Shear modulus and damping of soft Bangkok clays

2002 ◽  
Vol 39 (5) ◽  
pp. 1201-1208 ◽  
Author(s):  
Supot Teachavorasinskun ◽  
Pipat Thongchim ◽  
Panitan Lukkunaprasit
Keyword(s):  
Shear Modulus ◽  
Seismic Analysis ◽  
Damping Ratio ◽  
Soft Clay ◽  
Cyclic Stress ◽  
Large Strains ◽  
Cyclic Triaxial ◽  
Stress History ◽  
Load Frequency ◽  
Equivalent Shear Modulus

The shear modulus and damping ratio of undisturbed Bangkok clay samples were measured using a cyclic triaxial apparatus. Although abundant literature on this topic exists, selection of the most suitable empirical correlation for a seismic analysis cannot be done unless site specific data are obtained. The apparatus used in this research can measure the stress–strain relationships from strain levels of about 0.01%. The equivalent shear modulus measured at these strains was about 80% of the value obtained from the shear wave velocity measurements. The degradation curves of the equivalent shear modulus fell into the ranges reported in the literature, for clay having similar plasticity. The damping ratios varied from about 4–5% at small strains (0.01%) to about 25–30% at large strains (10%). The effects of load frequency and cyclic stress history on the shear modulus and damping ratio were also investigated. An increase in load frequency from 0.1 to 1.0 Hz had no influence on the shear modulus characteristic, but it did result in a slight decrease in the damping ratio. The effects of the small amplitude cyclic stress history on the subsequently measured shear modulus and damping ratio were almost negligible when the changes in void ratio were taken into account.Key words: soft clay, shear modulus, damping ratio, cyclic triaxial test, cyclic stress history.

Simple shear testing of sensitive, very soft offshore clay for wide strain range

2009 ◽  
Vol 46 (11) ◽  
pp. 1277-1288 ◽  
Author(s):  
G. Lanzo ◽  
A. Pagliaroli ◽  
P. Tommasi ◽  
F. L. Chiocci
Keyword(s):  
Shear Modulus ◽  
Simple Shear ◽  
Damping Ratio ◽  
Soft Clay ◽  
Strain Range ◽  
Small Strain ◽  
Cyclic Shear ◽  
Wide Range ◽  
Equivalent Shear Modulus ◽  
Two Stages

Stiffness and damping properties of sensitive, very soft clay sediments of the Italian Adriatic continental shelf are determined by means of two series of cyclic simple shear tests (one with 12 stages and one with two stages). The apparatus used in this research is capable of investigating the stress–strain behaviour of the soil in a wide range of shear strains from about 0.0004% to 1%. Test results were expressed in terms of small-strain shear modulus (G0), normalized equivalent shear modulus (Geq/G0), and damping ratio (D) versus cyclic shear-strain amplitude (γc). These parameters were analyzed in the framework of existing literature by comparison with empirical correlations developed for onshore materials of different plasticity and, limited to G0, also for soft soils. The dependence of G0, Geq/G0–γc, and D–γc on factors such as void ratio, stress history, and loading cycles is analyzed and discussed.

scholarly journals Shear modulus and damping ratio of a nonplastic silt at large shear strains

2019 ◽  
Vol 92 ◽  
pp. 08007
Author(s):  
Alper Sezer ◽  
Eyyub Karakan ◽  
Nazar Tanrinian
Keyword(s):  
Shear Modulus ◽  
Relative Density ◽  
Shear Strain ◽  
Stress Ratio ◽  
Damping Ratio ◽  
Cyclic Stress ◽  
Triaxial Tests ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
Cyclic Stress Ratio

Site response analyses and solution of dynamic soil-structure interaction problems need determination of variation of shear modulus and damping ratio with shear strain. Since many studies in literature concern evaluation of behavior of sands and silty sands, a series of cyclic triaxial tests were performed to determine the variation of shear modulus and damping ratio of a nonplastic silt with shear strain. Stress controlled cyclic triaxial tests on silt specimens of initial relative densities ranging among 30%, 50% and 70% were performed. Tests were carried out on identical samples under different CSR levels, and the confining pressure was selected as 100 kPa. Variation of shear modulus and damping ratio of silts with cyclic stress ratio amplitude, relative density and number of cycles were investigated. It was understood that soil relative density and cyclic stress ratio amplitude has a significant influence on shear modulus and damping ratio of silts. It was also observed that, as the cyclic stress ratio amplitude is increased, greater shear modulus and lower damping ratio values were obtained.

scholarly journals Undrained behaviour of intact soft clay under cyclic paths that match vehicle loading conditions

2018 ◽  
Vol 55 (1) ◽  
pp. 90-106 ◽  
Author(s):  
Lin Guo ◽  
Yuanqiang Cai ◽  
Richard J. Jardine ◽  
Zhongxuan Yang ◽  
Jun Wang
Keyword(s):  
Principal Stress ◽  
Water Pressure ◽  
Heavy Traffic ◽  
Damping Ratio ◽  
Soft Clay ◽  
Cyclic Stress ◽  
Shear Stresses ◽  
Traffic Loading ◽  
Wheel Loading ◽  
Stress Ratios

Vehicle traffic loading appears to contribute significantly to long-term settlement beneath highways, airport runways, and metro lines in China. Wheel loading imposes cycles in both the magnitude and direction of the principal stresses acting on the soils beneath pavement or rail-track structures. Conventional cyclic triaxial (CT) testing, which is not capable of imposing such stress paths, may underestimate how heavy traffic loading affects any underlying soft clay layers. A hollow cylinder apparatus (HCA) can simulate such traffic loading stress paths more accurately, including rotation of the principal stress directions. This paper presents a systematic experimental study of cyclic HCA (CHCA) tests on K0-consolidated saturated soft clay involving cyclic variations in both vertical and torsional shear stresses, along with a parallel programme of CT tests, considering the undrained response of saturated samples of intact soft clay. It is shown that when applied above certain critical cyclic stress ratios, principal stress rotation accelerates excess pore-water pressure and permanent strain development. Corresponding changes are also seen in the resilient modulus and damping ratio trends. The discrepancies between the behaviour of CHCA and equivalent CT tests grow as the cyclic stress ratios increase.

Shear Modulus and Damping Ratio of Unsaturated Kaolin Measured by New Suction-Controlled Cyclic Triaxial Device

2011 ◽  
Vol 34 (5) ◽  
pp. 103635 ◽  
Author(s):  
L. D. Suits ◽  
T. C. Sheahan ◽  
Mahnoosh Biglari ◽  
Mohammad Kazem Jafari ◽  
Ali Shafiee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Damping Ratio ◽  
Cyclic Triaxial

MODULUS REDUCTION AND DAMPING CURVES FOR SAND OF SOUTH-EAST COAST OF INDIA

2012 ◽  
Vol 06 (04) ◽  
pp. 1250016
Author(s):  
V. JAYA ◽  
G. R. DODAGOUDAR ◽  
A. BOOMINATHAN
Keyword(s):  
Shear Modulus ◽  
Triaxial Test ◽  
Damping Ratio ◽  
Triaxial Tests ◽  
Hyperbolic Model ◽  
Cyclic Triaxial Test ◽  
Cyclic Triaxial ◽  
Wide Range ◽  
Predictive Relationships ◽  
Modulus Reduction

Adequate information on dynamic soil properties, especially strain dependent shear modulus (G) and damping ratio (ξ) for each soil layer are the essential input data for seismic ground response analysis and soil-structure interaction studies. In the present study, the shear modulus and damping ratio of sand are estimated for a wide range of strains based on undrained strain-controlled cyclic triaxial tests. The bender elements are also utilized in the cyclic triaxial test to estimate the low strain shear modulus. For this purpose, the soil samples are taken from a nuclear power plant site located at the south-east coastal region of India. Based on the experimental results, an empirical expression is developed to calculate the maximum shear modulus, G max as function of void ratio and effective confining stress. Predictive relationships are also developed for estimating normalized shear modulus and damping ratio curves for the sand. The predictive relationships are based on the hyperbolic model and cyclic triaxial test results. The developed modulus reduction and damping ratio curves from the predictive relationships are compared with the previously available curves in the literature.

Laboratory Measurements of the Dynamic Properties of Intact and Remolded Offshore Clays From Campeche Bay

2003 ◽  
Author(s):  
Celestino Valle ◽  
Kenneth H. Stokoe
Keyword(s):  
Shear Modulus ◽  
Soil Properties ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Large Strains ◽  
Material Damping ◽  
University Of Texas ◽  
Dynamic Soil Properties ◽  
Intact Condition ◽  
The University

Comparisons of the dynamic properties of intact and remolded offshore clay specimens has been carried out. The clay specimens were obtained from Campeche Bay, offshore Mexico. Combined resonant column and torsional shear (RCTS) equipment at the University of Texas at Austin was used to determine the dynamic soil properties. Each soil specimen was tested twice, first in the intact condition and second as remolded material. Remolding was done by kneading the intact material and then reforming the specimen by compacting in a mold. The effects on the dynamic properties, expressed by shear modulus and material damping ratio, between intact and remolded conditions are discussed. As expected, shear modulus and material damping at small and large strains are affected by remolding. Interestingly, the normalized modulus degradation curves were changed very little by remolding up to strains between 0.06 and 0.1%. The results offer insight into the effects of sampling disturbance on linear and nonlinear dynamic soil properties.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

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