ABSTRACT

The mechanical properties of near-surface sediments – to a depth of approximately half a metre – are relevant to the design of cables, pipelines and other shallowly-embedded infrastructure, as well as benthic habitat characterisation. For this depth of interest, vertically-pushed penetrometers – such as the cone, T-bar or ball – can be supplemented by shallow rotational devices such as the toroid or hemiball. In this paper, we report vertical and shallow rotational penetrometer test procedures and show results obtained in project conditions on natural soil samples. By combining these different penetrometers, a wider and more reliable set of mechanical properties – spanning strength and consolidation behaviour – can be obtained, compared to conventional practice. The paper concludes with practical advice on testing protocols and interpretation methods to best characterise the shallow seafloor, including the use of novel shallow penetrometers.