• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.2
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• pp.37-44
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• 2008

A theoretical equation was proposed to consider the effect of ponding for the excess pore water pressure in agricultural reservoir on soft clay ground. The value of excess pore water pressure predicted using the proposed equation was compared to those predicted with the Terzaghi's method and the finite difference method(FDM), respectively, for the purpose of verification. The degree of consolidation according to ponding predicted by applying the proposed equation was close to the observed degree of consolidation on the double drainage condition(at DP-3) but it was less than the observed degree of consolidation on the single drainage condition(at DP-5). The equation was very applicable to practice because the analysis result by the equation was close to the observed data.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.5
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• pp.505-510
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• 2008

Excess sludge and raw sludge were treated by ball mill in order to promote solubilization, and it was known that the level of solubilization was higher in excess sludge rather than raw sludge. About solid concentration, with the increase of TS, the amounts of solubilization was increased. And excess sludge was solubilized more effectively with the increase of ball mill treatment time. Especially, in case of excess sludge, within 5 min of ball mill treatment, 6 times of solubilization was achieved compared with raw sludge. The effect of bead size was also tested and 1 mm bead was most desirable when applied to the TS 4% of excess sludge. Particle size decrease by the ball mill treatment was more effective in raw sludge, nevertheless the level of solubilization was always higher in excess sludge. This means that the results of particle analysis could not be understood as a indicator for sludge solubilization. Generally, excess sludge and raw sludge are mixed at the thicker in the STP, but considering a ball mill pretreatment as an alternative for sludge solubilization, it is desirable to treat not raw sludge but excess sludge alone in the aspect of solubilization yield and economical process.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.46-53
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• 2009

Phase equilibrium and dynamic behavior studies were performed in systems containing $C_{12}E_5$ nonionic surfactant solution and nonpolar hydrocarbon oil. The phase behavior result showed an oil-in-water(O/W) microemulsion(${\mu}E$) in equilibrium with excess oil phase at low temperatures and a water-in-oil(W/O) ${\mu}E$ in equilibrium with excess water phase at high temperatures. For intermediate temperatures a 3 phase region containing excess water, excess oil, and a middle-phase microemulsion was observed and the transition temperature was found to increase with an increase in the chain length of a hydrocarbon oil. Dynamic behavior at low temperatures showed that an oil drop size decreased linearly with time due to solubilization into micelles and the solubilization rate decreased with an increase in the chain length of a hydrocarbon oil. On the other hand, both spontaneous emulsification of water into oil phase and expansion of oil drop with time were observed because of diffusion of surfactant and water into oil phase. Under conditions of a 3 phase region including a middle-phase ${\mu}E$, both rapid solubilization and emulsification of oil into aqueous surfactant solution were found mainly due to the existence of ultra-low interfacial tension. Interfacial tensions were measured as a function of time for n-decane oil drops brought into contact with 1 wt% surfactant solution at $25^{\circ}C$. Both equilibrium interfacial tension and equilibration time were found to increase with an increase in the chain length of a hydrocarbon oil.

• Applied Chemistry for Engineering
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• v.20 no.5
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• pp.473-478
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• 2009

Phase equilibrium and dynamic behavior studies were performed on systems containing $C_{10}E_5$ nonionic surfactant solutions and nonpolar hydrocarbon oils. The phase behavior showed an oil in water (O/W) microemulsion (${\mu}E$) in equilibrium with excess oil phase at low temperatures and a water in oil (W/O) ${\mu}E$ in equilibrium with excess water phase at high temperatures. For intermediate temperatures a three-phase region containing excess water, excess oil, and a middle-phase microemulsion was observed and the transition temperature was found to increase with an increase in the chain length of a hydrocarbon oil. Dynamic behavior at low temperatures showed that an oil drop size decreased linearly with time due to solubilization into micelles and the solubilization rate decreased with an increase in the chain length of a hydrocarbon oil. On the other hand, both spontaneous emulsification of water into oil phase and expansion of oil drop were observed because of diffusion of surfactant and water into oil phase. Under conditions of a 3 phase region including a middle-phase ${\mu}E$, both rapid solubilization and emulsification of oil into aqueous solutions were found mainly due to the existence of ultra-low interfacial tension. Interfacial tensions were measured as a function of time for n-decane oil drops brought into contact with 1 wt% surfactant solution at $25^{\circ}C$. Both equilibrium interfacial tension and equilibration time increased with an increase in the chain length of a hydrocarbon oil.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.416-422
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• 2011

In this study, the effect of cosurfactant on the phase equilibrium and dynamic behavior was studied in systems containing NP7 nonionic surfactant solutions and nonpolar hydrocarbon oils. All cosurfactants used during this study such as n-pentanol, n-octanol and n-decanol acted as a hydrophobic additive and thus promoted the transition from an oil in water (O/W) microemulsion (${\mu}E$) in equilibrium with an excess oil phase to a three-phase region containing excess water, excess oil, and a middle-phase microemulsion and further to a water in oil (W/O) ${\mu}E$ in equilibrium with the excess water phase. The transition temperature was found to decrease with both increases in the chain length and amount of addition of a cosurfactant. Dynamic behavior studies under O/W ${\mu}E$ conditions showed that an oil drop size decreased with time due to the solubilization into micelles. On the other hand, both the spontaneous emulsification of water into the oil phase and the expansion of oil drop were observed under W/O ${\mu}E$ conditions because of the diffusion of surfactant and water into the oil phase. Under conditions of a three-phase region including a middle-phase ${\mu}E$, both the rapid solubilization and emulsification of the oil into aqueous solutions were found mainly due to the existence of ultra-low interfacial tension. Dynamic interfacial tension measurements have been found to be in a good agreement with dynamic behavior results.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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• pp.107-113
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• 2006

Earthquake motion is one of the most significant influence factors on the slope stability. In this paper, an effective stress analysis with the elasto-plastic model was carried out to investigate the behavior of the slope stability subjected to the successive two strong earthquake motions, fore and main shock. The major influence of fore shock to the slope stability was considered as the existence of the residual excess pore water pressure. The paper presents the influence of the existence of the fore shock to slope stability using the numerical analyses. In conclusion, the excess pore pressure by the fore shock was not dissipated during the 7hrs of consolidation. By this residual excess pore water pressure, the factor of safety at the sliding face showed the minimum values, and the deformations of slope was large when compared with the case that considered the main shock only. Furthermore, the minimum of the factor of safety came out after the end of the earthquake motion.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.763-770
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• 2006

The purpose of this study was to investigate the effects of mechanical(ball-mill) solubilization of excess sludge especially focused on the TSS(total suspended solid) reduction during the conventional aerobic digestion of sewage sludges including primary and/or excess sludge, HRT was examined at the 10 days and 20 days. According to the results of this study, TSS removal efficiency of solubilized excess sludge was almost two times higher than that of non-solubilized excess sludge. And as the proportion of the primary sludge increased, TSS removal efficiency became worse because primary sludge rarely contained microbial cells which could be easily solubilized physically. It was also proved that by the application of proper solubilization techniques to the excess sludge, HRT for the aerobic digestion could be lessened(above 50%) dramatically keeping the same or better digestion performance. The fact that between primary and excess sludges, only the excess sludge is quite effective in the sludge solubilization and in it's reduction says that excess sludge releasing sources are key-point in the sludge cake reduction field as a source control.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1098-1107
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• 2001

This study is to develop the pretreatment for the excess and digested sludge by elector-coagulation and dewatering. Electrocoagulation is applied to excess and digested sludge before transferring to the pistion type for dewatering. Piston type filter press as a laboratory scale plant was used to estimate the dewaterability. MMD of excess sludge was increased from initial diameter of particles ($34.16{\mu}m$) to the 87%($64.01{\mu}m$) after electrocoagulation. Al electrode is more effective than Fe electrode for the dewaterabiltity of excess sludge Electrodewatering after electrocoagulation as pretreatment makes the water content of sludge cake 50~60 wt%.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.27-37
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• 2011

Uplift phenomenon occurs when the apparent unit weight of buried geo-structures becomes smaller than that of the liquefied backfill due to the increase of an excess pore water pressure during strong earthquakes. In order to explain the relationship between the uplift displacement of the buried geo-structures and the increase of the excess pore water pressure ratio in backfill, dynamic centrifuge model tests are conducted. In the present study, primary and secondary factors against uplift behavior of the buried geo-structures are considered in the dynamic centrifuge model tests. Among these factors, the most important factors affecting the increase in the excess pore water pressure ratio were the ground water depth, the relative density of backfill, and the amplitude of the input acceleration, which were also largely affect the uplift amount of the buried geo-structures.

• Journal of Navigation and Port Research
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• v.37 no.2
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• pp.173-179
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• 2013

The interaction among wave, seabed and marine structure is an important issue in coastal engineering as well as geotechnical engineering. Understanding variations of stresses and pore water pressures generated in seabed induced by waves is important for civil engineers who have to design the foundation for various marine structures and verify the instability of seabed. In the matters on seabed instability, particularly, in the case of wave-induced liquefaction of seabed, it is turned out there are two different mechanisms through previous studies. These are caused by the transient or oscillatory nature and the residual or progressive nature of excess pore water pressure generated in seabed, respectively. In this study, it is analyzed dynamic characteristics of soils sampled in seabed around the port of Kochi, Japan, through the dynamic triaxial tests and the residual excess pore water pressure in the seabed induced by seepage force of wave. In addition, the calculated residual excess pore water pressures were compared with the field data observed in the port of Kochi.