The Breaching of Sand Investigated in Large-Scale Model Tests

Rhee, Cees van; Bezuijen, Adam

doi:10.1061/9780784404119.189

Cited by 16 publications

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“…Previous studies suggest that the excess pore pressure and the slope failure are coupled (Terzaghi, 1951;Meijer and van Os, 1976;Hampton et al, 1996;Van Rhee and Bezuijen, 1998;Flemings et al, 2008). However, studies on the mechanics of submarine slope failure so far separate the excess pore pressure and the slope failure.…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

“…Because breaching produces sustained turbidity currents, the sands delivered downslope may build thick uniform turbidites (Van den Berg et al, 2002). Previous studies associate breaching with fine-grained sand (de Koning, 1970;Meijer and van Os, 1976;Van Rhee and Bezuijen, 1998;Van den Berg et al, 2002); however, Houthuys (2011) speculated that breaching could also be the mechanism that contributes to building coarse sand turbidites. An understanding of the mechanism of breaching is important to correctly interpret these turbidites.…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

“…The increase in excess pore pressure decreases the effective stress between sediment grains and weakens the deposit (Terzaghi, 1951;Wood, 1990). During breaching the sediment dilates, which decreases the excess pore pressure (Meijer and van Os, 1976;Van Rhee and Bezuijen, 1998). The drop in excess pore pressure increases the effective stress between the sediment grains and strengthens the deposit (Wood, 1990).…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

“…the best studied cases are associated with contraction, increased pore pressures, and subsequent liquefaction (Terzaghi, 1951;Hampton et al, 1996;Iverson, 2005). On the other hand, dilation and the development of negative excess pore pressure near the failure surface lead to breaching (Meijer and van Os, 1976;Van Rhee and Bezuijen, 1998 et al (2011) proposed that breaching may be one of the processes by which sands are released into turbidity currents and transported down Scripps Canyon (offshore southern California). Because breaching produces sustained turbidity currents, the sands delivered downslope may build thick uniform turbidites (Van den Berg et al, 2002).…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

“…The increase in porosity during breaching is a result of both unloading and shear dilation as the deposit undergoes slow retrogressive failure (Meijer and van Os, 1976;Van Rhee and Bezuijen, 1998). Shear dilation is the dominant mechanism generating the negative excess pore pressure, or underpressure (Meijer and van Os, 1976).…”

Section: Chapter 1: Introductionmentioning

confidence: 99%

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Dynamics of dilative slope failure

You

Flemings

Mohrig

2012

Geology

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Section: Chapter 1: Introductionmentioning

confidence: 99%

Section: Chapter 1: Introductionmentioning

confidence: 99%

Section: Chapter 1: Introductionmentioning

confidence: 99%

Section: Chapter 1: Introductionmentioning

confidence: 99%

Section: Chapter 1: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Dynamics of dilative slope failure

You

Flemings

Mohrig

2012

Geology

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How heterogeneity in the shear dilation of a deposit controls the mechanics of breaching slope failure

et al. 2014

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Breaching is a type of retrogressive submarine slope failure associated with pore pressure drops in both space and time, and this drop strengthens the failing deposit. Breaching is characterized by a near‐vertical failure surface that retreats with a relatively constant velocity, on the order of a millimeter per second. Breaching is controlled by interactions between shear‐dilation‐generated pore pressure drops and pore pressure dissipation through intergranular fluid flow. Laboratory measurements show that shear dilation in a deposit increases with increasing effective stress ratio between the major principal effective stress and the minor principal effective stress as well as decreasing confining stress. We present a two‐dimensional numerical model that indicates how effective stress ratio and confining stress produce spatially varying dilation, affecting the mechanics of breaching. Experimental results show that dilation in a breaching deposit increases with proximity to the failure surface. As a result, the maximum magnitude of pore pressure drop is very close to the failure surface. The numerical model confirms that the sediment release is dominated by pore pressure dissipation through intergranular fluid flow in the horizontal direction. This allows the erosion rate to be treated as a constant in the vertical direction. Numerical model results also show that because dilation decreases with increasing vertical depth, the deposit becomes less stable with depth, suggesting a potential upper limit for the thickness of the deposit undergoing breaching.

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Location and probability of shoal margin collapses in a sandy estuary

Dijk

Mastbergen

Ham

et al. 2018

Earth Surf Processes Landf

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Channel bank failure, and collapses of shoal margins and beaches due to flow slides, have been recorded in Dutch estuaries for the past 200 years but have hardly been recognized elsewhere. Current predictions lack forecasting capabilities, because they were validated and calibrated for historic data of cross-sections in specific systems, allowing local hindcast rather than location and probability forecasting. The objectives of this study were to investigate where on shoal margins collapses typically occur and what shoal margin collapse geometries and volumes are, such that we can predict their occurrence. We identified shoal margin collapses, generally completely submerged, from bathymetry data by analyzing digital elevation models of difference of the Western Scheldt for the period 1959-2015. We used the bathymetry data to determine the conditions for occurrence, specifically to obtain slope height and angle, and applied these variables in a shoal margin collapse predictor. We found 299 collapses along 300 km of shoal margin boundaries over 56 years, meaning that more than five collapses occur on average per year. The average shoal margin collapse body is well approximated by a 1/3 ellipsoid shape, covers on average an area of 34 000 m 2 and has an average volume of 100 000 m 3 . Shoal margin collapses occur mainly at locations where shoals take up a proportionally larger area than average in the cross-section of the entire estuary, and occur most frequently where lateral shoal margin displacement is low. A receiver operating characteristic curve shows that the forecasting method predicts the shoal margin collapse location well. We conclude that the locations of the shoal margin collapses are well predicted by the variation in conditions of the relative slope height and angle within the Western Scheldt, and likely locations are at laterally relatively stable shoal margins. This provides hypotheses aiding the recognition of these features in sandy estuaries worldwide.

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The Breaching of Sand Investigated in Large-Scale Model Tests

Cited by 16 publications

References 0 publications

Dynamics of dilative slope failure

Dynamics of dilative slope failure

How heterogeneity in the shear dilation of a deposit controls the mechanics of breaching slope failure

Location and probability of shoal margin collapses in a sandy estuary

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