Apparent overconsolidation and its implications for submarine landslides: Fid-Bau Portal

Apparent overconsolidation and its implications for submarine landslides

Yenes, Mariano / Monterrubio, Serafín / Nespereira, José / Casas, David

Highlights • The existence of AOC is related to the formation of a structured sediment, generated mainly by processes of secondary consolidation and aging. • The structuring of the sediment by secondary consolidation is generated mainly when the sedimentary process is slow and continuous. • Sediment structuring by aging would only occur in the most superficial samples and would later be masked in the deeper samples. • The weakening that occurs immediately below the superficial layer due to AOC will facilitate the development of plane superficial slides. • This generates a subsequent stabilization of the ocean floor and, consequently, a lower recurrence of large landslides in these areas.

Abstract In recent years, apparent overconsolidation (AOC) has been observed in the most superficial sections of the sedimentary column of the seabed. AOC has been detected in sediment samples taken from deep and shallow waters, independent of the source area. Although the origin of this phenomenon remains controversial, it seems to be linked principally to physical-chemical bonds and ionic changes that cause strong attractions between particles. This work uses an experimental approach based on standardized oedometer tests to study the presence of AOC in surface sediments and its disappearance at depth. The results obtained show that the existence of AOC is related to the formation of a structured sediment generated by both secondary consolidation and aging processes. In addition, the results obtained facilitate a discussion of how AOC influences the potential development of plane translational slides. The development of this type of instability in areas affected by AOC generates a subsequent stabilization of the ocean floor and, consequently, a lower recurrence of large landslides in these areas than would be expected from a sedimentary process with no AOC.