed in the companion paper (Fan et al, 2020).…”

“…Pile installation leads to less marked changes in soil state than those reported here. This was demonstrated through pile installation analysis using a second pile geometry with D = 8 m and D/t = 80, with the effect on the lateral response discussed in the companion paper (Fan et al, 2020).…”

“…The post-installation soil state is mapped as the initial soil state for the lateral loading model. The effect of pile geometry on the subsequent response was further investigated in the companion paper (Fan et al, 2020).…”

Impact driving of monopiles in centrifuge: effect on the lateral response in sand

“…This was achieved by Fan et al (2019), who performed three direct monotonic push-over tests without stopping the centrifuge on a 50-mm monopile model monotonically jacked at 1g and 100g, and impact-driven at 100g into dry sand of medium density to a depth of 3.1D. Fan et al (2019) claimed that the global lateral response of the monopile was significantly influenced by the method of installation, and this was numerically confirmed by Fan et al (2021b). Fan et al (2021b) also revealed that the effect of the method of installation on the lateral response is affected by the initial density of soil, driving distance, geometry of the monopile, and the level of stress and eccentricity of the load.…”

Enhancement of a high‐cycle accumulation model by an adaptive strain amplitude and its application to monopile foundations

“…[28][29][30]62 Similar observations were made in experimental studies. 63,64 For the low-cycle phase of the HCA model, the Sanisand model (version of 2004) 65 is used. Up to now, the HCA model has been mainly used in combination with hypolasticity with intergranular strain extension.…”