• Geomechanics and Engineering
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• v.14 no.5
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• pp.479-489
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• 2018

In this paper, a comparative study of the effects of soil modelling on the interaction between tunnelling in soft soil and adjacent piled structure is presented. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles as well as tunnel internal forces during the construction of an underground tunnel. The soil is modelled by two material models: the simple, yet approximate Mohr Coulomb (MC) yield criterion; and the complex, but reasonable hardening soil (HS) model with hyperbolic relation between stress and strain. For the former model, two different values of the soil stiffness modulus ($E_{50}$ or $E_{ur}$) as well as two profiles of stiffness variation with depth (constant and linearly increasing) were used in attempts to improve its prediction. As these four attempts did not succeed, a hybrid representation in which the hardening soil is used for soil located at the highly-strained zones while the Mohr Coulomb model is utilized elsewhere was investigated. This hybrid representation, which is a compromise between rigorous and simple solutions yielded results that compare well with those of the hardening soil model. The compared results include pile cap movements, pile deformation, and tunnel internal forces. Problem symmetry is utilized and, therefore, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.7-12
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• 2016

In this study, a simplified collision model of pile protective structures against a navigation vessel was proposed and verified. The model of pile protective structure were composed by two plastic hinges at below of cap slab and the inside of ground. A nonlinear equation of motions was developed in consideration of the kinematic energy, potential energy and deformation energy in collision event. The developed simplified model were verified by the precise finite element collision analysis of the vessel and the protective structure.

• Journal of the Korean Geophysical Society
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• v.9 no.3
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• pp.181-188
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• 2006

The data, methodology, and the resulting accurate gravimetric geoid model for the Korean Peninsula (latitude from 32˚ N to 40˚ N and longitude from 124˚ E to 131˚ E) are presented in this study. The types of used data were a high degree geopotential model (the EGM96 spherical harmonic coefficient set), a set of 12,615 land gravity observations, 1,056,075 shipborne gravity observations, and KMS2002 gravity anomalies from satellite altimetry. The remove-restore technique was successfully applied to combining the above mentioned data sets using up to degree and order 112 of the EGM96 coefficient. The residual geoid was calculated with residual Free-Air anomaly values using the spherical Stokes' formula with a 37-km integration cap radius. The geoid model was referred to WGS84 geodetic system and was tested using a set of GPS/levelling geoid undulations. The absolute accuracy is 0.132 m and some improvement compared to the PNU95 geoid model was found.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.529-545
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• 2023

The coupled soil-pile-structure seismic response is recently in the spotlight of researchers because of its extensive applications in the different fields of engineering such as bridges, offshore platforms, wind turbines, and buildings. In this paper, a simple analytical model is developed to evaluate the dynamic performance of seismically isolated bridges considering triple interactions of soil, piles, and bridges simultaneously. Novel expressions are proposed to present the dynamic behavior of pile groups in inhomogeneous soils with various shear modulus along with depth. Both cohesive and cohesionless soil deposits can be simulated by this analytical model with a generalized function of varied shear modulus along the soil depth belonging to an inhomogeneous stratum. The methodology is discussed in detail and validated by rigorous dynamic solution of 3D continuum modeling, and time history analysis of centrifuge tests. The proposed analytical model accuracy is guaranteed by the acceptable agreement between the experimental/numerical and analytical results. A comparison of the proposed linear model results with nonlinear centrifuge tests showed that during moderate (frequent) earthquakes the relative differences in responses of the superstructure and the pile cap can be ignored. However, during strong excitations, the response calculated in the linear time history analysis is always lower than the real conditions with the nonlinear behavior of the soil-pile-bridge system. The current simple and efficient method provides the accuracy and the least computational costs in comparison to the full three-dimensional analyses.

• Advances in materials Research
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• v.1 no.2
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• pp.109-113
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• 2012

Electromigration-induced void evolutions in typical upper and lower layer dual-inlaid Copper (Cu) interconnect structures were simulated by applying a phenomenological model resorting to Monte Carlo based simulations, which considers redistribution of heterogeneously nucleated voids and/or pre-existing vacancy clusters at the Copper/dielectric cap interface during electromigration. The results indicate that this model can qualitatively explain the electromigration-induced void evolutions observations in many studies reported by several researchers heretofore. These findings warrant need to re-investigate technologically important electromigration mechanisms by developing rigorous models based on similar concepts.

• Food Science and Preservation
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• v.6 no.1
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• pp.37-42
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• 1999

The equilibrium moisture content(EMC) of Shiitake mushroom is and important factor because it has a close relationship to storage and drying problems. The determination of the EMC for Shiitake mushroom was made in atmospheres of various constant humidities at four different constant temperatures and the fitting of the five selected EMC models were performed with the experimental EMC data. The desorption equilibrium moisture contents for Shiitake mushroom were increased as the temperature was decreased and the relative humidity was increased. The significant difference of the equilibrium moisture content was appeared between the cap and the stipe of Shiitake mushroom. The Henderson-Thompson model was fitter than the others with the experimental data.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.55-60
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• 2005

A three-dimensional Gaussian heat source model is modified to include the effects of the gap and thickness-difference for the laser keyhole welding. The gap of the butt joint influences the welding efficiency such that the melting area decreases linearly with the gap. When the different plate thickness is used such as the tailored blank welding, melting areas of the thick and thin plates are predicted by introducing the thickness-difference factor. The calculated results using the modified heat source show reasonably good agreements with the experimental results.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.602-607
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• 2007

The heavy duty diesel engine must have a large output for maintaining excellent mobility. The compacted graphite iron (CGI) is a material currently under study for the engine demanded for high torque, durability, stiffness and fatigue. In this study, three dimensional finite element model of a heavy-duty diesel engine was developed to conduct the stress analysis by using property of CGI. The FE model of the heavy duty diesel engine section consisting with four half cylinder was selected. The heavy duty diesel engine section include cylinder block, cylinder head, liner, bearing cap, bearing and bolt. The loading conditions of engine are pre-fit load, assembly force and gas force.

• Journal of the Korean Society of Combustion
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• v.7 no.1
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• pp.52-57
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• 2002

A numerical investigation using a commercial CFD program of the Inter-Phase Slip Algorithm has been carried out for detail characteristics of particle motions and bubble behaviors in a two dimensional fluidized bed. The bed simulated has been operated with three different distributor geometries, such as bubble cap, nozzle, and perforated plate types. Experiments using a slit-type two-dimensional fluidized bed and a cylinder-type fluidized bed have been performed in order to confirm the simulation model. In addition, the numerical results are compared with the wellknown correlation of bubble sizes and bubble rising velocities by Mori and Wen [1]. The simulation model that we applied is shown to be useful to understand the relation between bubble behaviors and distributor geometries.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.402-413
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• 2006

Strength evaluation of soft soils is a formidable task because of difficulties in sampling, specimen preparation and setting in triaxial cells. In undrained triaxial testing, sampling disturbance, verticality of specimen and bedding effect give a great influence on shear strength measurements. In the other hand, shear wave measurements of specimens are less influenced by these factors. In this research, the bender elements were attached top cap and base pedestal of triaxial cell and shear wave velocities were measured. To initiate a methodology to evaluate shear strength indirectly by measuring shear wave velocity, a relationship between shear strength and shear wave velocity was developed with kaolinite specimens consolidated in the laboratory. Undrained shear strength turns out to increase linearly with shear wave velocity. Stress-strain curves can also be predicted with a hyperbolic model and shear wave measurements.