scholarly journals Evaluation of erosion characteristics of soils using the pinhole test

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ba Huu Dinh ◽  
Anh-Dan Nguyen ◽  
Seo-Yong Jang ◽  
Young-Sang Kim
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Erosion Rate ◽  
Critical Shear Stress ◽  
Soil Samples ◽  
Test Results ◽  
Coefficient Of Uniformity ◽  
Identification Parameter ◽  
Pinhole Test ◽  
Significant Factors

AbstractThis paper investigates the erosion characteristics of soils using the pinhole test. The tests were conducted with two undisturbed clay samples and five disturbed sandy soil samples. Based on the pinhole test results, a process to analyze the critical shear stress and erosion rate was proposed. The result indicates that the particle size distribution and coefficient of uniformity of soils are significant factors that affect the erosion characteristics of the soil. Samples with a grain size ranging from 0.2 to 0.6 mm is most susceptible to soil erosion. The erosion coefficients can be used to distinguish between the low erodible soils (ND3 and ND4) and high erodible ones (D1 and D2). Furthermore, it is interesting to note that the critical shear stress might be used as an identification parameter for erosion characteristics of the soil: τc > 3.5 Pa (ND3), 3.0 Pa < τc < 3.5 Pa (D2), and τc < 3.0 Pa (D1).

Study on Incipient Motion of Consolidated Cohesive Fine Sediment

2012 ◽  
Vol 204-208 ◽  
pp. 354-358
Author(s):  
Jun Wang ◽  
Wei Guo ◽  
Hai Tao Xu ◽  
Zhong Wu Jin ◽  
Yin Jun Zhou
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Fine Sediment ◽  
Weight Increase ◽  
Unit Weight ◽  
Incipient Motion ◽  
Mean Particle Size ◽  
Dry Unit Weight ◽  
The One

The incipient motion mechanism of cohesive fine sediment is different to the one of non-cohesive sediment. It is related to the consolidation while being influenced by the dry unit weight and particle size. By means of the rectangle piping flume, the influence mechanism of dry unit weight and particle size to critical shear stress of cohesive fine sediment is studied. Experimental results show that on the condition of consolidation, the influence of dry unit weight to incipient motion is divided into two different stages, one is that when dry unit weight increase quickly, but the influence to incipient motion is not greatly, another is that when dry unit weight increase slowly, but the influence to incipient motion is very greatly, the critical dry unit weight to two stages decline as mean particle size decrease. So the mean particle size is finer, the degree of dry unit weight influence to critical shear stress is stronger, and the incipient motion is more difficult when consolidation last longer; it is also shown consolidation is more disadvantageous to incipient motion.

scholarly journals Quantifying the restoration success of wood introductions to increase coho salmon winter habitat

2019 ◽  
Vol 7 (3) ◽  
pp. 841-857 ◽  
Author(s):  
Russell T. Bair ◽  
Catalina Segura ◽  
Christopher M. Lorion
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Coho Salmon ◽  
Critical Shear Stress ◽  
Stream Velocity ◽  
Limited Information ◽  
Winter Habitat ◽  
Model Predictions ◽  
Size Model ◽  
Bed Stability

Abstract. Large wood (LW) addition is often part of fish habitat restoration projects. However, there is limited information about the spatial–temporal variability in hydraulic changes after LW additions. We investigated reach-scale hydraulic changes triggered after the addition of LW that are relevant to juvenile coho salmon survival. We used Nays2DH, an unsteady two-dimensional flow model, to quantify the patterns and magnitudes of changes of stream velocity and shear stress in three alluvial gravel reaches. The study sites are located in low-gradient reaches draining 5 to 16 km2 in the Oregon Coast Range. Survivable habitat was characterized in terms of critical swim speed for juvenile coho and bed stability considering the critical shear stress required to mobilize the median bed particle size. Model predictions indicated that survivable habitat during bankfull conditions, measured as the area with velocity below the critical swim speed for juvenile coho, increased by 95 %–113 % after the LW restoration. Bed stability also increased between 86 % and 128 % considering the shear stress required to mobilize the median bed particle size. Model predictions indicated more habitat created in the larger site; however, considering that wood would move more frequently in this site there appears to be a trade-off between the timing and the resilience of restoration benefits. Overall, this study quantifies how the addition of LW potentially changes stream hydraulics to provide a net benefit to juvenile salmonid habitat. Our findings are applicable to stream restoration efforts throughout the Pacific Northwest.

Experimental Investigation on the Erosion Threshold and Rate of Gravel and Silty Clay Mixtures

2019 ◽  
Vol 62 (4) ◽  
pp. 867-875 ◽  
Author(s):  
Xiaojing Gao ◽  
Qiusheng Wang ◽  
Guowei Ma
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Erosion Rate ◽  
Critical Shear Stress ◽  
Clay Content ◽  
Silty Clay ◽  
Stress Model ◽  
Wilson Model ◽  
Excess Shear Stress ◽  
Better Than

Abstract. The field of cohesive and noncohesive mixture erosion is not fully understood because of the numerous factors that influence soil erodibility. In this study, erosion experiments were conducted on mixtures of gravel and silty clay in proportions varying from 0% to 100% by weight. The critical shear stress of erosion and the erosion rate were quantified using an erosion function apparatus (EFA). Experimental data revealed that the mixture critical shear stress first decreased and then increased with an increasing cohesive fraction for mixtures with silty clay contents up to 50%. The critical shear stress of the mixture showed an increasing trend as the silty clay content varied from 60% to 100%. A transition from noncohesive to cohesive erosion behavior occurred at silty clay contents between 30% and 35%. The appropriateness of a dimensionless nonlinear excess shear stress model and the Wilson model was tested based on the EFA experimental data. The dimensionless excess shear stress model was shown to be appropriate for noncohesive mixtures, while the Wilson model performed better than the dimensionless excess shear stress model for cohesive mixtures. Keywords: Critical shear stress, Erosion rate, Dimensionless nonlinear excess shear stress, Soil mixture, Wilson model.

Model for the Erosion Rate Curve of Cohesive Soils

2017 ◽  
Vol 2657 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Reza Rahimnejad ◽  
Phillip S. K. Ooi
Keyword(s):  
Shear Stress ◽  
Water Content ◽  
Erosion Rate ◽  
Critical Shear Stress ◽  
Cohesive Soil ◽  
Ordinary Least Squares ◽  
Plasticity Index ◽  
Rate Curve ◽  
Parameter Estimates ◽  
Cohesive Soils

The scour rate found by the cohesive soil-erosion function apparatus (SRICOS-EFA) method provides more accurate and realistic scour predictions than the Richardson and Davis equation, which tends to overpredict scour, especially in cohesive soils. Scour of cohesive soil occurs more slowly than scour of cohesionless soils. The time-dependent nature of scour of cohesive soils can be understood by considering both the variation of flood intensity over time and the scour characteristics of the soil, with an erosion rate curve obtained with an erosion function apparatus (EFA). One drawback of the SRICOS-EFA method is that the EFA requires a significant cost outlay. A model for the erosion rate curve is proposed on the basis of EFA tests conducted on 31 undisturbed fine-grained soils from five water channels on the island of Oahu, Hawaii. A hyperbolic regression model was developed with four explanatory variables: water content, liquid limit, plasticity index, and activity, which are easily measured in the laboratory. Parameter estimates for the model were then obtained using nonlinear ordinary least squares. A key element of the model is that the parameter estimates logically affect the sign and magnitude of critical shear stress, in accord with observed soil behavior—that is, it was found that the model captured the effects of water content and plasticity index on the critical shear stress quite effectively. Also, the model provided reasonable estimates of the 31 erosion rate curves. Use of this model in the SRICOS-EFA method to estimate scour depth can result in less scour and can result in significant bridge cost savings.

Role of fines on cohesive behavior of mine tailings inferred from critical shear stress

2011 ◽  
Vol 48 (4) ◽  
pp. 568-582 ◽  
Author(s):  
Africa M. Geremew ◽  
Ernest K. Yanful
Keyword(s):  
Shear Stress ◽  
Mine Tailings ◽  
Erosion Rate ◽  
Empirical Relation ◽  
Critical Shear Stress ◽  
Pressure Change ◽  
Laser Doppler Velocimeter ◽  
Shear Stresses ◽  
Boundary Shear ◽  
Boundary Shear Stress

The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on re-constituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%–55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess bed shear stress and the erosion rate. It is proposed that the value of β (the erosion rate constant) could be taken as 1 for mine tailings that show cohesive behavior.

scholarly journals Characteristic of Erosion Properties and Relationship With Geotechnical Properties for Red Riverbank Soil in Hanoi, Vietnam

2021 ◽  
Author(s):  
Toan Thi Duong
Keyword(s):  
Shear Stress ◽  
Erosion Rate ◽  
Critical Shear Stress ◽  
Clay Content ◽  
Geotechnical Properties ◽  
Initial Slope ◽  
Dry Density ◽  
Sand Mixture ◽  
Cohesion Force ◽  
Erosion Properties

Abstract Soil erosion properties are the main factors affecting riverbank and river channel stability. In this paper, a modified water flume in the laboratory was conducted to evaluate the characteristic of erosion properties including the critical shear stress, the slope of the erosion curve, and erosion rate. The relationships between erosion properties and geotechnical properties as dry density, grain size distribution, shear strength, and soil suction were built. Results obtained from laboratory tests indicate (i) the clay content, cohesion force, residual suction has a great effect and linear correlation in the relationships with the critical shear stress and erosion rate. While the change in clay content leads to a markedly change in the erosion rate. The difference of 5 % clay content enough to build great effects on the erosion rate curve for the Silt soil group; (ii) the sand content has the greatest influence on the slope of the erosion curve (the initial slope and the erosion slope); (iii) the density also has a close relationship with the critical shear stress and the erosion slope, but not for a fine–sand mixture with clay content less than 10%. Based on obtained results and relationships found in this paper, the cohesion force and residual suction should be considered in process of soil riverbank improvement and riverbank undercutting erosion protections.

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