Observations on bucket foundations under cyclic loading in dense saturated sand

Session report: offshore geotechnics at ICPMG 2014

“…As a starting point it is useful to compare the rate of accumulated rotation in 1g tests at low relative densities with that from recent centrifuge tests at high relative densities (Cox et al, 2014). The centrifuge data gave α = 0·3 for caissons with aspect ratios of 1 and 0·5, very similar to the consensus for monopiles (α = 0·31), and closer to α = 0·39 from the 1g tests at low relative density reported by Zhu et al (2013) than α = 0·18 from the 1g tests at high relative density reported by Foglia et al (2014). In the absence of a more definitive answer, it appears that scaling the relative density downwards in the 1g test (as one would do in consideration of capacity) provides a reasonable approximation of the rate of accumulated rotation at larger scales.…”

“…Abadie and Byrne (2014) showed that the rotation data from their 1g monopile tests in sand could be well described using α = 0·31, which is in exact agreement with the benchmark work of LeBlanc et al (2010a) (see Figure 19). For a suction caisson in sand with an aspect ratio (diameter to length) equal to 1, Foglia et al (2014) found α = 0·18, whereas Zhu et al (2013) showed that α = 0·39 for a caisson with an aspect ratio equal to 0·5 (also shown in Figure 19). Although the difference may be attributed to the different aspect ratios in the two studies, it is worth noting that, unlike the Foglia et al (2014) experiments, Zhu et al (2013) chose an appropriately low relative density so that the results from their 1g tests (at low stress levels) would be comparable with results at higher relative density from field or centrifuge tests (at higher stress levels).…”

Serviceability of suction caisson founded offshore structures

“…Accordingly the fitting exponents are summarised in Table 6. Within other investigations the accumulation of rotation was described in-terms of the relative load level ( ) and load directionality ( ) (LeBlanc et al, 2010a, Zhu et al, 2013and Foglia et al, 2014. From the behaviour seen within this investigation there appears to be no clear trend between the relative load level ( ) and the accumulation of structural rotation.…”

“…A similar exponent value of α = 0.31 was reported by LeBlanc et al, (2010a) and α = 0.13 by Nicolai and Ibsen, (2014), for monopiles subjected to a series of cyclic loading regimens. In addition both Zhu et al (2013) and Foglia et al (2014) …”

“…Similar behaviour was observed in analogous experiments by Lin and Liao, (1999), Verdure et al, (2003) and Li et al, (2010) who proposed a logarithmic relationship to describe the response of a cyclically loaded monopile foundation. Alternatively a power relationship was used by Long and Vanneste, (1994), LeBlanc et al, (2010a) and Klinkvort et al, (2010) for monopiles, and by Zhu et al, (2013) and Foglia et al, (2014) for caissons. From preliminary analysis it was found that the power relationship best described the observed behaviour.…”