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.

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.

Effect of particle size and strain conditions on the strength of crushed basalt

1983 ◽  
Vol 20 (4) ◽  
pp. 706-717 ◽  
Author(s):  
Mosaid Al-Hussaini
Keyword(s):  
Particle Size ◽  
Stress Level ◽  
Level Density ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Strain Diagram ◽  
Compression Tests ◽  
Cohesionless Soils ◽  
Lower Shear

This paper describes the results of an investigation carried out to study the influence of particle size, stress level, density, method of consolidation, and strain conditions on the strength and compressibility of crushed basalt. All specimens were prepared at medium or high density, consolidated isotropically or under K0 consolidation, and sheared under effective confining pressure ranging from 443 to 2297 kPa. The material used in the test program had a straight line grain size distribution with maximum particle size ranges from 0.63 to 76.2 mm and minimum particle size equivalent to No. 30 U.S. standard sieve size:The tests indicated that an increase in the particle size (i.e., gradation) increases the strength and decreases the axial and the volumetric strain at failure. The study indicated further that the crushed basalt under triaxial compression has a lower shear strength than when sheared under plane strain conditions. Particles crushed were significantly influenced by the stress level and gradation and to a lesser degree by density of material. Keywords: cohesionless soils, density (mass/volume), shear tests, stress–strain diagram, compression tests, rockfill dams.

scholarly journals Semi-empirical elastic–thermoviscoplastic model for clay

2016 ◽  
Vol 53 (10) ◽  
pp. 1583-1599 ◽  
Author(s):  
David Kurz ◽  
Jitendra Sharma ◽  
Marolo Alfaro ◽  
Jim Graham
Keyword(s):  
Stress Level ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Compression Tests ◽  
One Dimensional ◽  
Load Duration ◽  
Compression Creep ◽  
Overconsolidated Clays ◽  
Semi Empirical ◽  
Triaxial Compression Tests

Clays exhibit creep in compression and shear. In one-dimensional compression, creep is commonly known as “secondary compression” even though it is also a significant component of deformations resulting from shear straining. It reflects viscous behaviour in clays and therefore depends on load duration, stress level, the ratio of shear stress to compression stress, strain rate, and temperature. Research described in the paper partitions strains into elastic (recoverable) and plastic (nonrecoverable) components. The plastic component includes viscous strains defined by a creep rate coefficient ψ that varies with plasticity index and temperature (T), but not with stress level or overconsolidation ratio (OCR). Earlier elastic–viscoplastic (EVP) models have been modified so that ψ = ψ(T) in a new elastic–thermoviscoplastic (ETVP) model. The paper provides a sensitivity analysis of simulated results from undrained (CIŪ) triaxial compression tests for normally consolidated and lightly overconsolidated clays. Axial strain rates range from 0.15%/day to 15%/day, and temperatures from 28 to 100 °C.

Effect of ageing on stiffness of very loose sand

2002 ◽  
Vol 39 (1) ◽  
pp. 149-156 ◽  
Author(s):  
J A Howie ◽  
T Shozen ◽  
Y P Vaid
Keyword(s):  
Soil Structure ◽  
Stress Ratio ◽  
Triaxial Compression ◽  
High Stress ◽  
Volumetric Strain ◽  
Compression Tests ◽  
Close Attention ◽  
Stress Ratios ◽  
Creep Modulus ◽  
Triaxial Compression Tests

The paper presents the results of laboratory triaxial compression tests to study the stiffness of very loose Fraser River sands. The stiffness has been shown to be very dependent on the time of confinement prior to shearing and the stress ratio at which the sample is aged. Higher stress ratios resulted in very low initial moduli with no ageing, but the moduli increased by several hundred percent during the first 1000 min of ageing. For ageing at a stress ratio of 1.0 (i.e., isotropic ageing), the initial moduli were higher than those for ageing at high stress ratios, but the stiffness increased by only about 60% during the first 1000 min of ageing. The rate of stiffness increase was approximately linear with the logarithm of time up to ageing times of 10 000 min (>1 week). Ageing at any stress ratio resulted in reduced contractive volumetric strain during subsequent shearing, reflecting a change in soil structure during ageing. The dεv /dεa ratio under triaxial compression loading decreased as the ageing stress ratio increased. The results suggest that close attention must be paid to the age of laboratory samples prepared to study the stress–strain response of sands at strains up to about 0.1%, particularly in studies on loose sand.Key words: sands, ageing, creep, modulus.

True Shear Parameters of Saturated Clays

1973 ◽  
Vol 10 (4) ◽  
pp. 652-663
Author(s):  
A. Sridharan ◽  
S. Narasimha Rao
Keyword(s):  
Stress Level ◽  
Pore Water Pressure ◽  
Initial Conditions ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Strength Parameters ◽  
Test Procedures ◽  
Stress History ◽  
Triaxial Compression Tests

Ever since Hvorslev proposed a failure criterion incorporating intrinsic parameters, several test procedures have come into practice to determine these ‘true’ strength parameters. Several consolidated undrained triaxial compression tests with pore water pressure measurement were conducted on both montmorillonite and kaolinite clays and the results were analyzed using different existing methods. All the methods through which the data were analyzed fail to assign any unique true strength parameters. Even a particular method yields different values depending upon the initial conditions (stress history, water content) of the sample and stress level during testing. It has been reasoned that these variations are due to the probable differences in fabric between the samples which are involved in various methods. There seems to be a unique linear relationship between tan [Formula: see text] and Cc/pe irrespective of the sample state, stress level, and stress history in both undisturbed and remolded conditions for all the procedures adopted.

scholarly journals Mechanical Behavior and Permeability Evolution of Coal under Different Mining-Induced Stress Conditions and Gas Pressures

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2677
Author(s):  
Zetian Zhang ◽  
Ru Zhang ◽  
Zhiguo Cao ◽  
Mingzhong Gao ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Triaxial Compression ◽  
Volumetric Strain ◽  
Coal Mass ◽  
Gas Pressure ◽  
Stress Conditions ◽  
Permeability Evolution ◽  
Compression Tests ◽  
Induced Stress ◽  
Conventional Triaxial Compression ◽  
Gas Pressures

The gas permeability and mechanical properties of coal, which are seriously influenced by mining-induced stress evolution and gas pressure conditions, are key issues in coal mining and enhanced coalbed methane recovery. To obtain a comprehensive understanding of the effects of mining-induced stress conditions and gas pressures on the mechanical behavior and permeability evolution of coal, a series of mining-induced stress unloading experiments at different gas pressures were conducted. The test results are compared with the results of conventional triaxial compression tests also conducted at different gas pressures, and the different mechanisms between these two methods were theoretically analyzed. The test results show that under the same mining-induced stress conditions, the strength of the coal mass decreases with increasing gas pressure, while the absolute deformation of the coal mass increases. Under real mining-induced stress conditions, the volumetric strain of the coal mass remains negative, which means that the volume of the coal mass continues to increase. The volumetric strain corresponding to the peak stress of the coal mass increases with gas pressure in the same mining layout simulation. However, in conventional triaxial compression tests, the coal mass volume continues to decrease and in a compressional state, and there is no obvious deformation stage that occurs during the mining-induced stress unloading tests. The theoretical and experimental analyses show that mining-induced stress unloading and gas pressure changes greatly impact the deformation, failure mechanism and permeability enhancement of coal.

Initiation of static liquefaction and the role of K0 consolidation

2005 ◽  
Vol 42 (3) ◽  
pp. 892-906 ◽  
Author(s):  
A B Fourie ◽  
L Tshabalala
Keyword(s):  
Effective Stress ◽  
Triaxial Compression ◽  
Stress Path ◽  
Compression Tests ◽  
Predicting Factors ◽  
Static Liquefaction ◽  
Peak Shear Stress ◽  
Material State ◽  
Undrained Loading ◽  
Gold Tailings

The potential for static liquefaction of hydraulically placed sands and silts is now well recognised. A particular category of this type of operation, tailings disposal facilities constructed using the upstream method, has come under increased scrutiny due to the large number of failures of these structures. Although the conditions that render a particular deposit susceptible to potential liquefaction are now well known, being a combination of void ratio and mean effective stress that places the material state above its steady state value, the same cannot be said about our ability to predict the stresses at which liquefaction will be initiated. The concept of a collapse surface, derived from the locus of peak shear stress values from undrained compression tests on isotropically consolidated specimens, attempts to provide a method for predicting the onset of liquefaction. As confirmed in this paper, however, application of the collapse surface concept to actual tailings dam facilities results in factors of safety based on an effective stress approach that are significantly less than unity for facilities that have not failed. On the other hand, shear strength values derived from ultimate state conditions are unconservative, predicting factors of safety significantly in excess of unity for facilities that have failed. A comparison of monotonic undrained triaxial compression tests on both isotropically- and K0-consolidated specimens of gold tailings suggests that the resolution to this dilemma lies in the recognition that a kinematic yield surface, which is a function of the consolidation stress path followed, develops in stress space. The collapse surface derived from undrained loading of K0-consolidated loose specimens is shown to provide a greatly improved capacity for predicting the onset of liquefaction under undrained loading conditions.Key words: static liquefaction, tailings, collapse surface, anisotropic.

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.

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