Small-strain dynamic properties of dry sand from the free-free resonant column PDF Download

Author: Jaywantsinh G. Vaghela
Publisher:
ISBN:
Category :
Languages : en
Pages : 330

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Author: Z. X. Yang
Publisher:
ISBN:
Category : Soil dynamics
Languages : en
Pages : 26

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Book Description
The shear modulus and damping ratio of soils at low to medium strains are essential input parameters in dynamic response analysis of soils. As soil elements in the field always have a history of being subjected to vibrations due to earthquakes, construction works, and vehicle motions, etc., the previbration effect on the dynamic properties of soils needs to be addressed appropriately. This study presents a series of tests performed by a newly developed resonant column system that enables the assessment of the dynamic properties of soils that have only undergone dozens of vibration cycles to investigate the impact of the vibration history on the dynamic properties of dry sand. Both the shear modulus and damping ratio of sand under different confining pressures (p′) are measured after the application of a previbration with a wide range of vibration amplitudes (?pre) and number of cycles (N). The results show that an elastic threshold strain exists for the dynamic properties of sand, beyond which the effect of the vibration history can be identified from the shear modulus reduction and damping ratio curves. The results also confirm that the effect of the vibration history on dry sand depends on the test variables of?pre,N, andp′. In addition, a new interpretation method is proposed to quantify the combined effects of?preandNon the signature of the vibration history, which could potentially be useful for interpreting the dynamic properties of the in situ soils that may experience previbration.

Author: Sheng-Huoo Ni
Publisher:
ISBN:
Category : Axial loads
Languages : en
Pages : 476

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Author: Soheil Moayerian
Publisher:
ISBN:
Category :
Languages : en
Pages : 112

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Dynamic properties of soils (shear stiffness and damping ratio) are critical for the design of structures subjected to vibrations. The dynamic properties of a benchmark standardized laboratory sand (Ottawa silica sand) were evaluated with two different resonant column devices, utilising software with different analytical approaches for the evaluation of soil properties. The dynamic properties (shear modulus and damping ratio) are evaluated as a function of the shear strain level. The results are compared to evaluate the effect of the type of equipment and the form of the data analysis on the measured dynamic properties of the samples. The results are discussed in light of the applicability of the procedures in practice, the ease of the testing methods, and the errors they introduced into analysis and design. In general, the shear wave velocities obtained from the two different devices are in good agreement. However, the damping ratios they give show considerable differences as strains increase. Dynamic properties are typically measured by curve fitting of the transfer function between the excitation and the response using the resonant column device. However, the force function generated by sinusoidal sweep or random noise excitations induce different shear strain levels at different frequencies. Consequently, the shape of the measured transfer function is distorted and differs from the theoretical transfer function for an equivalent single-degree-of-freedom system. The difference between the measured and theoretical transfer functions as well as the bias in the computed dynamic properties becomes more pronounced with the increase in shear strain. This study presents a new methodology for the evaluation of dynamic properties from an equivalent constant-strain transfer function. The soil specimen is excited simultaneously using a sinusoidal excitation (carrier signal) at the required strain level and a small amplitude, narrow band random noise. The strain level induced by the fixed sine is shown to control the resonant frequency of the specimen; whereas the random noise introduces the required frequency bandwidth to determine the transfer function and hence the dynamic properties at a constant strain level. The new methodology also shows a good potential for the evaluation of frequency effects on the dynamic properties of soils in resonant column testing.

Author: David Umberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 792

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The results from an experimental study on the dynamic properties of sand with nonplastic silt are presented. Combined resonant column and torsional shear equipment is used to evaluate the effects of confining pressure, shearing strain, frequency, and number of cycles of loading on the dynamic properties of silty sand. The goal of this study is to determine if relationships in the literature for sands and gravels are accurate for predicting the shear modulus and material damping characteristics of soil with nonplastic fines or if the incorporation of a fines content parameter improves predictions. This goal was primarily accomplished by reconstituting and testing samples of an alluvial deposit from Dillon Dam, Dillon, Colorado according to predetermined gradation curves with variable amounts of non-plastic fines. Among the findings of this investigation are: (1) soil parameters such as Cu and D50 can be related to dynamic properties of soils with up to 25% fines, (2) the effects of non-plastic fines on the small-strain dynamic properties of soils are not very pronounced for soils with less than 25% fines, and (3) an increase in the amount of non-plastic fines in uniform soils or soils with more than 25% fines generally results in lower values of small-strain shear modulus, higher values of small-strain material damping, and more linear G/Gmax - log([gamma]) and D - log([gamma]) curves. The effect of non-contacting, larger granular particles in a finer soil matrix is also investigated along with the impact of removing larger particles from laboratory samples.

Author: Deron J. Van Hoff
Publisher:
ISBN:
Category : Marine sediments
Languages : en
Pages : 334

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Author: Frank Edwin Richart
Publisher: Prentice Hall
ISBN:
Category : Science
Languages : en
Pages : 444

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Book Description
For graduate students in soil dynamics with a background in statics and elementary dynamics.

Author: Yaning Wang (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 324

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The study of the dynamic properties of two specific kinds of granular soils is performed using torsional resonant column testing. The sandy soils are: (1) liquefiable sand from Christchurch, New Zealand, and (2) calcareous sand from Puerto Rico. The effects of isotropic effective confining pressure, shear strain amplitude, void ratio, and total unit weight on the small-strain and nonlinear dynamic properties of both types of sand are presented and discussed. Empirical models from previous studies are examined to determine how well the models fit the test results.

Author: RM. Chung
Publisher:
ISBN:
Category : Damping
Languages : en
Pages : 10

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Torsional resonant column tests were performed on Monterey No. 0 sand of 60% relative density under confining pressures ranging from 10 to 300 kPa to evaluate the dynamic properties of the sand. Both solid and hollow cylindrical specimens were used in testing, and shear moduli and damping ratios were determined for cyclic shear strain amplitudes from 10-4 to 5 × 10-2%. The test results indicated that the type of specimen, that is, solid or hollow cylinder, had no significant effect on the calculated shear moduli and damping ratios, except that at very low strain amplitudes (?

Author: 李翊群
Publisher:
ISBN:
Category :
Languages : en
Pages :

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