Abstract
Through two lab-scale experiments, we investigated the hydraulic and mechanical characteristics of sediment layers during water film formation, induced by elevated pore pressure—considered one of the triggers of submarine landslides. These involved (1) sandbox experiments to prove the effect of water films on mass movement in low slope gradients and (2) experiments to observe the effect of the tensile strength of semi-consolidated sediment layers on water film formation. Portland cement was used to mimic the degree of sediment cementation. We observed a clear relationship between the amount of cement and pore pressure during water film formation; pressure evolution and sediment deformation demonstrated the hydraulic and mechanical characteristics. Based on the results of these experiments, conditions of the sediment layers during water film formation are discussed in terms of pore pressure, permeability, tensile strength, overburden pressure, and tectonic stresses. The results indicate that the tensile strength of the sediment interface provides critical information on the lower limit of the water film formation depth, which is related to the scale of potential submarine landslides.
Highlights
Submarine landslides are known to damage offshore and coastal infrastructure and cause damaging tsunamis (Moore et al 1989; Hampton et al 1996; Locat and Lee 2002)
Through laboratory experiments on unconsolidated and semi-consolidated sediments, we observed hydraulic and mechanical characteristics during water film formation induced by elevated pore pressures
The pore pressure of semi-consolidated sediments was measured during water film formation, and the effect of tensile strength was observed
Summary
Submarine landslides are known to damage offshore and coastal infrastructure and cause damaging tsunamis (Moore et al 1989; Hampton et al 1996; Locat and Lee 2002). Elger et al (2018) used seismic data to show that elevated fluid pressures in the gas hydrate stability zone moved to shallower layers or the sediment interface through pipe formation. They showed that lateral overpressure built up in shallow sediments possibly triggers submarine landslides. Morita et al (2012) used 3D seismic data to show a typical slumping deformation, accompanied by parallel dikes that are considered as the Kawakita et al Progress in Earth and Planetary Science (2020) 7:62 evidence of dewatering structures They discussed the relationship between seafloor stability and dewatering structure, which was closely related to natural gas distribution and slumping formation mechanisms. The effect of compressibility and sedimentation rate on overpressure generation has been investigated to understand low-gradient and large submarine landslides (Urlaub et al 2015). Utsunomiya et al (2019) surveyed the stratigraphy and material features of coarse-ash and lapillituff beds, with intruding clastic dykes due to elevated fluid pressure, to understand the preferential formation of slip planes in submarine landslides
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