• Geomechanics and Engineering
• /
• v.19 no.5
• /
• pp.435-445
• /
• 2019

A series of element tests with different drainage conditions and strain rates were performed on compacted unsaturated non-plastic silt in unconfined conditions. Soil samples were compacted at water contents from dry to wet of optimum with the degree of saturation varying from 24 to 59.5% while maintaining the degree of compaction at 80%. The tests performed were shear infiltration tests in which specimens had constant net confining pressure, pore air pressure was kept drained and constant, just before the shear process pore water pressure was increased (and kept constant afterwards) to decrease matric suction and to start water infiltration. In constant water content tests, specimens had constant net confining pressure, pore air pressure was kept drained and constant whereas pore water pressure was kept undrained. As a result, the matric suction varied with increase in axial strain throughout the shearing process. In both cases, maximum shear strength was obtained for specimens prepared on dry side of optimum moisture content. Moreover, the gradient of stress path was not affected under different strain rates whereas the intercept of failure was changed due to the drainage conditions implied in this study.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.03a
• /
• pp.1060-1067
• /
• 2009

Previous research on the slope failure has mainly reported that most of the slope failures occur due to surface rainfall infiltration in the rainy season. A slope of which surface is protected by shotcrete or plants, can also fail due to increase in pore water pressure from the ground water flow beneath the surface, rather than from the surface. In this study such case of slope behavior is investigated using the model test and numerical method including strength reduction method. Hydraulic boundary conditions of the slopes is considered using coupled numerical scheme. The failure mechanism of the slope is investigated and the effect of pore water pressure on slope safety is identified. Increase in pore water pressure due to lateral infiltration has significantly reduced the stability of slope.

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.122.1-122.1
• /
• 2005

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.131-134
• /
• 2002

Braided carbon fiber reinforced Al matrix composites were developed and characterized. Braided carbon fiber preforms with braiding angles of $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$ were manufactured by using a braiding machine. The manufactured braided carbon fibers were used as reinforcement to fabricate Al matrix composites by employing a pressure infiltration casting method. In the processing of pressure infiltration casting, important processing parameters such as melting temperature, preheating temperature of preform and applied pressure were optimized. Prediction of elastic constants on composites was performed by using the volume averaging method, which utilizes the coordinate transformation and the averaging of stiffeness and compliance constants based upon the volume of each reinforcement and matrix material. The elastic moduli of composites were evaluated by using Resonant Ultrasound Spectroscopy(RUS) method and compared with the elastic moduli obtained from static tensile test method.

• Journal of the Korean Geotechnical Society
• /
• v.31 no.8
• /
• pp.5-15
• /
• 2015

One-dimensional rainfall laboratory tests using gneissic weathered soil were conducted to investigate effect of antecedent rainfall on infiltration characteristics. Experimental results using samples from Chuncheon and Chungju sites showed that rainfall onto the ground surface decreased initial negative pore water pressure of unsaturated soils, which recovered gradually after the end of rainfall. Rainfall intensity increases water infiltration rate, and infiltration rate during main rainfall is faster than that of the preceding rainfall. It is considered that higher water saturation after antecedent rainfall increases water infiltration rate during main rainfall. In particular, Chungju sample with higher clay content had slower recovery of negative pore water pressure and infiltration rate. Numerical results using finite element slope stability analysis showed that reduction of initial negative pore pressure due to rainfall infiltration deteriorates slope stability, and diffusion of pore water pressure after the end of rainfall further reduces FS of the slope in the short term. Main rainfall after prior rainfall further reduced factor of safety of the unsaturated slope. Pattern of antecedent rainfall has a significant impact on the magnitude and distribution of initial pore water pressure in unsaturated soils which are controlling factor to assess factor of safety of unsaturated slope during rainfall.

• The Journal of Engineering Geology
• /
• v.24 no.1
• /
• pp.1-8
• /
• 2014

Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 1999.11a
• /
• pp.83-87
• /
• 1999

The fabrication process and thermal properties of 50~71vol% SiCp/Al metal matrix composites (MMCs) were investigated. The 50~71vol% SiCp/Al MMCs fabricated by pressure infiltration casting process showed that thermal conductivities were 118~170W/mK and coefficient of thermal expansion (CTE) were 9.5~$6.5{\times}10^{-6}/K$. Specially, the thermal conductivity and CTE of 71vol%SiCp/Al MMCs were 115~156W/mK and 6~$7{\times}10^{-6}/K$. respectively, which showed a improved themal properties than the conventional electronic packaging materials such as ceramics and metals.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2001.03a
• /
• pp.147-152
• /
• 2001

This study investigated one-dimensional vertical infiltration to an unsaturated residual soil by numerical solutions, FDM. In order to estimate the parameters needed for numerical analysis, tire soil-water characteristic curve(SWCC) of Shinnae-dong soil, one of the most typical residual soils in Korea, were experimentally obtained. Then, the statistical analysis for obtaining the SWCC was performed. The numerical solution to the linearized governing equation for unsaturated groundwater flow provides the infiltration characteristics for the unsaturated residual soil represented by transient pressure profiles and water contents profiles.

• Proceedings of the KSR Conference
• /
• 2003.10b
• /
• pp.397-402
• /
• 2003

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.46 no.4
• /
• pp.250-257
• /
• 2020

Objectives: Palatal infiltration is the most painful and uncomfortable anesthesia technique for maxillary impacted third molar surgery (MITMS). This approach could cause patients distress and aversion to dental treatment. The aim of this study was to evaluate the anesthetic efficacy of a buccal infiltration injection without a palatal injection in MITMS. Materials and Methods: This prospective research study was a crossover split mouth-randomized controlled trial. Twenty-eight healthy symmetrical bilateral MITMS patients (mean age, 23 years) were randomly assigned to two groups. Buccal infiltration injections without palatal injections were designated as the study group and the buccal with palatal infiltration cases were the control group, using 4% articaine and 1:100,000 epinephrine. The operation started after 10 minutes of infiltration. Pain assessment was done using a visual analogue scale and a numeric rating scale after each injection and extraction procedure. Similarly, the success rate, hemodynamic parameters, and additional requested local anesthetic were assessed. Results: The results showed that the pain associated with local anesthetic injections between both groups were significantly different. However, the success rates between the groups were not significantly different. Postoperative pain was not significant between both groups and a few patients requested an additional local anesthetic, but the results were not statistically significant. For hemodynamic parameters, there was a significant difference in systolic pressure during incision, bone removal, and tooth elevation. In comparison, during the incision stage there was a significant difference in diastolic pressure; however, other steps in the intervention were not significantly different between groups. Conclusion: We concluded that buccal infiltration injection without palatal injection can be an alternative technique instead of the conventional injection for MITMS.