• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.191-206
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• 2007

The general theoretical solutions for the wavespeed and damping derived in Part 1 of this work, are incorporated into the computer code. In this paper the code is used in a parametric study of the influence of excitation frequency and variations in material properties on propagation velocity and damping. Compressional wave velocity for waves of the first kind is shown to vary as a function of the frequency-permeability product, with a zone where wavespeed transitions from a lower bound value to a higher bound value with increasing values of the product. Damping is seen to be a maximum where the rate of change in wavespeed is greatest. Waves of the second kind also show a transition in wavespeed from near zero at low values of the frequency-permeability product to an upper bound value at higher values of the product.

• Journal of the Korea Concrete Institute
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• v.27 no.4
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• pp.435-441
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• 2015

Concrete, as a porous media, has permeability and it is considered as a major parameter for durability evaluation. Cold joint caused by delayed placing of concrete accelerates water permeation and intrusion of harmful ions. In the paper, concrete specimens containing GGBFS (Ground Granulated Blast Furnace Slag) and OPC (Ordinary Portland Cement) are prepared with cold joint section, and water permeability and water flow at the age of 91 days are measured for 2 weeks. Sound concrete with GGBFS shows decreased permeability to 89% for sound concrete with OPC and 0.86 of decreasing ratio is evaluated in GGBFS concrete with cold joint. Through WPT (Water Penetration Test), the effects of mineral admixture and cold joint on water permeability are evaluated, and variation in water behavior via cold joint is analyzed through probabilistic method as well.

• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.1
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• pp.73-79
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• 2009

The hydraulic conductivity of porous media is the most important property in soil characteristics. The hydraulic conductivity is determined by outdoor and indoor methods. Indoor methods normally use soil columns for flow test. Assumption of the column test is that fluid one-dimensionally flows through the column. However, fluids may flow toward the wall of the column, resulting in "boundary flow". This study investigated the effect of boundary flow on the hydraulic conductivity by using a permeameter excluding boundary flow. The results showed that the hydraulic conductivity excluding boundary flow was much smaller than the hydraulic conductivity employing the conventional determination method. This study also investigated the effects of particle size and surfactant on the hydraulic conductivity. As the particle size increased, the hydraulic conductivity was increased. The hydraulic conductivity was reduced by increasing surfactant concentration. The result showed that the viscosity of fluid significantly affected the determination of hydraulic conductivity.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.11-21
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• 2020

One-dimensional analytical solutions were used for forward and back diffusion of trichloroethylene (TCE) and tetrachloroethylene (PCE) in a single system with high- and low-permeability layers. Concentration profiles in a low-permeability layer, diffusive fluxes at the interface between the high- and low-permeability layers, and contaminant persistence in the high-permeability layer due to back diffusion were simulated with a comparison of semi-infinite and finite analytical solutions. In order to validate the analytical solutions used in this study, the results of one-dimensional analytical solutions developed by Yang et al. (2015) were compared with Nash-Sutcliffe model efficiency coefficient (NSE). When compared with Yang et al. (2015), the analytical solutions used in this study showed good agreements (NSE = 0.99). When compared with semi-infinite analytical solutions, TCE and PCE concentration profiles in the low-permeability layer, the diffusive fluxes, and the contaminant tailings of the high-permeability layer were underestimated. In order to determine the appropriate analytical solutions based on the effective diffusion coefficient, the thickness of the low-permeability layer, and the diffusion time in the TCE and PCE contaminated site, a term of dimensionless diffusion length (Z_d) was used. If the Z_d is less than 0.7, the semi-infinite solutions can be used to simulate accurate concentration profiles in low-permeability layers. If the Z_d is greater than 0.7, the reliability of simulations may be improved by using the finite solutions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.4
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• pp.243-248
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• 1993

In this research, unsteady groundwater flow in unconfined and homogeneous three layer aquifers is studied theoretically and experimentally. Numerical solutions are obtained by Runge Kutta and Runge Kutta Gill method after transforming the governing nonlinear partial differential equations to nonlinear ordinary differential equations. Experimental apparatus includes a test section filled with fine, medium and coarse sands. Experimental results are compared with the numerical solutions and both experimental and numerical results correspond well with each other. This numerical approach may be also applied to the cases which have more aquifers.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.86-86
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• 2020

수리구조물에 관한 기존 연구들은 대부분 기능성과 안정성 측면에서 본체에 작용하는 유체력에 대한 안정성에 주안점을 두고 있다. 수리구조물 상·하류의 수위차에 기인한 기초지반내의 흐름 및 간극수압 변화는 하천 구조물의 안정성을 연구하는데 매우 중요하다. 해양에서는 파랑하중에 의한 과잉간극수압이 액상화를 발생시켜 해안구조물의 안정에 큰 영향을 미치는 것으로 보고되며, 이에 관련 연구들이 활발하게 진행되고 있다. 반면, 하천구조물 주변 지반의 흐름 및 간극수압 뿐 아니라, 액상화에 관한 연구는 아직 미진한 실정이다. 본 연구에서는 수리구조물 주변의 유동 및 와동 현상 뿐 아니라, 수위차에 따른 지반 내부 유동장과 간극수압에 관한 특성을 분석하기 위해 유체-구조물-지반 비선형 상호작용을 고려할 수 있는 수치수조를 새롭게 제안하였다. 그리고 제안하는 수치수조의 타당성 및 유효성을 검증하기 위해 기존 실험값과 비교·검토를 수행하였고, 그 결과는 거의 유사한 경향을 나타내었다. 또한 이 수치수조에 다양한 입사조건(상·하류 수위차)에 적용하여 유체-구조물-지반의 비선형동적상호간섭 해석을 수행하였다. 최종적으로 수치수조에서 측정한 구조물 주변의 유동, 와동, 수위로부터 수리특성을 논의하였다. 게다가 지반내의 흐름과 간극수압을 측정하여 상·하류 수위차가 수리구조물의 안정성에 미치는 영향을 분석할 수 있었다.

• The Journal of Engineering Geology
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• v.3 no.2
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• pp.203-214
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• 1993

Underground Injection Control regulations for Class I injection wells require that the vertical dufusion be considered as a mechanism for transport of contaninants in evaluating containment Due to the low permeability in the confining aquitard, the movement of contaminants over the long term is controlled by the molecular diffusion. The movement can be predicted, using the Fick' S second law of diffusion. The diffusion coefficient in Fick' s law has been determined experimentally in this study. Instantaneous injection of $^{51}Cr$ was used to trace the distribution of Cr(VI) in soil plugs and an analytical solution was applied to calculate the diffusion coefficients. This study shows the effect of environmental factors, such as temperature, chloride concentration, applied amount of $^{51}Cr$, and bulk density of injection formations on diffusion of Cr(VI)

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.344-350
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• 2019

In this study, waves2Foam implemented in OpenFOAM is used to simulate numerically the wave pressure on a verical caisson under the condition of with and without the placement of Tetrapods in front of the caisson. The comparisons of the numerical results and the experimental data show fairly good agreement between them. Based on this, it is possible to suggest an optimal combination of coefficients for an empirical formula to represent the protective TTP layer as porous media.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.109-122
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• 1993

ln this paper, a finite element analysis procedure is proposed for the incremental multi-step excavations in a fluid-saturated porous medium such as saturated soil ground. As the basis of derivation, Biot's equation was used. The proposed procedure was applied to some one- and two-dimensional problems under incremental excavations. Unsaturated cases as well as saturated cases were considered for comparison. Through numerical tests, the effects of permeability and excavation speed on the deformation history was investigated. Results showed that pore pressure built up during incremental excavation has a significant effect on the deformation and stresses of solid skeleton and validated the use of the present procedure for the analysis of multi-step excavations in fluid-saturated media such as in saturated shallow ground.

• Water for future
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• v.24 no.1
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• pp.109-117
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• 1991

The governing equation of flow in porous media is developed on the bases of the continuity equation of fluid for transient flow through a saturated-unsaturated zone, and substitution of Darcy's law. The numerical solutions are obtained by finite element method based on the Galerkin principles weighted residuals. The analysis are carried out by using the unsteady storm data observed and rainfall intensities which are obtained by using the rainfall excess model in considering of the initial losses. The functional relationships between the hydraulic conductivity, capillary pressure head and volumetric water content are applied to the flow of water through unsaturated soil varied with changes of water content.