• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.3
• /
• pp.389-407
• /
• 2017

In the current work, a series of three-dimensional finite element analysis was carried out to understand the behaviour of pile when the tunnel passes through the lower part of a single pile or group piles. At the current study, the numerical analysis analysed the results regarding the ground reinforcement condition between the tunnel and pile foundation. In the numerical modelling, several key issues, such as the pile settlements, the axial pile forces, the shear stresses and the total displacements near the tunnel have been thoroughly analysed. The pile head settlements of the single pile with the maximum level of reinforcement decreased by about 16% compared to the pile without ground reinforcement. Furthermore, the maximum axial force of the single pile with the maximum level of ground reinforcement experienced a 30% reduction compared to the pile without reinforcement. It has been found that the angle of ground reinforcement in the transverse direction affects the pile behaviour more so than the length of the ground reinforcement in the longitudinal direction. On the other hand, in the case of the pile group with the reinforced pile cap, the ground displacement near the pile tip appears to be similar to the corresponding ground displacement without reinforcement. However, it was found that the pile cap near the pile head greatly restrained the pile head movement and hence the axial pile force increased by about 2.5 times near the pile top compared to the piles in other analysis conditions. The behaviour of the single pile and group piles, depending on the amount of ground reinforcement, has been extensively examined and analysed by considering the key features in great details.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.16 no.6
• /
• pp.521-531
• /
• 2014

This paper is a study for behaviour of cavern type anchorage tunnels for suspension bridges with cable tension. Anchorage behaviour, design method for anchorage, and failure surface angle, ${\delta}$ are analyzed by comparing numerical analysis results and ultimate pullout capacities($P_u$) using bilinear corelation equation. Results show that design depths for cavern type anchorage tunnels are easily checked with linear relationships for $P/{\gamma}/H$ vs. displacement and $P_u/{\gamma}/H$ vs. H/b. The analysis results of maximum shear strain distribution and plastic status show that failure shapes are closer to circular arc model than soil cone model which frequently used. To an easy calculation of the ultimate pullout capacity, we propose a simple bilinear failure model in this study. The calculated ultimate pullout capacities from the proposed bilinear corelation equation using two failure angles results are similar to the ultimate pullout capacities from numerical analysis.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.38 no.2
• /
• pp.139-145
• /
• 2012

There is a unique type of fatty acid in the hair surface. 18-methyleicosanoic acid (18-MEA) is an unusual anteiso fatty acid covalently linked to the outermost surface of hair cuticle. A layer of 18-MEA is located in the upper ${\beta}$-layer of the CMC that is responsible for the low surface energy and low friction resistance of the hair's outer surface. The high mobility of 18-MEA molecule facilitates spreading of extraneous lipid by decreasing interfacial shear strength. In this study, we introduced N-hydroxyl succinimidyl ester functional group to the one end of C10 - 40 isoalkyl acid for regenerating hair surface with covalently bound fatty acid layer. The re-hydrophobicization of hair surface has been investigated by contact angle measurement. The inner moisture content of hair at different levels of humidity (40, 55, 70 %RH) was measured by electric moisture analyzer. Treatment with Hydroxysuccinimidyl C10 - 40 Isoalkyl Acidate (HCIA) was supposed to make hair surface smoother by filling the cracks between cuticles with covalently bound fatty acid monomolecular layer like cuticle glue. This glue effect was also confirmed with line profile of AFM images. Therefore, the moisture and structural components of inner hair were not easily flown out and the optimum moisture content could be kept constantly though the outside humidity level was changed. The lateral force microscopy (LFM) by using atomic force microscope showed that the friction force of hair surface treated with HCIA was decreased. It also showed the constantly sustained friction value even after shampooing repeated 15 times.

• Nuclear Engineering and Technology
• /
• v.24 no.1
• /
• pp.75-85
• /
• 1992

The texture changes and their effect on the 0.2% yield strength of Zircaloy-4 sheet were examined after quenched from the ($\alpha$+$\beta$) phase temperature. When the prior ($\alpha$+$\beta$) gram size was slightly larger than that of the $\alpha$-annealed, the observed texture was similar to the $\alpha$-annealed texture having an ideal orientation of the (0001) basal pole at 30$^{\circ}$away from the normal direction toward the transverse direction. When the prior ($\alpha$+$\beta$) grain size was twice as large as that of the $\alpha$-annealed, the location of maximum basal pole intensity was distributed between the transverse and the rolling direction making an angle 15$^{\circ}$from the normal direction, and the observed texture became isotropic. It was found that the Kearns texture parameter, fr, in the rolling direction increased steadily, and fr in the transverse direction increased slightly, while fr in the the normal direction decreased with increasing heat treatment time. With a small increase in fr, the 0.2% yield strength increased drastically. The influence of texture was analyzed by deriving the Schmid orientation factors and the resolved shear stresses for the deformation systems. It was found that the large increase in the 0.2% yield strength was attributed mainly to the microstructural changes and partly to the texture changes by the ($\alpha$+$\beta$) heat treatment.

• Journal of Korea Water Resources Association
• /
• v.43 no.7
• /
• pp.657-666
• /
• 2010

The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.

• Economic and Environmental Geology
• /
• v.53 no.1
• /
• pp.71-85
• /
• 2020

To understand behavior of fault cores in the field of geotechnical and geological engineering, we present an investigation of the physical properties (breccia and clay contents, unit weight, porosity, and water content) and friction characteristics (internal friction angle and cohesion) of fault cores, in granitic, sedimentary, and volcanic rocks in South Korea. The breccia contents in the fault cores are positively correlated with unit weight and negatively correlated with clay content, porosity, and water content. The inter-quartile ranges of internal friction angles and cohesion calculated from direct shear tests are 16.7-38.1° and 2.5-25.3 kPa, respectively. The influence of physical properties on the friction characteristics of the fault cores was analyzed and showed that in all three rock types the internal friction angles are positively correlated with breccia content and unit weight, and negatively correlated with clay content, porosity, and water content. In contrast, the cohesions of the fault cores are negatively correlated with breccia content and unit weight, and positively correlated with clay content, porosity, and water content.

• The Journal of Engineering Geology
• /
• v.14 no.4 s.41
• /
• pp.487-498
• /
• 2004

There is an increasing trend of construction works in mountainous areas by the urban development in Busan that is mainly composed of mountains. The study area, Hwangryeong Mt., is one of developing sites in the urban area, too. Landslides and cut-slope failures that occur large damages of human beings and the properties are influenced by soil characteristics as well as rock properties. This study analyzed geotechnical characteristics of soil dependent on geology at Hwangryeong Mt. where a large slope failure had been occurred in 1999. Geology of the study area is composed of the Cretaceous sedimentary rocks and volcanic rocks. Soil layer of the slopes can be grouped into sand mixed with clay and silt. The cohesion is plotted between $0.001\;and\;0.066kg/cm^2$. The friction angles are distributed in the ranges between $32^{\circ}\;and\;39^{\circ}$, meaning soil bearing a high friction angle. The permeability coefficients are plotted between $2.34\times10^{-4}cm/sec\;and\;2.58\times10^{-2}cm/sec$, indicating fine sand and loose silt with a medium grade of permeability. The sedimentary rocks area shows relatively higher permeability coefficients than those volcanic rocks area.

• The Journal of Engineering Geology
• /
• v.10 no.1
• /
• pp.1-12
• /
• 2000

Heaving of road and subsidence of slope took place at the Wiri region of the local highway 999 in Gyeongsangbukdo, Korea after heavy rain in the next year of construction. Although the state government had performed remedial treatments by reducing the angle and the height of the slope, deformation had never stopped. Therefore, we have preformed the analysis of deformation and stabilityof the slope. Study area consists of the Cretaceous shale, siltstone and sandstone and two faults are found. The major deformation occurred by sliding of rock mass along faults after heavy rain because not only thepore pressure at the fault plane and the unit weight of sliding mass increased, but did the shearstrength of saturated fault clay become very low. The decrease in shear strength of saturated fault clayis the major factor among the reasons for deformation. Numerical simulations using limit equilibriummodel, finite difference model and finite element model were performed for eight cross sections.Although safety factors are above 1.7 during the dry season, they become below 1.0 when groundwaterlevel raises to surface. The maximum displacement is about 15-3Ocm. However, safety factors increasedto above 2.4 and the maximum displacement is below 2.08cm after remedial treatment, Indicating thatthe slope becomes stable.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.325-334
• /
• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. A pushover analysis of the structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of the semi-rigid connection were adopted for the models. A fiber model was utilized for the moment-curvature relationship of the steel beam and the column, and a three-parameter power model was adopted for the moment-rotation angle of the semi-rigid connection. The top displacement, base-shear force, required ductility for the connection, sequence of the plastic hinge, and design factors such as the overstrength factor, ductility factor, and response modification coefficient were investigated using the pushover analysis of a 2D structure subjected to the equivalent static lateral force of KBC2005. The partial arrangement of the semi-rigid connection was found to have secured higher strength and lateral stiffness than that of the A-Semi frame, and greater ductility than the A-Rigid frame. The TSD connection was found suitable for use for economy and safety in the sample structure.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.2
• /
• pp.129-137
• /
• 2010

In this study, a five-story steel frame was designed in accordance with KBC2005 to evaluate the effect of the beam-column connection on the structural behavior. The connections were designed as a fully rigid connection and as a semirigid connection. A fiber model was utilized to describe the moment-curvature relationship of the steel beam and column, and a three-parameter power model was adopted for the moment-rotation angle of the semirigid connection. To evaluate the effects of higher modes on structural behavior, the structure was subjected to a KBC2005-equivalent lateral load and lateral loads considering higher modes. The structure was idealized as a separate 2D frame and as a connected 2D frame. The pushover analysis of 2D frames for the lateral load yielded the top displacement-base shear force, design coefficients such as overstrength factor, ductility ratio, and response modification coefficient, demanded ductility ratio for the semirigid connection,and distribution of plastic hinges. The sample structure showed a greater response modification coefficient than KBC2005, the higher modes were found to have few effects on the coefficient, and the lateral load of KBC2005 was found to be conservative. The TSD connection was estimated to secure economy and safety in the sample structure.