scholarly journals Stress-dependent behavior of saturated clay

2012 ◽  
Vol 49 (8) ◽  
pp. 907-916 ◽  
Author(s):  
Naeem O. Abdulhadi ◽  
John T. Germaine ◽  
Andrew J. Whittle
Keyword(s):  
Stress Level ◽  
High Pressures ◽  
Large Strain ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Peak Strain ◽  
Compression Tests ◽  
Stress Strain ◽  
Stress Dependent ◽  
Undrained Shear

A program of K0-consolidated undrained triaxial compression tests has been performed to investigate the effects of consolidation stress level on the compression and shear behavior of resedimented Boston blue clay (RBBC). Specimens were consolidated to maximum vertical effective stresses in the range 0.15–10 MPa and tested at three overconsolidation ratios (OCR): 1, 2, and 4. The results show that the virgin compression curves are essentially linear in e–log[Formula: see text] space over the consolidation stress range. However, the normally consolidated K0 stress ratio increases with the level of consolidation stress. The stress–strain–strength properties measured in undrained shear are significantly affected by the consolidation stress level at each OCR and show indications of non-normalizable behavior. At high pressures, the undrained shear stress–strain behavior becomes more ductile, requiring larger strains to mobilize peak resistance and exhibiting less post-peak strain-softening. The undrained strength ratio (su/[Formula: see text]) is not uniquely controlled by OCR as suggested by the SHANSEP equation, but consistently decreases with increasing consolidation effective stress. There is notable reduction in the stiffness ratio (Eu/[Formula: see text]) with stress level, and significant decrease in the large-strain friction angle.

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.

scholarly journals Shear Characteristics of Cement-Stabilized Sand Reinforced with Waste Polyester Fiber Fabric Blocks

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiangfeng Lv ◽  
Hongyuan Zhou
Keyword(s):  
Low Cost ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Polyester Fiber ◽  
Peak Strain ◽  
Compression Tests ◽  
Initial Stiffness ◽  
Cemented Sand ◽  
Aspect Ratios ◽  
Fiber Fabric

The present paper is devoted to investigate the effects of waste polyester fiber fabric blocks on the strength and mechanical behavior of cemented sand. In the investigation, samples were prepared at four different percentages of waste polyester fiber fabric block content (0.0%, 0.5%, 1.0%, and 1.5% by weight of soil) and two different aspect ratios (2 : 1 and 3 : 1), and conventional triaxial compression tests were carried out after the curing period. The test results indicated that the addition of fibers increased peak and residual shear strengths of cemented sand and changed its brittle behavior to a more ductile one. As the fabric block content increased, the brittleness index and initial stiffness decreased, and the peak strain and internal friction angle increased. The optimal combination of the content and aspect ratio was determined to be 0.5% and 3 : 1. The integration of the fabric blocks with the cemented sand matrix was analyzed by using the scanning electron microscopy (SEM). It is found that the reinforcement effect is related to the bond strength and friction at the interface. The micromechanical properties of the fiber/matrix interface were influenced by the undulations between the fabric block components. In summary, this study presented a low-cost and environment-friendly method for reinforcing cement-stabilized sand.

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.

Post-Peak Behaviour of Sensitive Clays in Undrained Shear

1968 ◽  
Vol 5 (2) ◽  
pp. 59-68 ◽  
Author(s):  
B Ladanyi ◽  
J P Morin ◽  
C Pelchat
Keyword(s):  
Shear Strength ◽  
Indirect Method ◽  
Peak Stress ◽  
Large Strains ◽  
Peak Strain ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Structural Breakdown ◽  
Undrained Shear

The post-peak stress-strain behaviour in undrained shear of three different clays has been investigated by using an indirect method. This method, which is in principle similar to that used by Kallstenius (1963), consists in first compressing a clay specimen to a given post-peak strain between two parallel platens and subsequently determining its current remoulded strength by the laboratory vane method. By a repeated compression procedure, axial strains of up to 200 per cent have been attained. As the three clays tested differed widely in sensitivity, a comparison of their post-peak behaviour made clearly apparent the effect of structural breakdown on the reserve shear strength at large strains.

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 Relation between the Friction Angle of Sand at Triaxial Compression and Triaxial Extension and Plane Strain Conditions

Geosciences ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 29 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Plane Strain ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Deformation Mode ◽  
Friction Angle ◽  
Failure Criteria ◽  
Compression Tests ◽  
Laboratory Test Results ◽  
Experimental Findings ◽  
Triaxial Extension

The strength of sand is usually characterized by the maximum value of the secant friction angle. The friction angle is a function of deformation mode, density, and stress level and is strongly correlated with dilatancy at failure. Most often, the friction angle is evaluated from results of conventional compression tests, and correlation between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions is a vital problem of soil mechanics. These correlations can be obtained from laboratory test results. The failure criteria for sand presented in literature also give the possibility of finding correlations between friction angles for different deformation modes. The general stress-dilatancy relationship obtained from the frictional state concept, with some additional assumptions, gives the possibility of finding theoretical relationships between the friction angle of sand at triaxial compression and triaxial extension and plane strain conditions. The theoretically obtained relationships presented in the paper are fully consistent with theoretical and experimental findings of soil mechanics.

Influence of Water Contents on Shear Strength of Rammed Earth Wall of Earth-Building

2011 ◽  
Vol 382 ◽  
pp. 172-175
Author(s):  
Ren Wei Wu ◽  
Xing Qian Peng ◽  
Li Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Friction Angle ◽  
World Heritage Site ◽  
Rammed Earth ◽  
Compression Tests ◽  
Rammed Earth Wall ◽  
Influence Of Water ◽  
Water Contents

As the "Fujian earth-building" have been inscribed by UNESCO in 2008 as World Heritage Site, attentions of protection about the "Fujian earth-building" has getting more and more. This article takes samples of a rammed-earth wall from Yongding earth-buildings and determines the shear strength of the samples with different water content through triaxial compression tests. The influence on shear strength of water content of rammed-earth samples is analyzed. Test results show that the shear strength of rammed-earth has much to do with the water content of the soil, the greater the water content is，the smaller the shear strength is. With water content increasing, cohesion and internal friction angle of rammed-earth were decreases, and its changing trend is of marked characteristic of stage. When water contents of rammed-earth is under some value, its cohesion changes in small ranges; when water contents of rammed-earth is over the value, its cohesion decreases with water content increasing.

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 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 Interpretation of undrained shear strength observed in confined triaxial compression tests on compacted clay

2021 ◽  
Author(s):  
Chee K. Wong ◽  
Martin Lun ◽  
Ron C.K. Wong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soil ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Undrained Shear Strength ◽  
Compacted Clay ◽  
Compression Tests ◽  
Basic Model ◽  
Triaxial Compression Tests ◽  
Undrained Shear

This paper presents an interpretation technique to quantify the effects of compaction state and matric suction on the undrained shear strength of compacted clay under confined undrained triaxial compression. This novel technique is based on the mathematical frameworks of SHANSEP (Stress History and Normalized Soil Engineering Property) method for saturated soil and BBM (Barcelona Basic model) for unsaturated soil. Test data of compacted Calgary till were analyzed and interpreted using the proposed technique. The interpretation technique is very useful in delineating the relative impacts of the factors on the behavioral trends in measured undrained shear strength. It was found that in addition to the initial compacted void ratio and suction, soil structure and failure mode exert significant influence on the undrained shear strength of compacted clay. This technique is attractive to engineering practitioners because the confined undrained compression tests (with no pore air and water pressure measurement) are much simpler and less time consuming compared to rigorous laboratory tests on unsaturated soil.

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