• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.235-244
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• 2016

Grouting is frequently used before the construction of subsea tunnels to mitigate problems that can occur in weak ground zones such as joints, faults or unconsolidated settlements during construction. The grout material injected into rock mass often flows through the discontinuities present in the host rock and hence, joint properties such as its distribution, roughness and thickness greatly affect the properties of grouting-improved rocks. The grouting-improved zones near subsea tunnels are also subjected to high water pressures that can cause long-term weathering in the form of changes in grout microstructure and crack formation and lead to subsequent changes in ground properties. Therefore, an assessment method is needed to accurately measure changes in the grouting-improved zones near subsea tunnels. In this study, the elastic wave propagation characteristics in grouting-improved rocks were tested for various axial stress levels, curing time, joint roughness and thickness conditions under laboratory conditions and the results were compared with wave velocity standards in different Korean rock mass classification systems to provide a basis for inferring improvement in grouted rock-mass.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1287-1296
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• 2007

Recently, the high speed railway comes into the spotlight as the important and convenient traffic infrastructure. In Korea, Kyung-Bu high speed train service began in about 400km section at 2004, and the Ho-Nam high speed railway will be constructed by 2017. The high speed train will run with a design maximum speed of 300-350km/hr. Since the trains are operated at high speed, the differential settlement of subgrade under the rail is able to cause a fatal disaster. Therefore, the differential settlement of the embankment must be controlled with the greatest care. Furthermore, the characteristics and causes of settlements which occurred under construction and post-construction should be investigated. A considerable number of studies have been conducted on the settlement of the natural ground over the past several decades. But little attention has been given to the compression settlement of the embankment. The long-term settlement of compacted fills embankments is greatly influenced by the post-construction wetting. This is called 'hydro collapse' or 'wetting collapse'. In spite of little study for this wetting collapse problem, it has been recognized that the compressibility of compacted sands, gravels and rockfills exhibit low compressibility at low pressures, but there can be significant compression at high pressures due to grain crushing by several researchers(Marachi et al. 1969, Nobari and Duncan 1972, Noorany et al. 1994, Houston et al. 1993, Wu 2004). The characteristics of compression of fill materials depend on a number of factors such as soil/rock type, as-compacted moisture, density, stress level and wetting condition. Because of the complexity of these factors, it is not easy to predict quantitatively the amount of compression without extensive tests. Therefore, in this research I carried out the wetting collapse tests, with focusing in various soil/rock type, stress levels, wetting condition more closely.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.3
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• pp.51-64
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• 2015

Climate change will make significant impact on species distribution in forest. Pinus koraiensis which is commonly called as Korean Pine is normally distributed in frigid zones. Climate change which causes severe heat could affect distribution of Korean pine. Therefore, this study predicted the distribution of Korean Pine and the suitable habitat area with consideration on uncertainty by applying climate change scenarios on an ensemble model. First of all, a site index was considered when selecting present and absent points and a stratified method was used to select the points. Secondly, environmental and climate variables were chosen by literature review and then confirmed with experts. Those variables were used as input data of BIOMOD2. Thirdly, the present distribution model was made. The result was validated with ROC. Lastly, RCP scenarios were applied on the models to create the future distribution model. As a results, each individual model shows quite big differences in the results but generally most models and ensemble models estimated that the suitable habitat area would be decreased in midterm future(40s) as well as long term future(90s).

• Journal of the Korean GEO-environmental Society
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• v.14 no.9
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• pp.57-65
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• 2013

Carbonate sands can be crushed under low confining pressure to achieve high compressibility. So particle crushing has significant influence on characteristics of strength and deformation. Trial embankment and hydrotest are conducted on Sabkha layer, consisting of carbonate sand to build tank structure. In this paper the settlement behavior was analyzed from each test. Particle crushing happened from 80 to 170kPa stress under compression test, and calcium was detected from chemical test. The test result came out Sabkha soil was very weak and easy to be crushing. About trial embankment test, particle crushing was not happen, and then extinction of pore water pressure and settlements were finished just during 2 days. On the other hand, the long-term settlement was happened in hydrotest. So the two test results did not correspond to each other. If loading stress is higher than yielding stress, instant settlement and secondary compression settlement are happened as a result of the particle crushing.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1223-1232
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• 2021

In this study, a new analysis method by using a "Discharge Gini Coefficient" is presented to determine the degree of inequality in daily discharge throughout the year. The Discharge Gini Coefficient can be calculated using the area relationship with the cumulative percentage of the daily mode discharge in the ascending order according to the cumulative percentage of the date of occurrence of the daily discharge throughout the year. The Discharge Gini Coefficient is presented as a value between 0 and 1, and the degree of inequality can be divided into 5 levels. The Discharge Gini Coefficient can be used to estimate the discharge stability of the downstream point relative to the upstream point. In addition, it is possible to quantify the influence of each reference discharge on the total inequality. The applicability of the Discharge Gini Coefficient was reviewed using long-term daily discharge data at eight points upstream and downstream of the four major rivers in Korea. The Discharge Gini Coefficient can also be used to analyze the discharge control effect in the downstream by the upstream dam.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.81-90
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• 2018

The 'Hyper-connected society' in which all objects such as people, device, place are connected via networks and share information being realized. As the information and communication environment changes, spatial information also faces a significant challenge. Korean government is striving to meet the social demand for spatial information that will bring 'Hyper-connectivity' such as autonomous vehicles, drones. Until now, however, it has only partially responded to urgent demand and has not prepared a fundamental countermeasure. In order to effectively and actively respond to the demand for spatial information that is needed in the Hyper-connected society, a strategy that can lead to mid- to long-term fundamental changes is needed. The purpose of this study is to analyze the future demand and application characteristics of spatial information confronted with a big paradigm shift called 'Hyper-connected society', and to search spatial information strategy that can cope with the demand of spatial information in future society.

• Geomechanics and Engineering
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• v.17 no.2
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• pp.119-131
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• 2019

Time dependent creep settlements are one of the most important causes of material deteriorations for the huge water structures such as concrete faced rockfill dams (CFRDs). For this reason, performing creep analyses of CFRDs is vital important for monitoring and evaluating of the future and safety of such dams. In this study, it is observed how changes viscoplastic behaviour of a CFR dam depending the time. Ilısu dam that is the longest concrete faced rockfill dam (1775 m) in the world is selected for the three dimensional (3D) analyses. 3D finite difference model of Ilısu dam is modelled using FLAC3D software based on the finite difference method. Two different special creep material models are considered in the numerical analyses. Wipp-creep viscoplastic material model and burger-creep viscoplastic material model were rarely used for the creep analyses of CFRDs in the last are taken into account for the concrete slab and rockfill materials-foundation, respectively. Moreover, interface elements are defined between the concrete slab-rockfill materials and rockfill materials-foundation to provide interaction condition for 3D model. Firstly, dam and foundation are collapsed under its self-weight and static behaviour of the dam is evaluated for the empty reservoir conditions. Then, reservoir water is modelled considering maximum water level of the dam and time-dependent creep analyses are performed for maximum reservoir condition. In this paper, maximum principal stresses, vertical-horizontal displacements and pore pressures that may occur on the dam body surface during 30 years (from 2017 to 2047) are evaluated in detail. According to numerical analyses, empty and maximum reservoir conditions of Ilısu dam are compared with each other in detail. 4 various nodal points are selected under the concrete slab to better seen viscoplastic behaviour changes of the dam and viscoplastic behaviour differences of these points during 30 years are graphically presented. It is clearly seen that horizontal-vertical displacements and principal stresses for maximum reservoir condition are more than the empty reservoir condition of the dam and significant pore pressures are observed during 30 years for maximum reservoir condition. In addition, horizontal-vertical displacements, principal stresses and pore pressures for 4 nodal points obviously increased until a certain time and changes decreased after this time.

• Journal of IKEEE
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• v.26 no.3
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• pp.355-363
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• 2022

Korea is pursuing a plan to switch and expand energy sources with a focus on renewable energy with the goal of becoming carbon neutral by 2050. As the instability of energy supply increases due to the intermittent nature of renewable energy, accurate prediction of the amount of renewable energy generation is becoming more important. Therefore, the government has opened a small-scale power brokerage market and is implementing a system that pays settlements according to the accuracy of renewable energy prediction. In this paper, a prediction model was implemented using a statistical model and an artificial intelligence model for the prediction of solar power generation. In addition, the results of prediction accuracy were compared and analyzed, and the revenue from the settlement amount of the renewable energy generation forecasting system was estimated.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.607-612
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• 2021

This study estimated the impact of the shock of housing price increase on the total fertility rate and the contribution of each variable to changes in the TFR. This study is differentiated by estimating the contribution rate of each variable to the fertility rate through the Shapley decomposition and the panel VAR's forecast error variance decomposition, which previous studies have not attempted. The main results of this study are as follows. First, the decline in the TFR in Korea has been strongly influenced by the recent decline in the total fertility rate, and this influence is expected to continue in the future. In the case of housing costs, in the past, housing sales prices had a relatively small contribution to changes in the total fertility rate compared to the jeonse prices, but their influence is expected to increase in the long term in the future. It has been demonstrated that private education expenses other than housing sale price and Jeonse price also acted as a major cause of the decline in the total fertility rate.

• Journal of the Korean Geotechnical Society
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• v.24 no.8
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• pp.61-79
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• 2008

Consolidation settlements on marine dredged clays are often greatly and potentially damaging to structures. Currently, large-scale projects are in planning or progressing in Korea. These projects have been performed on thick and soft clay layers. So, the evaluation of consolidation characteristics for dredged and reclaimed ground is very important in design and construction. Therefore, in this study, a series of conventional consolidation tests were performed to investigate the consolidation characteristics of marine dredged clays near Gwang-yang Port. Preconsolidation pressures were evaluated by applying previously proposed 8 methods for the conventional tests results in order to evaluate the legitimacy of these methods. In these methods, when estimating maximum past pressures for dredged and reclaimed ground, it was proved that Becker (1987), Silva (1970), Sridharan (1991)'s methods are excellent in legitimacy.