Unified dynamic shear moduli and damping ratios of sand and clay
TL;DR: In this article, the experimental data on dynamic shear moduli and damping ratios of various soils including non-plastic sands to highly plastic clays are collected and reanalyzed and brought into simple unified formulas.
About: This article is published in Soils and Foundations.The article was published on 1993-03-15 and is currently open access. It has received 616 citations till now. The article focuses on the topics: Shear modulus & Simple shear.
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TL;DR: In this article, a new empirical ground motion model for PGA, PGV, PGD and 5% damped linear elastic response spectra for periods ranging from 0.01-10 s was presented.
Abstract: We present a new empirical ground motion model for PGA, PGV, PGD and 5% damped linear elastic response spectra for periods ranging from 0.01– 10 s. The model was developed as part of the PEER Next Generation Attenuation (NGA) project. We used a subset of the PEER NGA database for which we excluded recordings and earthquakes that were believed to be inappropriate for estimating free-field ground motions from shallow earthquake mainshocks in active tectonic regimes. We developed relations for both the median and standard deviation of the geometric mean horizontal component of ground motion that we consider to be valid for magnitudes ranging from 4.0 up to 7.5–8.5 (depending on fault mechanism) and distances ranging from 0 – 200 km. The model explicitly includes the effects of magnitude saturation, magnitude-dependent attenuation, style of faulting, rupture depth, hanging-wall geometry, linear and nonlinear site response, 3-D basin response, and inter-event and intra-event variability. Soil nonlinearity causes the intra-event standard deviation to depend on the amplitude of PGA on reference rock rather than on magnitude, which leads to a decrease in aleatory uncertainty at high levels of ground shaking for sites located on soil. DOI: 10.1193/1.2857546
1,112 citations
01 Aug 2001
810 citations
Cites background or methods from "Unified dynamic shear moduli and da..."
...10 The effect of confining pressure on (a) normalized modulus reduction, and (b) material damping curves for non-plastic soils (Ishibashi and Zhang, 1993) ....
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...126 The data, which Ishibashi and Zhang (1993) synthesized, are the results of tests performed at confining pressures less than 10 atm....
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...1 1 Shearing Strain, γ , % Ishibashi and Zhang (1993) Non-Plastic PI = 50 %...
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...130 The set of equations proposed by Ishibashi and Zhang (1993) account for both soil plasticity and confining pressure on nonlinear behavior. However, these equations are based on data collected at confining pressures less than 10 atm and are observed to give unrealistic values at higher pressures. Also, the effect of soil plasticity on Dmin is not represented accurately in any of the generic curves widely used in the state-of-practice. The empirical curves from the EPRI (1993c) study are based on data collected over a relatively wider range of confining pressures and are consistent with the general trends outlined in Chapter Four....
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...11 Empirical (a) normalized modulus reduction, and (b) material damping curves proposed by Ishibashi and Zhang (1993)...
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TL;DR: The results of cyclic tests indicate that the Chinese criteria are not reliable for determining the liquefaction susceptibility of fine-grained soils as discussed by the authors, and the plasticity index (PI) is a better indicator of soil susceptibility.
Abstract: Observations from recent earthquakes and the results of cyclic tests indicate that the Chinese criteria are not reliable for determining the liquefaction susceptibility of fine-grained soils. Fine-grained soils that liquefied during the 1994 Northridge, 1999 Kocaeli, and 1999 Chi-Chi earthquakes often did not meet the clay-size criterion of the Chinese criteria. Cyclic testing of a wide range of soils found to liquefy in Adapazari during the Kocaeli earthquake confirmed that these fine-grained soils were susceptible to liquefaction. It is not the amount of “clay-size” particles in the soil; rather, it is the amount and type of clay minerals in the soil that best indicate liquefaction susceptibility. Thus plasticity index (PI) is a better indicator of liquefaction susceptibility. Loose soils with PI 0.85 were susceptible to liquefaction, and loose soils with 12 0.8 were systematically more resistant to liquefaction. Soils with PI>18 tested at low effective confining stresses ...
374 citations
TL;DR: In this article, a modified hyperbolic model and a statistical analysis of existing Resonant Column and Torsional Shear test results for 122 specimens obtained from South Carolina, North Carolina, and Alabama are presented.
Abstract: Predictive equations for estimating normalized shear modulus and material damping ratio of Quaternary, Tertiary and older, and residual/saprolite soils are presented in this paper. The equations are based on a modified hyperbolic model and a statistical analysis of existing Resonant Column and Torsional Shear test results for 122 specimens obtained from South Carolina, North Carolina, and Alabama. Variables used in the equations for normalized shear modulus are: shear-strain amplitude, confining stress, and plasticity index (PI). The equations for damping ratio are expressed in terms of a polynomial function of normalized shear modulus plus a minimum damping ratio. It is found that the Quaternary soils exhibit more linearity than soils of the other two groups. Also, it is found that the effect of PI on dynamic soil behavior is not as significant as previously thought. Data from all three groups exhibit significant variations with confining stress, similar to the variations determined by Stokoe et al. The uncertainties associated with the equations for PI of 0 and mean effective confining stress of 100 kPa are quantified using the point estimate method. A case study from Charleston, S.C. is provided to illustrate an application of the equations to seismic response analysis and the importance of considering confining stress and geologic age.
322 citations
263 citations
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TL;DR: In this paper, an equation and graph for the determination of shear modulus and damping of soils for use in design problems involving repeated loading or vibration of soils, are presented.
Abstract: Equations and graphs for the determination of shear modulus and damping of soils, for use in design problems involving repeated loading or vibration of soils, are presented. These equations and graphs are based on numerous laboratory tests on both remolded and undisturbed cohesive soils and on clean sands. Comparison of the measured and computed values shows good agreement. An example problem showing how these equations and curves are used is given.
1,710 citations
TL;DR: In this article, a study on the influence of the plasticity index (PI) on the cyclic stress-strain parameters of saturated soils needed for site response evaluations and seismic microzonation is presented.
Abstract: A study on the influence of the plasticity index (PI) on the cyclic stress‐strain parameters of saturated soils needed for site‐response evaluations and seismic microzonation is presented. Ready‐to‐use charts are included, showing the effect of PI on the location of the modulus reduction curve G/Gmax versus cyclic shear strain γc, and on the material damping ratio λ versus γc curve. The charts are based on experimental data from 16 publications encompassing normally and overconsolidated clays (OCR=1-15), as well as sands. It is shown that PI is the main factor controlling G/Gmax and λ for a wide variety of soils; if for a given γc PI increases, G/Gmax rises and λ is reduced. Similar evidence is presented showing the influence of PI on the rate of modulus degradation with the number of cycles in normally consolidated clays. It is concluded that soils with higher plasticity tend to have a more linear cyclic stress‐strain response at small strains and to degrade less at larger γc than soils with a lower PI. ...
1,608 citations
TL;DR: In this article, a simple relationship is proposed to relate the shear modulus of a cohesionless soil to a modulus stiffness coefficient, which is a soil property and depends on the characteristics of the soil, and the effective mean principal stress at any point in the soil.
Abstract: Data are presented concerning the shear modulus and damping ratios of sands and gravelly soils as determined by laboratory and field tests. A simple relationship is proposed to relate the shear modulus of a cohesionless soil to a modulus stiffness coefficient, which is a soil property and depends on the characteristics of the soil, and the effective mean principal stress at any point in the soil. Values for the modulus coefficient at low strains are suggested, and it is shown that these values for sands can be estimated from the standard penetration resistance of the sand. Values for gravels are generally greater than those for sands by factors ranging from 1.35–2.5. Suggestions are also made for determining the variation of shear modulus with shear strain and the damping ratios for both sandy and gravelly soils.
945 citations