scholarly journals Small-strain deformation behaviour of a clay at frozen and unfrozen states: A comparative study

2019 ◽  
Vol 92 ◽  
pp. 04001
Author(s):  
Satoshi Nishimura ◽  
Shota Okajima ◽  
Jinyuan Wang ◽  
Bhakta Raj Joshi
Keyword(s):  
Strain Rate ◽  
Axial Strain ◽  
Deformation Behaviour ◽  
Triaxial Compression ◽  
Small Strain ◽  
Small Scale ◽  
High Plasticity ◽  
Compression Tests ◽  
Small Strains ◽  
Displacement Sensors

The small-strain deformation behaviour of frozen high-plasticity clay, and the factors influencing it were investigated through parallel tests at frozen and unfrozen states. The first and second series involved temperature-controlled triaxial compression tests on unfrozen and frozen samples, respectively, with accurate strain measurement with local displacement sensors, fully calibrated for cold environment. The small-strain loading was conducted at different axial strain rates and temperatures. At pre-yield small strains in order of 0.001%, Young's modulus was independent of the strain rate, in a same manner as in unfrozen soils. The strain rate only affected the onset of small-scale yielding and the degradation of stiffness after that. The elastic strain range was greater at lower temperature, but the degree of stress-strain non-linearity seen at small strains remained on the whole similar between frozen and unfrozen states. An interesting feature of the frozen clay's stiffness, also confirmed by third test series adopting bender elements, is that it decreases when the soil is frozen from higher effective stress. A simple model was proposed to explain this feature.

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.

scholarly journals Deformation behaviour and strength of frozen sand

1980 ◽  
Vol 17 (1) ◽  
pp. 74-88 ◽  
Author(s):  
V. R. Parameswaran
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Deformation Behaviour ◽  
Unfrozen Water ◽  
Strain Rates ◽  
Linear Extrapolation ◽  
Compression Tests ◽  
Unconfined Compression ◽  
Ottawa Sand ◽  
Frozen Sand

Uniaxial unconfined compression tests were carried out on frozen saturated Ottawa sand containing about 20% by weight of water, at temperatures between −2 and − 15°C, and at strain rates varying between 10−7 and 10−2 s−1. The compressive strength and the initial tangent modulus increased with increasing strain rate and with decreasing temperature. At −2°C, values of strength and modulus were considerably lower than those predicted by linear extrapolation of the values observed at lower temperatures, on a log–log scale. This could be due to the presence of unfrozen water in the samples at −2°C.

scholarly journals The orientation dependence of the strength of ice single crystals

2000 ◽  
Vol 46 (152) ◽  
pp. 41-44 ◽  
Author(s):  
Y. L. Trickett ◽  
I. Baker ◽  
P. M. S. Pradhan
Keyword(s):  
Strain Rate ◽  
Single Crystals ◽  
Axial Strain ◽  
Constant Strain Rate ◽  
Peak Stress ◽  
Deformation Mode ◽  
Orientation Dependence ◽  
Compression Tests ◽  
Ice Flow ◽  
Critical Resolved Shear Stress

AbstractSingle crystals with a wide variety of orientations were cut from large pucks of laboratory-grown ice. Constant-strain-rate compression tests were performed on the crystals either at an axial strain rate of 1 × 10−5 s−1at –20°C or at axial strain rates from 1 × 10−6 s−1 to 1 × 10−4 s−1 at –10°C. In agreement with previous studies of ice flow, the compression tests showed a linearly rising stress with increasing strain, followed by a sharply declining stress after reaching a peak. With further strain, the sharp decline in stress slowed and the flow stress approached a plateau that was only weakly dependent on strain. For all crystallographic orientations, it was found that Schmid’s (critical resolved shear stress) law was obeyed by the peak stress. Slip lines clearly showed that basal slip was the deformation mode.

Small-strain behavior of frozen sand in triaxial compression

1995 ◽  
Vol 32 (3) ◽  
pp. 428-451 ◽  
Author(s):  
Glen R. Andersen ◽  
Christopher W. Swan ◽  
Charles C. Ladd ◽  
John T. Germaine
Keyword(s):  
High Pressure ◽  
Strain Rate ◽  
Yield Stress ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Stress Strain ◽  
Strain Behavior ◽  
Frozen Sand

The stress–strain behavior of frozen Manchester fine sand has been measured in a high-pressure low-temperature triaxial compression testing system developed for this purpose. This system incorporates DC servomotor technology, lubricated end platens, and on-specimen axial strain devices. A parametric study has investigated the effects of changes in strain rate, confining pressure, sand density, and temperature on behavior for very small strains (0.001%) to very large (> 20%) axial strains. This paper presents constitutive behavior for strain levels up to 1%. On-specimen axial strain measurements enabled the identification of a distinct upper yield stress (knee on the stress–strain curve) and a study of the behavior in this region with a degree of precision not previously reported in the literature. The Young's modulus is independent of strain rate and temperature, increases slightly with sand density in a manner consistent with Counto's model for composite materials, and decreases slightly with confining pressure. In contrast, the upper yield stress is independent of sand density, slightly dependent on confining pressure (considered a second order effect), but is strongly dependent on strain rate and temperature in a fashion similar to that for polycrystalline ice. Key words : frozen sand, high-pressure triaxial compression, strain rate, temperature, modulus, yield stress.

Behavior of a Sandy Silt Reinforced with Discontinuous Recycled Fiber Inclusions

2000 ◽  
Vol 1714 (1) ◽  
pp. 9-17 ◽  
Author(s):  
J. J. Murray ◽  
J. D. Frost ◽  
Y. Wang
Keyword(s):  
Shear Strength ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Value Added ◽  
Strength Loss ◽  
Dry Density ◽  
Compression Tests ◽  
Maximum Dry Density ◽  
Deformation Response ◽  
Sandy Silt

Laboratory compaction and triaxial compression tests were performed to assess the compaction characteristics and load deformation response of a sandy silt reinforced with randomly oriented recycled carpet fibers. Discrete, randomly distributed fiber inclusions significantly increase the peak shear strength, reduce the postpeak strength loss, increase the axial strain to failure, and, in some cases, change the stress-strain behavior from strain softening to strain hardening for a sandy silt. Fiber inclusions also impede the compaction process, causing a reduction in the maximum dry density of reinforced specimens with increasing fiber content. The strength losses associated with in-service saturation are significantly reduced with fiber reinforcement. It is suggested that large volumes of recycled waste fibers can be used as a value-added product to enhance the shear strength and load deformation response of soils.

scholarly journals Experimental Study on the Permeability of Weakly Cemented Rock under Different Stress States in Triaxial Compression Tests

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Gangwei Fan ◽  
Mingwei Chen ◽  
Dongsheng Zhang ◽  
Zhen Wang ◽  
Shizhong Zhang ◽  
...  
Keyword(s):  
Underground Mining ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Initial Permeability ◽  
Compression Tests ◽  
Mining Operations ◽  
Stress Strain ◽  
Loading And Unloading ◽  
Stress States

Mudstone and shaly coarse sandstone samples of Jurassic units in northwestern China were collected to study the seepage mechanism of weakly cemented rock affected by underground mining operations. Samples were studied using seepage experiments under triaxial compression considering two processes: complete stress-strain and postpeak loading and unloading. The results show that permeability variations closely correspond to deviatoric stress-axial strain during the process of complete stress-strain. The initial permeability is 7 times its minimum, contrasting with lesser differentials of initial, peak, and residual permeability. The magnitude of permeability ranges from 10−17 to 10−19 m2, representing a stable water-resisting property, and is 1 to 2 orders lower in mudstone than that in shaly coarse sandstone, indicating that the water-resisting property of the mudstone is much better than that of the shaly coarse sandstone. Permeability is negatively correlated with the confining pressure. In response to this pressure, the permeability change in mudstone is faster than that in shaly coarse sandstone during the process of postpeak loading and unloading. Weakly cemented rock has lower permeability according to the comparison with congeneric ordinary rocks. This distinction is more remarkable in terms of the initial permeability. Analyses based on scanning electron microscope (SEM) observations and mineral composition indicate that the samples are rich in clay minerals such as montmorillonite and kaolin, whose inherent properties of hydroexpansiveness and hydrosliming can be considered the dominant factors contributing to the seepage properties of weakly cemented rock with low permeability.

Comparison of the Dynamic Properties and Undrained Shear Strengths of Offshore Calcareous Sand and Artificially Cemented Sand

2003 ◽  
Author(s):  
Celestino Valle ◽  
Beatriz I. Camacho ◽  
Kenneth H. Stokoe ◽  
Alan F. Rauch
Keyword(s):  
Sodium Silicate ◽  
Dynamic Properties ◽  
Triaxial Compression ◽  
Calcareous Soils ◽  
Sodium Silicate Solution ◽  
Small Strain ◽  
Compression Tests ◽  
Calcareous Sand ◽  
Cemented Sand ◽  
Undrained Shear

Calcareous sand specimens were obtained from Campeche Bay in the southern Gulf of Mexico. The dynamic properties of these specimens were measured in resonant column and torsional shear (RCTS) tests, while the undrained shear strength was measured in unconsolidated-undrained (UU) triaxial compression tests. For weakly cemented, natural materials like this, it is difficult to obtain reliable properties from laboratory tests because sampling and handling of the soil specimens damages the particle cementation to an unknown degree. Artificially cemented specimens can be studied to better understand this problem. In this work, the strength and dynamic properties of artificially cemented sand were also measured using RCTS and UU tests. The artificially cemented specimens were formed by mixing uniform sand with a sodium silicate solution. The degree of cementation was varied by using different sodium silicate concentrations. This approach could be used to reproduce cemented test specimens in the laboratory with similar mechanical properties as cemented offshore soils. The results from this limited study show that the small-strain dynamic properties measured in the laboratory, and their variation with confining pressure, clearly identifies disturbance in the calcareous soils.

Undrained triaxial strength and stress–strain characteristics of a glacial till soil

1988 ◽  
Vol 25 (3) ◽  
pp. 428-439 ◽  
Author(s):  
J. H. Atkinson ◽  
J. A. Little
Keyword(s):  
Critical State ◽  
Soil Mechanics ◽  
Triaxial Compression ◽  
Practical Importance ◽  
Small Strain ◽  
Compression Tests ◽  
Triaxial Strength ◽  
Current State ◽  
Boulder Clay ◽  
Triaxial Compression Tests

Undrained triaxial compression tests were carried out on reconstituted and nominally undisturbed tubed samples of a lodgement till from the Vale of St. Albans in Hertfordshire, England. The soil is a matrix-dominant, chalky boulder clay of Anglian age with little discernable engineering fabric. Electron microscope observations showed the presence of crystalline calcite in tube samples.The test results were examined within the general framework of critical state soil mechanics using normalizing procedures to take account of the different states and stress histories of the samples. These analyses demonstrate the practical importance of accounting for the current state and stress history in the interpretation of soil test data.The present results form a self-consistent pattern of behaviour. Differences between reconstituted and tubed samples were found only at small strain and may be attributed to cementing in tubed samples, which is broken down during reconstitution and during relatively large straining in recompression and shearing. Key words: boulder clay, cemented soil, critical state, shear strength, soil mechanics, stiffness, till, triaxial test.

scholarly journals Effect of Compaction Banding on the Hydraulic Properties of Porous Rock: Part I—Experimental Investigation

2021 ◽  
Author(s):  
Julia Leuthold ◽  
Eleni Gerolymatou ◽  
Maximiliano R. Vergara ◽  
Theodoros Triantafyllidis
Keyword(s):  
Hydraulic Properties ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Shear Bands ◽  
Experimental Investigations ◽  
Porous Rocks ◽  
Compression Tests ◽  
Compaction Bands ◽  
Maximum Permeability ◽  
Triaxial Compression Tests

AbstractThe mechanical behavior and the influence of compaction banding on the hydraulic properties in soft porous rocks were studied. The tested rock was Calcarenite Tuffeau de Maastricht. In the frame of experimental investigations, triaxial and oedometric tests were conducted under dry and drained conditions. The results demonstrated that the rock is forming discrete compaction bands under high confining stresses and steep angle shear bands under low confining stresses. Permeability measurements during the oedometric and triaxial compression tests under drained conditions demonstrated that the axial permeability decreases with increasing axial strain. The maximum permeability decrease was three orders of magnitude for 40% of axial strain.

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