Biogenic Particles Crushability as a Key Factor for Sediment Behavior: Insights from Mayotte Submarine Slope Case Study (SW Indian Ocean)

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4. Biogenic Particles Crushability as a Key Factor for Sediment Behavior: Insights from Mayotte Submarine Slope Case Study (SW Indian Ocean)

Since May 10, 2018, the island of Mayotte, located in the Comoros Archipelago of the Indian Ocean, has been experiencing significant volcanic and seismic activity. Detailed bathymetric studies of Mayotte's eastern regions have revealed steep underwater slopes, with some areas having inclines exceeding 35°. These slopes, in a high seismic activity scenario, could become susceptible to ground shaking and potentially generate tsunamis. The submarine sediments offshore Mayotte consist of carbonate and hemipelagic particles from the barrier reef, as well as volcanic grains from continental and volcanic erosion. During periods of high sea levels (when the barrier reef is submerged), aragonite and high-magnesium calcite dominate the sediment composition, while during low sea levels, planktic-origin low-magnesium calcite is more prevalent. Results of previous work have shown that liquefaction-prone layers are associated with periods of low sea levels, and that particle crushability is likely the reason for failure at the particle level. In the current study, we produced synthetic samples by mixing fines with biogenic particles recovered from Mayottes slopes to test particle crushing reproducibility and compare results with undisturbed sediments. Our findings indicate that biogenic particles embedded in a fine matrix can crush under external loading, significantly affecting the overall behavior of sediments, even in the presence of high amount of fines. This highlights the importance of naturally sedimented structures in the overall behavior of soils.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

3 - Constitutive models and soil behaviour modelling