An experimental study on the effects of physical, mechanical, and electrochemical properties of natural cohesive soils on critical shear stress and erosion rate

2016 ◽  
Vol 31 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Navid Kimiaghalam ◽  
Shawn P. Clark ◽  
Habib Ahmari
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Electrochemical Properties ◽  
Erosion Rate ◽  
Critical Shear Stress ◽  
Cohesive Soils

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.

Methods for Analyzing Submerged Jet Erosion Test Data to Model Scour of Cohesive Soils

2021 ◽  
Vol 64 (3) ◽  
pp. 785-799
Author(s):  
Tony L. Wahl
Keyword(s):  
Shear Stress ◽  
Erosion Rate ◽  
Rate Coefficient ◽  
Critical Shear Stress ◽  
Cohesive Soils ◽  
Simple Linear Regression ◽  
Submerged Jet ◽  
Rate Versus ◽  
Erosion Test ◽  
Stress Parameters

HighlightsFifty-two jet erosion tests performed on four cohesive soils were analyzed by nine different methods.Nonlinear methods performed well on some individual tests but fit inconsistently overall.Several alternate linear solution methods outperformed the widely used Blaisdell method.Simple linear regression of erosion rate versus applied shear stress provided the most consistent relationship between erosion rate and critical shear stress parameters.Abstract. The submerged jet erosion test (JET) is widely used in lab and field settings to quantify erodibility of cohesive soils and determine erosion rate coefficients and critical shear stress values. Test devices with different scales and configurations have been developed in recent years, along with several alternative methods for processing the collected data to determine parameters of linear and nonlinear soil erosion equations. To facilitate standardization, 52 JET experiments were conducted on four different cohesive soils compacted at optimum water content and 2% dry and wet of optimum. Each test was analyzed using nine different methods, four based on the linear excess stress equation (including the commonly used Blaisdell method) and five based on nonlinear erosion equations, including two using the recently popular Wilson model. Results were analyzed to determine the erosion equations and parameter-fitting methods that most effectively represent the observed erosion rates and are of greatest utility for soil erosion modeling and the ranking and classification of soils according to erodibility. Methods based on nonlinear erosion equations fit some data sets well, but they exhibited poor correlation between the erosion rate coefficient and the threshold shear stress parameter for initiating erosion, which is problematic for soil erodibility classification work. Linear methods that simultaneously optimized erosion equation parameters to best fit the total depth of scour or the elapsed time needed to reach specific depths of scour performed better than the Blaisdell method, which has been the informally accepted standard of practice since the late 1990s. However, they also exhibited weak correlation of the erosion rate and critical shear stress parameters. Simple linear regression of average scour rate versus average applied stress provided an effective method for representing the erosion rate versus applied stress curve and exhibited the strongest correlation of the erosion rate coefficient and critical shear stress parameters. Keywords: Cohesive soil, Critical shear stress, Erodibility, Erosion, Erosion laws, Erosion models, Jet erosion test, Shear strss, Soil moisture.

Experimental Study on Critical Shear Stress of Cohesive Soils and Soil Mixtures

2021 ◽  
Vol 64 (2) ◽  
pp. 587-600
Author(s):  
Xiaojing Gao ◽  
Qiusheng Wang ◽  
Chongbang Xu ◽  
Ruilin Su
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Soil ◽  
Future Research ◽  
Cohesive Soils ◽  
List Type ◽  
Soil Mixture ◽  
Linear Relationships ◽  
Soil Mixtures

HighlightsErosion tests were performed to study the critical shear stress of cohesive soils and soil mixtures.Linear relationships were observed between critical shear stress and cohesion of cohesive soils.Mixture critical shear stress relates to noncohesive particle size and cohesive soil erodibility.A formula for calculating the critical shear stress of soil mixtures is proposed and verified.Abstract. The incipient motion of soil is an important engineering property that impacts reservoir sedimentation, stable channel design, river bed degradation, and dam breach. Due to numerous factors influencing the erodibility parameters, the study of critical shear stress (tc) of cohesive soils and soil mixtures is still far from mature. In this study, erosion experiments were conducted to investigate the influence of soil properties on the tc of remolded cohesive soils and cohesive and noncohesive soil mixtures with mud contents varying from 0% to 100% using an erosion function apparatus (EFA). For cohesive soils, direct linear relationships were observed between tc and cohesion (c). The critical shear stress for soil mixture (tcm) erosion increased monotonically with an increase in mud content (pm). The median diameter of noncohesive soil (Ds), the void ratio (e), and the organic content of cohesive soil also influenced tcm. A formula for calculating tcm considering the effect of pm and the tc of noncohesive soil and pure mud was developed. The proposed formula was validated using experimental data from the present and previous research, and it can reproduce the variation of tcm for reconstituted soil mixtures. To use the proposed formula to predict the tcm for artificial engineering problems, experimental erosion tests should be performed. Future research should further test the proposed formula based on additional experimental data. Keywords: Cohesive and noncohesive soil mixture, Critical shear stress, Erodibility, Mud content, Soil property.

Practical Determination of Critical Shear Stress in Cohesive Soils

2017 ◽  
Vol 143 (10) ◽  
pp. 04017045 ◽  
Author(s):  
Hicham (Sam) Salem ◽  
Colin D. Rennie
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Soils

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).

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.

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