• Journal of agriculture & life science
• /
• v.52 no.6
• /
• pp.139-153
• /
• 2018

This study analyzes the economic effect of rehabilitation and upgrading of reservoirs as a prevented method against natural disasters under recent abnormal weather conditions and dam-break. For the analysis, we divide the purpose of rehabilitation and upgrading of reservoirs into the stable supply of rural water under uncertain weather conditions and the prevention of collapse due to the aging of the reservoir. We measure the economic effect of rehabilitation and upgrading of reservoirs by estimating the resident's willingness-to-pay for the project through Contingent Valuation Method(CVM). The result shows that distributions of willingness-to-pay to prevent natural disasters and dam-break are similar to each other. About 66% of the residents in sample regions are willing to pay for the project. The resident's willingness-to-pay to protect natural disasters and dam-break are 32,250 to 46,147 won and 28,427 to 47,308 won respectively on average for all sample regions. The comparison of willingness-to-pay by type of regions shows that paddy field areas are the highest followed by facility cultivation areas and urban areas. In addition, total expected value of the projects calculated based on the resident's willingness-to-pay for paddy field areas and facility cultivation areas are much larger than actual project costs. This implies that rural residents are fully aware of the importance of the project to prevent natural disasters and dam-break and are willing to pay for additional costs if needed.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.5
• /
• pp.281-302
• /
• 2021

Railway projects have been consistently increasing in Korea. In relation to this trend, the mechanized tunneling using Tunnel Boring Machine (TBM) is preferably applied for mining urban areas and passing under rivers. The TBM tunneling under difficult grounds like mixed faces with high water pressure could require ground improvements for stable TBM advance or safe cutter head intervention (CHI). In this study, pre-grouting works for CHI in Daegok-Sosa railway project are presented in terms of the grouting zone design, the executions and the results, the lessons learned from the experience. It should be mentioned that the grouting from inside TBM was carried out several times and turned out to be inefficient in the project. Therefore, grouting experiences from the surface are highlighted in this study. Jet grouting was implemented on CHI points on land, while permeation grouting off shore in the Han River, which mostly allow to access the cutter head of TBM in free air with stable faces. The results of CHI works have been analyzed and the lesson learned are suggested.

• Journal of Wetlands Research
• /
• v.23 no.2
• /
• pp.122-132
• /
• 2021

We reviewed the methods employed in Korean tidal flat surveys to measure the local abundance of the endangered wildlife and marine protected species, the fiddler crab, Austruca lactea. A complete census for infinite population is impossible even in a limited habitat within a tidal flat, and density estimates from samples strongly vary due to diverse biological and ecological factors. The habitat boundaries and areas shift with periodicities or rhythmic activities of organisms as well as measurement errors. Hence the local abundance calculated from density and habitat areas should be regarded as transient. This conjecture was valid based on the spatio-temporal variations of the density averages, standard error ranges, and spatial distribution of the crab, A. lactea observed for 3 years (2015-2017) in Songdo tidal flat in Incheon. We proposed the potential habitat areas using the occurrence probability of 50% from logistic regression model, reflecting the importance of habitat conservation value as an alternative to local abundance. The spatial shape of potential habitat predicted from a generalized model would remain constant over time unless the species' critical environmental conditions change rapidly. The species-specific model is expected to be used for the introduction of desired species in future habitat restoration/creation projects.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.15 no.5
• /
• pp.1666-1689
• /
• 2021

The red line of Permanent Basic Farmland is the most important part in the "three-line" demarcation of China's national territorial development plan. The scientific and reasonable delineation of the red line is a major strategic measure being taken by China to improve its ability to safeguard the practical interests of farmers and guarantee national food security. The delineation of Permanent Basic Farmland zoning (DPBFZ) is essentially a multi-objective optimization problem. However, the traditional method of demarcation does not take into account the synergistic development goals of conservation of cultivated land utilization, ecological conservation, or urban expansion. Therefore, this research introduces the idea of artificial immune optimization and proposes a multi-objective model of DPBFZ red line delineation based on a clone selection algorithm. This research proposes an objective functional system consisting of these three sub-objectives: optimal quality of cropland, spatially concentrated distribution, and stability of cropland. It also takes into consideration constraints such as the red line of ecological protection, topography, and space for major development projects. The mathematical formal expressions for the objectives and constraints are given in the paper, and a multi-objective optimal decision model with multiple constraints for the DPBFZ problem is constructed based on the clone selection algorithm. An antibody coding scheme was designed according to the spatial pattern of DPBFZ zoning. In addition, the antibody-antigen affinity function, the clone mechanism, and mutation strategy were constructed and improved to solve the DPBFZ problem with a spatial optimization feature. Finally, Tongxu County in Henan province was selected as the study area, and a controlled experiment was set up according to different target preferences. The results show that the model proposed in this paper is operational in the work of delineating DPBFZ. It not only avoids the adverse effects of subjective factors in the delineation process but also provides multiple scenarios DPBFZ layouts for decision makers by adjusting the weighting of the objective function.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.6
• /
• pp.559-575
• /
• 2021

Due to the increase in ground excavation work, the possibility of ground subsidence accidents is increasing. And it is very difficult to prevent these risk fundamentally through institutional reinforcement such as the special law for underground safety management. As for the various cases of urban ground excavation practice, the ground subsidence behavior characteristics which is predicted using various information before excavation showed a considerable difference that could not be ignored compared to the results real construction data. Changes in site conditions such as seasonal differences in design and construction period, changes in construction methods depending on the site conditions and long-term construction suspension due to various reasons could be considered as the main causes. As the countermeasures, the safety management system through various construction information is introduced, but there is still no suitable system which can predict the effect of excavation and risk assessment. In this study, a web-based system was developed in order to predict the degree of impact on the ground subsidence and surrounding structures in advance before ground excavation and evaluate the risk in the design and construction of urban ground excavation projects. A system was built using time series analysis technique that can predict the current and future behavior characteristics such as ground water level and settlement based on past field construction records with field monitoring data. It was presented as a geotechnical data visualization (GDV) technology for risk reduction and disaster management based on web-based system, Using this newly developed web-based assessment system, it is possible to predict ground excavation impact prediction and risk assessment.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.5
• /
• pp.681-691
• /
• 2022

Zostera marina (ZM), a type of seagrass registered as a marine protected species in South Korea, provides valuable ecosystem services to humans, such as improving marine water quality, providing food, spawning grounds and habitats for marine life, and absorbing carbon dioxide. Therefore, the government is seeking to preserve ZM by designating ZM-protected areas. This study examined the public willingness to pay (WTP) for the preservation of ZM using contingent valuation. The one-and-one-half-bounded model was adopted for WTP elicitation, and the single-bounded model was also applied for comparison. The spike model was employed to deal with many zero WTP responses. The household average WTP was estimated as KRW 4,087 per year, securing statistical significance. The national value was KRW 84.1 billion per year. The preservation value of ZM estimated in this study can be used as important data for economic analysis of various projects or policy implementation for its preservation.

• Korean Journal of Environment and Ecology
• /
• v.36 no.4
• /
• pp.422-432
• /
• 2022

Soil and micro-climatic environmental monitoring was conducted to evaluate the factors causing tree growth impediments at the Baekdudaegan ecological axis restoration project site. As a result, it was found that the nutrient supply was insufficient in the restoration project site due to the lack of organic matter, total nitrogen and cation exchange capacity of the soil compared to the surrounding forest. After the completion of the restoration, the soil moisture in the autumn decreased more than 7 times faster than that of the surrounding forest, and it was evaluated that the soil moisture was significantly low due to the lack of silt and clay content. In the case of the restoration site, the annual potential evapotranspiration was analyzed to be 975mm, which is approximately two times higher than that of the surrounding forest. The soil moisture of the restoration site in the summer decreased rapidly during the daytime when the amount of insolation increased and this was found to be strongly influenced by the increase in potential evapotranspiration. In order to improve the above factors affecting the tree growth at the Baekdudaegan ecological axis restoration project site, it is necessary to induce the smooth supply of nutrients and water to plants by improving physical proprieties and cation exchange capacity, i.e., using litterfall, humus soil, soil conditioner and organic fertilizer. The results of this study are expected to serve as basic data for the design, construction, and management of ecological axis restoration projects in the future.

• Korean Journal of Construction Engineering and Management
• /
• v.24 no.2
• /
• pp.88-97
• /
• 2023

The purpose of this study is to forecast future changes in the construction market following the reorganization of the construction production system by analyzing the possible market size in which general contractors and specialty contractors may participate in each other, and by carrying out a survey. The ratio of correlation between general construction and specialty construction industries was derived by analyzing the relevance of work area of general contractors and specialty contractors, the similarity of registration standards, and the market in which general contractors and specialty contractors may be able to mutually participate. In order to overcome the limitation of previous studies which analyze the changes in construction market based on the statistical data, and to analyze in more detail the impact of reorganization of construction production system from market participants' view, a survey targeting general contractors and specialty contractors for their willingness and method of participating in the mutual market was conducted. As a result of the survey, it was found that 52% of general contractors were willing to participate in the specialized construction market and 55.1% of specialty contractors were willing to participate in the general construction market. It was found that there was a high willingness to participate in the earthworks, reinforced concrete works, facility maintenance and management, water and sewage facility works, and interior works, and high competition is expected for projects with a scale of 500 million to less than 3 billion won. Through this study, it will be possible for general and specialty contractors to understand the changes in the construction market due to the reorganization of the construction industry production system, and to respond effectively to these changes.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.2
• /
• pp.127-138
• /
• 2023

A variety of decarbonized energy sources are being developed globally to realize carbon neutrality (Net Zero) by 2050 as a measure to address the global climate crisis. As the Korean government has also established a Renewable Energy 3020 policy and promoted energy development plans using solar or wind power, large-scale offshore development projects not present before in coastal waters, such as offshore wind farms, are being promoted. From ships' point of view, offshore facilities present obstacles to safe navigation, and with the installation of marine facilities, ship collisions or contact accidents between ships and marine facilities may occur in the narrowed water areas. In addition, there are concerns about environmental pollution and human casualties caused by marine accidents. Accordingly, we review overseas and domestic offshore wind farm development plans, analyze whether institutional devices are in place to ensure the safe passage of ships in wind farm areas, and study the safe operation of large-scale offshore wind farms and safe passage of ships along the Korean coast by comparing overseas legislative cases with domestic laws and presenting a proposal to illuminate the legal blind sectors.

• Journal of the Korea Institute of Building Construction
• /
• v.23 no.4
• /
• pp.337-348
• /
• 2023

The central objective of this study is to curtail the leakage of mortar or cement paste, often resultant of ill-constructed formwork, by implementing thixotropy in the formulation of high-fluidity, standard-strength concrete. When such concrete is utilized in smaller scale construction projects, instances of formwork gaps due to suboptimal construction precision may lead to significant leakage of mortar and paste, a problem not typically encountered with traditional slump-flow concrete. In this investigation, Polyvinyl Alcohol(PVA) and borax are incorporated into the concrete mixture to induce thixotropy. The experimental design includes varying methodologies for integrating PVA and borax, while assessing alterations in diverse concrete performances, including thixotropy and leakage reduction potential that simulates formwork gap conditions. Under the experimental conditions defined within this study, it was found that replacing, rather than merely adding PVA and borax, aids in averting water addition via suspensions. This approach yielded promising results in terms of concrete properties and proved efficacious in stemming leakage in concrete possessing sufficient thixotropy. Notably, when a 6% PVA suspension was substituted, a significant reduction in leakage was observed. Consequently, it is projected that construction quality can be ensured, even with lower precision formwork, by applying thixotropy to concrete through the use of PVA and borax.