• Journal of Korea Water Resources Association
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• v.45 no.4
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• pp.349-360
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• 2012

A horizontally curvilinear non-hydrostatic free surface model that was applicable to three-dimensional viscous flows was developed. The proposed model employed a top-layer equation to close kinematic free-surface boundary condition, and an isotropic k-${\varepsilon}$ model to close turbulence viscosity in the Reynolds averaged Navier-Stokes equation. The model solved the governing equations with a fractional step method, which solved intermediate velocities in the advection-diffusion step, and corrects these provisional velocities by accounting for source terms including pressure gradient and gravity acceleration. Numerical applications were implemented to the wind-driven currents in a two-dimensional closed basin, the flow in a steep-sided trench, and the flow in a strongly-curved channel accounting for secondary current by the centrifugal force. Through the numerical simulations, the model showed its capability that were in good agreement with experimental data with respect to free surface elevation, velocity, and turbulence characteristics.

• Geotechnical Engineering
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• v.11 no.4
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• pp.125-140
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• 1995

Generally, the groundwater pressure is not considered in the design of concrete lining of bottom drainage tunnel. This design method implies that the phreatic surface is drawdown to the bottom of tullnel. When tile groundwater is continually supplied without changing of groundwater table, there is a possibility at which the groundwater pressure acting on the tunnel lining after the completion of tunnel. Therefore, the safety of tunnel lining must be checked in this case. In this paper, the stability of bottom drainage tunnel which is affected by groundwater discharge is analzed by using of the Finite Element Method at the 2 sections of subway where the groundwater level has a tittle change during the construction. As the result of analysis, the grouting for the water tightness and the permanent monitoring system of tunnel are required for maintaining of long-term stability of bottom drainage tunnel for the case of groundwater plassure acting on the tunnel lining is greater than that of design stage.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.99-106
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• 2008

This study is concernsed with the effect of a chimney drainage system installed at the back of reinforced soil block on preventing the pore water pressure development. A series of finite-element analyses based on transient seepage analysis were performed for a number of cases with different patterns of the chimney drainage system. The results were thoroughly analyzed to get insight into the mechanism of pore water pressure reduction effect of the chimney drainage system. It is shown that a vertical drainage system installed at the back of reinforced zone can be an effective means of maintaining the wall stability during rainfall by preventing pore pressure increase in the reinforced as well as the backfill zones. Also shown is that the optimum height of the chimney drain is 50% of the wall height. Practical implications of the findings were discussed.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1996.03a
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• pp.43-54
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• 1996

장대 터널, 지하철, 양수발전소, 유류 비축기지, 핵폐기물 지하처분장 및 농축산물 지하 저장소 등 지하공간개발의 구상 및 그 건설이 활발한 가운데, 그 관련기술에 대한 관심이 고조되고 있다. 특히 지하공간개발을 위한 사전 설계단계 및 시공에 있어 국내ㆍ외적으로 현지암반 초기응력 측정은 중요한 요소로 대두되고 있다. (중략)

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.249-256
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• 2002

The stability of slurry trench system is closely associated with the characteristics of the filter cake (assumed impervious membrane) transferring the hydrostatic force of slurry to the trench walls. The effectiveness of this assumption in a wide range of trench systems has been examined with the aid of a Finite Element program. Build up of excess porewater pressure in the soil mass behind the filter cake is a function of the slurry density, the properties of filter cake, the ground conditions, time, the geometry of trench and the original ground water level. These factors were all investigated by the Finite Element Method. The most significant factors were found to be the ground conditions and the properties of filter cake.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.2
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• pp.1-11
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• 1997

During hydroproof test of composite pressure vessel, acoustic emission signal was measured and analyzed to evaluate structural integrity of composite motor case. When pressure was held for 1 min. at constant pressure from low pressure level to high pressure level, the pattern of hit rate of good composite pressure vessel is increased with higher value than that of bad composite pressure vessel. This report also presents detection possibility of burst location approximately in the range of 25∼36％ of burst pressure using energy rate. In case that it is difficult to detect burst location of composite motor case, it is possible to detect burst location, i.e. structurally weak location of composite pressure vessel with applying same pressure lower than maximum expected operating pressure(MEOP) repeatedly.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.313-318
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• 2001

To establish nondestructive test method for aerospace composite materials, various composite specimens were tested and analyzed using acoutic emission. The hit rate of acoustic emission closely was rotated with crack initiation and propagation. This report also presents defection capability of crack initiation pressure, initial crack active location, and crack propagation using acoustic emission.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.123-133
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• 2004

The magnitudes of wall thrust acting on quay walls can easily vary due to the development of excess pore pressure in backfill. In this research, a new displacement model was proposed to predict the displacement of the wall considering such magnitude variations of the wall thrust. This model is based on Newmark sliding block concept. The magnitude variation of the wall thrust is modelled by varying the magnitude of yield acceleration. The parametric study was performed to analyze the effects of input parameters on the seismic displacement of the wall, and the validity of this model was verified by comparing its predicted displacements with those of Is shaking table tests.

• Journal of the Korean Institute of Gas
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• v.16 no.1
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• pp.46-50
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• 2012

The performance of the Type3 hydrogen composite cylinder whose pressure is 70 MPa using hydrostatic cycling test equipment was evaluted in this study. It also includes the finite element method analysis on the performance of the cylinder when the pressure is applied. As a result, cylinder body parts of the Type3 hydrogen composite cylinder, which draws attention with its safe status and the lightness, was ruptured first and the same result has been found out through the finite element method. The dome knuckle and the cylinder body were proved as the weakest parts since the cylinder body parts was expanded under the pressure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.4
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• pp.291-304
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• 2011

Recently concern for subsea tunnels is increasing, The effect of high water pressure can not be ignored in the case of a deep subsea tunnel. Reinforcement like grouting is necessary for the stability of such a subsea tunnel. In this study, therefore, it was investigated how the water barrier and shear strength increment resulted from grouting had an effect on the stability of a subsea tunnel. To this end, two-dimensional hydromechanical coupled analyses were performed for a sensitivity analysis in terms of different range, permeability coefficient, and cohesion of grouting reinforcement for the rock classes I, III, and V with respect to RMR system. The mutual relationship between strength increment and water pressure increased by barrier effect due to grouting was investigated by analyzing the numerical results.