Small-Strain Stiffness of Unsaturated Soils Using a Suction-Controlled Resonant Column Device with Bender Elements

2011 ◽  
Author(s):  
L. R. Hoyos ◽  
E. A. Suescun ◽  
A. J. Puppala
Keyword(s):  
Unsaturated Soils ◽  
Small Strain ◽  
Resonant Column ◽  
Bender Elements ◽  
Small Strain Stiffness ◽  
Resonant Column Device

Small strain stiffness for granite residual soil: effect of stress ratio

2021 ◽  
Author(s):  
Xianwei Zhang ◽  
Xinyu Liu ◽  
Lingwei Kong ◽  
Gang Wang ◽  
Cheng Chen
Keyword(s):  
Stress Ratio ◽  
Small Strain ◽  
Residual Soil ◽  
Resonant Column ◽  
Residual Soils ◽  
Column Tests ◽  
Small Strain Stiffness ◽  
Deviator Stress ◽  
Granite Residual Soil ◽  
Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

scholarly journals The small strain stiffness from bender elements tests for clayey soils

2018 ◽  
Vol 50 (4) ◽  
pp. 353-371
Author(s):  
Katarzyna Markowska-Lech ◽  
Wojciech Sas ◽  
Mariusz Lech ◽  
Katarzyna Gabryś ◽  
Alojzy Szymański
Keyword(s):  
Field Tests ◽  
Small Strain ◽  
Test Results ◽  
Bender Elements ◽  
Element Analysis ◽  
Factors Affecting ◽  
Small Strain Stiffness ◽  
Seismic Wave Velocities ◽  
Case Basis ◽  
Hardening Soil Model

Abstract The shear modulus of soils at small strain (G0) is one of the input parameters in a finite element analysis with the hardening soil model with small strain stiffness, required in the advanced numerical analyses of geotechnical engineering problems. The small strain stiffness can be determined based on the seismic wave velocities measured in the laboratory and field tests, but the interpretation of test results is still under discussion because of many different factors affecting the measurements of the wave travel time. The recommendations and proposed solutions found in the literature are helpful as a guide, but ought to be adopted with a certain measure of care and caution on a case-by-case basis. The equipment, procedures, tests results and interpretation analyses of bender elements (BE) tests performed on natural overconsolidated cohesive soils are presented.

Effects of wetting–drying and stress ratio on anisotropic stiffness of an unsaturated soil at very small strains

2009 ◽  
Vol 46 (9) ◽  
pp. 1062-1076 ◽  
Author(s):  
C. W.W. Ng ◽  
J. Xu ◽  
S. Y. Yung
Keyword(s):  
Unsaturated Soils ◽  
Stress Ratio ◽  
Shear Stiffness ◽  
Small Strain ◽  
Matric Suction ◽  
Bender Elements ◽  
Shear Moduli ◽  
Small Strains ◽  
Stiffness Anisotropy ◽  
Stress Dependent

The very small strain shear modulus of soil, G0, is affected by many factors including soil properties, current stress state, stress history, and matric suction. Very little research has been conducted on anisotropic shear moduli of unsaturated soils. In this study, the effects of wetting–drying and stress ratio on anisotropic shear stiffness of an unsaturated completely decomposed tuff (CDT) at very small strains have been investigated using a modified triaxial testing system equipped with three pairs of bender elements. During drying and wetting tests, the measured very small strain shear moduli increased in a nonlinear fashion, but at a reduced rate as the matric suction increased. Similar to the stress-dependent soil-water characteristic curves (SDSWCCs), there was hysteresis between the drying and wetting curves showing the variations in shear moduli with matric suction. Variation in suction on the specimens under isotropic conditions produced changes in stiffness anisotropy (expressed as G0(hh)/G0(hv)) together with anisotropic strains. In shearing tests at constant suctions, significant stress-induced stiffness anisotropy was observed due to a change in the stress ratio. While shearing at a constant stress ratio, G0(hh)/G0(hv) appeared to be constant.

scholarly journals Small Strain Stiffness of Artificially Cemented Soft Clay: Modelling the Effect of Structure Degradation

2019 ◽  
Vol 92 ◽  
pp. 11009
Author(s):  
Qasim Khan ◽  
Yannick Ng ◽  
Taeseo Ku
Keyword(s):  
Soft Clay ◽  
Small Strain ◽  
Kaolin Clay ◽  
Bender Elements ◽  
Confining Stress ◽  
Soft Clays ◽  
Small Strain Stiffness ◽  
Structure Degradation ◽  
Before And After ◽  
Vertically Aligned

This paper presents a study on the evolution of small strain stiffness (Gmax) along vertical and horizontal directions for lightly cemented clay. Soft clays have historically been a subject for studying the evolution of stiffness anisotropy under varying loading conditions. These studies have focused on stress history (overconsolidation) effects as well. However, for lightly cemented clays, such studies are limited and their main scope has primarily been on the evolution of vertically aligned stiffness (GVH) at varying effective confining stresses. This study investigates the effect of isotropic loading on uncemented and lightly cemented kaolin clay. Kaolin clay mixed with 10% cement is used in this study. Stiffness measurements have been conducted using bender elements for obtaining GVH and GHH hence resulting in the measurement of vertical and horizontal stiffness values respectively. By comparing the behaviour of both samples, the influence of bonding and fabric due to cementation on the evolution of stiffness and anisotropy is studied. In order to characterize the behavior of structure in cemented soil with confining stress, a modelling equation is applied for the cemented sample to predict the variation of Gmax before and after yielding.

Effects of stress paths on the small-strain stiffness of completely decomposed granite

2005 ◽  
Vol 42 (4) ◽  
pp. 1200-1211 ◽  
Author(s):  
Y. Wang ◽  
C WW Ng
Keyword(s):  
Shear Strain ◽  
Shear Stiffness ◽  
Stress Path ◽  
Small Strain ◽  
Bender Elements ◽  
Small Strain Stiffness ◽  
Small Strains ◽  
Average Shear ◽  
Decomposed Granite ◽  
Completely Decomposed Granite

Research on the small-strain (0.001%–1%) characteristics of sedimentary soils and sands has advanced to the stage where it has been utilized in engineering analysis and design for some time. Despite the progress, the stiffness characteristics of weathered materials such as completely decomposed granite (CDG) at small strains have still attracted relatively little research attention. This paper describes a systematic laboratory investigation of the small-strain characteristics of intact CDG subjected to various triaxial stress paths, including drained compression and extension tests. The small-strain stiffness was measured using bender elements and internal local transducers. Measurements from bender elements illustrate that the elastic shear modulus of CDG increases as the mean effective stress increases and the void ratio decreases. Significant nonlinear shear stiffness – shear strain and bulk modulus – volumetric strain relationships were observed. At 0.01% shear strain, the measured average shear stiffness obtained from the extension tests was about 60% higher than that from the compression tests. The average shear stiffness for the tests with a 90° rotation of the stress path was about 50%–70% higher than that of tests without a change in the direction of the stress path after saturation.Key words: completely decomposed granite, nonlinearity, small strains, extension, compression, recent stress history.

Small to intermediate strain properties of fly ashes with various carbon and biomass contents

2016 ◽  
Vol 53 (1) ◽  
pp. 35-48 ◽  
Author(s):  
H. Choo ◽  
N.N. Yeboah ◽  
S.E. Burns
Keyword(s):  
Void Ratio ◽  
Small Strain ◽  
Interparticle Contact ◽  
Bender Elements ◽  
Fly Ashes ◽  
Small Strain Stiffness ◽  
Initial Void Ratio ◽  
Constrained Modulus ◽  
Stiffness Anisotropy ◽  
Biomass Particles

High-carbon-content fly ashes with biomass particles are typically landfilled in accordance with the ASTM C618 regulation. To quantify their geotechnical properties relating to storage and disposal, this study evaluates the small to intermediate strain properties of fly ashes with various carbon and biomass contents. Tested fly ashes had carbon contents ranging from 1.1% to 9.6%, resulting from co-combusting coal with biomass (biomass contents ranging from 0% to 8.2% by weight). The small-strain stiffness and intermediate-strain constrained modulus were evaluated using consolidation tests performed in a modified oedometer cell equipped with bender elements. It was found that initial void ratio governed the compressibility (or constrained modulus) of fly ashes, and with an increase in carbon and biomass contents, the small-strain stiffness of fly ashes decreased due to the decrease in number of direct contacts between microspheres. In addition, the interfine void ratio, ef, was employed instead of global void ratio to capture the alteration of interparticle contact or interparticle coordination between microspheres, due to the change in carbon and biomass contents. Finally, the stiffness in an overconsolidated state and the stiffness anisotropy of fly ashes were evaluated.

Effects of net stress and suction history on the small strain stiffness of a compacted clayey silt

2007 ◽  
Vol 44 (4) ◽  
pp. 447-462 ◽  
Author(s):  
Roberto Vassallo ◽  
Claudio Mancuso ◽  
Filippo Vinale
Keyword(s):  
Shear Stiffness ◽  
Small Strain ◽  
Resonant Column ◽  
Stress History ◽  
Small Strain Stiffness ◽  
Maximum Value ◽  
Clayey Silt ◽  
Triaxial Cell ◽  
The Mean ◽  
Suction History

An experimental study was carried out to investigate the effects of the mean net stress and suction history on the initial shear stiffness, G0, of a compacted clayey silt. Isotropic tests were performed using two suction-controlled devices, a triaxial cell and a resonant column torsional shear (RCTS) cell, so as to investigate the volumetric behaviour of this material. As for saturated soils, one can expect to find a strong correlation among stress history, volumetric state, and G0. Initial shear stiffness was measured almost continuously along various isotropic stress paths, including compressions and drying–wetting single stages or cycles, by using the RCTS cell. The collected data demonstrate a strong dependency of G0 on mean net stress (p – ua) and suction (ua – uw). Cycles of suction, in particular increasing suction beyond the past maximum value, induce significant accumulation of irreversible strains and increase of stiffness, confirming that G0 is not univocally related to the stress state (p – ua, ua – uw).Key words: unsaturated, compacted, small strain, stiffness, volumetric behaviour, stress history.

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