Static and dynamic properties of a lightly cemented silicate-grouted sand

2012 ◽  
Vol 49 (10) ◽  
pp. 1117-1133 ◽  
Author(s):  
Daniela Porcino ◽  
Vincenzo Marcianò ◽  
Raffaella Granata
Keyword(s):  
Dynamic Properties ◽  
Triaxial Compression ◽  
High Stress ◽  
Small Strain ◽  
Compression Tests ◽  
Bender Elements ◽  
Liquefaction Resistance ◽  
Cyclic Shear ◽  
Loose Medium ◽  
Triaxial Compression Tests

This paper describes the results of an experimental investigation on the behaviour of a lightly grouted loose medium sand under both monotonic and cyclic loading. The experimental programme in the present study was carried out on both untreated and treated sand specimens stabilized with a silica-based grout, and comprises isotropic triaxial compression tests equipped with bender elements, drained triaxial monotonic shearing tests, and undrained cyclic tests in a simple shear (SS) apparatus. The results highlight that the weak cementation level induced by chemical treatment was sufficient to moderately increase small-strain stiffness and stress–dilatancy of the grouted sand during drained monotonic shear. A small cohesion intercept was observed in the analyzed failure envelope, while cyclic liquefaction resistance exhibited a much more significant increase, with a different pattern of behaviour between low and high stress levels. Finally, undrained cyclic SS test results evidenced that silicate grout employed in this research improves undrained cyclic shear strength in a manner similar to densification of the same material up to a density index of approximately 75%.

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.

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.

A Simple Unconsolidated Undrained Triaxial Compression Test Emulator

2015 ◽  
Vol 771 ◽  
pp. 104-107
Author(s):  
Riska Ekawita ◽  
Hasbullah Nawir ◽  
Suprijadi ◽  
Khairurrijal
Keyword(s):  
Triaxial Compression ◽  
Measurement Data ◽  
Radial Strain ◽  
Compression Tests ◽  
Viscous Effects ◽  
Axial Pressure ◽  
Strain Stress ◽  
The University ◽  
And Storage ◽  
Triaxial Compression Tests

An unconsolidated undrained (UU) test is one type of triaxial compression tests based on the nature of loading and drainage conditions. In order to imitate the UU triaxial compression tests, a UU triaxial emulator with a graphical user interface (GUI) was developed. It has 5 deformation sensors (4 radial deformations and one vertical deformation) and one axial pressure sensor. In addition, other inputs of the emulator are the cell pressure, the height of sample, and the diameter of sample, which are provided by the user. The emulator also facilitates the analysis and storage of measurement data. Deformation data fed to the emulator were obtained from real measurements [H. Nawir, Viscous effects on yielding characteristics of sand in triaxial compression, Dissertation, Civil Eng. Dept., The University of Tokyo, 2002]. Using the measurement data, the stress vs radial strain, stress vs vertical strain, and Mohr-Coulomb circle curves were obtained and displayed by the emulator.

Strength envelope of granular soil stabilized by multi-axial geogrid in large triaxial tests

2020 ◽  
Vol 57 (3) ◽  
pp. 448-452 ◽  
Author(s):  
A.S. Lees ◽  
J. Clausen
Keyword(s):  
Triaxial Compression ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Failure Envelope ◽  
Element Analysis ◽  
Linear Elastic ◽  
Perfectly Plastic ◽  
Elastic Perfectly Plastic ◽  
Triaxial Compression Tests ◽  
Properties Of Soil

Conventional methods of characterizing the mechanical properties of soil and geogrid separately are not suited to multi-axial stabilizing geogrid that depends critically on the interaction between soil particles and geogrid. This has been overcome by testing the soil and geogrid product together as one composite material in large specimen triaxial compression tests and fitting a nonlinear failure envelope to the peak failure states. As such, the performance of stabilizing, multi-axial geogrid can be characterized in a measurable way. The failure envelope was adopted in a linear elastic – perfectly plastic constitutive model and implemented into finite element analysis, incorporating a linear variation of enhanced strength with distance from the geogrid plane. This was shown to produce reasonably accurate simulations of triaxial compression tests of both stabilized and nonstabilized specimens at all the confining stresses tested with one set of input parameters for the failure envelope and its variation with distance from the geogrid plane.

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.

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