Showing papers by "Dong-Soo Kim published in 2000"
TL;DR: In this article, the propagation and attenuation characteristics of various source generated vibrations were investigated by analyzing particle motions, and the measured attenuation data matched well with the predicted data when using the suggested geometric damping coefficient, and estimated soil damping ratios were quite reasonable taking soil type of the site and experiencing strain level into consideration.
184 citations
TL;DR: In this article, the authors used synthetic specimens of varying stiffness (4.3 to 1500 MPa) to measure the compliance of testing equipment and to improve the measurement setups, which indicated that all the testing devices were well calibrated over a wide stiffness range.
Abstract: For reliable deformation measurements at small strains, in both static and dynamic analyses, calibration of the entire testing system in addition to routine transducer calibrations are very important. Seven synthetic specimens of varying stiffness (4.3 to 1500 MPa) were constructed and tested to measure the compliance of testing equipment and to improve the measurement setups. Testing equipment used in this study included a resonant column device (RC), a torsional shear device (TS), a free-free resonant column device (FF-RC), a cyclic resilient modulus testing device (M sub R), and a static compression testing device. For the reliable comparison of test results obtained from various types of testing equipment, the measured modulus values should be adjusted to the values at a given frequency of concern. Moduli of synthetic specimens determined by various types of testing equipment, after the frequency correction was applied, were almost identical, if the effect of loading frequency was considered. This indicated that all the testing devices were well calibrated over a wide stiffness range. To verify the effectiveness of calibration on soil testing, two subgrade soils were tested, and moduli determined by various tests compared well. Use of synthetic calibration specimens shows potential for calibrating testing equipment and determining its capability and limitation for small-strain deformation measurements. Synthetic specimens of known stiffness characteristics have also shown potential in assessing and solving system compliance problems.
7 citations
TL;DR: In this article, the effects of various variables on modulus were studied, and two representative modulus reduction curves for Korean subgrade soils were suggested, and it was shown that the modulus values evaluated by various testing methods are comparable to each other fairly well.
Abstract: Deformational characteristics of subgrade soils are important parameters in the mechanistic design of flexible pavement. The subgrade soils are mostly non-plastic sandy in Korea, and seven representative subgrade soils were collected for testing from the actual pavement projects. To evaluate the deformational characteristics of subgrade soils, RC/TS, TX, FF-RC, and cyclicM
R
tests were performed. The effects of various variables on modulus were studied. The modulus of subgrade soil increases with loading frequency. The maximum shear modulus,G
max
, was significantly affected by confining pressure and water content, but normalized modulus (G/G
max
) reduction curves were almost identical and independent of water content and confining pressure below about 41 kPa. Two representative modulus reduction curves for Korean subgrade soils are suggested. The variation in the modulus with number of loading cycles is small and can be ignored in a practical sense. It has been shown that when the effects of those factors are properly taken into account, the modulus values evaluated by various testing methods are comparable to each other fairly well.
4 citations