• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.329-336
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• 2013

The infrastructure of flexible pavement is composed of aggregate subbase, anti-frost layer, and subgrade. In particular, the subgrade performance is affected by climates such as frost action and precipitation. The method of TDR(Time Domain Reflectometry) sensors to measure moisture contents in subgrade layer has been used in the research. Due to the TDR method using dielectric permitivity of soil and water, the sensors can be affected by the low subgrade temperatures. The air temperatures frequently drops below $-20^{\circ}C$ in the winter in Korea. As a result, it is necessary to estimate the accuracy of the TDR moisture sensors in the range of below zero temperatures. In this study, the subgrade temperatures of lower than $-2^{\circ}C$ were extended to evaluate temperature sensitivity of the TDR moisture sensors. The test results revealed that the moisture contents around the sensors were reduced while those of the upper part of specimen showed a tendency to increase as the specimen surface temperature drops below zero under the volumetric moisture contents(VMC) of 20% and 30%. However, the impact of temperature on the function of the sensor at lower water contents was found to be negligible if any.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.662-671
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• 2020

The uplift force acts directly on the foundation and causes a building to float to the upper ground. To examine the stability of a structure according to the uplift force, four sites (Paju, Anyang, Osan, and Gangneung) were selected, and sensors were installed on the foundations for the field tests. The rainfall characteristics were analyzed around June~September, and the changes in the water level of the adjacent river were considered. The maximum uplift force except for Gangneung did not exceed 72% of the water pressure when the groundwater level was up to the surface. On the other hand, the maximum uplift force in Osan was approximately 67%, but the reliability was slightly inferior because the difference from the average (46%) was large. The minimum uplift force was within 10% except for Anyang (~ 41%). At the Gangneung site on soft rock where the permanent drainage facility was installed before the measurement, the maximum and minimum uplift force was approximately 14% and 3.5%, respectively. Based on the measurement results, the possibility of overdesigning or underdesigning comes from the design by the hydrostatic pressure when the groundwater level is up to the surface.

• Journal of the Korean Society of Safety
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• v.35 no.2
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• pp.28-33
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• 2020

Recently, the overseas construction market has been actively promoted for about 10 years, and overseas dam construction has been continuously performed. For the economic and safe construction of the dam, it is important to prepare the main dam construction plan considering the design frequency of the diversion tunnel and the cofferdam. In this respect, the prediction of river level during the rainy season is significant. Since most of the overseas dam construction sites are located in areas with poor infrastructure, the most efficient and economic method to predict the water level in dam construction is to use the upstream water level. In this study, a linear regression model, which is one of the simplest statistical methods, was proposed and examined to predict the downstream level from the upstream level. The Pyeongchang River basin, which has the characteristics of the upper stream (mountain stream), was selected as the target site and the observed water level in Pyeongchang and Panwoon gaging station were used. A regression equation was developed using the water level data set from August 22th to 27th, 2017, and its applicability was tested using the water level data set from August 28th to September 1st, 2018. The dependent variable was selected as the "level difference between two stations," and the independent variable was selected as "the level of water level in Pyeongchang station two hours ago" and the "water level change rate in Pyeongchang station (m/hr)". In addition, the accuracy of the developed equation was checked by using the regression statistics of Root Mean Square Error (RMSE), Adjusted Coefficient of Determination (ACD), and Nach Sutcliffe efficiency Coefficient (NSEC). As a result, the statistical value of the linear regression model was very high, so the downstream water level prediction using the upstream water level was examined in a highly reliable way. In addition, the results of the application of the water level change rate (m/hr) to the regression equation show that although the increase of the statistical value is not large, it is effective to reduce the water level error in the rapid level rise section. Accordingly, this is a significant advantage in estimating the evacuation water level during main dam construction to secure safety in construction site.

• Korean Journal of Ecology and Environment
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• v.34 no.4 s.96
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• pp.267-276
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• 2001

The downstream reach of the Han River adjoining Seoul in Korea was the upper boundary of an estuary where tidal effect on the flow rate could be exerted. According to the comprehensive river regulation project, the river was channelize dand impounded by two overflow dams, which provided favorable condition for algal growth in this sewage polluted eutrophic reach. In this study primary productivity of phytoplankton was measured in the down reach and the autochthonous and allochthonous organic carbon loadings were estimated. Primary production of phytoplankton measured by C-14 uptake and P-I model method ranged from 140 to $4,890\;mgC\;m^{-2}\;d^{-1}$ (median value $1,865\;mgC\;m^{-2}\;d^{-1}$) showing the level of eutrophic lakes. Phytoplankton density that varied according to water flow rate was highest in spring. Allochthonous organic carbon loading was dominated by sewage input through tributaries in most of days except flood flow period. The average proportion of autochthonous carbon generation by phytoplankton was 40.9%, which is very high proportion for a lotic habitat.

• Explosives and Blasting
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• v.26 no.1
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• pp.23-37
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• 2008

The Dongdaemoon complex stadium is scheduled to remodelled into an international park, which will be named Design Plaza. The Dongdaemoon baseball field was constructed with Rahmen Structure which comprised beams, slabs and columns. In order to assure for viewing, the stadium was composed unusual structure that the height of the front column and the back column was designed differently. The bleachers was an upper arch form for viewing. The slab was not flat unliked the general infrastructure and tilted in stairway type for viewing. If we had applied the mechanical demolition method, we could have predicted several problems. Firstly, the stand could be unstable when the heavy equipment was to crush the reinforced concrete on the slab. Because the slab was not flat. Secondly, the construction expense and construction duration could be increase when the large equipment was to crush the reinforced concrete on the ground. Because the height of the stand was too high to crush on the ground so it needed to build a filling. Thus, we applied both the mechanical demolition method and explosives demolition method at the design stage. The result of explosives demolition was of complete success in terms of structural movement and controlled blasting noise and vibration. This case study provided a good example for a successful application of explosives demolition in urban areas.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.431-444
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• 2017

This study was carried out to review the guidelines being used by law and national policy concerned on river environments management and suggest the applicability of newly developed river environment assessment system. In the current legal system, the national river environment management system is insufficient in securing an independent status in the legal institutional system which is separated to the Ministry of Land, Transport and Infrastructure and the Ministry of Environment. And the river environment assessment system of the national standard, which is a core matter, has not been established yet. In particular, there is a lack of integrated approach between the upper and lower plan or related plans on water resources, water quality, river environment and aquatic ecosystem management. In addition, the consistency and effectiveness as the process of planning and design according to the current status and comprehensive analysis and evaluation of the river environment were not secured either. To integrate national river environment management system and improve efficiency, I proposed the establishment of hierarchy and connection between national river plans, and the adoption and application of developed assessment system based on characteristics of river environment in Korea. Finally, I proposed the separated application with dividing the developed assessment system including the naturalness of river environment and suitability of water friendly activity into both assessment method for management plan of water resources of river basins & basic river plan respectively.

• Economic and Environmental Geology
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• v.53 no.3
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• pp.321-336
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• 2020

The Headquarters for Earthquake Research Promotion (HERP) represents the upper-most level of Japan's earthquake disaster prevention governance. Its policy committee establishes the national earthquake investigation research promotion plan. The earthquake investigation committee of HERP collects survey geo-data and evaluates the research results of each earthquake disaster prevention agency. The establishment of an earthquake-related geo-resilience research strategy is both necessary and desirable for Korea. The concept of geo-resilience entails the ability to improve disaster resilience through the application of research results and the convergence of geoscience with science and technology (S&T) including the humanities and social sciences. The achievement of geo-resilience requires a national long-term roadmap and strategy for earthquake prediction research, the development of earthquake disaster prediction and prevention technology, Geo-ICT convergence technology development, implementation of a geocyber physics system (Geo-CPS), the use of geo-mimetics, and geoscientific R&D as it relates to local communities. Through such efforts, the national research institutes of Korea will be able to develop earthquake prediction capacities in relevant fields, reinforce proactive response capabilities, enhance community-level confidence in geodata and its research results, foster next-generation geoscientific manpower, and expand geoscientific infrastructure.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.10
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• pp.691-697
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• 2014

Though the upper stream basin area of Gwanpyung-Cheon in Daejeon, Korea is protected as Green Belt Zone, the stream is under constant environmental pressure due to current agricultural practices and infrastructure development in its basin area. To develop appropriate integrated water resources management plan for the stream, it is necessary to consider not only water quality problems but also water quantity aspect. In this study, Storm Water Management Model (SWMM) was calibrated and validated with sets of field measurements to predict for future water flow and water quality conditions for any rainfall event. While flow modeling results showed good agreement by showing correlation coefficient is greater than 0.9, water quality modeling results showed relatively less accurate levels of agreements with correlation coefficient between 0.67 and 0.87. Hypothetical basin development scenarios were developed to compare effect on stream water quality and quantity when Low Impact Development (LID) technologies are applied in the basin. The results of this study can be used effectively in decision making processes of urban development Gwanpyung-Cheon area by comparing basin management alternatives such as LID methods.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.955-962
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• 2005

Still no accurate theory exists for predicting ultimate shear strength of deep reinforced concrete beams because of the structural and material non-linearity after cracking. Currently, the load capacity assesment is performed for the upper structure of the bridges and containing non-reliability in the applications and results. The purpose in this study is to evaluate analytically the complex shear behaviors and normal strength for the reinforced concrete deep beams and to offer the accuracy load capacity assesment method based on the reliability theories. This paper presents a method for the load capacity assesment of reinforcement concrete deep beams using nonlinear finite element analysis. A computer program named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Material non-linearity is taken Into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. From the results, determine the reliability index for the failure base on the Euro Code. Then, calculate additional reduction coefficient to satisfy the goals from the reliability analysis. The proposed numerical method for the load capacity assesment of reinforced concrete deep beams is verified by comparison with the others methods.

• The Transactions of the Korea Information Processing Society
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• v.4 no.2
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• pp.531-542
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• 1997

In this paper,we propose applicable methodology using simple scenarios for the architecture and its procedure of sibnalling at the NNI for B-ISDN in Korea.By the recent technologies,the flexible and intergrated networks of the future are designed, and the infrastructure hardware and software of those networks are sdsigned based on the modular concepts.Also the ATM-based B-ISDN must be able to support the broadband transmission function for providing various services with diverse bandwidths such as multimedia serivce and the function for controlling services and bandwidth is necessaty.Currently,the trquirements at the NNI for B-ISDN in korea atr based on the network mode connection type which is connection setup strucuture.They must show the upper/lower layer conformance to have the flexibility in new services and guarantee the interoperability between the network functions.But,network functions and protocol specifications described in this paper are limity to the first stage target system in korea.Therefore,we present the modular architecture which is corresponding to the B-ISUP of HAN/B-ISDN with those characteristics.Currently applicable architecture and procedure for B-ISUP and the functions of expandable modular architecture are also proposed.