scholarly journals Mechanical behavior of an unsaturated clayey silt: an experimental and constitutive modelling study

2019 ◽  
Vol 56 (10) ◽  
pp. 1461-1474
Author(s):  
Enrique Romero ◽  
Marcelo Sánchez ◽  
Xuerui Gai ◽  
Mauricio Barrera ◽  
Antonio Lloret
Keyword(s):  
Triaxial Compression ◽  
Constitutive Modelling ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Compression Tests ◽  
Stress Strain ◽  
Hardening Law ◽  
Clayey Silt ◽  
Constant Suction ◽  
Realistic Description

This paper reports an experimental study and subsequent constitutive modelling focused on the stress-strain and volumetric responses during deviatoric stress application of a partially saturated clayey silt. The material was statically and isotropically compacted at constant water content towards a pre-defined pre-consolidation stress. A series of strain-controlled triaxial compression tests on a state of the art device and isotropic experiments are presented and discussed. The triaxial tests started at the same stress state (i.e., identical matric suction and mean net stress) and were conducted at the same constant suction. Several stress paths under isotropic conditions (i.e., drying–wetting, loading–unloading, and wetting–drying) were followed to induce different overconsolidated states before shearing the specimens. The test results are initially interpreted using the elastoplastic Barcelona Basic Model (BBM). Independent tests were selected to determine the model parameters associated with the volumetric behavior of the soil. The BBM was not able to capture the dilatant behavior observed during shearing. An enhancement of the BBM is proposed in this work, which includes both, a more general hardening law and sub-loading concepts. The main capabilities and limitations of the original BBM and the enhanced model are discussed and compared. The modified BBM was able to handle the dilatancy observed in the experiments and provided a more realistic description of the experimental stress-strain response.

scholarly journals Stress–dilatancy of gravel for triaxial compression tests

2018 ◽  
Vol 50 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Shear Strain ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
State Theory ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Stress Strain ◽  
Characteristic Points ◽  
Triaxial Compression Tests

Abstract The stress–plastic dilatancy relationships for gravel are analyzed based on drained triaxial tests experiments described in literature. For this, Frictional State Theory is used. The characteristic points and stages of shearing may be defined from the analysis of η–Dp relationship. The characteristic points and stages of shearing cannot be identified from ordinary stress–strain, volumetric strain–shear strain relationships that are shown in literature.

Stress–strain–time behavior of deep sea clays

1983 ◽  
Vol 20 (3) ◽  
pp. 517-531 ◽  
Author(s):  
A. J. Silva ◽  
K. Moran ◽  
S. A. Akers
Keyword(s):  
Deep Sea ◽  
Triaxial Compression ◽  
Constant Strain Rate ◽  
Triaxial Tests ◽  
Time Behavior ◽  
Compression Tests ◽  
Creep Tests ◽  
Stress Strain ◽  
The North ◽  
Deep Sea Sediments

Summary results are presented of a comprehensive experimental study to investigate the strength, stress–strain properties, and creep behavior of fine-grained deep sea sediments. Isotropically (CIU) and anisotropically (CAU) consolidated undrained triaxial tests and drained triaxial creep tests were performed on undisturbed and reconstituted–reconsolidated (remolded) samples of smectite-rich and illite-rich deep sea clays from the North Central Pacific.The CIU Mohr–Coulomb parameters for remolded smectite [Formula: see text] were nearly identical to the undisturbed material [Formula: see text]. The parameters for remolded illite [Formula: see text] were also not significantly different than for the undisturbed material [Formula: see text].The undrained shear strength versus water content relationship (qf vs. wf) for remolded smectite is much lower than for the undisturbed material, whereas for illite the remolded strength is only slightly lower. Therefore it appears that smectite is much more sensitive than illite to the type of remolding used in these studies.The CAU tests showed that K0 agrees well with the Jaky equation, [Formula: see text]. The Mohr–Coulomb parameters were somewhat lower than the corresponding CIU results.Undisturbed and remolded samples were tested at stress levels of 10, 25, 40, and 65% of the Mohr–Coulomb strength for the determination of triaxial drained creep properties. Different relationships between stress level, strain, and time were determined for the two materials. A secondary state of creep, defined as a period of constant strain rate, was not consistently observed. Comparisons with terrestrial clays and near shore material display similar strengths of the deep sea sediments and greater deformation potential during long-term loading. Keywords: stress–strain behavior, creep, deep sea sediments, stress–strain–time behavior, triaxial compression tests.

Anisotropic three-dimensional behavior of a normally consolidated clay

1993 ◽  
Vol 30 (5) ◽  
pp. 848-858 ◽  
Author(s):  
M.M. Kirkgard ◽  
P.V. Lade
Keyword(s):  
Pore Pressure ◽  
San Francisco ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Failure Surface ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Principal Stresses ◽  
Stress Strain ◽  
Strain Behavior

An experimental study is presented of the influence of the intermediate principal stress on the stress–strain, pore-pressure, and strength characteristics of a normally consolidated, natural anisotropic clay, San Francisco Bay Mud, under undrained conditions. Consolidated undrained triaxial compression tests and triaxial tests with independent control of all three principal stresses on cubical specimens were performed. The stress–strain behavior and the pore-pressure characteristics as well as the effective stress failure surface can be described as being cross-anisotropic. Key words : anisotropic soils, clays, deformation, shear strength, triaxial tests.

scholarly journals Constitutive modelling of root-reinforced granular soils – preliminary studies

2018 ◽  
Vol 27 (2) ◽  
pp. 103-113
Author(s):  
Barbara Świtała ◽  
E. Fern
Keyword(s):  
Large Scale ◽  
Triaxial Compression ◽  
Constitutive Modelling ◽  
Model Parameters ◽  
Granular Soils ◽  
Compression Tests ◽  
Dune Stability ◽  
Dry Soil ◽  
Triaxial Compression Tests ◽  
Implementation In Matlab

A novel solution for the problem of modelling of soil reinforced with vegetation roots. An extension of the Nor–Sand model and its application to granular saturated or dry, soil–root composites. Model implementation in MATLAB: numerical simulations of drained triaxial compression tests, investigation of the sensitivity of the solution to different values of model parameters. Capturing the most important features of soil–root composites. Accounting for the progressive activation of the root’s strength. Indication of the ability of further model application to large-scale problems, such as slope or dune stability.

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 Triaxial Testing of Geosynthetics Reinforced Tailings with Different Reinforced Layers

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1943
Author(s):  
Fu Yi ◽  
Changbo Du
Keyword(s):  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Test Results ◽  
Compression Tests ◽  
Strength Index ◽  
Stress Strain ◽  
High Confining Pressure ◽  
Zhang Model ◽  
Triaxial Compression Tests

To evaluate the shear properties of geotextile-reinforced tailings, triaxial compression tests were performed on geogrids and geotextiles with zero, one, two, and four reinforced layers. The stress–strain characteristics and reinforcement effects of the reinforced tailings with different layers were analyzed. According to the test results, the geogrid stress–strain curves show hardening characteristics, whereas the geotextile stress–strain curves have strain-softening properties. With more reinforced layers, the hardening or softening characteristics become more prominent. We demonstrate that the stress–strain curves of geogrids and geotextile reinforced tailings under different reinforced layers can be fitted by the Duncan–Zhang model, which indicates that the pseudo-cohesion of shear strength index increases linearly whereas the friction angle remains primarily unchanged with the increase in reinforced layers. In addition, we observed that, although the strength of the reinforced tailings increases substantially, the reinforcement effect is more significant at a low confining pressure than at a high confining pressure. On the contrary, the triaxial specimen strength decreases with the increase in the number of reinforced layers. Our findings can provide valuable input toward the design and application of reinforced engineering.

An Improved Method of Determining the Disturbed State Concept Model Parameters

2014 ◽  
Vol 919-921 ◽  
pp. 1345-1349
Author(s):  
Wei Lu ◽  
Jia Jun Pan
Keyword(s):  
Triaxial Compression ◽  
Model Parameters ◽  
Improved Method ◽  
Stress Strain ◽  
Material Parameters ◽  
Concept Model ◽  
Strain Relation ◽  
Stress Strain Relation ◽  
Disturbed State Concept

The method of postulate of relatively intact model in the disturbed concept model is reached. Because it is more difficult to assume relatively intact curve by observed experimental data, a method which could automatically calculate the stress strain relation curve of relative intact by triaxial compression test data is raised, so that the determination of material parameters becomes easier, and the improved method is verified by numerical calculation. The results show that this method can effectively determine the stress strain relation curve of relative intact.

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.

Duncan-Chang Nonlinear Elastic Model Considered Loess Structure

2011 ◽  
Vol 90-93 ◽  
pp. 176-181
Author(s):  
Chang Lu Chen ◽  
Sheng Jun Shao ◽  
Lin Ma
Keyword(s):  
Nonlinear Model ◽  
Stress Ratio ◽  
Structural Parameters ◽  
Strain Curve ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Elastic Model ◽  
Stress Strain ◽  
Nonlinear Elastic ◽  
Intact Loess

Duncan-Chang nonlinear model has been modified and applied to the structural loess calculation. Based on structural studies and conventional triaxial tests, this paper has analyzed the mechanical properties of intact loess and the relationship between the stress ratio structural parameters and the strain, then the expression of generalized shear strain and stress ratio structural parameters are given to facilitate the engineering applications. On this basis, the stress-strain curve of intact loess was corrected by the use of the stress ratio structural parameters. The form of the intact loess stress-strain curves which have been revised has changed hardening from the softening or weak softening. The results show that the modified stress-strain curves of intact loess can apply Duncan- Chang nonlinear model to calculate and the model parameters are reasonable and effective. This method provides Duncan-Chang nonlinear model which is widely used in engineering with a new ways and means in intact structural loess application.

Anisotropic shear strength of a residual soil of sandstone

2008 ◽  
Vol 45 (3) ◽  
pp. 367-376 ◽  
Author(s):  
Adriano Virgilio Damiani Bica ◽  
Luiz Antônio Bressani ◽  
Diego Vendramin ◽  
Flávia Burmeister Martins ◽  
Pedro Miguel Vaz Ferreira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Yield Surface ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Compression Tests ◽  
Soil Stiffness ◽  
Particle Bonding

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.

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