Yielding and Flow of Sand in Triaxial Compression: Part I

1966 ◽  
Vol 3 (4) ◽  
pp. 179-190 ◽  
Author(s):  
H B Poorooshasb ◽  
I Holubec ◽  
A N Sherbourne
Keyword(s):  
Eigenvalue Problems ◽  
Triaxial Compression ◽  
Flow Rule ◽  
Sand Sample ◽  
Triaxial Apparatus ◽  
Plastic Potential ◽  
Constant E ◽  
The Subject ◽  
Yield Loci ◽  
Stress And Deformation

A theoretical and experimental study of the nature of deformation of a sand sample when tested in the triaxial apparatus is presented. The medium is shown to be elastic-strain hardening plastic but does not conform to certain rules usually adopted in the classical theory of plasticity. Experimental verification of an earlier suggestion by Poorooshasb (1961) leads to a proof of the existence of a potential function, known as the plastic potential, of the form Ψ(σ, e) the parameters σ representing the stress and e the voids ratio. The plastic potential curves defined by Ψ = constant, e = constant, trace a family of geometrically similar curves when plotted in a stress space. The yield loci, on the other hand, are found to be independent of voids ratio and are only functions of the ratio of the second invariant of the stress deviation tensor to the first invariant of the stress tensor. It is noted, therefore, that the plastic potential and yield surface are not coincidental. This defies the normality condition and in this respect the medium's behaviour appears to deviate from that of a classical plastic body. Although the scope of the study is limited, being applicable only to stress conditions provided in a triaxial compression test, extensions are made to incorporate stress and strain in their more general form. This is done to stimulate further research on the subject, although a fair amount of evidence is available to support, qualitatively at least, the validity of the propositions made. The paper is concluded by presenting the flow rule for the medium and discussing the application of the theory presented to the solution of equilibrium and eigenvalue problems involving stress and deformation.

Yielding and Flow of Sand in Triaxial Compression: Parts II and III

1967 ◽  
Vol 4 (4) ◽  
pp. 376-397 ◽  
Author(s):  
H B Poorooshasb ◽  
I Holubec ◽  
A N Sherbourne
Keyword(s):  
Plastic Strain ◽  
Experimental Evidence ◽  
Potential Function ◽  
Triaxial Compression ◽  
Strain Increment ◽  
Flow Rule ◽  
Plastic Strain Increment ◽  
Yield Loci

In Part I,* based on experimental evidence, the existence of a potential function to define the gradient of the plastic strain increment vector was proved. The study is continued in Part II by defining the term yielding, a discussion of the form of the yield loci and a presentation of the “flow rule.”

scholarly journals Non-normal flow rules affect fracture angles in sea ice viscous–plastic rheologies

2021 ◽  
Vol 15 (6) ◽  
pp. 2873-2888
Author(s):  
Damien Ringeisen ◽  
L. Bruno Tremblay ◽  
Martin Losch
Keyword(s):  
Sea Ice ◽  
Axial Compression ◽  
Yield Curve ◽  
Axial Loading ◽  
The Arctic ◽  
Flow Rule ◽  
Normal Flow ◽  
Fracture Deformation ◽  
Plastic Potential ◽  
Ice Model

Abstract. The standard viscous–plastic (VP) sea ice model with an elliptical yield curve and a normal flow rule has at least two issues. First, it does not simulate fracture angles below 30∘ in uni-axial compression, in contrast with observations of linear kinematic features (LKFs) in the Arctic Ocean. Second, there is a tight, but unphysical, coupling between the fracture angle, post-fracture deformation, and the shape of the yield curve. This tight coupling was identified as the reason for the overestimation of fracture angles. In this paper, these issues are addressed by removing the normality constraint on the flow rule in the standard VP model. The new rheology is tested in numerical uni-axial loading tests. To this end, an elliptical plastic potential – which defines the post-fracture deformations, or flow rule – is introduced independently of the elliptical yield curve. As a consequence, the post-fracture deformation is decoupled from the mechanical strength properties of the ice. We adapt Roscoe's angle theory, which is based on observations of granular materials, to the context of sea ice modeling. In this framework, the fracture angles depend on both yield curve and plastic potential parameters. This new formulation predicts accurately the results of the numerical experiments with a root-mean-square error below 1.3∘. The new rheology allows for angles of fracture smaller than 30∘ in uni-axial compression. For instance, a plastic potential with an ellipse aspect ratio smaller than 2 (i.e., the default value in the standard viscous–plastic model) can lead to fracture angles as low as 22∘. Implementing an elliptical plastic potential in the standard VP sea ice model requires only small modifications to the standard VP rheology. The momentum equations with the modified rheology, however, are more difficult to solve numerically. The independent plastic potential solves the two issues with VP rheology addressed in this paper: in uni-axial loading experiments, it allows for smaller fracture angles, which fall within the range of satellite observations, and it decouples the angle of fracture and the post-fracture deformation from the shape of the yield curve. The orientation of the post-fracture deformation along the fracture lines (convergence and divergence), however, is still controlled by the shape of the plastic potential and the location of the stress state on the yield curve. A non-elliptical plastic potential would be required to change the orientation of deformation and to match deformation statistics derived from satellite measurements.

A Simple and Practicable Approach on Implementing for the Reduced Triaxial Extension by the Conventional Triaxial Apparatus

2011 ◽  
Vol 250-253 ◽  
pp. 2089-2092
Author(s):  
Rong Jian Li ◽  
Xi An Li ◽  
Gao Feng Che ◽  
Wen Zheng ◽  
Wen Jun Chen
Keyword(s):  
Triaxial Compression ◽  
Stress Path ◽  
Test Results ◽  
Triaxial Apparatus ◽  
Eolian Sand ◽  
Conventional Triaxial Compression ◽  
The Difference ◽  
Shear Behaviors ◽  
The Impact ◽  
Triaxial Extension

Stress path is one of the very important factors of soil strength. It is significant to study the strength and reveal the importance of the impact of sand in different stress path conditions. Firstly, an ameliorating approach on implementing for the reduced triaxial extension by the conventional triaxial apparatus was discussed. Then, In order to study shear behaviors of the eolian sand under different stress path, two monotonic shearing tests with the conventional triaxial compression and the reduced triaxial extension stress path were performed and analyzed. The test results not only indicate that the amelioration on conventional triaxial apparatus is simple, practicable and inexpensive, but also reveal the difference of strength’s parameter between the reduced triaxial extension and conventional triaxial compression stress path. In sum, the stress path has important effect on the strength of the eolian sand.

The Safety Analysis for Underground Tunnel of Civil Engineering by the Stress and Deformation of Rock Mass Material

2012 ◽  
Vol 568 ◽  
pp. 222-225 ◽  
Author(s):  
Xiong Gang Xie ◽  
Zhao Yang Yu ◽  
Ze Biao Jiang
Keyword(s):  
Rock Mass ◽  
Shear Failure ◽  
Civil Engineering ◽  
Flow Rule ◽  
Underground Tunnel ◽  
Comparison Results ◽  
Stress And Deformation ◽  
Real Practice ◽  
Coulomb Criterion ◽  
Associated Flow Rule

The Mohr-Coulomb criterion is used in this paper to describe the strength of rock mass in tunnel of civil engineering. The position of a stress point on this envelope is controlled by a non-associated flow rule for shear failure, and an associated rule for tension failure. Excavation of tunnel will lead to the redistribution of stress in rock mass, in order to compare the analytical and numerical solution of rock mass response to predict the safety degree of underground tunnel, to predict the safety degree of tunnel, some calculations are done by theoretical and numerical methods. The comparison results can give guidance for the real practice

scholarly journals Stress and Deformation Analysis of Joint Plate Depending on Truss Joint Design of Carrying Structure

TEM Journal ◽  
2021 ◽  
pp. 892-899
Author(s):  
Elizabeta Hristovska ◽  
Sevde Stavreva
Keyword(s):  
Finite Element Method ◽  
Software Package ◽  
Dynamic Loads ◽  
Local Analysis ◽  
Deformation Analysis ◽  
Load Carrying ◽  
Static And Dynamic Loads ◽  
The Subject ◽  
Stress And Deformation ◽  
Load Conditions

This article presents the stress and deformation shape of joint plate in two commonly used constructive designs of truss joints of a rotating excavator’s load-carrying structure. A local analysis of stresses and deformations of the joint plate have been conducted taking into consideration the most loaded truss joint of the working wheel’s load-carrying structure on specific rotating excavator, having a riveted design, as well as the theoretically determined forces affecting the joining trusses of the truss joint. These activities are performed employing FEM (Finite Element Method) modelling of the truss joint and using a software package for this purpose, in view of defined characteristic static and dynamic loads. Nowadays, the load-carrying structures are more often made by welding, so it is in our interest as it would affect the stress and deformation shape of the subject truss joint in welded design, bearing the same load conditions.

scholarly journals A Framework for Versatile Shape of Yield Surfaces for Structured Aniso-tropic Soft Soils

2016 ◽  
Author(s):  
Nallathamby Sivasithamparam ◽  
Jorge Castro
Keyword(s):  
Yield Surface ◽  
Earth Pressure ◽  
Type Model ◽  
Flow Rule ◽  
Lateral Movement ◽  
Plastic Potential ◽  
Yield Surfaces ◽  
Anisotropic Clays ◽  
Associated Flow Rule ◽  
Cam Clay

A framework based on logarithmic contractancy is proposed to produce versatile shapes of yield surfaces for structured anisotropic clays. The recently proposed constitutive model (E-SCLAY1S) is an extension of existing model called S-CLAY1S, which is a Cam Clay type model that accounts for anisotropy and structure. A new parameter called contractancy parameter is introduced to control the shape of the yield surface as well as the plastic potential (as an associated flow rule is applied). This new parameter can be used to fit the coefficient of earth pressure at rest, the undrained shear strength or the stiffness under shearing stress paths predicted by the model. The model predicts the uniqueness of the critical state line and its slope is independent of the contractancy parameter. The effect of the shape of the yield surface was investigated on computed results of a benchmark embankment constructed on Bothkennar (Scotland) clay by employing the E-SCLAY1S model as a user-defined soil model into the PLAXIS finite element code. The results demonstrate that the contribution of the shape of yield surface (logarithmic contractancy parameter) have a relatively large effect on lateral movement of subsoil beneath the toe of the embankment compared to the settlement of subsoil at the centre of the embankment.

scholarly journals A microstructure-based elastoplastic model to describe the behaviour of a compacted clayey silt in isotropic and triaxial compression

2020 ◽  
Vol 57 (7) ◽  
pp. 1025-1043 ◽  
Author(s):  
Guido Musso ◽  
Arash Azizi ◽  
Cristina Jommi
Keyword(s):  
Water Retention ◽  
Triaxial Compression ◽  
Double Porosity ◽  
Degree Of Saturation ◽  
Water Retention Capacity ◽  
Flow Rule ◽  
Retention Capacity ◽  
Clayey Silt ◽  
Hydromechanical Behaviour ◽  
As Stress

The paper focuses on the hydromechanical behaviour of an unsaturated compacted clayey silt, accounting for fabric changes induced by drying–wetting cycles occurring at low stress levels. The response along isotropic compression and triaxial compression (shear) at constant water content was investigated by laboratory tests on both as-compacted and dried–wetted samples. Compaction induces a microstructural porosity pertinent to clay peds and a macrostructural porosity external to the peds. Drying–wetting cycles decrease the microporosity and increase the macroporosity, which reduces the water retention capacity, increases the compressibility, and promotes higher peak strengths with more brittle behaviour during triaxial compression. A coupled double-porosity elastic–plastic model was formulated to simulate the experimental results. A nonassociated flow rule was defined for the macrostructure, modifying a stress–dilatancy relationship for saturated granular soils to account for the increase in dilatancy with suction observed in the experiments. The average skeleton stress and suction were adopted as stress variables. As correctly predicted by the model, the shear strength at critical state is not significantly influenced by the degree of saturation or by the hydraulic history. On the contrary, the higher peak strength, brittleness, and dilatancy of the dried–wetted samples are mostly explained by their reduced water-retention capacity.

scholarly journals Stress-strain Relationship in Homogeneous and Two-layered Triaxial Test Specimens

2020 ◽  
Author(s):  
Gabriel Oliveira ◽  
Isabel Falorca
Keyword(s):  
Soil Mechanics ◽  
Triaxial Compression ◽  
Nonlinear Behavior ◽  
Confining Pressure ◽  
Test Method ◽  
Compression Tests ◽  
Stress Strain ◽  
Triaxial Apparatus ◽  
Strain Relationship ◽  
The Stability

The stress-strain relationship of a homogeneous specimen, obtained from triaxial compression test, allows to determine stiffness parameters for numerical-method based analyses in common geotechnical software. Stiffness parameters are defined as the ratio of stress to strain along an axis. However, when a heterogeneous specimen is tested, the equivalent elastic modulus that represents a simplification of the nonlinear behavior is complex. This paper presents a study intended to contribute to the debate about the degree to which conventional soil mechanics approaches can be applied to layered specimens. Triaxial compression tests were carried out on both homogeneous and two-layered specimens under a low effective confining pressure of 30 kPa. The triaxial apparatus was chosen since the applied stress and specimen boundary conditions are well defined, and the repeatability of the test method is good. The behavior of both specimens was studied in terms of the stress-strain relationship and stiffness. The main differences were crucial to understanding the composite soil-aggregate interaction, which is discussed and compared. The results indicate that the interface between composite soil and aggregate is important to keep the stability of the layer of aggregate over the soft composite soil, and practical methods of achieving that are suggested.

scholarly journals Non-normal flow rules affect fracture angles in sea ice viscous-plastic rheologies

2020 ◽  
Author(s):  
Damien Ringeisen ◽  
L. Bruno Tremblay ◽  
Martin Losch
Keyword(s):  
Sea Ice ◽  
Yield Curve ◽  
Confining Pressure ◽  
The Arctic ◽  
Flow Rule ◽  
Normal Flow ◽  
Loading Test ◽  
Fracture Angle ◽  
Plastic Potential ◽  
Ice Model

Abstract. The standard viscous-plastic (VP) sea ice model with an elliptical yield curve and normal flow rule does not simulate fracture angles below 30° in uni-axial compression, in stark contrast with observations of Linear Kinematic Features (LKFs) in the Arctic Ocean. In this paper, we remove the normality constraint in the standard VP model and study its impact on the fracture angle in a simple uni-axial compressive loading test. To this end, we introduce a plastic potential independent of the yield curve that defines the post-fracture deformations or flow rule. The numerical experiments show that the fracture angle strongly depends on the flow rule details. For instance, a plastic potential with an ellipse aspect ratio smaller than that of the standard ellipse gives fracture angles that are as low as 22°. A newly adapted theory – based on one developed from observations of granular material – predicts numerical simulations of the fracture angles for plastic materials with a normal or non-normal flow rule with a root-mean-square error below 1.3°. Implementing an elliptical plastic potential in the standard VP sea ice model requires only minor modifications. The modified rheology, however, takes longer to solve numerically for a fixed level of numerical convergence. In conclusion, the use of a plastic potential addresses several issues with the standard VP rheology: the fracture angle can be reduced to values within the range of satellite observations and it can be decoupled from the exact shape of the yield curve. Furthermore, a different plastic potential function will be required to change the post-fracture deformation along the fracture lines (convergence or divergence) and to make the fracture angle independent on the confining pressure (as in observations).

scholarly journals Numerical Triaxial Apparatus and Application

2013 ◽  
Vol 353-356 ◽  
pp. 3251-3255 ◽  
Author(s):  
Xiao Liang Wang ◽  
Jia Chun Li
Keyword(s):  
Granular Materials ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Good Prediction ◽  
Strain Response ◽  
Compression Tests ◽  
Dilatancy Angle ◽  
Triaxial Apparatus ◽  
Dem Model

A numerical triaxial apparatus based on discrete element method is developed on the platform of Yade using Python script. A DEM model with rolling resistance contact considered is proposed for dense granular materials, which is then applied in triaxial compression test of Chende sand. Stress-strain response and volume-axial strain response of the DEM model agree well with that of experiments, with a good prediction of dilatancy angle. Degradation of granular materials duo to particle erosion is also investigated using triaxial compression tests. It is indicated that peak friction angle decreases with the remove of particles if strong force network of granular materials is destroyed.

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