New apparatus and techniques for performing synchronised multi-scale particle image velocimetry or digital image correlation (PIV/DIC) soil deformation measurements have been developed. A central camera records a full field of view (FoV) of the model capturing the ‘macro’ deformation mechanism and the boundaries of the model. Simultaneously, an adjacent slave camera records a subset of the full FoV capturing the ‘micro’ soil response in a region of special interest, such as under the corner of footing. The ‘micro’ FoV images have higher resolution in terms of particle/pixel size ratio (d/p), resulting in the ability to measure localised deformations that are invisible to lower resolution images. Recommendations are made with respect to appropriate subset size and spacing for high-resolution images. A photogrammetric correction process requiring a small number of static control points is proposed and the performance is validated against a conventional photogrammetric calibration utilising a large array of static control points. Lastly, results from a validation experiment are presented comparing the PIV/DIC output from the ‘macro’ and ‘micro’ FoV, illustrating that: (a) the photogrammetric correction method proposed is robust and (b) that there has been an improvement in spatial resolution of the strain measurements that can be obtained through the ‘micro’ FoV camera.

In Southeast Asia, the characteristic operating environment is strong and persistent currents with small to moderate waves, which encourages vortex induced motion (VIM) in floating platforms. Scaled model tests have always been used by the industry to check the performance of floating platforms including VIM. With improved hardware and software capacilities, numerical methods such as Computational Fluid Dynamics (CFD) analysis are now able to simulate floating platform motions in viscous fluid flow and thus have the potential to complement model tests in VIM studies. Hull appurtenances such as tendon porches, steel catenary riser (SCR) porches, caissons, pipes, chains, fairleads and anodes interact with the boundary layers and affect the points of flow separation along the hull columns which control the vortex shedding pattern of the hull. In this study, the effect of appurtenances on the VIM performance of a Tension Leg Platform (TLP) for Southeast Asian environment is investigated using a series of model tests and CFD analysis.The findings from this study may be used as a reference to properly account for the effect of VIM. The measured or calculated amplitudes of VIM may be used as input for additional load conditions to be considered in the design of the tendon mooring and riser systems of the TLP.Previous studies by others on the same subject were carried out for spars. Multi-column floating platforms do not have strakes on the columns unlike spars. Thus, significant difference in VIM behaviors between multi-column floating platforms and spars is expected. The wake is expected to remain turbulent in both full scale and model scale. For smooth cylinders, the separation point along the columns is scale dependent and this may affect the VIM responses. If the flow separates from a sharp appurtenance like a pipe, the VIM behaviors should be similar in full scale and in model scale. The results from CFD analysis generally agree with those from model test. The differences in the results from the two methods are discussed and areas for further investigation suggested.Significant VIM can adversely impact the platform mooring and riser systems in terms of both strength and fatigue life requirement and has to be properly accounted for in the platform design. Left unchecked, VIM can lead to loss of production due to unplanned repairs of the risers.

This paper details analysis of deformation behaviour of silica and carbonate sands under a rectangular foundation subject to uniaxial vertical load based on results from a series of centrifuge model tests. A multiscale Particle Image Velocimetry/Digital Image Correlation (PIV/DIC) technique was used to record and analyse the foundation tests with high resolution and measurement precision. Cone penetrometer and pressuremeter tests provide in situ soil characterisation of the tested sand sample in the centrifuge environment. The soil behaviour is analysed through foundation load-settlement response and the observed soil deformation measurements. Different soil deformation mechanisms and strain behaviours were observed in the different sands tested, and particle shape effect is considered, with data from scanning electron microscopy, to explain the differences. The results and analyses contribute towards better understanding of different soil behaviours under shallow foundations in different sands.

This paper reports the deformation behavior of silica and carbonate sands under a strip foundation subjected to uniaxial vertical load. Small-scale physical modelling tests of a strip surface foundation under vertical load were conducted in a geotechnical centrifuge and Particle Image Velocimetry/Digital Image Correlation (PIV/DIC) was used to analyze images of an exposed plane of the model beneath the foundation to visualize the failure mechanisms. The observed mechanisms are interpreted in conjunction with load-settlement response and cone penetrometer resistance profiles. The failure mechanisms are illustrated through normalized vertical and horizontal displacement fields and shear and volumetric strain fields derived from the PIV analysis. Different soil deformation mechanisms and load-settlement responses were observed in the different sands. Soil resistance profiles measured using a miniature cone penetrometer do not correlate with the measured foundation bearing resistance and an interpretation of particle shape effect is introduced to explain the differing behaviors. The results presented improve understanding of the different responses in carbonate sands and silica sand beneath a shallow foundation under vertical load.