• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.661-669
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• 1999

이 논문은 탄성지반위에 놓인 원호형 곡선보의 자유진동에 관한 연구이다. 회전관성 및 전단변형을 고려하여 두 개의 매개변수로 표현되는 탄성지반위에 놓인 원호형 곡선보의 자유진동을 지배하는 미분방정식을 유도하고, 이를 수치적분기법과 시행착오적 행렬값탐사법이 결합된 수치해석기법으로 해석하였다. 회전-회전, 회전-고정 및 고정-고정의 단부조건을 갖는 곡선보의 최저차모드 3개의 고유진동수를 산출하였다. 곡선보의 수평높이 지간길이비, Winkler 지반계수, 전단지반계수에 따른 고유진동수 변화를 분석하였으며, 회전관성 및 전단변형의 영향을 고찰하였다.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.79-88
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• 2012

In this study, the tunnel loads acting on the concrete lining are analyzed by comparing three methods - Terzaghi table, Terzaghi formula and Ground-Lining Interaction (G.L.I) model. The tunnel loads are analyzed by FLAC 2D. And the G.L.I model is analyzed under various rock mass ratings, tunnel depths (20~80m) and in-situ stress ratios ($K_0$=0.5~2.0). Terzaghi's method can be applied only to weathered rocks and soils, and cannot reflect the effect of various tunnel depths and in-situ stress ratio. The proposed G.L.I model can not only be applied to various ground conditions, but also relieves the tunnel loads by up to 30%.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.101-115
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• 2005

For the site characterization at two inland areas, Gyeongju and Hongsung, which represent geomorphic and geologic characteristics of inland region in Korea, in-situ seismic tests containing borehole drilling investigations and resonant column tests were peformed and site-specific seismic response analyses were conducted using equivalent linear as well as nonlinear scheme. The soil deposits in Korea were shallower and stiffer than those in western US, from which the site coefficients and site classification system in Korea were derived. Most sites were categorized as site classes C and D based on the mean shear wave velocity $(V_s)$ of the upper 30 m $(V_s30)$, ranging between 250 and 650 m/s. According to the acceleration response spectra determined from the site response analyses, the site coefficients specified in the current Korean seismic design guide underestimate the ground motion in the short-period band and overestimate the ground motion in mid-period band. These differences can be explained by the differences in the bedrock depth and the soil stiffness profile between Korea and western US. The site coefficients, $F_a$ for short-period and $F_v$ for mid-period, were re-evaluated and the site classification system, in which sites C and D were subdivided according to $V_s20,\;V_s15,\;and\;V_s10$ together with the existing $V_s30$ was introduced accounting for the local geologic conditions at inland region of the Korean peninsula. The proposed site classification system in this paper is still rudimentary and requires modification.

• Geotechnical Engineering
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• v.13 no.1
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• pp.47-58
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• 1997

The predicted consolidation behavior of in-situ soft clay is quite different from the meas ureal one mainly due to the approximate numerical modelling techniques as well as the uncertainties involved in soil properties and geological configurations. In order to improve the prediction, this paper takes the following pinto consideration : an optimization technique should be adopted for characterizing the in-situ properties from measurements and also an equivalent and efficient model be considered to incorporate the actual 3-D effects. The soil parameters used be the modified Camflay model, which have an effect on the process of consolidation, were back-analyzed by BFGS scheme on the basis of settlements and pore pressures measured in real sites. The optimization technique was implemented in a general consolidation analysis program SPINED. By using the program, one may be able to appropriately analyze the timetependent consolidation behavior of soft deposits.

• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.41-49
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• 2012

In this study, laboratory test, in-situ vane shear test and piezocone penetration test in the study area were conducted to investigate the engineering characteristics of soft soils at Cheongra District, Songdo District in Incheon City, the west coast of Gyeonggi province, and Sihwa District in Ansan city. The correlations among compression index, and in-situ vane shear test, and cone resistance were obtained. The variations of liquid limit, plasticity index, water content and compression index with respect to depth exhibit strong similarity. This means that they have strong correlations, which can be used to evaluate the local characteristics of the study area. Thus, the correlations between compression index and physical properties were analysed to investigate the engineering characteristics of soft soil in the study area. The relationships between the measured piezocone factor by empirical methods, and undrained shear strength obtained by triaxial compression test or in-situ vane shear test were compared. It shows the significant correlation and piezocone factors, $N_{kT}$are suggested for the study area.

• Journal of the Korean GEO-environmental Society
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• v.11 no.11
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• pp.19-26
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• 2010

An influence factors for soundness evaluation of river levee include consisting embankment in case piping, permeability coefficient of ground, height of embankment, the width of crest, material characteristics of embankment and foundation ground, shape of embankment slope, an influence for penetration of rainfall or river water in case slope stability. In this study, it was operated a feasibility investigation of existing design result, stability evaluation for permeability coefficient use and permeability coefficient change of foundation ground to investigate an influence in line with permeability coefficient change for result of river levee penetration analysis. The evaluation results of influence factors, the permeability coefficient was used in design and it was evaluated influence in safety factor of piping. After the evaluation of influence factors, the permeability coefficient used in the design appears with the fact that differs in a design report about same soil.

• The Journal of Engineering Geology
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• v.29 no.1
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• pp.23-35
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• 2019

Landslides occur due to heavy rainfall in the summer season. Some of water may infiltrate into the ground; it causes a high saturation condition capable of causing a landslide. Soil properties are crucial in estimating slope stability and debris flow occurrence. The main study areas are Gwanaksan, Suraksan and Bukhansan (Mountain) in Seoul. A total of 44 soil samples were taken from the study area; and a series of geotechnical tests were performed. Physical and mechanical properties were obtained and compared based on region. As a result, among well-graded soils, they are classified as a clayey sand. Coarse-grained and fine-grained contents are approximately 95% and 5%, respectively, with very low amount of clay content. Density, liquid limit and dry unit weight are ranged in $2.62{\sim}2.67g/cm^3$, 27.93~38.15% and $1.092{\sim}1.814g/cm^3$. Cohesion and internal friction angle are 4 kPa and $35^{\circ}$ regardless of mountain area. Coefficient of permeability is varied between $3.07{\times}10^{-3}{\sim}4.61{\times}10^{-2}cm/sec$; it means that it results in great seepage. Permeability is inversely proportional to the uniformity coefficient and is proportional to the effective particle size. In the formal case, there was a difference by mountain area, while in the latter, the tendency was almost similar.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.21-33
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• 2020

Ground response analysis has been conducted for each borehole data in Pohang area, using 1D equivalent linear method program, to investigate the applicability of amplification factor to estimate peak ground acceleration. Earthquake motions for ground response analysis were prepared by matching response spectrums for return period of 500, 1000, and 2400 years suggested by seismic design code (MOIS, 2017). Ground survey data were acquired from Geotechnical Information DB System. It has been confirmed that response spectrum obtained from ground response analysis showed good agreement with those from seismic design code irrespective of ground classification. However, PGA (Peak Ground Accelerations) of ground response analysis did not coincide with PGA calculated using amplification factor suggested by seismic design code.

• Journal of the Korean Geosynthetics Society
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• v.5 no.2
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• pp.1-8
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• 2006

The properties of contaminated soil, contaminants and elapsed time are important considering factors to in-situ soil remediation. Gabr et. al. (1996) derived the solution equation of contaminant concentration ratio as initial one ($C/C_0$) with time and spatial changes in contaminated area which are embedded with vertical drains. The contaminant concentration ratio ($C/C_0$) is analyzed with time and spatial changes as varying the effective diameter, porosity, shape factor, density of contaminated soil, temperature in ground, unit weight and viscosity of contaminants by using FLUSH1 model modified from FLUSH. Results from numerical analysis indicate that the most important factor to the in-situ soil remediation in vertical drain system is the effective diameter of contaminated soil. It also shows that the next important factors are the viscosity of contaminants, porosity of soil, shape of soil, temperature in ground, unit weight of contaminants and density of soil, in order. However, the others except the effective diameter of contaminated soil are insignificant to the soil remediation.

• Geotechnical Engineering
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• v.6 no.1
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• pp.43-58
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• 1990

In order to get ultimate pullout resistance of ground anchor, the position of failure surface, normal stress and friction angle on the failure surface should be known. In this study, the position of failure surface is obtained by observing deformation of ground around anchor, and stresses on the anchor surface are analyzed by measuring normal and shear stresses on the anchor surface through model anchor test in plane strain. In addition, the relationship between lateral earth pressure and the position of failure surface is analyzed and the formula for calculating ultimate pullout resistance of anchor is proposed by using non-dimensional coefficient of ultimate pullout resistance.