Estimation of runoff critical shear stress for soil erosion from soil shear strength

CATENA ◽  
2004 ◽  
Vol 57 (3) ◽  
pp. 233-249 ◽  
Author(s):  
J Léonard ◽  
G Richard
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Soil Erosion ◽  
Critical Shear Stress ◽  
Soil Shear Strength

scholarly journals The Effect of Root Native Tree Species on Soil Shear Strength on Hillslopes of Sierra Madre Oriental, Mexico

2020 ◽  
Author(s):  
Rebeca Guadalupe Zavala-González ◽  
Israel Cantú-Silva ◽  
Humberto González-Rodríguez
Keyword(s):  
Shear Strength ◽  
Soil Erosion ◽  
Tree Species ◽  
Native Species ◽  
Testing Machine ◽  
Effective Control ◽  
Sierra Madre Oriental ◽  
Root Cohesion ◽  
Sierra Madre ◽  
Soil Shear Strength

Abstract Background: The presence of vegetation reduces soil erosion and shallow slope failure both by reinforcing soil shear resistance and influencing the geo-mechanic conditions of soil. For this reason, vegetation strategies in areas vulnerable to erosion are considered to be an effective control measure for soil erosion. Method: The tree species used in this research are widespread in the slopes of Chipinque mountain of Sierra Madre Oriental and belong to four native species: Cercis canadensis, Celtis laevigata, Quercus rysophylla and Ligustrum lucidum. In order to investigate the mechanical characteristics of roots, single roots specimens were sampled and tested for tensile strength. The tests were conducted with the Universal Testing Machine Shimadzu type SLFL-100KN to evaluate the influence of root shear strength on the soil using the Wu Model (Wu et al., 1979) as well as to analyze root cohesion and Root Area Ratio (RAR). The latter was calculated by taking both direct (field) and indirect measurements on image processing.Results: The results show that C. laevigata roots have the strongest tensile strenght, followed by Q. rysophylla > C. Canadensis > L. lucidum. RAR ranges from C. laevigata (0.0587%) > C. Canadensis (0.0585%) >L. lucidum (0.0504%) > Q. rysophylla (0.0441%). L. lucidum provides the less increase soil shear strength through root cohesion (16.12 kN/m2) > C. canadensis (53.70 kN/m2) > Q. rysophylla (89.07 kN/m2) to C. laevigata (97.41 kN/m2)

scholarly journals Site-Specific Erodibility in Claypan Soils: Dependence on Subsoil Characteristics

2017 ◽  
Vol 33 (5) ◽  
pp. 705-718 ◽  
Author(s):  
Stacey E. Tucker-Kulesza ◽  
Gretchen F. Sassenrath ◽  
Tri Tran ◽  
Weston Koehn ◽  
Lauren Erickson
Keyword(s):  
Electrical Conductivity ◽  
Shear Stress ◽  
Soil Erosion ◽  
Soil Profile ◽  
Crop Production ◽  
Electrical Resistivity Tomography ◽  
Critical Shear Stress ◽  
Productive Capacity ◽  
Clay Layer ◽  
Resistivity Tomography

Abstract. Soil erosion is a primary factor limiting the productive capacity of many crop production fields and contributing to sediment and nutrient impairments of water bodies. Loss of topsoil is especially critical for areas of limited topsoil depth, such as the claypan area of the central United States. More than a century of conventional agricultural practices have eroded the topsoil and, in places, exposed the unproductive clay layer. This clay layer is impervious, limiting water infiltration and root penetration, and severely restricting agricultural productivity. Previous studies have documented changes in topsoil thickness using apparent electrical conductivity (ECa). However, that methodology is limited by its shallow depth of measurement within the soil profile, and as such cannot adequately explore factors within the soil profile that potentially contribute to topsoil erosion. In this study, we identified areas of limited topsoil depth using crop yields and ECa. Two areas within the production field varying in crop production and ECa were selected for detailed measurements using Electrical Resistivity Tomography. This methodology allowed delineation of soil stratigraphy to a depth of 5.3 m. The erodibility of undisturbed soil samples from the two areas were measured in an Erosion Function Apparatus to obtain the critical shear stress, or the applied stress at which soil begins to erode. Based on resistivity measurement, the highly productive region of the field had a thick (1.0-2.0 m) soil layer of saturated clayey sand soil over a uniform sandy material, with minimal clay layer. This soil had a critical shear stress of 12 Pa. The extent of historical erosion was evident in the poorly-producing area, as only a thin band of topsoil material remained over a thicker clay layer. The unproductive area with exposed clay layer had a critical shear stress of 128 Pa, indicating it was more resistant to erosion than the highly productive region. The clay layer was found to extend to 1.3-1.5 m in depth in the soil profile in the poorly producing area. Below this layer was a layer with similar resistivity to the high-producing region. The data reveal the extent of historical erosion within the crop production field and highlight significant variability in measured soil properties within a field of identical production practices. While spatial variations in topsoil have long been considered in developing management practices to improve soil health and productive capacity, our results indicate the importance of identifying variability of subsoil characteristics to address long-term impacts on soil erosion and productivity. Keywords: Soil erosion, Soil electrical conductivity, Claypan soil, Productive capacity, Electrical resistivity tomography.

Pressure conditions in the hole erosion test

2015 ◽  
Vol 52 (1) ◽  
pp. 114-119 ◽  
Author(s):  
Jaromír Říha ◽  
Jan Jandora
Keyword(s):  
Shear Stress ◽  
Soil Erosion ◽  
Numerical Study ◽  
Critical Shear Stress ◽  
Technical Note ◽  
Hydraulic Gradient ◽  
Hydraulic Gradients ◽  
Erosion Test ◽  
The Difference

The hole erosion test (HET) is used in the study of soil erosion in the case of what is known as “piping” when concentrated leaks occur. The HET enables the determination of soil erosion characteristics such as the critical shear stress along the pre-formed hole (pipe) and the coefficient of soil erosion. Normally, in the HET, the hydraulic gradient is determined from the difference between the piezometric heads measured at the inflow and outflow chambers (upstream and downstream of the soil specimen). Hydraulic analysis shows that such measurements ignore losses at the entrance and exit of the hole, causing the overestimation of the hydraulic gradient along the length of the hole, and thus the calculated shear stress. In this technical note, the results of preliminary analysis using the Bernoulli principle and of numerical study of the pressure conditions in the HET apparatus are shown. The turbulent flow in the HET apparatus was calculated using ANSYS commercial CFD (computational fluid dynamics) software. The analysis was performed for various hole entrance shapes. The conclusion of this note details the differences between traditionally determined hydraulic gradients and those numerically derived along the length of a hole.

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.

scholarly journals RESUSPENSION OF DEPOSITED COHESIVE SEDIMENT BEDS

1982 ◽  
Vol 1 (18) ◽  
pp. 95 ◽  
Author(s):  
Ashish J. Mehta ◽  
Emmanuel Partheniades
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Critical Shear Stress ◽  
Cohesive Sediment ◽  
Significant Feature ◽  
Bed Shear Stress ◽  
Laboratory Investigations ◽  
Shear Stength ◽  
The Difference ◽  
Consolidation Time

Surfieial layers of estuarial fine, cohesive sediment beds are deposited from flow and often are in a state of partial consolidation. A series of laboratory investigations were carried out to elucidate the erosional behavior of deposited cohesive sediment beds in flumes using kaolinite. A significant feature of such beds is that they are stratified with respect to the density and the cohesive shear stength. Under a given bed shear stress, erosion occurs at a continuously decreasing rate up to a depth at which the bed shear stress equals the shear strength. This bed shear stress is therefore also equal to the critical shear stress for erosion at that depth. An expression for the rate of erosion relating this rate to the difference between the bed shear stress and the critical shear stress has been obtained. The critical shear stress increases both with depth and with the bed consolidation time. The rate of erosion decreases with increasing consolidation time.

scholarly journals Variations in Soil Erosion Resistance of Gully Head Along a 25-Year Revegetation Age on the Loess Plateau

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3301
Author(s):  
Zhuoxin Chen ◽  
Mingming Guo ◽  
Wenlong Wang
Keyword(s):  
Shear Stress ◽  
Soil Erosion ◽  
Erosion Resistance ◽  
Stable State ◽  
Critical Shear Stress ◽  
Soil Erodibility ◽  
Undisturbed Soil ◽  
Concentrated Flow ◽  
Detachment Rate ◽  
Gully Head

The effects of vegetation restoration on soil erosion resistance of gully head, along a revegetation age gradient, remain poorly understood. Hence, we collected undisturbed soil samples from a slope farmland and four grasslands with different revegetation ages (3, 10, 18, 25 years) along gully heads. Then, these samples were used to obtain soil detachment rate of gully heads by the hydraulic flume experiment under five unit width flow discharges (2–6 m3 h). The results revealed that soil properties were significantly ameliorated and root density obviously increased in response to restoration age. Compared with farmland, soil detachment rate of revegetated gully heads decreased 35.5% to 66.5%, and the sensitivity of soil erosion of the gully heads to concentrated flow decreased with revegetation age. The soil detachment rate of gully heads was significantly related to the soil bulk density, soil disintegration rate, capillary porosity, saturated soil hydraulic conductivity, organic matter content and water stable aggregate. The roots of 0–0.5 and 0.5–1.0 mm had the highest benefit in reducing soil loss of gully head. After revegetation, soil erodibility of gully heads decreased 31.0% to 78.6%, and critical shear stress was improved by 1.2 to 4.0 times. The soil erodibility and critical shear stress would reach a stable state after an 18-years revegetation age. These results allow us to better evaluate soil vulnerability of gully heads to concentrated flow erosion and the efficiency of revegetation.

The Study of Soil-Roots Strength Performance of Soil Slope by Using Guinea Grass

2015 ◽  
Vol 802 ◽  
pp. 10-15 ◽  
Author(s):  
Mohd Syazwan bin Zainordin ◽  
Nor Azizi bin Yusoff ◽  
Tuan Norhayati binti Tuan Chik ◽  
Muhamad Ali Hanapiah bin Ab Manap ◽  
Zulhazmi Sayuti ◽  
...  
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Water Runoff ◽  
Test Plot ◽  
Soil Medium ◽  
Strength Performance ◽  
Construction Period ◽  
Direct Shear Tests ◽  
Soil Shear Strength ◽  
Guinea Grass

Vegetation has been proven for establishing and implementing resistive measures against erosion and failure of slopes, river banks, removal of air pollution and reduced storm water runoff. Installation of cover crop involved soil element usage as growth medium which create several interaction between both strands. This study was carried out to investigate the soil strength performance by using Guinea grass at different construction period up to three months. Grass was planted in a 300 mm x 300 mm x 700 mm test plot with a suitable soil medium. Direct shear tests were conducted for each plot to determine the soil shear strength according to different construction period. Some basic geotechnical testing also were carried out. The results showed there is an increment in shear strength for soil sample over the time at various depths. During period of 1st, 2nd and 3rd month, the average shear stress of 100 mm depth was 50.56 kPa, 63.96 kPa, and 96.59 kPa respectively. Meanwhile, for 200 mm depth the result was 40.843 kPa, 53.91 kPa and 62.93 kPa respectively. Lastly, on 300 mm depth, shear stress was 37.21 kPa, 51.09 kPa, and 59.27 kPa respectively. Based on the result, the higher shear strength was obtained at different construction period and at varying depths. From the observation, roots mass increased for different construction period. In terms of tensile strength, the diameter of the root affects the rate of resistance against the tensile forces. This indicated that the roots structure growth affects the soil shear strength.

Finite Element Modeling of a Mechanically Stabilized Earth Trial Wall

2021 ◽  
pp. 036119812110164
Author(s):  
Andrew Lees ◽  
Michael Dobie
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Retaining Wall ◽  
Back Analysis ◽  
Soil Parameters ◽  
Failure Behavior ◽  
Valuable Insight ◽  
Deformation And Failure ◽  
First Case ◽  
Soil Shear Strength

Polymer geogrid reinforced soil retaining walls have become commonplace, with routine design generally carried out by limiting equilibrium methods. Finite element analysis (FEA) is becoming more widely used to assess the likely deformation behavior of these structures, although in many cases such analyses over-predict deformation compared with monitored structures. Back-analysis of unit tests and instrumented walls improves the techniques and models used in FEA to represent the soil fill, reinforcement and composite behavior caused by the stabilization effect of the geogrid apertures on the soil particles. This composite behavior is most representatively modeled as enhanced soil shear strength. The back-analysis of two test cases provides valuable insight into the benefits of this approach. In the first case, a unit cell was set up such that one side could yield thereby reaching the active earth pressure state. Using FEA a test without geogrid was modeled to help establish appropriate soil parameters. These parameters were then used to back-analyze a test with geogrid present. Simply using the tensile properties of the geogrid over-predicted the yield pressure but using an enhanced soil shear strength gave a satisfactory comparison with the measured result. In the second case a trial retaining wall was back-analyzed to investigate both deformation and failure, the failure induced by cutting the geogrid after construction using heated wires. The closest fit to the actual deformation and failure behavior was provided by using enhanced fill shear strength.

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