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 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.

scholarly journals Damage Evolution of Coal with Inclusions Under Triaxial Compression

2021 ◽  
Author(s):  
Yufeng Zhao ◽  
Heinz Konietzky ◽  
Martin Herbst
Keyword(s):  
Damage Evolution ◽  
Laboratory Tests ◽  
Numerical Models ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Confining Pressure ◽  
Fracture Network ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Deformation State

AbstractAlong with the advance of the working face, coal experiences different loading stages. Laboratory tests and numerical simulations of fracture and damage evolution aim to better understand the structural stability of coal layers. Three-dimensional lab tests are performed and coal samples are reconstructed using X-ray computer tomography (CT) technique to get detailed information about damage and deformation state. Three-dimensional discrete element method (DEM)-based numerical models are generated. All models are calibrated against the results obtained from uniaxial compressive strength (UCS) tests and triaxial compression (TRX) tests performed in the laboratory. A new approach to simulate triaxial compression tests is established in this work with significant improved handling of the confinement to get realistic simulation results. Triaxial tests are simulated in 3D with the particle-based code PFC3D using a newly developed flexible wall (FW) approach. This new numerical simulation approach is validated by comparison with laboratory tests on coal samples. This approach involves an updating of the applied force on each wall element based on the flexible nature of a rubber sleeve. With the new FW approach, the influence of the composition (matrix and inclusions) of the samples on the peak strength is verified. Force chain development and crack distributions are also affected by the spatial distribution of inclusions inside the sample. Fractures propagate through the samples easily at low confining pressures. On the contrary, at high confining pressure, only a few main fractures are generated with orientation towards the side surfaces. The evolution of the internal fracture network is investigated. The development of microcracks is quantified by considering loading, confinement, and structural character of the rock samples. The majority of fractures are initiated at the boundary between matrix and inclusions, and propagate along their boundaries. The internal structure, especially the distribution of inclusions has significant influence on strength, deformation, and damage pattern.

Numerical Simulation for the Deformation of Composite Wall Insulation System

2011 ◽  
Vol 374-377 ◽  
pp. 187-190
Author(s):  
Tao Cheng
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Constitutive Relations ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Constitutive Model ◽  
Isotropic Consolidation ◽  
Composite Wall ◽  
Triaxial Compression Tests

The nonlinear constitutive relations of clay are investigated with different initial stress conditions. Two series of triaxial compression tests are performed, respectively after consolidation and isotropic consolidation. On the basis of the framework of ~ model, a uniform nonlinear constitutive model is proposed by fitting of the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison of the experimental stress-strain curves with the predicted results by the constitutive model is made. It is shown that the model prediction is reasonable, which can reflect the stress-strain behavior of the soil under the consolidation and isotropic consolidation conditions.

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.

Nonlinear Constitutive Model for Clay on K0 Consolidation Conditions

2011 ◽  
Vol 368-373 ◽  
pp. 515-518
Author(s):  
Tao Cheng
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Constitutive Relations ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Constitutive Model ◽  
Isotropic Consolidation ◽  
Nonlinear Constitutive Relations ◽  
Triaxial Compression Tests

The nonlinear constitutive relations of clay are investigated with different initial stress conditions. Two series of triaxial compression tests are performed, respectively after consolidation and isotropic consolidation. On the basis of the framework of ~ model, a uniform nonlinear constitutive model is proposed by fitting of the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison of the experimental stress-strain curves with the predicted results by the constitutive model is made. It is shown that the model prediction is reasonable, which can reflect the stress-strain behavior of the soil under the consolidation and isotropic consolidation conditions.

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 Experimental Study of Stress-Seepage Coupling Properties of Sandstone under Different Loading Paths

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Xi Chen ◽  
Wei Wang ◽  
Yajun Cao ◽  
Qizhi Zhu ◽  
Weiya Xu ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Pore Pressure ◽  
Complex Loading ◽  
Friction Angle ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Biot Coefficient ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

The study on hydromechanical coupling properties of rocks is of great importance for rock engineering. It is closely related to the stability analysis of structures in rocks under seepage condition. In this study, a series of conventional triaxial tests under drained condition and hydrostatic compression tests under drained or undrained condition on sandstones were conducted. Moreover, complex cyclic loading and unloading tests were also carried out. Based on the experimental results, the following conclusions were obtained. For conventional triaxial tests, the elastic modulus, peak strength, crack initiation stress, and expansion stress increase with increased confining pressure. Pore pressure weakened the effect of the confining pressure under drained condition, which led to a decline in rock mechanical properties. It appeared that cohesion was more sensitive to pore pressure than to the internal friction angle. For complex loading and unloading cyclic tests, in deviatoric stress loading and unloading cycles, elastic modulus increased obviously in first loading stage and increased slowly in next stages. In confining pressure loading and unloading cycles, the Biot coefficient decreased first and then increased, which indicates that damage has a great impact on the Biot coefficient.

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