Small strain behavior of a silty sand in controlled-suction resonant column – torsional shear tests

2002 ◽  
Vol 39 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Claudio Mancuso ◽  
Roberto Vassallo ◽  
Anna d'Onofrio
Keyword(s):  
Shear Stiffness ◽  
Small Strain ◽  
Bulk Water ◽  
Silty Sand ◽  
Resonant Column ◽  
Soil Behavior ◽  
Soil Response ◽  
Strain Behavior ◽  
Torsional Shear ◽  
Constant Suction

An experimental study has been carried out using a new resonant column – torsional shear cell to investigate the small strain behavior of an unsaturated compacted silty sand. The device, recently developed at the Dipartimento di Ingegneria Geotecnica di Napoli (Italy), is fitted for controlled-suction testing using the axis-translation technique. Both optimum and wet of optimum compacted specimens have been tested to analyze the effects of suction and fabric on soil behavior. Shear stiffness measurements have been taken during constant-suction tests. Collected data indicate an S-shaped initial shear stiffness versus suction variation, which can be explained considering the progressive change from a bulk-water regulated soil response to a menisci-water regulated soil response. A model is proposed to account for the observed trend. Results highlight significant effects of suction and fabric on soil behavior.Key words: compacted soil, small strain behavior, shear stiffness, suction, soil fabric.

Small-strain stiffness of Zenoz kaolin in unsaturated conditions

2012 ◽  
Vol 49 (3) ◽  
pp. 311-322 ◽  
Author(s):  
Mahnoosh Biglari ◽  
Anna d’Onofrio ◽  
Claudio Mancuso ◽  
Mohammad Kazem Jafari ◽  
Ali Shafiee ◽  
...  
Keyword(s):  
Shear Stiffness ◽  
Stress Path ◽  
Small Strain ◽  
Complex Stress ◽  
Resonant Column ◽  
Wetting And Drying ◽  
Isotropic Compression ◽  
Remarkable Effect ◽  
Constant Suction

An experimental study has been carried out to investigate the effects of isotropic compression, wetting, and drying on the initial shear stiffness of Zenoz kaolin, an unsaturated lean clay, both in normally consolidated and overconsolidated conditions. The proposed study was conducted using fixed–free resonant column – torsional shear (RCTS). Specimens were compacted using the undercompaction technique. Initial shear stiffness was measured almost continuously along complex stress paths including (i) an initial equalization stage to a suction value of 0, 50, 150, and 300 kPa; (ii) an isotropic compression stage at constant suction, up to a net stress high enough to move the loading collapse line; (iii) an isotropic unloading stage at constant suction; (iv) a wetting and (or) drying path. The mentioned stress path allowed elimination or determination of the overconsolidation effect on the initial shear stiffness measured. The behavior observed is qualitatively similar to that of saturated soil, while wetting data clearly indicate that G0 depends significantly on volumetric behavior. In normally consolidated samples where wetting is accompanied by collapse, reduction in suction has no remarkable effect on G0. Conversely, in overconsolidated samples G0 reduces significantly as suction decreases.

Measurement of small-strain shear modulus Gmax of dry and saturated sands by bender element, resonant column, and torsional shear tests

2008 ◽  
Vol 45 (10) ◽  
pp. 1426-1438 ◽  
Author(s):  
Jun-Ung Youn ◽  
Yun-Wook Choo ◽  
Dong-Soo Kim
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Shear Wave Velocity ◽  
Small Strain ◽  
Resonant Column ◽  
Test Results ◽  
Bender Element ◽  
Small Strain Shear Modulus ◽  
Torsional Shear ◽  
Saturated Sands

The bender element method is an experimental technique used to determine the small-strain shear modulus (Gmax) of a soil by measuring the velocity of shear wave propagation through a sample. Bender elements have been applied as versatile transducers to measure the Gmax of wet and dry soils in various laboratory apparatuses. However, certain aspects of the bender element method have yet to be clearly specified because of uncertainties in determining travel time. In this paper, the bender element (BE), resonant column (RC), and torsional shear (TS) tests were performed on the same specimens using the modified Stokoe-type RC and TS testing equipment. Two clean sands, Toyoura and silica sands, were tested at various densities and mean effective stresses under dry and saturated conditions. Based on the test results, methods of determining travel time in BE tests were evaluated by comparing the results of RC, TS, and BE tests. Also, methods to evaluate Gmax of saturated sands from the shear-wave velocity (Vs) obtained by RC and BE tests were investigated by comparing the three sets of test results. Biot’s theory on frequency dependence of shear-wave velocity was adopted to consider dispersion of a shear wave in saturated conditions. The results of this study suggest that the total mass density, which is commonly used to convert Gmax from the measured Vs in saturated soils, should not be used to convert Vs to Gmax when the frequency of excitation is 10% greater than the characteristic frequency (fc) of the soil.

scholarly journals Loading rate effect on mechanical properties of an unsaturated silty sand

2021 ◽  
Vol 337 ◽  
pp. 01018
Author(s):  
Christian Barahona ◽  
Luis Sandi ◽  
Juan Carlos Rojas ◽  
Di Emidio Gemmina ◽  
Adam Bezuijen ◽  
...  
Keyword(s):  
Specific Volume ◽  
Loading Rate ◽  
Silty Sand ◽  
Triaxial Tests ◽  
Strain Rates ◽  
Soil Behavior ◽  
Stress Strain ◽  
Loading Rates ◽  
Strain Behavior ◽  
Strain Paths

This paper presents the results of an experimental study on the effects of testing rate on stress-strain behavior and volumetric changes of soil. A series of suction-controlled triaxial tests has been performed on reconstituted specimens of a silty sand (SM), at different stress-rates and strain-rates, respectively. The stress-strain paths were applied by using a modified version of a Bishop and Wesley device (USPv2), capable of applying independently pore-water and air pressure at both ends of the soil sample. During the isotropic compression stages loading rates of 2 and 32 kPa/h have been applied under constant suction values of 15 and 45 kPa. The drained deviator stages were conducted at the same suction levels under strain rates of 0.25 and 2.50 %/h. Results are presented in terms of applied loading rates as a function of the specimens specific volume, preconsolidation pressure, soil compressibility and deviatoric stress against strain rate. A comparison of results was made to a former study, under similar testing conditions of suction and loading rates at University of Napoli Federico II. The effect of loading rate on the soil behavior seems to have an insignificant effect on the specific volume variations, for the imposed values during the testing campaign.

scholarly journals Laboratory study of small-strain behavior of a compacted silty sand

2013 ◽  
Vol 50 (2) ◽  
pp. 179-188 ◽  
Author(s):  
Ana Heitor ◽  
Buddhima Indraratna ◽  
Cholachat Rujikiatkamjorn
Keyword(s):  
Moisture Content ◽  
Structural Changes ◽  
Initial Moisture Content ◽  
Small Strain ◽  
Matric Suction ◽  
Point Of View ◽  
Silty Sand ◽  
Degree Of Saturation ◽  
Compacted Soil ◽  
Strain Behavior

Small-strain behavior is a key indicator for assessing the performance of compacted fills. Compaction conditions, i.e., initial moisture content and applied energy, govern compaction effectiveness and thus, the structure and matric suction of compacted soil. This paper presents an experimental study of the small-strain behavior of compacted silty sand prepared with different compaction conditions. Specimens with varying initial moisture contents and compaction energies were tested with bender elements to determine the small-strain shear modulus (G0), while the post-compaction matric suction was measured using the filter paper method and tensiometer. The experimental data suggest a pronounced relationship between G0 and the degree of saturation (Sr) of the as-compacted soil specimens. X-ray computed tomography (CT) scans were performed to examine structural changes of selected specimens upon compaction. The laboratory results are also examined in light of common end-product specifications, which show that it is beneficial to compact the soil slightly dry of optimum moisture content from the modulus point of view.

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.

scholarly journals Small Strain Behavior of Geomaterials: Modelling of Strain Rate Effects

1997 ◽  
Vol 37 (2) ◽  
pp. 127-138 ◽  
Author(s):  
Hervé Di Benedetto ◽  
Fumio Tatsuoka
Keyword(s):  
Strain Rate ◽  
Small Strain ◽  
Strain Rate Effects ◽  
Strain Behavior ◽  
Rate Effects

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.

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