scholarly journals Stress-strain behaviour of Toyoura sand in undrained triaxial compression

2019 ◽  
Vol 92 ◽  
pp. 15010 ◽  
Author(s):  
Katarzyna Dołżyk-Szypcio
Keyword(s):  
Stress Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
State Theory ◽  
Natural State ◽  
Strain Behaviour ◽  
Characteristic Points ◽  
Toyoura Sand ◽  
Undrained Conditions ◽  
Parameter Values

The stress-plastic dilatancy relationship for Toyoura sand sheared under undrained triaxial conditions was analysed by use of Frictional State Theory. Under undrained conditions, plastic strain increments are counterbalanced by elastic strain increments. The linear stress ratio-plastic dilatancy relationships at different stages of sand shear were obtained by assuming that Poisson's ratio is a function of shear strain. Contrary to a drained condition, natural state parameter values are not special for characteristic points of sand behaviour under undrained conditions.

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.

scholarly journals Stress-Dilatancy for Soils. Part II: Experimental Validation for Triaxial Tests

2016 ◽  
Vol 38 (4) ◽  
pp. 59-65 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Test Data ◽  
Experimental Validation ◽  
Triaxial Compression ◽  
Shear Resistance ◽  
State Theory ◽  
Triaxial Tests ◽  
Macro Scale ◽  
Undrained Conditions ◽  
Particle Rolling ◽  
Drained And Undrained Conditions

Abstract Different forms of the stress-dilatancy relations obtained based on the frictional theory for the triaxial condition are presented. The analysed test data show that the shear resistance of many soils is purely frictional. The angle Φ0 represents the resistance of the soil as a combined effect of sliding and particle rolling on the macro-scale during shear at the critical frictional state. The stress-plastic dilatancy relations differ not only for triaxial compression and extension but also for drained and undrained conditions. The experiment investigated shows the correctness of the frictional state theory in the triaxial condition.

scholarly journals Stress–Dilatancy For Crushed Latite Basalt

2018 ◽  
Vol 40 (1) ◽  
pp. 6-10 ◽  
Author(s):  
Katarzyna Dołżyk-Szypcio
Keyword(s):  
Triaxial Compression ◽  
State Theory ◽  
Advanced Stage ◽  
Compression Tests ◽  
Strain Behaviour ◽  
Initial Stage ◽  
The Mean ◽  
Straight Lines ◽  
The Relationship ◽  
Triaxial Compression Tests

AbstractIn this article, the stress–dilatancy relationship for crushed latite basalt is analysed by using Frictional State Theory. The relationship is bilinear, and the parameters α and β determine these two straight lines. At the initial stage of shearing, the mean normal stress increment mainly influences breakage, but at the advanced stage, it is shear deformation that influences breakage. At the advanced stage of shearing, the parameter αpt represents energy consumption because of breakage and βpt mainly represents changes in volume caused by breakage during shear. It is also shown that breakage effect is significant at small stress levels and the η-Dp plane is important to fully understand the stress–strain behaviour of crushed latite basalt in triaxial compression tests.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

A New Nonlinear Stress-Strain Model for Soils at Various Strain Levels

2013 ◽  
Vol 631-632 ◽  
pp. 782-788
Author(s):  
Cheng Chen ◽  
Zheng Ming Zhou
Keyword(s):  
Compression Test ◽  
Triaxial Compression ◽  
Small Strain ◽  
Empirical Formulas ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Proposed Model ◽  
Nonlinear Stress ◽  
London Clay ◽  
Strain Model

Soils have nonlinear stiffness and develops irrecoverable strains even at very small strain levels. Accurate modeling of stress-strain behaviour at various strain levels is very important for predicting the deformation of soils. Some existing stress-strain models are reviewed and evaluated firstly. And then a new simple non-linear stress-strain model is proposed. Four undetermined parameters involved in the proposed model can be obtained through maximum Young’s module, deformation module, and limit deviator stress and linearity index of soils that can be measured from experiment directly or calculated by empirical formulas indirectly. The effectiveness of the proposed stress-strain model is examined by predicting stress-strain curves measured in plane-strain compression test on Toyota sand and undrained triaxial compression test on London clay. The fitting results of the proposed model are in good agreement with experimental data, which verify the effectiveness of the model.

scholarly journals Parameter Selection in the Parameter Estimation of Grade Transitions in a Polyethylene Plant

2015 ◽  
Vol 3 (1) ◽  
pp. 1
Author(s):  
Niklas Andersson ◽  
Per-Ola Larsson ◽  
Johan Åkesson ◽  
Niclas Carlsson ◽  
Staffan Skålén ◽  
...  
Keyword(s):  
Parameter Estimation ◽  
Steady State ◽  
State Parameter ◽  
Parameter Selection ◽  
Selection Algorithm ◽  
Parameter Estimations ◽  
Dynamic Case ◽  
Nominal Parameter ◽  
Best Parameter ◽  
Parameter Values

A polyethylene plant at Borealis AB is modelled in the Modelica language and considered for parameter estimations at grade transitions. Parameters have been estimated for both the steady-state and the dynamic case using the JModelica.org platform, which offers tools for steady-state parameter estimation and supports simulation with parameter sensitivies. The model contains 31 candidate parameters, giving a huge amount of possible parameter combinations. The best parameter sets have been chosen using a parameter-selection algorithm that identified parameter sets with poor numerical properties. The parameter-selection algorithm reduces the number of parameter sets that is necessary to explore. The steady-state differs from the dynamic case with respect to parameter selection. Validations of the parameter estimations in the dynamic case show a significant reduction in an objective value used to evaluate the quality of the solution from that of the nominal reference, where the nominal parameter values are used.

scholarly journals Stress–Dilatancy Relationship of Erksak Sand under Drained Triaxial Compression

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 353
Author(s):  
Katarzyna Dołżyk-Szypcio
Keyword(s):  
Stress Ratio ◽  
Triaxial Compression ◽  
Stable Condition ◽  
Compression Tests ◽  
Ultimate State ◽  
Dense Sand ◽  
The One ◽  
Two Parameters ◽  
Relationship Of ◽  
Triaxial Compression Tests

Analyzing the results of triaxial compression tests under drained conditions for Erksak sand published in the literature, the stress–dilatancy relationships were described using the frictional state concept. At all phases of shearing, the linear stress ratio–plastic dilatancy relationship can be expressed by the critical frictional state angle and two parameters of the frictional state concept. At failure, dense sand exhibits purely frictional behavior (α = 0, β = 1) and the stress ratio–dilatancy relationship may be correctly described by the Rowe, Bolton, and frictional state concept relationships. Very loose Erksak sand sheared under drained triaxial compression at the ultimate state reaches a stable condition, but the reached stress ratio is significantly smaller than the one at a critical state.

scholarly journals The influence of particle breakage on stress-dilatancy relationship for granular soils

2019 ◽  
Vol 92 ◽  
pp. 09004 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Internal Energy ◽  
Stress Level ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Stress Path ◽  
State Theory ◽  
Particle Breakage ◽  
Compression Tests ◽  
Particle Crushing ◽  
Soil Gradation

The influence of particle breakage on soil behaviour is important from theoretical and practical perspectives. Particle breakage changes the internal energy in two ways. First, internal energy is consumed for particle crushing and second, the internal energy changes because of additional volumetric strain caused by particle crushing. These two effects may be quantified by use of Frictional State Theory. The analysed drained triaxial compression tests of Toyoura sand, gravel and Dog's Bay sand at different stress level and stress path revealed that the effect of particle breakage is a function of soil gradation, strength of soil grains, stress level and stress path.

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