Stress path effects on shear stiffness, damping ratio and volumetric behaviour of normally consolidated unsaturated compacted clay

2010 ◽  
pp. 199-204 ◽  
Author(s):  
M Biglari ◽  
A d’Onofrio ◽  
C Mancuso ◽  
M Jafari ◽  
A Shafiee
Keyword(s):  
Damping Ratio ◽  
Shear Stiffness ◽  
Stress Path ◽  
Compacted Clay

Improving Damping Properties of Railway Ballast by Addition of Tire-Derived Aggregate

2019 ◽  
Vol 2673 (5) ◽  
pp. 299-307 ◽  
Author(s):  
Weimin Song ◽  
Baoshan Huang ◽  
Xiang Shu ◽  
Hao Wu ◽  
Hongren Gong ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Damping Ratio ◽  
Shear Stiffness ◽  
Damping Properties ◽  
Railway Ballast ◽  
Loading Test ◽  
Interface Shear ◽  
Peak Shear Stress ◽  
Dilation Effect ◽  
Tire Derived Aggregate

The damping properties of railway ballast are critical to the safe operation of trains. This study aimed to improve the damping properties of railway ballast through the addition of tire-derived aggregate (TDA) and to evaluate the effect of TDA on other properties of ballast. The damping property and other mechanical properties of ballast mixed with different contents of TDA were tested utilizing a large direct shear test (DST) under static and cyclic loading conditions. The cyclic loading test was performed in accordance with ASTM D 7499, from which the resilient interface shear stiffness and damping ratio were obtained. The results showed that TDA significantly increased the damping ratio of railway ballast, but decreased the resilient interface shear stiffness. The stress-strain behavior of the ballast-TDA mixes was obtained from the static loading test, showing that TDA significantly decreased the peak shear stress and the dilation effect. According to the Mohr-Coulomb failure criterion, TDA also decreased the cohesion strength and the internal friction angle of the ballast. Based on the test results from this study, 5% rubber is recommended for use in railway ballast.

scholarly journals Experimental Investigation of Dynamic Characteristics of Subsea Sand-Silt Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tugen Feng ◽  
Yu Tang ◽  
Qiyenan Wang ◽  
Jian Zhang ◽  
Jian Song
Keyword(s):  
Cement Content ◽  
Damping Ratio ◽  
Shear Stiffness ◽  
Confining Pressure ◽  
Dynamic Responses ◽  
Resonant Column ◽  
Dynamic Shear ◽  
Column Tests ◽  
Mixture Ratio ◽  
Curing Age

In this paper, extensive resonant column tests were conducted to investigate dynamic responses of subsea sand-silt mixtures. The effects of confining pressure, mixture ratio, curing age, and cement content were evaluated. For the test condition considered in this study, the measured damping ratio is the smallest when the ratio of subsea sand to silt is in a range of 1.5 to 2.0. Moreover, unsolidified subsea sand-silt mixed at a ratio of 1.5 has almost the same maximum shear stiffness as the pure sand. For solidified subsea sand-silt mixture, cement can significantly increase the dynamic shear stiffness when the curing age is less than 14 days. However, the increase of the maximum dynamic shear stiffness is negligible when the curing age is longer than 14 days. When the cement content is 2%, the damping ratio of the solidified mixtures is very close to that of the unsolidified mixture. When the cement content is higher than 4%, the damping ratio of the solidified mixtures reduces significantly. This is mainly due to hydration reactions occurring in the solidified mixtures.

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-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.

Undrained and drained (?) stress-strain response

2000 ◽  
Vol 37 (5) ◽  
pp. 1126-1130 ◽  
Author(s):  
Y P Vaid ◽  
A Eliadorani
Keyword(s):  
Effective Stress ◽  
Void Ratio ◽  
Effective Strain ◽  
Shear Stiffness ◽  
Stress Path ◽  
Stress Increment ◽  
Stress Strain ◽  
Field Problem ◽  
Deformation Response ◽  
Do So

The deformation response of saturated soils to a total stress increment at the ambient void ratio and effective stress state is shown to be dependent on the direction of the effective strain increment. It is argued that in a given field problem, most soil elements neither deform fully drained nor undrained, but do so partially drained. The degree of partial drainage controls the direction of the effective stress increment and hence the deformation response. Experimental data are presented which demonstrate how shear stiffness changes with the direction of effective stress increment as a function of the ambient effective stress state.Key words: stress-strain, undrained, drained, partially drained, stress path, stiffness.

scholarly journals Experimental study on the shear stiffness and damping ratio of the coarse-grained soil against geogrid interface

2020 ◽  
Vol 22 (7) ◽  
pp. 1606-1617
Author(s):  
Chunhui Su ◽  
Aijun Chen ◽  
Junhua Chen ◽  
Xianyuan Tang ◽  
Zhaoyao Yuan
Keyword(s):  
Experimental Study ◽  
Damping Ratio ◽  
Shear Stiffness ◽  
Coarse Grained ◽  
Stiffness And Damping ◽  
Coarse Grained Soil

scholarly journals Dynamic Parameters and Hysteresis Loop Characteristics of Frozen Silt Clay under Different Cyclic Stress Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Furong Liu ◽  
Zhiwei Zhou ◽  
Wei Ma ◽  
Shujuan Zhang ◽  
Zhizhong Sun
Keyword(s):  
Hysteresis Loop ◽  
Phase Difference ◽  
Resilient Modulus ◽  
Axial Stress ◽  
Damping Ratio ◽  
Hysteresis Loops ◽  
Confining Pressure ◽  
Stress Path ◽  
Cyclic Stress ◽  
Dynamic Parameters

In cold regions, the long-term stability of engineering facilities is unavoidably influenced by the negative temperature, freeze-thaw process, dry-wet process, and dynamic loading conditions induced by earthquakes and traffic loads. In order to investigate the effects of different cyclic stress paths on the evolution of dynamic mechanical properties of frozen silt clay, a series of cyclic triaxial tests with variation confining pressure (VCP) or constant confining pressure (CCP) were performed. Triaxial low-temperature apparatus (MTS-810) was taken advantage of to simulating various cyclic stress paths by changing cyclic loading conditions of axial stress and confining pressure. In this paper, the evolution features of the axial resilient modulus, damping ratios, and the shape of hysteresis loops with an increase in the number of load cycles under different dynamic stress paths are comprehensively studied. The results show that the loading angle of cyclic stress path and the phase difference between cyclic axial stress and confining pressure are the main factors that remarkably affect the development characteristics of the resilient modulus and damping ratio. With increasing of the loading angle and phase difference, the resilient modulus increases, but damping ratio increases with increasing of loading angle and with decreasing of phase difference. With the continuous increase in the number of loading cycles, the samples of frozen soil show compacting and hardening characteristics. With an increase in the number of load cycles, the shape of hysteresis loop becoming narrows, the resilient modulus decreases at the initial stage and then gradually increases, and the damping ratio stably decreases. According to contrastively analyzing the evolution of dynamic parameters and the shape features of hysteresis loops under various cyclic stress paths, it can be clearly discovered that the evolution of sample microstructure and the development of dynamic characteristics of frozen samples have obvious dependence on the cyclic stress path. Therefore, the effects of variable confining pressure (VCP) on dynamic behaviors of frozen soils are nonnegligible in practical cold region engineering.

scholarly journals Experimental Study on the Dynamic Modulus and Damping Ratio of Compacted Loess under Circular Dynamic Stress Paths

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Liguo Yang ◽  
Shengjun Shao ◽  
Zhi Wang
Keyword(s):  
Principal Stress ◽  
Dynamic Stress ◽  
Dynamic Compression ◽  
Damping Ratio ◽  
Stress Path ◽  
Compression Modulus ◽  
Dry Density ◽  
Dynamic Shear Modulus ◽  
Dynamic Shear ◽  
Compacted Loess

Dynamic loads such as earthquakes and traffic will simultaneously generate vertical dynamic stress and horizontal shear stress in the foundation soil. When the vertical dynamic stress amplitude is twice the horizontal shear dynamic stress amplitude, and the phase difference between them is 90°, a circular dynamic stress path is formed in the τ z θ d ∼ σ zd − σ θ d / 2 stress coordinate system. To simulate the stress state of soil in the area of the circular dynamic stress path caused by bidirectional dynamic stress coupling, a series of tests of compacted loess under the action of a circular dynamic stress path were carried out using a hollow cylindrical torsion shear apparatus. The effects of the mean principal stress, dry density, and deviatoric stress ratio (the ratio of deviator stress to average principal stress) on the dynamic modulus and damping ratio of compacted loess were mainly studied. The test results show that, under the action of the circular dynamic stress path, the larger the mean principal stress is, the larger the dynamic compression modulus and dynamic shear modulus are. The dynamic compression modulus increases obviously with increasing dry density, but the dynamic shear modulus increases only slightly. When the deviator stress ratio increases from 0 to 0.4, the dynamic compression modulus and dynamic shear modulus increase to a certain extent. In addition, the greater the dry density and deviatoric stress ratio are, the greater the initial dynamic compression modulus and initial dynamic shear modulus of the compacted loess. The dynamic compression damping ratio of compacted loess increases with increasing mean principal stress, but the dynamic shear damping ratio decreases with increasing mean principal stress. Dry density basically has no effect on the dynamic compression damping ratio and dynamic shear damping ratio of compacted loess. When the dynamic strain exceeds 1%, the greater the deviatoric stress ratio is, the smaller the dynamic compression damping ratio and the dynamic shear damping ratio are. The research results can provide reference for the study of dynamic modulus and damping ratio of loess under special stress paths.

Experimental observations on the response of loose sand under simultaneous increase in stress ratio and rotation of principal stresses

2008 ◽  
Vol 45 (5) ◽  
pp. 597-610 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Yoginder P. Vaid
Keyword(s):  
Principal Stress ◽  
Stress Ratio ◽  
Shear Stiffness ◽  
Stress Path ◽  
Simultaneous Increase ◽  
Loose Sand ◽  
Horizontal Shear ◽  
Principal Stresses ◽  
Inherent Anisotropy ◽  
Strain Paths

The drained response of loose sand (relative density of 30%) under simultaneous increase in principal stress ratio (R = σ'1/σ'3) and the inclination of major principal stress to the vertical (ασ) is examined using data from hollow cylinder torsional shear testing. The study specifically pertains to the behaviour of loose sand subject to monotonic linear stress path loadings in the R–ασ space, within the domain of R ≤ 2, ασ < 45°, while intermediate principal stress parameter (b) and effective mean normal stress (σ'm) are held constant. The relationship between horizontal shear stress (τzt) and horizontal shear strain (γzt) of loose sand under such loadings is shown to be unique and stress-path independent. At any stress state, the horizontal shear stiffness (dτzt/dγzt) for a given σ'm depends only on the current value of τzt, and not on the value of individual components of normal effective stress, or their increments. When R and ασ are increased simultaneously in a linear manner, loose sand initially exhibits linear strain paths, suggesting no significant changes to the inherent anisotropy during the early stages of such loading. The directions of principal stress increment (αΔσ) and principal strain increment (αΔε) are found coincident, when αΔσ < 45°. An approach to predict the response of loose sand under simultaneous increase in R and ασ with constant b and σ'm has been developed based on these findings.

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