• International Journal of Highway Engineering
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• v.6 no.3 s.21
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• pp.65-77
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• 2004

Deformational characteristics of subbase materials are important parameters in the mechanistic design of pavement. The subbase materials are mostly unbound granular materials in Korea, and seven representative subbase materials were collected for testing from the pavement construction sites. To evaluate the deformational characteristics of subbase materials, RC/TS, TX and FF-RC tests were performed. The effects of various variables on modulus were studied. The variation in the modulus with number of loading cycles and loading frequency are very small and can be ignored in a practical sense. The modulus of subbase materials were significantly affected by confining pressure and strain level. The representative modulus reduction curve and constitutive models for Korean subbase materials were suggested.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.578-585
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• 2004

Hardness test is performed for determination of the other properties, such as strength, wear resistance and deformation resistance, as well as hardness itself. And it is performed for prediction of residual lifetime by analysis of hardness reduction or hardness ratio. However, hardness test has limitation that observation of residual indent is needed for determination of hardness value, and that is the reason for not to be widely used in industrial field. Therefore, in this study, we performed researches to obtain Brinell hardness value from quantitative numerical formula by analysing relationship between indentation depths from indentation load-depth curve and mechanical properties such as work hardening exponent, yield strength and elastic modulus.

• Journal of the Korean Geotechnical Society
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• v.25 no.11
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• pp.5-15
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• 2009

Dynamic shear properties of Nak-Dong river sand were investigated to build a soil property database for Nak-Dong delta region. Samples were taken from the estuary and the midstream of the river. Laboratory specimens were prepared by air pluviation method, and were tested by using RC/TS apparatus at various confining stresses, relative densities and numbers of cycles. Shear modulus reduction and damping curves were developed using Ramberg-Osgood and Modified Hyperbolic Models. The developed curves, compared to those reported by other investigators, show only a slight difference. The outcome of this RC/TS experiments can be very important resources when accessing the dynamic response of sandy soils in Nak-Dong delta region in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.57-62
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• 2014

This paper proposes the improving the equalization performance using the adaptive modulus concept to the MCMA blind equalizer in order to the reduction of intersymbol interference which occurs in the band limited and time dispersive communication channel. In MCMA blind algorithm, it is possible to reducing the amplitude and phase rotation of intersymbol interference without training sequence, the fixed constant modulus of transmission signal is used. But in proposed algorithm, the modulus are adaptively varies according to the equalizer output signal, then the improved equalization performance were obtained by the computer simulation. For this, the recovered signal constellation that is the output of the equalizer, the convergence performance by MSE, MD (maximum distortion) and residual isi characteristic learning curve were used. The propose algorithm has fairly good performance compared to the traditional MCMA algorithm in the same adaptive equalization algorithm.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.767-772
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• 2002

Free-field ground motion during earthquake is significantly affected by the local site conditions and it is essential in the seismic design to perform the accurate site-specific ground response analysis. In this paper, one-dimensional seismic characteristics of waste landfill are studied based on the vertical propagation of horizontal shear waves through the column of soil/waste. Seismic response analysis is peformed for short-period, long-period and artificial earthquake ground motions using a computer program for seismic response analysis of horizontally layered soil deposits. The computed peak ground accelerations are compared with the values calculated according to Korean seismic design guidelines. The analysis result shows that the long-period earthquake causes the largest peak ground acceleration while the artificial earthquake results in the smallest one.

• Geotechnical Engineering
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• v.10 no.2
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• pp.85-96
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• 1994

Resonant column test huts been widely used as a primary laboratory testing technique in investigating dynamic soil properties expressed in therms of shear and Young's moduli and material damping. In thin Paper, dynamic Properties of typical Korean subgrade boils are investigated at shearing strains between 10-4% and 10-1% using Stokoe-type resonant column teat. The elastic threshold strains(yte) above which shear modulus and damping ratio are affected by strain amplitude, are defined at strain amplitude of about 10-3%. Below yte", small-strain shear modulus (Gmn) increases with confining pressure (Qc) as proportional to (Qe)0.61, and small-strain damping ratio(Dmin) ranges between 1% and 5.7%. Above yte, normalized shear modulus reduction curve(G/Gma. versus log strain) can be quite well expressed with Ramberg Osgood stress -strain equation and match well the curve suggested for sand by Seed and Idriss.riss.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.55-63
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• 2007

Deformational characteristics of subgrade soils are important properties in the mechanistic analysis and design of pavement system. In this study, to evaluate the effect of specimen construction methods on deformational characteristics of subgrade soils in Korea, resonant column tests were performed for specimens constructed by various methods. Specimen construction method affected to the modulus value but the variation in the normalized modulus reduction curve was almost identical. The effects of specimen construction method on modulus are decreased with increasing confining pressure. The average maximum variation in the modulus value with different specimen construction methods was estimated as 16.8%. The differences in the modulus value of the specimens with same water content and dry density conditions that made by gyratory compaction and impact compaction were very small within 5.2%. The impact compaction method was proposed as a specimen construction method for determining the design input parameter testing considering that impact compaction method is much simpler and require less expensive specimen construction equipment and setup than gyratory compaction method.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.479-489
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• 2014

In the present study a parametric analysis is conducted to study the effect of pile dimension and soil properties on the nonlinear dynamic response of pile subjected to lateral sinusoidal load at the pile head. The study is conducted on soil-pile model of different pile diameter, pile length and soil modulus, and results are compared to get the effect. The soil-pile system is modelled using Finite element method. The programming is done in MATLAB. Time history analysis of model is done for varying non-dimensional frequency of load and the results are compared to get the non-dimensional frequency at which pile head displacement is maximum in each case. Maximum possible bending moment and soil-pile interacting forces for the dynamic excitation of the pile is also compared. When results are compared with the linear response, it is observed that non-dimensional frequency is reduced in nonlinear response on account of reduction in the soil stiffness due to yielding. Nonlinear response curve shows high amplitude as compared to linear response curve.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.729-732
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• 2004

An experimental and numerical approach has been carried out for to see the noise characteristics of a circular diamond saw. The noise level measurement result for the several kinds of shanks shows us that the noise level reduction in high frequency range could be an effective way to control the noise problem. Sandwich type shank whose center part is laminated with a low Young‘s modulus material greatly reduces the noise level. The noise level for the shank where several curve shaped slits are provided in the circumferential direction is reduced considerably too. The response spectrum analysis by the FEM shows us to be an alternative for predicting the noise characteristics of the shank.

• Geotechnical Engineering
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• v.13 no.5
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• pp.89-100
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• 1997

It is very improtant to evaluate the reliable nonlinear deformational characteristics of soils not only in the analysis of geotechnical structures under working stress conditions but also for the soil dynamic problems. Field testings such as crosshole and pressuremeter tests can be used to determine the modulus of soils under in-situ conditions, but it is not possible to determine the modulus over the entire strain amplitude range. Laboratory methods such as resonant column 1 torsional shear test can be used to determine the modulus over the whole strain amplitude range, but it is very difficult to obtain the representative undisturbed samples on the sixte. For the reliable evaluation of nonlinear deformation characteristics of soils on a typical site, small strain modulus obtained from field testy and nomalized modulus reduction curve determined by laboratory bests need to be combined. In this paper, laboratory and Held testy were performed at a sixte which consisted of granite wearthered residual boils to evaluate the nonlinear deformational characteristics of coils such as the effects of strain amplitude, loading frequency, confining pressure and sample disturbance. It has been shorn that when the effects of these factors are properly taken into account, the stiffness values evaluated by various field and labrotary tests are comparable to each other fairly well. Finally, the procedure to evaluate the nonlinear deformstional characteristics of the sixte was proposed.