scholarly journals Study on Parameters of Two Widely Used Cohesive Soils Erosion Models

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3621
Author(s):  
Qiusheng Wang ◽  
Pengzhan Zhou ◽  
Junjie Fan ◽  
Songnan Qiu
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Cohesive Soils ◽  
Stress Model ◽  
Wilson Model ◽  
Erosion Models ◽  
Erodibility Coefficient ◽  
Proportional Relationship ◽  
Model Equations ◽  
Parameter Values

The erosion rate of cohesive soils was typically modeled with the excess shear stress model and the Wilson model. Several kinds of research have been conducted to determine the erodibility parameters of the two models, but few attempts have been made hitherto to investigate the general trends and range of the erodibility parameter values obtained by the commonly used Erosion Function apparatus. This paper collected a database of 177 erosion function apparatus tests to indicate the variability of all erodibility parameters; the range of erodibility parameters is determined by data statistics and parameter theoretical value derivation. The critical shear stress (τc) and erodibility coefficient (Z0) in the over-shear stress model have a positive proportional relationship when the data samples are sufficient. However, there is no such relationship between the erodibility coefficient (b0) and erodibility coefficient (b1) in the Wilson model. It is necessary to express the soil erosion resistance by considering all erosion parameters in the erosion model. Equations relating erodibility parameters to water content, plasticity index, and median particle size were developed by regression analysis.

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.

In situ jet-testing of the erosional resistance of cohesive streambeds

2007 ◽  
Vol 34 (9) ◽  
pp. 1192-1195 ◽  
Author(s):  
Daniel Shugar ◽  
Ray Kostaschuk ◽  
Peter Ashmore ◽  
Joe Desloges ◽  
Leif Burge
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Sediment Surface ◽  
Cohesive Soils ◽  
Flood Events ◽  
Southern Ontario ◽  
Submerged Jet ◽  
Erodibility Coefficient ◽  
Bed Scour

Fletcher’s Creek is located in an urbanizing basin near Toronto and has a bed and banks composed primarily of cohesive Halton Till. Critical shear stress and an erodibility coefficient for the till were determined using an in situ jet-tester that directs a submerged jet of water perpendicular to the sediment surface. The results from 10 jet-tests indicate that the till has a relatively low critical shear stress and relatively high erodibility coefficient and could be susceptible to bed scour during flood events. Many other streams in southern Ontario have urbanizing watersheds with cohesive till beds that may also be susceptible to erosion.Key words: critical stress, submerged jet, erodibility, cohesive soils.

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 Assessment of land use impact on hydraulic threshold conditions for gully head cut initiation

2016 ◽  
Vol 20 (7) ◽  
pp. 3005-3012 ◽  
Author(s):  
Aliakbar Nazari Samani ◽  
Qiuwen Chen ◽  
Shahram Khalighi ◽  
Robert James Wasson ◽  
Mohammad Reza Rahdari
Keyword(s):  
Land Use ◽  
Shear Stress ◽  
Soil Erosion ◽  
Critical Shear Stress ◽  
Gully Erosion ◽  
Threshold Condition ◽  
Stream Power ◽  
Threshold Phenomenon ◽  
Erosion Models ◽  
Dry Farming

Abstract. A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15 m  ×  0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τcr). The threshold unit stream power value (ωu) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5  ×  10−5 m s−1, respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τcr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τcr. In addition, based on the findings of this research, the use of threshold values of τcr  =  35 dyne cm−2 and ωu  =  0.4 cm s−1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion.

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