• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.1
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• pp.71-78
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• 2002

In this study, the influence of the presence of discontinuity planes on the load transfer mechanism and the pattern of loosening zone was studied based on the laboratory test. The trap-door and the reaction plates are installed as the bottom plane of the model box. The vertical discontinuity plane is installed in the dry sand. Various overburden heights and locations of discontinuity planes are applied as major factors in this study. The results show that at higher overburden heights over about 1.5 times the excavation width, the ratio of the transferred stress to the insitu stress converges to a certain value even if the overburden height increases further. The results also show that the discontinuity plane gives relatively larger influence on the load transfer mechanism, that produces the unsymmetrical load concentration, when the discontinuity plane locates within the tunnel width. When the discontinuity plane locates outside the tunnel width, the unsymmetrical load concentration is reduced considerably.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.27-27
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• 2007

Cu via fill 도금 시, void, seam과 같은 내부 defects는 공정 중 신뢰성을 떨어뜨리며, 전기신호 전달속도를 느리게 한다. 또한 Cu via fell 도금 공정 중 발생하는 과도한 Cu 표면 도금층은 wafer thenning 공정의 생산성 저하와 공정 비용 상승을 유발한다. 3D Interconnection용 직경 30${\mu}$m, 깊이 120${\mu}$m (Aspect Ratio : 4) Via를 이용하여 정류방법, 전류 parameter, 첨가제 조성에 따른 Cu via felling 특성과 overburden두께 변화를 실험적으로 검증하였다.

• Research in Community and Public Health Nursing
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• v.14 no.2
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• pp.263-273
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• 2003

Objectives: The purpose of this study was to identify the family phenomenon and characteristics by ICNP such as family shape, life standard. area, and development stage. Method: 1. Sample size was 115. 2. Data analysis method included frequency analysis including ratio. Results: 1. On the distribution of the family phenomena by family shape, the nuclear family showed a higher ratio on the distribution in family communication and the unhealthy life style. The nuclear family was related to children andhad a higher ratio on the inadequate care management of the sick member. The extended family showed the highest ratio on the inadequate care management of sick member. 2. On the distribution of the family phenomena by family life standard, the family with medium life standard showed a higher ratio on the inappropriate family coping, whereas the family with lower life standard appeared to have a higher ratio on the inadequate care management of the sick member. 3. On the distribution of the family phenomena by area. the large city area showed the highest ratio on the inappropriate family coping, the medium and small city area appeared to have the highest ratio on the unhealthy life style. The county area showed the highest ratio on the inadequate care management of sick member. 4. On the distribution of the family phenomena by development stage, the family in rearing period showed a higher ratio on the inappropriate family coping and the lack of family intimacy. Families with preschool children showed a higher ratio on the unhealthy life style, and families with school age children showed the highest ratio on the inappropriate family coping. Families with adolescents appeared to have the highest ratio on the disturbance in family communication, and families with launching young adults showed the highest ratio on the inadequate care management of sick member. 5. On the distribution of the family characteristics by family shape, the nuclear family showed a higher ratio on the family characteristics such as less communication chances among family members and neglect of general child rearing, whereas the third generation family appeared to have a higher ratio on the characteristics such as overburden of housewife's role and short of caring among family members. 6. On the distribution of the family characteristics by family life standard, the family of medium life standard showed higher ratio on the family characteristics such as a few communication chance among family and overburden of housewife's role, and the family of lower life standard appeared to higher ratio on the family characteristics such as short of caring among family members. 7. On the distribution of the family characteristics by area. the large city area showed a higher ratio on the family characteristics such as overburden of housewife's role and neglect of general child rearing. The medium and small city area appeared to have a higher ratio on the family characteristics such as less communication chancec among family members. The county area showed a higher ratio on the family characteristics such as short-term care among family members. 8. On the distribution of the family characteristics by development stage, the family with rearing period showed a higher ratio on the family characteristics such as neglect of general child rearing. Families with preschool children showed a higher ratio on the family characteristics such as less communication chancec among family members. Families with school age children showed a higher ratio on the family characteristics such as overburden of housewife's role. Families with adolescents appeared to have a higher ratio on the family characteristics such as less communication chances among family members. Families with launching young adults showed a higher ratio on the family characteristics such as less communication chances and short-term care among family members.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.37-47
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• 2004

In Korea, over three hundreds of the coal mines were closed or abandoned due to the depression of the mining industry since the late 1980s. Many of them locate in the steep mountain valleys and the coal mine wastes had been disposed without a proper treatment From these mines, enormous amounts of coal mine overburdens have been abandoned in the slopes and the ample amounts of acid mine drainage (AMD) from either portal or overburdens have been discharging directly to the streams, causing the detrimental effects on soil and water qualities. Objectives of this research were to reclaim the coal mine overburdens using the lime waste cake from the soda ash production by stabilizing the overburden slopes, introducing the vegetation alleviate the environmental problems caused by the closed coal mines. The percentages of the grass distribution ratio (%) and the surface coverage ($\textrm{cm}^2$) in each treatment plot were determined during June to August after seed spraying grasses such as orchard grass (Dactylis glomerata L), Kentucky Bluegrass (Poa pratensis L.) and Eulalia (Miscanthus sinensis Anderss) at the end of May. The grasses covered only 15.5 % of the coal overburden plot at the early stage but the coverage was increased with time to 33% in August. Growth of such grasses was enhanced with the combined treatments of lime waste and topsoil resulting in the increased surface coverage by the grasses. The Increment of the surface coverage from June to August was higher with lime waste treatments. The distribution percentages and surface coverage were highest when the lime wastes were treated at 25 % of the lime requirement. This might be related with the high salt contents in the hire wastes. Results demonstrated that the amounts of lime wastes at 25% of the lime requirement were sufficient for neutralizing the acidic coal overburden and introducing the re-vegetation. Either layering between the coal waste and topsoil or mixing with coal overburdens could be adopted as the lime waste treatment method. The combined treatment of lime wastes and topsoil was recommended for re-vegetation in the coal overburden slopes. The lime wastes from the soda ash production might have a potential to be recycled for the reclamation of the abandoned coal mines to alleviate the environmental problems associated with coal mine waste.

• Geomechanics and Engineering
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• v.24 no.4
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• pp.389-397
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• 2021

Pile foundation is a typical form of bridge foundation and viaduct, and large-diameter rock-socketed piles are typically adopted in bridges with long span or high piers. To investigate the effect of a mountain slope with a deep overburden layer on the bearing characteristics of large-diameter rock-socketed piles, four centrifuge model tests of single piles on different slopes (0°, 15°, 30° and 45°) were carried out to investigate the effect of slope on the bearing characteristics of piles. In addition, three pile group tests with different slope (0°, 30° and 45°) were also performed to explore the effect of slope on the bearing characteristics of the pile group. The results of the single pile tests indicate that the slope with a deep overburden layer not only accelerates the drag force of the pile with the increasing slope, but also causes the bending moment to move down owing to the increase in the unsymmetrical pressure around the pile. As the slope increases from 0° to 45°, the drag force of the pile is significantly enlarged and the axial force of the pile reduces to beyond 12%. The position of the maximum bending moment of the pile shifts downward, while the magnitude becomes larger. Meanwhile, the slope results in the reduction in the shaft resistance of the pile, and the maximum value at the front side of the pile is 3.98% less than at its rear side at a 45° slope. The load-sharing ratio of the tip resistance of the pile is increased from 5.49% to 12.02%. The results of the pile group tests show that the increase in the slope enhances the uneven distribution of the pile top reaction and yields a larger bending moment and different settlements on the pile cap, which might cause safety issues to bridge structures.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.260-266
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• 2010

In this study, wish to analyze effect that affect on each tunnel (right and left tunnel) according as proceeding of leading tunnel (right tunnel), following tunnel (left tunnel) and pilot tunnel excavation through behavior of tunnel and surrounding base by model tests. And stress-transfer mechanism that occurs from in-situ loosing area and arching effect by difference of stiffness ratio and overburden heights were verified experimentally. The model tests were carried out by varying the stiffness of reinforced area and overburden height, measured deformation of tunnel and displacement of surrounding base. The model tests followed exactly the real 2-Arch tunnel construction stages.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.1
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• pp.63-71
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• 2018

In this study, the torque and horizontal stress acting on vane were measured and then used to determine a friction angle of sand. A dry Nakdong River sand was prepared for loose and dense conditions in a cell and then pressurized with 25, 50, 75 or 100 kPa from the surface of sand. A vane (5cm in diameter and 10cm in height) was rotated and the torque and horizontal stress were measured at real time. A maximum torque was 3.5-9.5Nm for loose sand and 7.4-17.6Nm for dense sand, respectively. The maximum torque increased as an overburden pressure increased. The maximum torque obtained at 14-20 degrees of vane rotation, which was not influenced by the initial alignment of earth pressure and vane blade. An initial horizontal stress ratio was 0.33-0.35 on the average. The horizontal stress increased initially and then decreased due to particle disturbance. A friction angle was calculated from real time varying horizontal stress and torque, which decreased with increasing overburden pressure. The friction angle of loose sand from vane shear test was similar to that of direct shear test but that of dense sand was overestimated.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.905-912
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• 2009

1-g shaking table test is conducted to evaluate the dynamic behavior of a soil-structure system under seismic loading condition. A consistent similitude law between the model and prototype is needed to predict the behavior of the prototype structure, quantitatively. The natural frequency of geomaterial decreases with the increase of shaking intensity because of the non-linear property of the geomaterial. This phenomenon affects the applicability of similitude laws in 1-g shaking table tests. In this study, a simple method is suggested to determine the frequency of the input motions in 1-g tests in order to enhance the applicability of similitude laws. Modified input frequency is calculated using the frequency ratio with consideration of the variation of the natural frequency according to the intensity of input ground acceleration. To verify the applicability of the suggested method, a series of 1-g shaking table tests were performed for three different sizes of model piles having an overburden mass on their heads by varying the acceleration and the frequency of input motion. The acceleration amplification ratio on the overburden mass, the lateral displacement at the pile head and the maximum bending moment along the pile depth were measured. The projected behaviors of the virtual prototype based on the measured values of the model tests, where the input frequencies were calculated by the new method, showed good consistency, verifying the applicability of the suggested method.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.197-209
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• 2020

Evidence of liquefaction during the 2017 Pohang earthquake has highlighted the urgent need to evaluate the current seismic design standard for liquefaction in Korea, particularly the liquefaction triggering standard. With the simplified method, which is the most popular method for evaluating liquefaction triggering, the factor of safety for liquefaction triggering is calculated via the cyclic stress ratio (CSR) and the cyclic resistance ratio (CRR). The parameters in the CSR and CRR have undergone changes over time based on new research findings and lessons learned from liquefaction case-histories. Hence, the current design standard for liquefaction triggering evaluation in Korea should also reflect these changes to achieve seismic safety during future earthquakes. In this study, liquefaction susceptibility criteria were discussed initially and this was followed by a review of the current liquefaction triggering codes/guidelines in other countries and Korea. Next, the parameters associated with the CSR such as the maximum ground acceleration, stress reduction factor, magnitude scaling factor, and overburden correction factor were discussed in detail. Then, the evaluation of the CRR using the SPT N-value and CPT qc-value was elaborated along with overburden and clean-sand correction factors. Based on this review of liquefaction triggering evaluation standards, recommendations are made for improving the current seismic design standard related to liquefaction triggering in Korea.

• Structural Engineering and Mechanics
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• v.29 no.4
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• pp.433-453
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• 2008

The equation of motion of a one way (vertical) spanning strip wall, as an assembly of two rigid bodies, is presented. Only one degree of freedom is needed to completely describe the wall response as the bodies are assumed to be perfectly rectangular and are allowed to rock but not to slide horizontally. Furthermore, no arching action occurs since vertical motion of the upper body is not restrained. Consequently, the equation of motion is nonlinear, with non constant coefficients and a Coriolis acceleration term. Phenomena associated with overburden to self weight ratio, motion triggering, impulsive energy dissipation, amplitude dependency of damping and period of vibration, and scale effect are discussed, contributing to a more complete understanding of experimental observations and to an estimation of system parameters based on the wall characteristics, such as intermediate hinge height and energy damping, necessary to perform nonlinear time history analyses. A comparison to a simple standing, or parapet, wall is developed in order to better highlight the characteristics of this assembly.