The Granular Structure of Two Marine Carbonate Sediments

Abstract

Calcareous sediments are prominent throughout the low-latitudinal offshore environment and have been known to be problematic for offshore foundation systems. These fascinating soils consist largely of the skeletal remains of single-celled marine organisms (plankton and zooplankton) and can be as geologically complex as their onshore siliceous counter parts. To enable an adequate understanding of their characteristics, in particular, their intra-granular micro-structure, it is important that geotechnical engineers do not forget about the multifaceted biological origins of these calcareous sediments and the different geological processes that created them. In this paper, the 3D models of soils grains generated from micro-computed tomography scans, scanning electeron microscope images, and optical microscope images of two calcareous sediments from two different depositional environments are presented and their geotechnical implications discussed. One is a coastal bioclastic sediment from Perth, Western Australia that is geologically similar to carbonate sediments typically used in micro-mechanics and particle crushing studies in the literature. The other is a hemipelagic sediment from a region of the North West Shelf of Australia that has historically been geotechnically problematic for engineers. The results show there is a marked difference between coastal bioclastic and hemipelagic sediments in terms of geological context and the associated particle micro-structures. This brings into question whether a coastal bioclastic calcareous sediment is a good micro-mechanical substitute for a hemipelagic one.

Towards a regional high-resolution bathymetry of the North West Shelf of Australia based on Sentinel-2 satellite images, 3D seismic surveys, and historical datasets

“…Paumard et al, 2020;Nyberg and Howell, 2016;Ainsworth et al, 2019), the geotechnical properties of marine sediments (e.g. Beemer et al, 2019Beemer et al, , 2018Senders et al, 2013), or geohazards affecting the area (e.g. Lane and Tyler, 2015;Hogan et al, 2017;Scarselli et al, 2019;Hengesh et al, 2013).…”

Towards a regional high-resolution bathymetry of the North West Shelf of Australia based on Sentinel-2 satellite images, 3D seismic surveys and historical datasets

“…The digital elevation model provides the full picture of modern sedimentary systems, from the source of the sediments (e.g., fluvial and carbonate systems) to their accumulation grounds along the shelf and in the basin. Parts of these modern systems can be used to better understand past sedimentary record (Paumard et al, 2020;Nyberg and Howell, 2016;Ainsworth et al, 2019), the geotechnical properties of marine sediments (Beemer et al, 2019;Beemer et al, 2018;Senders et al, 2013) or the geohazards affecting the area (Lane and Tyler, 2015;Hogan et al, 2017;Scarselli et al, 2019;Hengesh et al, 2013). Therefore, the integration of regional high-resolution bathymetry can constitute a step change and allow researchers to ponder their results with regard to the regional context and hence support the development of more reliable interpretations and models.…”

Image based simulation of one-dimensional compression tests on carbonate sand

“…A significant characteristic of shelly sands is the shape of the constituent grains, comprising a mixture of plate-like and hollow bulky shaped grains both characterized by high angularity values. Despite the variety of grain morphologies found in carbonate sands, typical shapes can often be associated to a finite number of species in a given sediment [6].…”