Eighth International Conference on Case Histories in Geotechnical Engineering

Impact of Biology on Particle Crushing in Offshore Calcareous Sediments

ABSTRACT

Sandy hemipelagic calcareous sediments are quite complex soils. In some instances, they can consist entirely of the skeletal remains of microorganisms, such as foraminifera tests. These calcium carbonate test (shell) producing protozoa are common in marine environments, accounting for the majority of the calcium carbonate in the open ocean. Foraminifera come in a variety of species, each with unique test morphological adaptation suited to their local environment. For example, planktic species have relatively low density tests and live in the water column, while benthic species have dense shells and live on the seafloor. This paper explores the impact of biologically driven morphology on the physical properties (e.g. crushing) of calcareous sand from the Browse Basin, offshore North West Australia. X-ray microtomography scans were performed to visualize and measure the test structure and the Weibull statistic of particle strength for Trilobatus sacculifer, a common planktic foraminifera, and Cibicidoides sp., a benthic foraminifera. These are compared with clastic siliceous and calcareous sands. Overall it is shown, that the biological taxonomy can play a significant role in the crushing behavior and mechanical properties of deep sea calcareous sediments.