This paper reports results from a series of model tests undertaken to provide insight into the behaviour of a stiffened caisson anchor during installation and monotonic pullout in lightly overconsolidated calcareous silt. The tests were carried out in a beam centrifuge, varying the installation process (jacked in or jacked in followed by suction assisted installation), and the consolidation period prior to anchor pullout. The mudline load inclination was also varied to encompass various mooring configurations. The centrifuge data were used to calibrate analytical installation and vertical pullout capacity models, based on conventional bearing and frictional resistance factors but with strain rate dependent and strain softened undrained shear strength for the soil. Piezocone based direct design approaches were also proposed, deriving end bearing and frictional resistance from cone tip resistance and sleeve friction, respectively. Holding capacity of suction caisson under inclined loading was presented as failure envelopes expressed in terms of dimensionless vertical and horizontal components of caisson net resistance, which agreed well with a plastic limit analysis based envelope developed for suction caissons in clay. The regain of anchor capacity was found to be in good agreement with predictions based on the cavity expansion framework.

A geotechnical investigation was carried out to characterise a subaqueously deposited, primarily silt, iron ore tailings. Piezocone penetration tests (CPTu) were carried out followed by piston tube sampling at a selected target depth. Piston samples provided measures of in situ density (by means of gravimetric water content), and supplied material for reconstituted and intact laboratory testing. Reconstituted samples prepared using moist tamping (MT) for determination of the critical state locus (CSL), along with intact specimens, were both tested. The potential existence of layering within the recovered specimens was also assessed, indicating near-homogenous samples. The laboratory testing of intact specimens suggested that they appeared to tend towards the same CSL as that obtained from reconstituted loose MT specimens. This tentative result differs from some previous comparisons – with the agreement seen in this case being suggested to primarily result from a lack of layering. In situ state as inferred from both CPTu data and comparison of tube densities to the CSL suggested a loose state.

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