scholarly journals The mechanism of the plant roots’ soil-reinforcement based on generalized equivalent confining pressure

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10064
Author(s):  
Ping Guo ◽  
Zhenyao Xia ◽  
Qi Liu ◽  
Hai Xiao ◽  
Feng Gao ◽  
...  
Keyword(s):  
Shear Strength ◽  
Root Distribution ◽  
Plant Root ◽  
Friction Angle ◽  
Confining Pressure ◽  
Distribution Patterns ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Plant Roots ◽  
Root Content

Background To quantitatively evaluate the contribution of plant roots to soil shear strength, the generalized equivalent confining pressure (GECP), which is the difference in confining pressure between the reinforced and un-reinforced soil specimens at the same shear strength, was proposed and considered in terms of the function of plant roots in soil reinforcement. Methods In this paper, silt loam soil was selected as the test soil, and the roots of Indigofera amblyantha were chosen as the reinforcing material. Different drainage conditions (consolidation drained (CD), consolidation undrained (CU), and unconsolidated undrained (UU)) were used to analyse the influences of different root distribution patterns (horizontal root (HR), vertical root (VR), and complex root (CR)) and root contents (0.25%, 0.50%, and 0.75%) on the shear strength of soil-root composites. Results The cohesion (c) values of the soil-root composites varied under different drainage conditions and root contents, while the internal friction angle (φ ) values remain basically stable under different drainage conditions. Under the same root content and drainage conditions, the shear strength indexes ranked in order of lower to higher were HR, VR and CR. The GECP of the soil-root composites with a 0.75% root content was 1.5–2.0 times that with a 0.50% root content and more than 5 times that with a 0.25% root content under the CD and CU conditions. The GECP in reinforced soil followed the sequence of CD > CU > UU. The GECP of the plant roots increased as confining pressure increased under CD and CU conditions while showed a complex change to the confining pressure under the UU condition. Conclusion It was concluded that the evaluation of plant root reinforcing soil based on GECP can be used to measure effectively the influences of roots on soil under different drainage conditions and root distribution patterns.

Experimental Study on Shear Strength of Root-Soil Composite of Different Grass and Shrub Plants in Three Gorges Reservoir Region

2013 ◽  
Vol 838-841 ◽  
pp. 981-986
Author(s):  
Mo Zhen Hu ◽  
Zhen Yao Xia ◽  
Yue Shu Yang ◽  
Li Deng ◽  
Xiao Pei Xu
Keyword(s):  
Shear Strength ◽  
Cynodon Dactylon ◽  
Plant Root ◽  
Reinforced Soil ◽  
Purple Soil ◽  
Soil Shear Strength ◽  
Plant Root System ◽  
The Relationship ◽  
Root Content ◽  
Peak Value

This paper discusses the relationship between shear strength of soil-root composite and root content of different plant species. The direct shear test of root - soil composite was made by grass and shrub plants -- alfalfa, Indigofera amblyatha, cynodon dactylon and purple soil .That how plant root system can improve the soil shear strength was analyzed. The results show that the shear strength of reinforced soil is increased. When the same plant root-soil composite is under the same root content, the shear strength is enhanced with the increase of normal stress. The peak value of shear strength appears in 0.4 - 0.5g per 60 cubic centimeter.

scholarly journals Model Test of the Reinforcement of Surface Soil by Plant Roots under the Influence of Precipitation

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Hengxing Wang ◽  
Yulong He ◽  
Zufeng Shang ◽  
Chunpeng Han ◽  
Yilu Wang
Keyword(s):  
Water Content ◽  
Model Test ◽  
Surface Soil ◽  
Plant Root ◽  
Root Systems ◽  
Reinforced Soil ◽  
Plant Roots ◽  
Interfacial Friction ◽  
Negative Power ◽  
Pull Out

We present the results of the reinforcement of plant root systems in surface soil in a model test to simulate actual precipitation conditions. In the test, Eleusine indica was selected as herbage to reinforce the soil. Based on the various moisture contents of plant roots in a pull-out test, a fitting formula describing the interfacial friction strength between the roots and soil and soil moisture content was obtained to explain the amount of slippage of the side slope during the process of rainfall. The experimental results showed that the root systems of plants successfully reinforced soil and stabilized the water content in the surface soil of a slope and that the occurrence time of landslides was delayed significantly in the grass-planting slope model. After the simulated rainfall started, the reinforcement effect of the plant roots changed. As the rainfall increased, the interfacial friction between the roots and the soil exhibited a negative power function relationship with the water content. These conclusions can be used as a reference for the design of plant slope protection and reinforcement.

scholarly journals Triaxial Testing on Geogrid-reinforced Granular Soils

2021 ◽  
Vol 1200 (1) ◽  
pp. 012030
Author(s):  
Tigo Mindiastiwi ◽  
Po-Kai Wu ◽  
Agus Bambang Siswanto ◽  
Mukhamad Afif Salim
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Reinforced Soil ◽  
Deviatoric Stress ◽  
Granular Soils ◽  
Peak Shear Strength ◽  
Compression Tests ◽  
Soil C ◽  
Dense Sand

Abstract Laboratory triaxial compression tests were carried out to investigate the mechanical behavior of dense sand and geogrid-reinforced granular soils. The tested sand having its mean particle size (D50) equal to 0.6 mm was adopted. Three geogrids with different longitudinal and transverse nominal strengths were used. The dimensions of the cylindrical soil specimen were 70 mm (diameter) × 160 mm (height). The relative density was equal to 70% for all tests. The reinforced sand specimens with one or two geogrid layers were sheared under effective confining pressures (σ′3) equal to 50 kPa. The test results of unreinforced sand indicate the general stress-strain behavior of dense sand when sheared, whereas the deviatoric stress reaches its peak value, after which it gradually decreases to ultimate value (σ1 - σ3)ult. The difference of effective confining pressure indicates that the peak of deviatoric stress Δσd = (σ1 - σ3) increases with the increase in effective confining pressure (σ′3), while the peak principal stress ratio (σ′1/σ′3) decreases with the increase (σ′3). The friction angle (ϕ′)and cohesion (c′), defined by analytical and graphical methods for unreinforced sand. Geogrid as reinforcement increasing peak shear strength. The increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness. Increased in confining stress inside reinforced soil mass (Δσ3R) can be interpreted by cohesive reinforced soil (CR).

scholarly journals Peningkatan Stabilitas Lereng pada Ruas Jalan Tawaeli – Toboli dengan Vegetasi/Bioengineering

2021 ◽  
pp. 23-32
Author(s):  
S.A. Wandira ◽  
A. Rahayu
Keyword(s):  
Shear Strength ◽  
Slope Stability ◽  
Safety Factor ◽  
Friction Angle ◽  
Soil Samples ◽  
Plant Roots ◽  
Soil Conditions ◽  
Mountainous Area ◽  
Stability Calculation ◽  
The Road

Tawaeli - Toboli is one of the road that often undergo landslide. Most of these roads are in a mountainous area with high steep slopes and poor soil conditions. The road conditions worsened, especially in rainy season resulting the citizen do not know anywhere that is prone to landslides such as in Km 16 to 17. The purpose of this study was to analyze slope stability using bioengineering methods, determine the shear strength of soil without plant roots and soil with plant roots and to determine the potential for landslides that will occur. Bioengineering is used to increase the strength of the soil, and stabilize slopes and reduce erosion on slopes. The slope stability calculation using the Bishop slice method. The calculating of safety factor analyzed using the Slope / W application and manually. Soil samples were taken from 3 (three) points and the soil strength parameters,  soil cohesion and friction angle, were obtained through laboratory testing. Tests were carried out using rootless and rooted soil samples. In addition, direct field observations were made to obtain slope angles and slope heights. The results showed that the parameters of soil shear strength, cohesion and friction angle increased with the presence of plant roots. The results of the slope stability analysis show that the conditions of the slope are stable at slope 1 (Km 16) and slope 3 (Km 17) with a safety factor greater than 1.5. While slope 2 (Km 16 +300) has the potential for landslides as a safety factor of less than 1.5. The use of bioengineering increases the safety factor to be greater than 1.5. The calculation of the value of the safety factor using the Slope / W program and the Bishop manual is not much different, but the calculation time with the Slope / W program is faster

Quantification of mechanical and hydric components of soil reinforcement by plant roots

2015 ◽  
Vol 52 (11) ◽  
pp. 1839-1849 ◽  
Author(s):  
G. Veylon ◽  
M. Ghestem ◽  
A. Stokes ◽  
A. Bernard
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Failure Modes ◽  
Friction Angle ◽  
Soil Reinforcement ◽  
Plant Roots ◽  
Mechanical Reinforcement ◽  
Mechanical Component ◽  
Apparent Cohesion

The use of vegetation to stabilize slopes with regard to shallow landslides is an ecological and economic alternative to traditional solutions of civil engineering. This study aims at quantifying the effect of soil water content on the reinforcement of soil by plant roots and determines how soil water content influences the failure modes of roots during shear. Direct shear box tests were performed on three species used in hillslope reforestation programs in Yunnan, China. Reinforcement was quantified and divided into a hydric component corresponding to the effect of water removal and a mechanical component reflecting the influence of roots on apparent cohesion and friction angle. It was shown that the hydric component of reinforcement can be of the same order as the mechanical component and that root system architectural traits influence the type of mechanical reinforcement (cohesive or frictional). We also demonstrate the potential development of matric suction effects on the shear strength of soil.

Gravel Content Effect on the Shear Strength of Clay-Gravel Mixtures

2011 ◽  
Vol 71-78 ◽  
pp. 4685-4688 ◽  
Author(s):  
Chen Wang ◽  
Chuan Ni Zhan
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Triaxial Compression ◽  
Constant Strain Rate ◽  
Friction Angle ◽  
Confining Pressure ◽  
Internal Friction Angle ◽  
Compression Tests ◽  
Gravel Content ◽  
Confining Pressures

Gravel content is an important factor affecting the mechanical properties of clay-gravel mixtures. To study the effects of gravel content on the shear strength of clay-gravel mixtures, constant-strain-rate drained triaxial compression tests were conducted for various mixtures. The gravel contents were 30%, 40%, 50% and 70%. The confining pressures were varied from 50kPa to 300kPa. Test results indicate that the deviator stress at failure under the same confining pressure increases with the increase in gravel content. As the gravel content in the mixtures is between 30% and 50%, the shear strength is jointly attributed by clay and gravel. An increase in gravel content results in slight increases in both the cohesion intercept and internal friction angle. At gravel content of up to 70%, the shear strength of the mixture is controlled by that of the gravel, and the cohesion intercept and the internal friction angle increase sharply.

scholarly journals Study on Mechanical and Ecological Properties of Fly Ash Substrate for Ecological Slope Protection

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Juan Wan ◽  
Jun Zhu ◽  
Henglin Xiao ◽  
Qiang Ma
Keyword(s):  
Shear Strength ◽  
Fly Ash ◽  
Moisture Content ◽  
Friction Angle ◽  
Ash Content ◽  
Class V ◽  
Ecological Requirements ◽  
Msw Incineration ◽  
Standard Limit ◽  
Root Content

In order to realize the resource utilization of fly ash, a kind of ecological slope protection substrate was prepared by mixing fly ash produced by MSW incineration into slope protection soil. Through the direct shear test and a leaching experiment on ion pollutants, the influence that shear strength of the substrate changed with root content, ash content, and moisture content and the ecological effects of leach liquor were investigated. The results showed the following: (1) When the optimum moisture content is about 24.9%, the shear strength of the substrate is the maximum. (2) Fly ash can improve the shear strength of the soil, which can reach 1.67 times as much as that of plain soil, and the optimum content of fly ash is 5%–6.7%. (3) The root system can increase the cohesion and internal friction angle of the substrate soil but mainly increases the cohesion of the substrate soil. (4) Plants grow taller in ash-mixed soil than in plain soil. (5) When the fly ash content is 20%, the ion concentrations of Cl, Cu, and Zn are the highest: 220.7, 0.153, and 1.526 mg/L, respectively. All of them are lower than the standard limit of class V water and gradually decrease with time. Therefore, the leaching liquid will not cause environmental pollution and meet the ecological requirements.

Effect of roughness on shear behavior of red clay – concrete interface in large-scale direct shear tests

2015 ◽  
Vol 52 (8) ◽  
pp. 1122-1135 ◽  
Author(s):  
Xiaobin Chen ◽  
Jiasheng Zhang ◽  
Yuanjie Xiao ◽  
Jian Li
Keyword(s):  
Surface Roughness ◽  
Shear Strength ◽  
Large Scale ◽  
Shear Failure ◽  
Friction Angle ◽  
Confining Pressure ◽  
Shear Behavior ◽  
Interfacial Shear ◽  
Red Clay ◽  
Direct Shear Tests

Few studies have focused on evaluating regular surface roughness and its effect on interfacial shear behavior of the red clay – concrete interface. This paper presents the results of a series of laboratory large-scale direct shear tests conducted using different types of red clay – concrete interfaces. The objective is to examine the effect of surface roughness on these types of soil–concrete interfaces. In the smooth-interface tests, the measured peak and residual shear strength values are very close to each other, with no observed shear dilation. The surface roughness is found to have a remarkable effect on the interfacial shear strength and shear behavior, with the shear strength increasing with increased surface roughness level. The shear dilation is likely to occur on rougher interfaces under lower confining pressure due to the behavior of compressed clay matrices. Owing to the clay matrix’s cohesion and friction, the interfacial shear strength on rough interfaces consists of cohesive and frictional forces between the clay and concrete surfaces. The friction angle value is observed to fluctuate between the clay’s friction angle and the smooth interface’s friction angle. This can be related to the position change of the shear failure slip plane. The confining pressure and surface roughness could change the shear failure plane’s position on the interface. Furthermore, the red clay – structure interface is usually known as the weakest part in the mechanical safety assessment.

The main influencing factors of soil mechanical characteristics of the gravity erosion environment in the dry-hot valley of Jinsha river

2018 ◽  
Vol 16 (1) ◽  
pp. 796-809 ◽  
Author(s):  
Yangyi Zhao ◽  
Xu Duan ◽  
Jiaojiao Han ◽  
Kun Yang ◽  
Yang Xue
Keyword(s):  
Shear Strength ◽  
Soil Erosion ◽  
Root System ◽  
Mechanical Characteristics ◽  
Plant Root ◽  
Friction Angle ◽  
Plant Root System ◽  
The Impact ◽  
Erosion Environment ◽  
Mass Erosion

AbstractThe dry-hot valley region counts as one of the most eco-sensitive zones in China, the issue of soil erosion is critical in regional ecological environment, soil mechanical property is one of the primary factors confining the occurrence of erosion, and it is attached crucial significance to in ascertaining the characteristics and principal factors of soil mechanics, and how to prevent and control soil erosion in arid red soil area of dry-hot valley. Through monitoring field location and directly shearing, the soil mechanical characteristics and the primary influencing factors of the mass erosion environment in the basin were ascertained. As the result indicates: (1) The soil moisture content, cohesion and internal friction angle are evidently correlated with each other abiding by power function, the relationship among soil cohesion, internal friction angle and volume moisture content goes as:$$\begin{array}{} \displaystyle c=80.107e^{-5.451\frac{{\it\omega}}{1.64\,+\,{\it\omega}}},\phi=65.646{\rm e}^{-3.325\frac{\omega}{1.64\,+\,\omega}}; \end{array}$$(2) The soil being large in pore radius vary in number and distribution evidently with structure and destruction degree (P<0.05). Soil aggregation was also significantly different (P<0.05), with the increasing of structural failure rate, the shear strength of soil decreased, and the probability of damage was increased as the external load increaseing. (3) The disintegration of soil can be effectively decelerated, and anti-disintegration ability of soil can be enhanced by the root system. The impact exerted by plant root system on shear strength of soil decreased as soil got deeper, more than a certain depth can be ignored; the impact exerted by plant root system on small-scale gravitational erosion was particularly evident, whereas the impact exerted by large-scale mass erosion was comparatively small. The ability of plant roots to optimize soil resistance was primarily through the roots shorter than 2 mm, the effective fibrous roots in the soil of the Leucaena Benth and the Dodonaea angustifolia were comparatively small, and the root of the herbaceous plants was comparatively large.

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