• Journal of the Korean Geotechnical Society
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• v.21 no.9
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• pp.35-44
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• 2005

Recently, underground cavities such as limestone cavity and abandoned mine give rise to a lot of damage in SOC facilities. But there are many difficult problems such as delay of the working terms and enormous economic losses in finding a new method and changing construction design. In this study, a new filling material for underground cavities was developed using the stone-dust classified as industry waste polluting environment. As a result of test, filling material properties was that a compressive strength was $34{\~}60\;kgf/cm^2$, a change ratio in length was $0.268{\~}0.776\%$ and water absorption was $34.3{\~}46.9\%$. Also as a result of suspended mass test and pH test, it was confirmed that the developed filling material has a characteristic of non-separating in water and it was an environmentally friendly material.

• Geotechnical Engineering
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• v.14 no.5
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• pp.29-38
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• 1998

The purpose of this research is to develop an amended clay liner by utilizing waste lime produced as a by-product in chemical industries. Waste lime contains various kinds of organics which affect the permeability, compactability, and unconfined compressive strengths of soil. The geotechnical engineering properties of waste were improved by adding other materials so that they might meet the EPA requirement of clay liner. Granite weathered soil, which is abundant in Korea and can be obtained easily in the field. was used as a primary additive to improve geotechnical engineering properties of waste lime. Various kinds of laboratory tests related to geotecnnical engineering properties, required to evaluate the design criteria for the clay liner in the solid waste landfill. were carried out by changing miRing ratio of waste lime with additive. According to the laboratory test results, in order to obtain the appropriate amended clay liner. the effective miffing ratio of waste lime in granite weathered soil was proved to be about 20~30%.

• Journal of the Korean GEO-environmental Society
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• v.15 no.9
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• pp.59-67
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• 2014

With increasing underwater structure construction, there is high interest in offshore foundation and underwater grout and various study has been done in this area. For grout materials constructed underwater, it may be washed away by water or easily disturbed and material separation phenomenon during curing period always happens. As a result, it is difficult to ensure construction quality and this has a significant influence on the design strength of structure. In this study, to understand application effects of anti-washout admixture for the preplaced construction method, where grout is injected in monopile after filled with aggregates, laboratory tests on bleeding and compressive strength of anti-washout admixture were performed under various test conditions varying size of aggregate, water and cement ratio and admixture, and test results were compared and evaluated.

• Geotechnical Engineering
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• v.13 no.4
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• pp.85-94
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• 1997

The design and construction of underground structures contain many substantial mincer dainties. A reasonable estimation of geotechnical parameters is of paramount importance and must be one of the most difficult tasks in designing and constructing underground structures. If the plastic zone exists by tunnel excavation, the ground response may also be dependent on the yield criterion mainly composed of strength parameters. In order to estimate unknown model parameters from the in-situ measurements as well as prior estimates for designing tunnels which have plastic zones, the Extended Bayesian Method(EBM) is adopted : an elasto-plastic finite element program is linked to the EBM as a mathematical model to predict the ground response. Mohr-Coulomb failure criterion is used to represent the plastic behavior. A hypothetical underground site, where the ground behaves elasto-plastically, is adopted to demonstrate the validity of the proposed feedback system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1815-1829
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• 2014

Recently frequent collapse of old fill dams has taken place, which increases social awareness in the safety of the infrastructure. Fill dams in Korea has been incautiously regarded as safe once the fill dam is considered to have a full capacity to retain a conservative design flood determined by government authorities. However, developed foreign countries has been managing their fill dams by introducing systematic risk assessment techniques over a long period of time. In this study, the system response probabilities of the deteriorated old fill dams in Korea were systematically evaluated and analyzed by using the internal erosion toolbox based on the event tree analysis technique. The probability of the existence of flaw and the magnitude of the hydraulic gradient through a potential crack can significantly influence the geotechnical system response probability. The results of this study show that the probability of the existence of flaw and the magnitude of the hydraulic gradient through a potential crack can significantly influence the geotechnical system response probability and the risk of the deteriorated fill dam can be quantitatively assessed.

• Geomechanics and Engineering
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• v.11 no.1
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• pp.77-94
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• 2016

A forked tunnel, as a special complicated underground structure, is composed of big-arch tunnel, multi-arch tunnel, neighborhood tunnels and separate tunnels according to the different distances between two separate tunnels. Due to the complicated process of design and construction, surrounding jointed rock mass stability of the big-arch tunnel which belongs to the forked tunnel during excavation is a hot issue that needs special attentions. In this paper, an elasto-plastic damage constitutive model for jointed rock mass is proposed based on the coupling method considering elasto-plastic and damage theories, and the irreversible thermodynamics theory. Based on this elasto-plastic damage constitutive model, a three dimensional elasto-plastic damage finite element code (D-FEM) is implemented using Visual Fortran language, which can numerically simulate the whole excavation process of underground project and perform the structural stability of the surrounding rock mass. Comparing with a popular commercial computer code, three dimensional fast Lagrangian analysis of continua (FLAC3D), this D-FEM has advantages in terms of rapid computing process, element grouping function and providing more material models. After that, FLAC3D and D-FEM are simultaneously used to perform the structural stability analysis of the surrounding rock mass in the forked tunnel considering three different computing schemes. The final numerical results behave almost consistent using both FLAC3D and D-FEM. But from the point of numerically obtained damage softening areas, the numerical results obtained by D-FEM more closely approach the practical behaviors of in-situ surrounding rock mass.

• Journal of the Korean Geotechnical Society
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• v.37 no.2
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• pp.33-48
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• 2021

The rock anchorage of a suspension bridge is an outstanding anchorage type from environmental and economical perspective, although it should be applied when the bearing foundation is fresh enough to resist large cable loads. In practice, geotechnical engineers have encountered difficulties in designing the anchorage structure due to the fact that the physical behaviors of rocks against cable loads have not yet been fully proved and its design method was not established yet. In this study, model tests and numerical studies were performed to evaluate the behavior of the rock anchorage system planned under hard rock layers in domestic islands, and results suggest that the shape of asymmetric rock wedges can resist the tension loads with self weight and shear resistance. Additionally, real scale trial tests were carried out to verify the accuracy of an inclined drilling penetrating hard rock layers to install tendon to the bearing plate.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.532-539
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• 2024

Among various risk factors that need managing in large scale complex infrastructure projects, geotechnical risk is one of the most prominent factor particularly for underground works like tunnels. Uncertainties in soil conditions cannot be avoided 100% even after extensive geotechnical investigations. Therefore, underground works face large delays and cost overrun especially for hydropower projects in developing countries. Its uncertainty ex ante and ex post directly cause increased transaction cost in terms of contract administration, claims, variation orders and disputes. It also reduces trust and increases opportunistic behaviors due to asymmetric information between the parties. Subsequently, parties are spending more time on claim management rather than handling the project execution. Traditional project management tools are becoming less effective under these conditions. FIDIC published the Conditions of Contract for Underground Works wherein a Geotechnical Baseline Report (GBR) sets out the allocation of risks between the parties for subsurface physical conditions determining the foreseeable and unforeseeable conditions. At the same time, Building Information Modeling (BIM) is being adopted for efficient design, quality control and cost management. In this study, soil classification along the tunnel alignment for on-going hydropower projects is modelled in the virtual environment of Autodesk Revit (2024). The actual soil encountered along the tunnel during construction stage can be compared with the baseline conditions. In addition, BIM serves as a central source providing symmetric information to the Parties to develop an environment of trust and coordination. It is anticipated that these tools will improve the project management skills for underground works through minimizing the opportunistic behavior and transaction cost.

• Journal of the Korean Geotechnical Society
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• v.35 no.8
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• pp.31-42
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• 2019

A total of 73 pile design data for prebored PHC piles was analyzed to study the current design method. Based on the design data, a ratio of skin friction to total capacity from the pile design data was about 20~53%. Such low ratio of skin friction to total capacity tends to underestimate skin friction. Considering this tendency, the current design method should be improved. Also, an average design efficiency of PHC pile capacity was 70% and an average design efficiency for bearing capacity of soil or weathered rock was 80%, which shows slightly higher value than the former. This is probably due to the fact that the allowable bearing capacity is estimated to be equal to or slightly higher than the design load. Hence, the allowable bearing capacity should be estimated to be higher than the long-term allowable compressive force of the PHC pile. In the current design method, skin friction is calculated to be about 2.2 times lower than end bearing. The current design method for prebored PHC piles applied foreign design methods without any verification of applicability to the domestic soil or rock condition. Therefore, the current design method for prebored PHC piles should be improved.

• Geotechnical Engineering
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• v.5 no.3
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• pp.39-50
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• 1989

A method is investigated to analyze the reliability of the gravity retaining wall which is designed to allow a limiting translational movement induces by the earthquake loading. Application of FOSM method to the Richards and Elms model yields a practical procedure for the analyses of the reliability and sensitivity of the retaining wall sujected to the earthquake. After examination of the practice (or the earthquake design of the retaining wall, the methods of the reliability analysis are considered. Finally, this study presents the step-by.step procedure for analyzing the reliability of the earth retaining structure for pratical convinience.