Erosion Behavior of Sand‐Silt Mixtures: Revisiting the Erosion Threshold

Yao, Peng; Su, Min; Wang, Zheng Bing; Rijn, Leo C. van; Stive, M.J.F.; Xu, Conghui; Chen, Yongping

doi:10.1029/2021wr031788

Cited by 18 publications

(17 citation statements)

References 55 publications

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“…The observation that the sediment mobility increases when adding coarse silt to the bed is in line with what can be expected from experiments with gravel-sand mixtures, but opposes previous observations in laboratory experiments with sand-silt mixtures. and Yao et al (2022) observed that non-cohesive silt stabilizes the sediment bed, but at different concentrations (∼1.4% silt and >35%, respectively), whereas, in our experiments, even at 50% coarse silt the mobility of the sediment was increased. Interestingly, , whose experiments fall in the range of pore bridging (D coarse / D f ines = 5.5), explained the filling of pore space as a reason for increased stability of the bed due to reduced hyporheic flow, rather than a reason for increased mobility of the coarse fraction as found in gravel-sand experiments (Section 4.2.1).…”

Section: 22contrasting

confidence: 65%

“…Yet, none of these studies discussed the potential impact of silt content on bedforms. This is an important research gap, because an increase in bed stability, as observed by and Yao et al (2022), could theoretically reduce bedform formation and growth due to a decrease in sediment transport, whilst 's suspensionload dominated high-efficiency regime would also mean suppression of bedform formation and growth, but then because bedload transport gets increasingly replaced by suspended load transport, which is incapable of forming bedforms. Clearly, the effect of silt in sand-silt mixtures on the resulting bedform geometry is largely unexplored.…”

Section: Introductionmentioning

confidence: 99%

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Fine sediment in mixed sand-silt environments impacts bedform geometry by altering sediment mobility

Lange,

Niesten,

Veen

et al. 2024

Preprint

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Geometric characteristics of subaqueous bedforms, such as height, length and leeside angle, are crucial for determining hydraulic form roughness and interpreting sedimentary records. Traditionally, bedform existence and geometry predictors are primarily based on uniform, cohesionless sediments. However, mixtures of sand, silt and clay are common in deltaic, estuarine, and lowland river environments, where bedforms are ubiquitous. Therefore, we investigate the impact of fine sand and silt in sand-silt mixtures on bedform geometry, based on laboratory experiments conducted in a recirculating flume. We systematically varied the content of sand and silt for different discharges, and utilized a UB-Lab 2C (a type of acoustic Doppler velocimeter) to measure flow velocity profiles. The final bed geometry was captured using a line laser scanner. Our findings reveal that the response of bedforms to an altered fine sediment percentage is ambiguous, and depends on, among others, bimodality-driven bed mobility and sediment cohesiveness. When fine, non-cohesive material (fine sand or coarse silt) is mixed with the base material (medium sand), the hiding-exposure effect comes into play, resulting in enhanced mobility of the coarser material and leading to an increase in dune height and length. However, the addition of weakly-cohesive fine silt reduces the mobility, suppressing dune height and length. Finally, in the transition from dunes to upper stage plane bed, the bed becomes unstable and bedform heights vary over time. The composition of the bed material does not significantly impact the hydraulic roughness, but mainly affects roughness via the bed morphology, especially the leeside angle.

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Section: 22contrasting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Fine sediment in mixed sand-silt environments impacts bedform geometry by altering sediment mobility

Lange,

Niesten,

Veen

et al. 2024

Preprint

View full text Add to dashboard Cite

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“…The results of this part of our study show that the presence of cohesiveness in a fine‐grained sediment environment makes the empirical formula no longer applicable. It is worth noting that current laboratorial research uses similar strategies to modify empirical formulas and achieves comparable outcomes (Yao et al., 2022).…”

Section: Resultsmentioning

confidence: 99%

Turbulence Intermittency Effects on the Initiation Threshold of Sediment Motion in Natural Waters

Li,

Wang,

Gao

2024

Water Resources Research

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The initiation threshold of sediment motion, a key component in quantifying sediment transport, has potential link to intermittent turbulence bursts. Here, we elaborated in situ experiments on coastal sea bottom covered with cohesive sediments, to obtain intermittency parameters. The variable “waiting time” between turbulence bursts was utilized to capture the occurrence of sediment initiation events in natural waters. A relationship between waiting time and shear stress reveals the different intermittency features of sediment flux time series before and after reaching the threshold, which can be used to determine the initiation threshold of sediment motion. Multi‐site results demonstrate the limitations of traditional empirical formulae for fine‐grained sediments, where cohesiveness becomes more pronounced as grain size decreases and the deviation can reach 600%. The empirical formula was modified using grain size, and the modified calculations were in good agreement with observed values, which will greatly assist in sediment transport and geomorphology model predictions.

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“…For instance, the influence of salinity on the erosion of kaolinite varies as a function of particle size, pH, and temperature (Hoomehr et al., 2018; Raudkivi & Hutchison, 1974). In addition, sediment mixtures of cohesive and non‐cohesive sediments display mechanical characteristics that contrast with pure clay (Van Ledden et al., 2004; Yao et al., 2022) and are beyond the scope of this work.…”

Section: Discussionmentioning

confidence: 99%

Impact of Salinity on the Erosion Threshold, Yield Stress, and Gelatinous State of a Cohesive Clay

San Juan,

Wei,

Yang

2024

JGR Earth Surface

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Clay is the main component that contributes to sediment cohesiveness. Salinity impacts its transport, which controls the electrochemical force among the sediment grains. Here, we quantify the impacts of salinity on the erosion threshold, yield stress, and the microstructures of a fluorescently labeled smectite clay, laponite, by combining flume experiments, rheometer measurements, and macro‐ and microscopic imaging. We show that the critical shear stress for clay erosion, τb,crit, increases by one order of magnitude with increasing salinity when salinity <1.5 ppt and slightly decreases when salinity >1.5 ppt showing a weaker dependency upon salinity. We further show that the yield stress, τy, of the clay remains roughly a constant at salinity less than 1.5 ppt and decreases by over one order of magnitude at salinity larger than 1.5 ppt. This change in the dependency of τb,crit and yield stress on salinity corresponds to a change in the gelatinous state of clay, from gel‐like structures to phase‐separated structures as salinity increases. Our results provide a quantitative characterization of the dependency of clay erosion threshold and yield stress on salinity and highlight the importance of the clay gelatinous state in controlling clay transport.

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Erosion Behavior of Sand‐Silt Mixtures: Revisiting the Erosion Threshold

Cited by 18 publications

References 55 publications

Fine sediment in mixed sand-silt environments impacts bedform geometry by altering sediment mobility

Fine sediment in mixed sand-silt environments impacts bedform geometry by altering sediment mobility

Turbulence Intermittency Effects on the Initiation Threshold of Sediment Motion in Natural Waters

Impact of Salinity on the Erosion Threshold, Yield Stress, and Gelatinous State of a Cohesive Clay

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