Cyclic soil-root mechanical interaction

2021 ◽  
Author(s):  
Anthony Leung ◽  
Ali Akbar Karimzadeh ◽  
Zhaoyi Wu
Keyword(s):  
Triaxial Compression ◽  
Reinforced Soil ◽  
Plant Roots ◽  
Triaxial Tests ◽  
Uniaxial Tensile ◽  
Mechanical Interaction ◽  
Liquefaction Resistance ◽  
Cyclic Stress Ratio ◽  
Geotechnical Centrifuge ◽  
Wide Diameter

<p>Plant roots have been considered to be effective to reinforce shallow soil slopes under rainfall conditions. Recent evidence from geotechnical centrifuge modelling shows that plant roots could improve earthquake-induced slope stability and reduce slope crest settlement. However, the underlying fundamental mechanisms of soil-root mechanical interaction against seismic loading are unclear. Although there has been a large volume of studies focusing on root reinforcement, cyclic soil-root mechanical interaction has rarely been investigated. Moreover, whether plant roots could reduce the liquefaction potential of rooted soil. This presentation will present some new test data and evidence about (1) cyclic root biomechanical behaviour and (2) cyclic responses of root-reinforced soil. In part (1), results of cyclic uniaxial tensile tests on roots of a wide diameter range will be presented, including any root hardening or softening and change in the size of hysteresis loops under displacement-controlled loading condition. Special attention will be paid on any observation of cyclic-induced root mechanical fatigue. In part (2), results of a comprehensive set of monotonic and cyclic triaxial tests on rooted soil will be presented. The cyclic behaviour observed will be interpreted through the monotonic behaviour observed along both the triaxial compression and extension paths. Any change in soil failure mechanism from limited flow failure to cyclic mobility due to plant roots, and how/when this change occurs at different root volume and cyclic stress ratio, will be discussed in detailed. A new attempt to interpret the liquefaction resistance through an energy-based approach will be made to evaluate the energy dissipation mechanism in rooted soils.</p>

Numerical Simulation of Mechanical Properties of Reinforced Red-Sandstone Granular Soil Based on 3D Discrete Element Method

2013 ◽  
Vol 353-356 ◽  
pp. 802-805
Author(s):  
Jian Qing Jiang
Keyword(s):  
Mechanical Properties ◽  
Discrete Element Method ◽  
Triaxial Compression ◽  
Discrete Element ◽  
Reinforced Soil ◽  
Triaxial Tests ◽  
Granular Soil ◽  
Compression Tests ◽  
Red Sandstone ◽  
Element Method

Red-sandstone granular soil reinforced with gabion-mesh is a new concept of composite reinforced soil. In order to reveal the mechanical properties of this composite reinforced soil, a series of laboratory triaxial compression tests on specimens reinforced with gabion-mesh were carried out, and 3D discrete element method was introduced to simulate the triaxial tests. The macro stress-strain relation of red-sandstone specimens reinforced with gabion-mesh was reproduced by the 3D discrete element model. The results show that 3D discrete element method is an ideal technique to study the meso-mechanical nature characteristics of gabion-mesh reinforced red-sandstone granular soil.

La compression triaxiale des sols armés

1980 ◽  
Vol 17 (2) ◽  
pp. 153-164 ◽  
Author(s):  
Robert P. Chapuis
Keyword(s):  
Limit Equilibrium ◽  
Triaxial Compression ◽  
Reinforced Soil ◽  
Soil Reinforcement ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Reinforced Earth ◽  
The Difference ◽  
The One ◽  
Compression Triaxiale

For a better understanding of the mechanical behaviour of reinforced soils, the paper presents a study of triaxial compression tests on soils reinforced by identical, equally spaced, plane ties. Soil–reinforcement interactions are considered by using a method similar to the one that resulted in the introduction of the cohesion effect concept in reinforced earth retaining walls. The material's limit-equilibrium equation is established for any tie orientation. These ties give to a reinforced soil a strength higher than the unreinforced soil strength. The difference may be considered as a cohesion term, which usually depends on the strength, concentration, and inclination of the ties, as well as on the radial stress level. The cohesion term given by triaxial tests is different from the cohesion effect term already introduced in reinforced earth walls, as there is no cohesion effect in a triaxial test. The paper also presents a study of adhesion conditions. By examining stress distribution in the soil between the ties, it is established that beyond a given inclination, no traction can be developed in the ties.

scholarly journals Monotonic and cyclic behaviour of root-reinforced sand

2021 ◽  
Author(s):  
Ali Akbar Karimzadeh ◽  
Anthony Kwan Leung ◽  
Saied Hosseinpour ◽  
Zhaoyi Wu ◽  
Pedram Fardad Amini
Keyword(s):  
Friction Angle ◽  
Cyclic Stress ◽  
Reinforced Soil ◽  
Triaxial Tests ◽  
Root Volume ◽  
Liquefaction Resistance ◽  
Mechanical Reinforcement ◽  
Cyclic Mobility ◽  
Cyclic Behaviour ◽  
Stress Ratios

Plant roots are known to provide mechanical reinforcement to soils upon shearing and seismic loading. However, the effects of different stress paths on root reinforce-ment are unclear. Moreover, whether, and how, roots provide resistance to soil lique-faction upon cyclic loading have rarely been studied. The objective of this study is to conduct a series of undrained triaxial tests to investigate the monotonic and cyclic behaviour of rooted sand. Roots of vetiver grass (Chrysopogon zizanioides L), which has been advocated for use in shallow slope stabilisation purposes, were used for testing. The root diameters ranged between 0.3 to 1.5 mm, while the root volume ra-tios were 0.23%, 0.45% and 0.67%. It was discovered that the root reinforcement ef-fect was anisotropic and path-dependent. Along the extension path when the major principal stress was perpendicular to the predominant root orientation, the root-induced increase in soil friction angle was approximately 10o. This increase was much greater than the case along the compression path where the change was min-imal. The presence of roots prevented the limited flow failure (which occurred in the unreinforced sand), and the failure mode of root-reinforced soil switched to cyclic mobility. The liquefaction resistance was improved with an increase in root volume, and this improvement was more remarkable at higher cyclic stress ratios.

The Experimental Study on the Performance of the Reinforced Red Mudstone Using Triaxial Tests

2012 ◽  
Vol 446-449 ◽  
pp. 1445-1449
Author(s):  
Shuai Zhuo ◽  
Ning Wang ◽  
Ping Lu ◽  
Yong Yao
Keyword(s):  
Ambient Pressure ◽  
Triaxial Compression ◽  
Reinforced Soil ◽  
Triaxial Tests ◽  
Steel Material ◽  
Reinforcement Material ◽  
Strain Relationship ◽  
Material Sample ◽  
Better Than ◽  
Compaction Degree

via the red mudstone proceed of the unconsolidated and non-drained triaxial compression test, the research in different degree of compaction reinforcement material under the influence of red mudstone strength. To the different reinforcement layers, different ambient pressure test, analyses not reinforcement material layer number of decorate the more the better, decorate three layer of steel material is better than the four layers of reinforcement decorate material sample. The analysis in different degree of compaction element soil and reinforced soil under test result, the reinforcement material that can obviously increase the strength of the soil, and in different degree of compaction soil under the different strength, and with the degree of compaction to improve the stress-strain relationship curves by strain softening type to strain change sclerosis type. Analysis of the С value of the red mudstone compaction degree with the increased and rise, but theφ rise and reduced.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

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 The effect of confinement in liquefaction tests carried out in a cyclic simple shear apparatus

2019 ◽  
Vol 92 ◽  
pp. 08002 ◽  
Author(s):  
Lucia Mele ◽  
Stefania Lirer ◽  
Alessandro Flora
Keyword(s):  
Simple Shear ◽  
Initial Conditions ◽  
Confining Pressure ◽  
Cyclic Stress ◽  
Shear Tests ◽  
Liquefaction Resistance ◽  
Pressurized Water ◽  
Cyclic Stress Ratio ◽  
Complex Behaviour ◽  
Continuous Rotation

The cyclic simple shear tests can be used to reproduce in laboratory the complex behaviour of the soil during an earthquake, simulating the continuous rotation of the principal stress axes. In this research a comparison of results between cyclic simple shear tests carried out with confining pressure or confining rings is reported. A cyclic simple shear apparatus is used to carry out tests with confining rings (the conventional way to carry out cyclic simple shear tests) and with a confining pressure applied to the specimen through pressurized water, where the K0 condition during consolidation is guaranteed by a sophisticated control system. The apparatus, in both the configurations, is described in detail. All tests were carried out on reconstituted specimens of an Italian sand with similar initial conditions, such as low relative density and confining pressure. All experimental results are reported in the plane cyclic stress ratio (CSR) and number of cycles where liquefaction occurs (Nliq) in order to evaluate the effect of confinement on the liquefaction resistance of the studied sand.

Deep sampling and testing in soft stratified clay

2003 ◽  
Vol 40 (3) ◽  
pp. 575-586 ◽  
Author(s):  
Simon James Cummings ◽  
Vinayagamoorthy Sivakumar ◽  
Isaac Gregg Doran ◽  
Jim Graham
Keyword(s):  
Triaxial Compression ◽  
Relevant Literature ◽  
Thick Layer ◽  
Site Investigation ◽  
Anisotropic Elasticity ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Lower Zone ◽  
A Site ◽  
Triaxial Compression Tests

A 37-m thick layer of stratified clay encountered during a site investigation at Swann's Bridge, near the sea-coast at Limavady, Northern Ireland, is one of the deepest and thickest layers of this type of material recorded in Ireland. A study of the relevant literature and stratigraphic evidence obtained from the site investigation showed that despite being close to the current shoreline, the clay was deposited in a fresh-water glacial lake formed approximately 13 000 BP. The 37-m layer of clay can be divided into two separate zones. The lower zone was deposited as a series of laminated layers of sand, silt, and clay, whereas the upper zone was deposited as a largely homogeneous mixture. A comprehensive series of tests was carried out on carefully selected samples from the full thickness of the deposit. The results obtained from these tests were complex and confusing, particularly the results of tests done on samples from the lower zone. The results of one-dimensional compression tests, unconsolidated undrained triaxial tests, and consolidated undrained triaxial compression tests showed that despite careful sampling, all of the specimens from the lower zone exhibited behaviour similar to that of reconstituted clays. It was immediately clear that the results needed explanation. This paper studies possible causes of the results from tests carried out on the lower Limavady clay. It suggests a possible mechanism based on anisotropic elasticity, yielding, and destructuring that provides an understanding of the observed behaviour.Key words: clay, laminations, disturbance, yielding, destructuring, reconstituted.

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