• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.141-148
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• 1996

Use of stone column for deep ground treatment in soft clay soils is an effective method. The stone column significantly increases load carrying capacity of the soft clay soil. A analysis method for bearing capacity of stone column in soft clay soil is developed. The capacity made by developed method are compared wity observed values from field load test and a reasonable correlation is noted.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.65-84
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• 2002

The Observational Method proposed by Terzaghi can be applied for the safe and economic construction projects where the exact prediction of the behavior of the structures is difficult as in the underground excavation. The method consists of measuring lateral displacement, ground settlement and axial force of supports in the earlier stage of the construction and back analysis technique to find the best fit design parameters such as earth pressure coefficient, subgrade reaction etc, which will minimize the gap between calculated displacement and measured displacement. With the results, more reliable prediction of the later stage can be obtained. In this study, back analysis programs using the Direct Method, based on the Hill Climbing Method were made and evaluated, and to overcome the limits of the method, Genetic Algorithm(GA) was applied and tested for the actual construction cases.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.46-52
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• 2003

In this study, the full scale testing method of the geogrid-reiuorced soil Segmental Retaining Walll(SRW) under the simulated train loading were proposed in order to evaluate the applicability of reinforced soil SRW in railway embankment. The train loading was simulated by the design static wheel load and the impact coefficient due to the train passing velocity. This test was focused on the static performance of reinforced soil SRW in terms of the following measuring systems ; the horizontal earth pressure displacement acting on the facing block and the tensile strain along the geogrid. The data gathered from this full scale testing was compared with numerical analysis results by FLAC.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.65-72
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• 1983

Dry sand specimens for both normally consolidated and overconsolidated triaxial compression tests were prestressed on the path with five different coefficients of earth pressure 1.0, 3/4, 0.55, $K_0$ and 1/3. Deformation resistance of normally consolidated sand increased with increasing the initial stress for all coefficients of earth pressure during consolidation, and the deformation modulus at a certain initial stress showed a tendency to increase with increasing the coefficient of earth pressure. And deformation moduli($E_i$, $E_{50}$), were found to be proportional to the $n_{th}$ power of initial stresses[${\sigma}_{m0}{^{\prime}}$, ${\sigma}_{10}{^{\prime}}$, ${\sigma}_{30}{^{\prime}}$, $({\sigma}_1-{\sigma}_3)_0$] for both isotropically and anisotropically normally consolidated samples, where n varied from 0.37 to 0.92. Overconsolidated sand with the higher overconsolidation ratio showed the higher deformation modulus. It is concluded that the $K_0$-anisotropically consolidated triaxial compression test is necessary to obtain the more accurate value of in-situ deformation modulus.

• The Journal of Engineering Geology
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• v.33 no.2
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• pp.307-322
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• 2023

Rock-mass grouting plays a crucial role in the construction of dams and deep caverns, effectively preventing seepage in the foundations, enhancing stability, and mitigating hazards. Most rock grouting is affected by hydrogeological and rock engineering indices such as rock quality designation (RQD), rock mass quality (Q-value), geological strength index (GSI), joint spacing (Js), joint aperture (Ap), lugeon value (Lu), secondary permeability index (SPI), and coefficient of permeability (K). Therefore, accurate geological analysis of basic rock properties and guidelines for grouting construction are essential for ensuring safe and effective grouting design and construction. Such analysis has been applied in dam construction sites, with a particular focus on the geological characteristics of bedrock and the development of prediction methods for grout take. In South Korea, many studies have focused on grout injection materials and construction management techniques. However, there is a notable lack of research on the analysis of hydrogeological and rock engineering information for rock masses, which are essential for the development of appropriate rock grouting plans. This paper reviews the current state of research into the correlation between the grout take with important hydrogeological and rock engineering indices. Based on these findings, future directions for the development of rock grouting research in South Korea are discussed.

• Journal of the Korean earth science society
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• v.40 no.1
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• pp.9-23
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• 2019

Super-refraction of radar beams tends to occur primarily under a particular vertical structure of temperature and water vapor pressure profiles. A quality control process for the removal of anomalous propagation (AP) ehcoes are required because APs are easily misidentified as precipitation echoes. For this purpose, we collected X-band polarimetric radar parameters (differential reflectivity, cross-correlation coefficient, and differential phase) only including non-precipitation echoes (super-refraction and clear-sky ground echoes) and precipitation echoes, and compared the echo types regarding the relationships among radar reflectivities, polarimetric parameters, and the membership functions. We developed a removal algorithm for the non-precipitation echoes using the texture approach for the polarimetric parameters. The presented algorithm is qualitatively validated using the S-band Jindo radar in Jeollanam-do. Our algorithm shows the successful identification and removal of AP echoes.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.85-94
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• 2012

Evaluation of the smear effect caused by mandrel penetration into soft ground for a vertical drain installation is very important to predict the consolidation time of soft ground improvement. 30 kinds of laboratory model tests considering in situ conditions were conducted to investigate the formation of a smear zone and the decrease of coefficient of permeability in the disturbed zone. Three types(C(clay):M(silt)=1:1, 0.5:0.5, and 0:1) of reconstituted samples were used for 3 dimensional smear zone test. An experimental study was performed focusing on length of mandrel penetration, mandrel shape and size, earth pressure, and ground condition(unit weight and grain size distributions). Laboratory test results show that the length of mandrel penetration is the most critical factor for the formation of smear zone. As a result, the ratio between diameter of the smear zone($d_s$) and that of mandrel($d_m$) at field using long mandrel becomes larger than conventional $d_s/d_m$. The ratio between $d_s$ and $d_m$ ranges from 1.89 and 2.48 with the sample at C:M=1:0. It was also found that the $d_s/d_m$ value with the round shape of the mandrel is smaller than that of diamond one. The value of $d_s/d_m$ decreased with larger mandrel size, lower unit weight, and higher earth pressure. However, higher silt content led to increase of $d_s/d_m$. The ratio between coefficient of horizontal permeability in the smear zone($k_{hs}$) and that of undisturbed zone($k_{ho}$) ranged from 0.70 to 0.85. The test results imply that factors and values affecting $k_{hs}/k_{ho}$ show similar tendency with $d_s/d_m$.

• Journal of the Korean Geosynthetics Society
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• v.22 no.3
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• pp.11-25
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• 2023

In this study, the design and numerical analysis method of the inclined self-supported wall using cement treated soil were studied. In the case of the inclined self-supported wall, the active earth pressure decreased due to the decrease in the coefficient, Ka according to the slope (angle) and the weight decreasing effect, thereby increasing the overall stability. The wall with the slope caused a change in failure mode from overturning to sliding on the excavation side, and the optimal slope was evaluated to be about 10°. Compared to the strength reduction method, the overall stability in numerical analysis results in conservative results in limit equilibrium analysis, so it was found that this method should be attended when designing. As a result of the parameteric study, the stability on bearing capacity and compression failure did not significantly increase above the slope of 10° when the surcharge was small (about 20kPa or less). In the case of cohesion of the backfill, The results similar to numerical analysis were found to consider cohesion. It was evaluated that stability on sliding, oveturning, shear, and tension failure increases in proportion to the thickness of the wall, but there is no significant change in the stability on the bearing capacity and compressive failure regardless of the thickness of the wall above a certain angle (about 10°).

• Journal of the Korean Geotechnical Society
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• v.26 no.5
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• pp.37-48
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• 2010

In this study, the seepage flow monitoring method by the hydraulic head loss rate was developed for the purpose of application to offshore construction site enclosed by cofferdams in which seepage force varies periodically. The amount of the hydraulic head loss rate newly defined in this graph was in a range between 0 and 1. The zero of the rate means the existence of flow with no seepage resistance. The 1 of the rate means no seepage flow through the ground. The closer to 1 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows is stable. The closer to 0 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows was unstable and the higher the possibilities of existence of empty space or of occurrence of piping on the seepage flow pass in the ground is. The hydraulic head loss graph makes it possible to monitor sensitively the situation of seepage flow state, and the graph helps to understand easily the seepage flow state at the specific section on the whole cofferdam.

• Geotechnical Engineering
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• v.10 no.1
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• pp.63-70
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• 1994

In-situ soil is anisotropically consolidated at rest, and the coefficient of earth pressure at rest $K_0$ is dependent on the properties of soil and stress history. In order to estimate roughly the in-situ undrained shear strength of a $K_0$-anisotropically normally consolidated clay from isotropic consolidated undrained test, consolidated undrained shear testy with four different consolidation pressure ratios ($K={\sigma}'_{3c}/{\sigma}'_{1c}$) were performed and test results showed K-$\alpha$ relationship, representing the strength ratio $\alpha$ as ($S_u/{\sigma}'_{1c})_{CKU}=\alpha(S_u/{\sigma}'_{1c})_{CIU}$. Strength ratio u increases with increasing consolidation pressure ratio. And the angle of internal friction $\Phi'$and angle ratio $\Phi'_{CKU}/\Phi'_{CIU}/$ are increased with the increament of K-value.