• The Journal of Engineering Geology
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• v.26 no.2
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• pp.251-260
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• 2016

Groundwater flow due to hydraulic gradients across a geologic barrier surrounding a dam reservoir can cause swamps or wetlands to form on the downstream side of the dam, thereby restricting land use. The difference in head between the reservoir level and the downstream groundwater level creates a hydraulic gradient, allowing water to flow through the geologic barrier. We constructed a drainage system at the Daecheong dam to study the effects on groundwater levels and soil moisture contents. The drainage system consisted of a buried screened pipe spanning a depth of 1-1.5 m below a land surface. Groundwater levels were monitored at several monitoring wells before and after the drainage system was installed. Most well sites recorded a decline in groundwater level on the order of 1 m. The high-elevated site (monitoring well W1) close to the reservoir showed a significant decline in groundwater level of more than 2 m, likely due to rapid discharge by the drainage system. Soil moisture contents were also analyzed and found to have decreased after the installation of the drainage system, even considering standard deviations in the soil moisture contents. We conclude that the drainage system effectively lowered groundwater levels on the downstream side of the dam. Furthermore, we emphasize that water seepage analyses are critical to embankment dam design and construction, especially in areas where downstream land use is of interest.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.425-434
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• 2007

In this paper, the stability standards of slopes reclaimed by soils mixed with stone dust were proposed to manage the stone dust as recovery soils. First of all, the mixed ratio between stone dust and natural soil is classified into 5 groups, and a series of soil test was performed in each group. As the results of tests, the shear strength and the maximum dry unit weight were increased in decrease of the mixed ratio of stone dust. On the basis of the investigation to the safety factor standards of embankment slopes in and outside the country, a slope stability rank of slopes reclaimed by mixed soils were divided into 3 stages such as unstable stage, attention stage and stable stage. The slope angle, the slope height and the mixed ratio with stone dust were proposed by the result of stability analysis of slopes reclaimed by mixed soils. As the result of slope stability analysis, the slope angle of 1 : 1.8 at the reclaimed slope should be constructed in case of the slope height of 10 m. Also, the slope angle of 1 : 1.8 and the mixed ratio of stone dust less than 50% should be constructed in case of the slope height of 15 m. The analysis result of reclaimed slope constructed inside the quarry is similar to that of reclaimed slope constructed on the open ground in same conditions of the slope angle, the slope height and the mixed ratio with stone dust. The proposed stability standards of slopes reclaimed by soils mixed with stone dust can be used practically at the quarrying site.

• The Journal of Engineering Geology
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• v.30 no.2
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• pp.147-160
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• 2020

Unsaturated hydraulic conductivity of near-surface unconsolidated layers depends on the physical properties and water content of the unconsolidated layers. So far, many studies have been conducted on the unsaturated hydraulic conductivity of near-surface unconsolidated layers. However, researches on hydraulic conductivity of unsaturated fractured rocks have been relatively rare. In relation to the construction of a low/intermediate level radioactive waste surface-disposal facility, this study compared and analyzed van Genuchten parameters (α, n) in the laboratory and the hydraulic conductivity obtained in field tests for fractured hornfels at a radioactive-waste disposal site of Korea. The relationship between the field hydraulic conductivity and van Genuchten parameters using data from the ten depth intervals of three boreholes resulted in that the correlation coefficient (R) between the hydraulic conductivity and the van Genuchten parameter α was 0.7607, showing positive correlation whereas the R between the hydraulic conductivity and the van Genuchten shape-defining parameter n was -0.8720, showing negative correlation. Hence, this study confirmed the relationship between the field hydraulic conductivity and the van Genuchten unsaturated functions for the unsaturated fractured hornfels.

• Journal of Environmental Impact Assessment
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• v.24 no.2
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• pp.163-174
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• 2015

Urbanization caused various environmental problems like destruction of natural water cycle and increased urban flood. To solve these problems, LID(Low Impact Development) deserves attention. The main objective of LID is to restore the water circulation to the state before the development. In the previous studies about the LID, the runoff reduction effect is mainly discussed and the effects of each techniques of LID depending on rainfall types have not fully investigated. The objective of this research is to evaluate the effect of LID using the quantitative simulation of rainwater runoff as well as an amount of infiltration according to the rainfall and LID techniques. To evaluate the water circulation of LID on the development area, new land development areas of Hanam in South Korea is decided as the study site. In this research, hydrological model named STORM is used for the simulation of water balance associated with LID. Rainfall types are separated into two categories based on the rainfall intensity. And simulated LID techniques are green roof, permeable pavement and swale. Results of this research indicate that LID is effective on improvement of water balance in case of the low intensity rainfall event rather than the extreme event. The most effective LID technique is permeable pavement in case of the low intensity rainfall event and swale is effective in case of the high intensity rainfall event. The results of this study could be used as a reference when the spatial plan is made considering the water circulation.

• Journal of Hydrogen and New Energy
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• v.13 no.2
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• pp.143-150
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• 2002

The thermal behavior of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ prepared by a co-precipitation wasinvestigated for Hz generation by the thermochemical cycle. The reduction reaction of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ started from $480^{\circ}C$, and the weight loss was 1.6 wt% up to $1100^{\circ}C$. At this reaction, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ was reduced by release of oxygen bonded with the $Fe^{3+}$ ion in the B site of ($CO_{0.5}$ $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidationof reduced $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$. The crystal structure of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ for reduction reaction maintained spinel structure and the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ ($8.41\AA$) was enlarged to $8.45\AA$. But the lattice constant of $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ after $H_2O$ decomposition reaction did not change to $8.45\AA$. Then, $(Co_{0.5}\;Mn_{0.5})Fe_2O_4$ is excellent material in the thermochemical cyclic reaction due to release oxygen at low temperature for the reduction reaction and produce $H_2$ maintaining crystal structure for redox reaction.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.161-172
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• 2007

By prosperous condition of construction economy in the early 90s in Korea, the government needed a lot of the qualified professional engineers (PE) to manage the construction site. In order to meet the high demand of P.E., Government has established the admitted engineer systems(AES) in 1995 that give the authority of principal engineers to the admitted engineers who do not take the written examination but have equivalent working experience. Since 2000, professional $engineer^{\circ}{\phi}s$ shortage has been resolved. however, the opposite situation, which is serious over-supply of construction engineers has occurred. Thus, Government announced that would abolish the admitted engineer systems as recognized the existent admitted engineers(about 1,000,000 persons) from 2007. However, Professional Engineers Institution has strongly insisted that Government should not recognize existent admitted engineers. From this point of view, it is critical to make the supply-demand forecast systems as a derivative approach of System Dynamics also, that is useful in comparing the argument between Government and Professional Engineers Institution. This paper describes about principal $engineer^{\circ}{\phi}s$ supply change by admitted engineer system abrogation and suggests the idea to regulate the supply and demand with the improvement of the regal system.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.118-128
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• 2012

As the bearing wall structure, which has been widely applied to domestic apartment buildings since the 1980s, cause many problems during remodeling of buildings, the government encourages constructors to adopt flat plate or rahmen structure through legal incentives. In line with such a trend, the green frame, an eco-friendly rahmen structure that has removed the shortcomings of previous structures, was developed to enhance structural safety, constructability, and eco-friendliness. The construction of green frame can reduce the labor cost and facilitate the composition of iron bars to reduce rebar loss through calculating the quality and establishing the bar bending schedule automatically on the precast concrete member data collected over the design phase. Therefore, the purpose of this study is to develop the algorithm to automate the calculation of iron bar volume for the green frame designed on composite precast concrete members. Automated algorithm to calculate concrete structural design information and design information. Practices through the application site should prove efficacy. The database established by the developed algorithm will automate the establishment of iron bar processing map and bar cutting list and the calculation of optimal composition and order volume to minimize the rebar loss. This will also reduce the expenses on management staff and overall construction cost through the minimization of rebar loss.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.14-23
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• 2012

Due to the increase of aged housing demolition in preparation for the rapid growth of the market, Eco-friendly remodeling demolition work which can minimize environmental destruction have been studied. However, the owner or contractor to apply for eco-friendly remodeling demolition work does not reflect the characteristics of the site can not have a potential for many variables. In addition, There is no standard which can find effective part and catch a problem by performing eco-friendly remodeling demolition. Therefore, the project owner and construction company executives in the Pre-construction stage to the implementation of eco-friendly remodeling demolition construction by providing a model for the pre-evaluating the project. In this paper, the performance of eco-friendly remodeling of demolitions is proposed for the pre-evaluating model. After the eight items were drawn affecting the performances which are influence to accomplishment of the eco-friendly remodeling demolition, evaluation criteria was suggested for each item. Also By classifying and assessing the evaluation items, It will be able to identify the problems and supplements for eco-friendly remodeling demolition. Through the final evaluation sheet, The works of the appropriacy and supplement will be checked for the eco-friendly remodeling demolition. Finally The preinvestigation model is helpful for making the plan of systematic demolition, futhermore It is contribute to the expansion of the eco-friendly remodeling demolition.

• Korean Journal of Construction Engineering and Management
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• v.9 no.5
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• pp.194-203
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• 2008

Construction Research and Development (R & D) projects have been begun with the investment of 1.2 billions in 1994 and have been reached to 30 billions in 2004. During this ten-year period, a total of investment for construction R&D amounts to 125.7 billions (Total 418 construction R&D projects). However, the results of each R&D project could not apply to real construction site because each project has been performed by a small size (0.5 billions). In addition to those, the social interest on the construction R&D projects has not been received and those importance has not been recognized. Especially, there aren't still standardized methodologies or weighted measurement data for evaluating research performance of the construction R&D projects up to now. The construction R&D projects has been Invested on the basis of an annual technology demand survey rather than the research performance outcome. Therefore, it is important to establish a qualitative performance measurement model for evaluating construction R&D projects. This paper proposes a new research methodology for analyzing the performance measurement of the construction R&D projects. First of all, the Balanced Score Card (BSC) is used to evaluate the construction STAR technologies selected in this research. The performance items of BSC has been modified as four criteria such as "productivity, "knowledge accumulation," "training of students," and "welfare." The new research methodology developed in this paper is expected to use in establishing resonable construction R&D budget in the future.

• Korean Journal of Construction Engineering and Management
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• v.14 no.4
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• pp.3-14
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• 2013

Recently, as the size of construction projects is getting bigger and higher, construction disasters have been being serious such as death, also it is hard to manage efficiently since there are plenty of informations about safety management. Thus on the spot & real time safety management is required and one of the ways to support these needs, conjunction with Information Technology(IT) has been being noticed. Accordingly, Personal Digital Assistant(PDA), Palmtop Computer and Tablet Personal Computer and so on have been adopted. However another inefficient sides are showed up such as limitation of equipment(weight, inconvenience of control and others). Meanwhile, exchanging and processing data are improved at wide area due to advance of mobile communication and introduction of smart mobile, which is a simple and convenient, is a proven at many aspects. In this research, to support effective safety management, the framework is realized in connection with smart mobile with finding the problems of safety management and deriving demands. Two smart mobile applications, which are Safety Management application and Safety Guideline application, enable that safety management in real time, less re-work and using safety information.