• Journal of The Korean Society of Grassland and Forage Science
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• v.7 no.2
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• pp.109-112
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• 1987

This experiment was to study the effects of soil compaction and artificial pore space on the shoot density of tall fescue (Festuca arundinacea Schreb.). Tall fescue subjected to compaction treatments with control, 10, 20 and 40 kg power roller, used for two times bi-weekly during six months. Artificial pore space treatments were control, 13.5, 37.5 and 84.5% at 0-lOcm depth, respectively. 1. Soil compaction increased soil hardness and soil bulk density.2. Compaction level of lOkg (soil hardness 2.5kg/$cm^3$) showed the highest shoot density than that of other treatments. 3. Artificial pore space was positive significant correlated (p<0.01) with shoot density. 4. When over the 37.5% of total pore space could be mainternance for high shoot density after the soil compacted.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.181-191
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• 2016

In geological storage of $CO_2$, the behavior of $CO_2$ is influenced by pore network of rock. In this study, the drilling cores from Pohang Basin were analyzed quantitatively using three-dimensional images acquired by X-ray micro computed tomography. The porosities of sandstone specimens around 740 m-depth (T1), 780 m-depth (T2) and 810 m-depth (T3) which were target strata were 25.22%, 23.97%, 6.28%, respectively. Equivalent diameter, volume, area, local thickness of pores inside the sandstone specimens were analyzed. As a result, the microstructural properties of T1 and T2 specimens were more suitable for geological storage of $CO_2$ than those of T3 specimens. The result of the study can be used as input data of the site for decision of injection condition, flow simulation and so on.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.714-721
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• 2004

The purpose of this study is to find out the similitude laws for dissipation velocity of excess pore pressure after liquefaction according to magnitude of input accelerations and height of model soils from the results of impulse load tests. In impulse load tests, model soils were constructed to the height of 25cm, 50cm, and 100cm in acrylic tubes whose inside diameters were 19cm and 38cm respectively, and impulse loads were applied at the bottom of each model soil to liquefy the entire model soil. Excess pore pressure distribution by depth and settlement of soil surface were measured in each test. Dissipation curves of excess pore pressure measured in each tests were simulated by solidification theory, and dissipation velocities of excess pore pressure were determined from the slope of simulated dissipation curves. From the results of impulse load tests, dissipation velocity of excess pore pressure was not affected by magnitude of input acceleration, and from this fact, dissipation process was proved to be different from dynamic phenomenon. However, dissipation velocity of excess pore pressure increased as height of model soil increased and showed little difference as diameter of model soil increased. Therefore, the similitude law for dissipation velocity could be expressed by the similitude law for model height to 0.2 without regard to the diameter of model soil.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.45-55
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• 1999

Wave-induced response, liquefaction and stability of unsaturated seabed are studied. The unsaturated seabed is modeled as a fluid-filled polo-elastic medium. The coupled process of fluid flow and the deformation of soil skeleton is formulated in the framework of Biot's theory. The resulting governing equations are solved using a semi-analytical method to evaluate the stresses and pore water pressure of unsaturated and multi-layered seabed. The semi-analytical method can be applied to calculate a pore pressure and the stresses of in anisotropic inhomogeneous seabed. The results indicate that the degree of saturation influences mostly on the magnitudes of a pore pressure and the stresses of unsaturated and multi-layed seabed. Based on the pore pressure and stresses in seabed, the analysis on the possibilities of liquefaction and shear failure was performed. The results show that the maximum depth of shear failure occurrence is deeper than the maximum liquefaction depth.

• Membrane Journal
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• v.5 no.3
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• pp.119-128
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• 1995

The effects of coarsening on microstructure formation in polystyrene-cyclohexane solutions and membranes made from them were studied by scanning electron miccoscopy(SEM). Thermal analysis of the polymer solutions was carried out with a differential scanning calorimeter and the binodal curve was determined from the onset temperature of the heat of demixing peak. Using thermally induced phase separation(TIPS) and a freeze drying technique, it was demonstrated that polymer membrane microstructure can be changed significantly by controlling coarsening time and quench route. For systems undergoing phase separation by spinodal decomposition, resulting in a well interconnecmd, microporous structure with nearly uniform pore sizes, it was found that extending the phase separation time prior m freezing and solvent removal can result in a significant increase in pore or cell size which is highly dependent on both quench depth and coarsening time. Also this study has revealed the important role of polymer concentration in dictating the material continuity of the membranes.

• Journal of the Society of Disaster Information
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• v.15 no.1
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• pp.84-97
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• 2019

Purpose: The consolidation settlement of soft ground is dependent on the distribution of pore water pressure which is also affected by hydraulic conductivities (boundary condition) of layers, thickness of clayey soil layer and surcharge. Results: However, the current consolidation analyses are mostly based on Terzaghi's consolidation theory that assumes the initial pore water pressure ratio with depth to be constant. In this study, numerical analysis are carried out to investigate the variation of pore water pressure dissipation with depth and thickness of clayey soil layer, time, surcharge as well as drainage conditions. Conclusion: Comparative study with Terzaghi's consolidation theory is also conducted. The result shows that Terzaghi's consolidation theory should be used with caution unless it is ideally corresponded to the isochrone.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.2
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• pp.105-113
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• 2010

To investigate the restoration procedure on soil physical properties at the surface of visiting road affected by rest-year system. This study was carried out at visiting roads of stream of Chilsun in Jirisan. Mean soil strength in 20cm of soil depth was lower in the Rest-Year System areas (1.5-1.9 times in Site 2, 1.1-7.5 times in Site 3) than in the control (Site 1). Soil strength was recovered by the Rest-Year System in the national park. Mesopore rate (pF 2.7) in 0-15 cm of soil depth was higher in the Rest-Year System areas (1.2 times) than in the control. This indicates that mesopore rate is rapidly restoring in the Rest-Year System areas. Pore space rate in 0-7.5 cm of soil depth was higher in the Rest-Year System areas (23.2% in Site 2, 23.6% in Site 3) than in the control (22.4% in Site 1). Pore space rate in 7.5-15 cm of soil depth was also higher in the Rest-Year System areas (22.9% in Site 2 and Site 3) than in the control (18.9% in Site 1). Soil pore space was remediable by the Rest-Year System. Bulk density in 0-7.5 cm of soil depth was lower in the Rest-Year System areas (1.674g/$cm^3$ in Site 2, 1.668g/$cm^3$ in Site 3) than in the control (1.723g/$cm^3$ in Site 1). Bulk density in 7.5-15 cm of soil depth was lower in the Rest-Year System areas (1.785g/$cm^3$ in Site 2 and 1.721g/$cm^3$ in Site 3) than in the control (1.721g/$cm^3$ in Site 1). Soil bulk density was decreased in the Rest-Year System areas of the national park. Amount of soil erosion was lower in the Rest-Year System areas ($0.017m^3$/km/yr in site 2, $0.023m^3$/km/yr in site 3) than in the control ($0.054m^3$/km/yr in site 1).

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.74-77
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• 2003

This paper investigated the apparent chloride diffusivity of various concretes. Ten mixtures of concrete were initially prepared and tested to estimate diffusion property. The penetration depth and concentration of chloride ion were examined at the same water-binder ration. The binders were composed of normal portland cement, fly ash, ground granulated blast-furnace slag, and silica fume. From the results, it was concluded that using the mineral admixtures had a filling effect on the pore structure of cements matrix due to those pozzoanic reaction with the hydrates of cement, which increases the tortuosity of pore and makes large pore finer. And diffusivity of chloride is following: NPC100 > F10N90 > F30N70 > F20N80 > F20S05 > G30N70 > F10S05 > G30S05 > G30F15 > G50N50.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.257-265
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• 2021

In this study, we report niobium (Nb) with hierarchical porous structure produced by a one-pot, HF-free electrochemical etching process. It is proved experimentally that a well-defined hierarchical porous structure is produced from the combination of a limited repetition of pulse etching and high concentration of aggressive anion (i.e., SO₄^2-), which results in hierarchical pores with high order over 3. A formula is derived for the surface area of porous Nb as a function of the hierarchical order of pores while the experimental surface area is estimated on the basis of the electrochemical gas evolution rate on porous Nb. From the comparison of the theoretical and experimental surface areas, an in-depth understanding was gained about porous structure produced in this work in terms of the actual pore shape and hierarchical pore order.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.1
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• pp.79-89
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• 1996

It is expected that the soil hehaviours in the seahed subjected to cyclic wave loads are much different from that on the ground Cyclic shear stresses developed below the ocean bed as a result of a passing wave train may progressively build up pore pressure in certain soils. Such build-up pore pressure may be developed dynamic behaviour such as liquefaction and significant deformation of the seabed. Currently available analytical and testing methods for the seabed subjected to cyclic wave loads are not general. The purpose of the study are to provide a test method in laboratory and to analyse the mechanism of wave-induced stresses and liquefactions potentials of the unsaturated silty marine sand. It is showed that the test set-up made especially for this study delivers exactly oscillatory wave pressures of the form of sine function. Laboratory test results defining the cyclic shear strength of the unsaturated porous medium that is homogenously sedimented. It is understood that the pore water pressure due to induced-waves is not accumulated as the wave number increases but reveals periodical change on the still water surface. The magnitude of the pore water pressure tends to be attenuated radically with a certain time lag under the action of both high and low waves as depth increases.