Effects of Consolidation under a Penetrating Footing in Carbonate Silty Clay

Numerical modelling of the effects of consolidation on jack-up spudcan penetration

“…The observed decrease in punch-through distance in particular, of roughly 50% from Figure 18 shows the effects of T on the re-penetration profiles, where intuitively both k = 0.05 ( Figure 18a) and k = 0.2 (Figure 18b) present q peak values proportional to T. An increasing gap between the re-penetration profiles and the reference case (dashed line) is observed when approaching w/D = 2.0, confirming the long-lasting effect of enhanced bearing capacity post-consolidation described experimentally by Bienen et al (2015) for the same carbonate silty clay. For k = 0.05, an increment in T leads to higher q peak values and more pronounced long-term beneficial effects, whereas for k = 0.2 the severity of the punch-through is worsened by higher T, with the extent of uncontrolled leg penetration increasing from 0.25 D for T = 0.005 to more than 0.7 D for T = 0.746.…”

“…For example, on average, in the experiments, 18% of the total load-hold induced settlement had already occurred before V < 80. Upon re-penetration after consolidation, a peak in the experimental curves is observed, followed by a continuous increase of the bearing capacity as the penetration advances towards w/D = 2.0, behaviour already described by Bienen et al (2015). The numerical analyses were able to reproduce the same trend, illustrating once again low risk for a potential consolidation-generated punch-through, as no bearing capacity reduction post-peak is observed, in contrast for example with the kaolin clay responses studied in Bienen & Cassidy (2013).…”

“…Barbosa-Cruz (2007) and Bienen & Cassidy (2013) carried out a small number of centrifuge experiments on spudcan penetration-consolidation-penetration cycles, with the latter highlighting the punch-through risk created through pauses in footing penetration in kaolin clay. In a natural soil recovered from offshore Australia (a carbonate silty clay) further centrifuge experiments revealed the potential for a beneficial increase in bearing capacity due to consolidation without the elevation of the risk of punch-through (Bienen et al 2015). The mechanisms of jack-up foundation penetration pre-and post-consolidation were seen to differ in Particle Image Velocimetry (PIV) experiments, as reported in Stanier et al (2014).…”

“…The validation of the numerical model involved the retrospective simulations of centrifuge model data on spudcan installation with a pause during penetration from Bienen et al (2015).…”

“…Given the observation of shear bands in the samples and the inability of the model to capture this phenomenon, the response of the simulations is quite different to the experimental response (this discrepancy is revisited in a later discussion at the end of this section). However, the slope of the critical state line M was nonetheless captured.Back-analysis of the results from the centrifuge tests ofBienen et al (2015) underpinned the calibration of the remaining parameters. A series of experiments involving full spudcan penetrating into carbonate silty clay was carried out in a beam centrifuge at the University of Western Australia (UWA) at enhanced gravity level of a = 200g.…”