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.

scholarly journals Calculation of erosion scour of cohesive soil

2021 ◽  
pp. 187-195
Author(s):  
А.Ю. Виноградов ◽  
О.В. Зубова ◽  
Е.А. Парфенов
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Shear Stress ◽  
Cohesive Soil ◽  
Cohesive Soils ◽  
Large Specific Surface Area ◽  
Empirical Relationships ◽  
Clay Particles ◽  
Angle Of Internal Friction

Проведен анализ существующих способов оценки размыва грунтов в гидротехнических и водопропускных сооружениях, показывающий, что определение глубины и скорости размыва проводится без учета физических свойств связных грунтов. Таким образом, данные параметры оцениваются по эмпирическим зависимостям и с существенными погрешностями. Опытные данные по размыву связных грунтов доказывают, что большая удельная поверхность и гидрофильность глинистых частиц приводят к разуплотнению и выносу микроагрегатов грунта в поток. Предложена математическая модель расчета глубины размыва связных грунтов в зависимости от касательного напряжения в грунте. Учет показателей сцепления и угла внутреннего трения в данной модели позволит избежать погрешностей в расчетах. The analysis of existing methods for assessing soil erosion in hydraulic engineering and culverts, showing that the determination of the depth and rate of erosion is carried out without taking into account the physical properties of cohesive soils. Thus, these parameters are estimated using empirical relationships and with significant errors. Experimental data on erosion of cohesive soils prove that the large specific surface area and hydrophilicity of clay particles lead to decompaction and the removal of soil microaggregates into the flow. A mathematical model is proposed for calculating the depth of erosion of cohesive soils depending on the shear stress in the soil. Taking into account the adhesion indicators and the angle of internal friction in this model will avoid errors in the calculations.

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.

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

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.

scholarly journals Experimental Investigation of Erosion Characteristics of Fine-Grained Cohesive Sediments

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1511
Author(s):  
Bommanna Gounder Krishnappan ◽  
Mike Stone ◽  
Steven Granger ◽  
Hari Upadhayay ◽  
Qiang Tang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
River System ◽  
Cohesive Sediment ◽  
Erosion Process ◽  
Fine Grained ◽  
Annular Flume ◽  
Two Factors ◽  
Sediment Deposit

In this short communication, the erosion process of the fine, cohesive sediment collected from the upper River Taw in South West England was studied in a rotating annular flume located in the National Water Research Institute in Burlington, Ontario, Canada. This study is part of a research project that is underway to model the transport of fine sediment and the associated nutrients in that river system. The erosion experimental data show that the critical shear stress for erosion of the upper River Taw sediment is about 0.09 Pa and it did not depend on the age of sediment deposit. The eroded sediment was transported in a flocculated form and the agent of flocculation for the upper River Taw sediment may be due to the presence of fibrils from microorganisms and organic material in the system. The experimental data were analysed using a curve fitting approach of Krone and a mathematical model of cohesive sediment transport in rotating circular flumes developed by Krishnappan. The modelled and measured data were in good agreement. An evaluation of the physical significance of Krone’s fitting coefficients is presented. Variability of the fitting coefficients as a function of bed shear stress and age of sediment deposit indicate the key role these two factors play in the erosion process of fluvial cohesive sediment.

scholarly journals Modelling of the Response of Partially Saturated Non-cohesive Soil Subjected to Undrained Loading

2018 ◽  
Vol 65 (1) ◽  
pp. 11-29
Author(s):  
Waldemar Świdziński ◽  
Jacek Mierczyński ◽  
Marcin Smyczyński
Keyword(s):  
Experimental Data ◽  
Triaxial Compression ◽  
Cohesive Soil ◽  
Original Model ◽  
Saturated Soils ◽  
Cohesive Soils ◽  
Partially Saturated ◽  
Partially Saturated Soils ◽  
Undrained Conditions ◽  
Undrained Loading

AbstractThe paper deals with the modelling of the undrained response of non-cohesive partially saturated soils subjected to triaxial compression. The model proposed is based on an incremental equation describing the pre-failure response of non-cohesive soils during shearing. The original model, developed by Sawicki, was modified by taking into account pore fluid compressibility. The governing equation makes it possible to simulate effective stress paths under undrained conditions. Numerical results are compared with experimental data.

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