• Fire Science and Engineering
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• v.27 no.4
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• pp.21-26
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• 2013

This study was performed to test the combustive properties of Pinus rigida plates treated with bis-(dimethylaminomethyl) phosphinic acid (DMDAP), bis-(diethylaminomethyl) phosphinic acid (DEDAP), and bis-(dibuthylaminomethyl) phosphinic acid (DBDAP). Pinus rigida specimens were painted in three times with 15 wt% bis-(dialkylaminoalkyl) phosphinic acid solutions at the room temperature. After drying specimen treated with chemicals, combustive properties were examined by the cone calorimeter (ISO 5660-1). It is supposed that the combustion-retardation properties were improved by the partial due to the treated bis-(dialkylaminoalkyl) phosphinic acids in the virgin Pinus rigida. Especially, the specimens treated with chemicals showed both the lower total smoke release rate (TSRR) ($16.94{\sim}18.92m^2/m^2$) and lower $CO_{2mean}$ production (1.98~2.09 kg/kg) than those of virgin plate. However the specimens treated with chemicals showed both the higher peak mass loss rate (PMLR) (0.1250~0.1297 g/s) and higher 1st-smoke production rate (SPR) (0.0153~0.0167 g/s) than those of virgin plate. Compared with virgin Pinus rigida plate, the specimens treated with the bis-dialkylamimoalkyl phosphinic acids showed partially low combustive properties.

• Journal of Korea Water Resources Association
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• v.53 no.9
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• pp.681-690
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• 2020

Generally, the design capacity of the rainwater harvesting unit is determined by trial and error method that is repeatedly calculating various analysis scenarios with capacity, reliability, and rainwater utilization ratio, etc. This method not only takes a lot of time to analyze but also involves a lot of calculations, so analysis errors may occur. In order to solve the problem, this study suggested a way to directly determine the minimum capacity to meet arbitrary target reliabilities using the global optimization method. The method was implemented by simulation model with particle swarm optimization (PSO) algorithms using Python language. The pyswarm that is provided as an open-source of python was used as optimization method, that can explore global optimum, and consider constraints. In this study, the developed program was applied to the design data for the rainwater harvesting constructed in Cheongna district 1 in Incheon to verify the efficiency, stability, and accuracy of the analysis. The method of determining the capacity of the rainwater harvesting presented in this study is considered to be of practical value because it can improve the current level of analytical technology.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.23-33
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• 2017

Due to the rapid development of cities, densities and heights of urban structures are increased, and much larger and more underground spaces are being developed accordingly. Increasing development of underground spaces has induced more ground sinks and underground cavities. Therefore, safety of people is threatened by potential ground collapses and possible accidents, which may result from underground cavity. To actively respond against potential danger of ground sink, evaluation of existing cavity grade and development of recovery procedure are important. There exists the ground sinking management grade system of expressway developed as local standards in Japan. Recently, ground sinking management grade system of Seoul was developed with consideration of road and asphalt conditions. In this study, 209 underground cavities of ${\bigcirc}{\bigcirc}$ area were explored and their cavity shapes and grades were evaluated based on both ground sinking management grade systems of Japan and Seoul. Comparison is made between cavity grades evaluated based on both grading systems from Japan and Seoul. As a result of comparative analysis, the conservatively-estimated cavity grades requiring emergency restoration based on the Japanese management grade system of expressway result from neglection of layer thickness of surface pavement, considering only width and cover depth of a cavity.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.41-51
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• 2012

Soils are commonly unsaturated in the near surface. The stiffness of soils is affected by the amount of air and water. The objective of this study is to evaluate the porosity of the unsaturated soils by using the elastic waves including compressional and shear waves. The elastic waves are measured at different degrees of saturation by controlling the matric suction. Thus, the unsaturated soils are characterized at different levels of the matric suction. Shear and compressional waves are measured by using the bender elements and the piezo disk elements, respectively. Both transducers are installed on the walls of the rectangular cell. The unsaturated soils are prepared by using uniform size sands and silts. Test results show that both compressional and shear wave velocities change according to the matric suction. The elastic modulus, the shear modulus, and the Poisson's ratio are estimated based on the measured elastic wave velocities. In addition, the void ratio of the unsaturated soils estimated using elastic wave velocities matches well with the volume based void ratio. This study demonstrates that the elastic waves can be effectively used for the characterization of unsaturated soils.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.534-545
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• 2010

To examine 1) rainfall pattern (i.e., type and intensity) regulating surface erosion on hillslopes in postwildfire area and 2) its effect on variation in sediment yield along the gradient of severity wildfire regimes and elapsed years, we surveyed the amount of sediment yield with respect to daily or net-effective rainfall in 9 plots in eastern coastal region, Republic of Korea. Before field investigation, all plots classified into three groups: low-, mixed- and high-severity wildfire regimes (3 plots in each group). We found that, with decreasing wildfire regimes and increasing elapsed years, the rainfall type regulating surface erosion changed from daily rainfall to net-effective rainfall (considering rainfall continuity) and its intensity increased continuously. In general, wildfires can destroy the stabilized forest floors, and thus rainfall interception by vegetation and litter layer should be reduced. Wildfires can also decrease soil pores in forest floors, and thus infiltration rates of soil are reduced. These two processes lead to frequent occurrence of overland flows required to surface erosion, and sediment yields in post-wildfire areas should increase linearly with increasing rainfall events. With the decreasing severity wildfire regimes and the increasing elapsed years, these processes should be stabilized, and therefore their sediment yields also decreased. Our findings on variations in sediment yields caused by the wildfire regimes and the elapsed years suggest understanding of hydrogeomorphic and ecologic diversities in post-wildfire areas, and these should be carefully examined for both watershed management and disaster prevention.

• Journal of the Korean GEO-environmental Society
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• v.21 no.7
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• pp.17-26
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• 2020

The soft ground in the southwest coastal area composed of marine clay is greatly influenced by sediment composition, particle size distribution, particle shape, adsorption ions and pore water characteristics, tide and temperature. In addition, the geotechnical properties are very complex due to stress history, change in pore water, dissolution process and gas formation. In this study, the physical and mechanical properties of the soft ground were evaluated through field tests and laboratory tests to investigate the strength increase characteristics according to consolidation on the soft ground in the southwest coast. In addition, in order to understand the consolidation behavior of soft ground such as subsidence, pore water pressure, horizontal displacement of soil by embankment load, measuring instruments such as pore water pressuremeter, settlement gauge, inclinometer and differential settlement gauge was installed, and a piezocon penetration test was carried out step by step to confirm the increase in shear strength of the ground. Through this, it was confirmed that the shear strength of the ground is increased according to the stages of filling. In addition, by evaluating the properties of consolidation behavior, strength increase and consolidation prediction by empirical methods and theories were compared to analyze the characteristics of strength increase rate and consolidation behavior in consideration of regional characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.468-473
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• 2016

The aim of this study was to measure the opening force of an access door of a pressurized smoke control zone and verify the reliability of the opening force. For the access door opening force, the opening load of the access door was measured before and after pressurized air had entered the smoke control zone. The reliability of the measured values was verified using the Anderson Darling's statistical analysis method of the Minitab Program. Because the analyzed P values were greater than 0.05 except for some floors before and after the operation of the smoke control equipment, the opening force was found to have 95% reliability. The normal distribution of the measured values showed no relationship with the operation of the smoke control equipment and the precision of the force gauge was believed to be reliable. The major factors for the optimal design of the pressurized smoke control equipment include the precision and reliability of the force gauge, the correct posture of the measuring person, and the same conditions for access doors. Therefore, a digital force gauge is believed to be suitable for measuring the opening force of the access door of a pressurized smoke control zone. In addition, standardization of the posture of a measuring person, the setup of the initial opening force of an access door, etc., are major variables for effective measurements of the door opening force of an access door.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.499-510
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• 2015

Artificial accelerated weathering test evaluated rocks from near the circuit road of Ulleungdo island, approximately 120 km from east of the Korean Peninsula. The tests subjected rock specimens to conditions based on the climate of the island. The specimens (such as basaltic breccia, trachyte, volcanic breccia) were preliminarily classified using a TAS diagram (XRF data) and based on the constituent minerals (XRD data); they were further classified by weathering degree according to their absorption ratios. During the artificial accelerated weathering, the absorption ratio of most of the specimens increased, but the point-load strength did not decrease in most cases, except for the volcanic breccia. The greater initial absorption ratio of trachyte rock specimen in comparison with the other specimens led to a greater increase of its absorption ratio during the artificial accelerated weathering test. The volcanic breccia specimens showed the greatest increase of absorption ratio and the biggest reduction ratio of the point- load strength during the tests. These results could aid prediction of the weathering rate of rocks in Ulleungdo island subjected to weathering processes; trachyte which appears to accelerate with time, and volcanic breccia whose mechanical strength can largely decrease in a relative short period of time. Proper measures therefore appear necessary for the prevention of natural disaster such as rock fall and landslide around the circuit road.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.268-274
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• 2011

BACKGROUND: A large scale of sediment load delivered from watershed causes substantial waterway damages and water quality degradation. Controlling sediment loading requires the knowledge of the soil erosion and sedimentation. The various factors such as watershed size, slope, climate, land use may affect sediment delivery processes. Traditionally sediment delivery ratio prediction equations have been developed by relating watershed characteristics to measured sediment yield divided by predicted gross erosion. However, sediment prediction equations have been developed for only a few regions because of limited sediment data. Besides, little research has been done on the prediction of sediment delivery ratio for asia monsoon period in mountainous watershed. METHODS AND RESULTS: In this study Tank model was expanded and applied for estimating sediment yield to Oship River of east coast. The rainfall-runoff in 2006 was verified using the Tank model and we derived good result between observed and calculated discharge in 2009 at the same conditions. In relation to sediment yield, the sediment delivery rate of 2006 was very high than 2009 regardless of methods for estimating sediment load. It was thought to be affected by heavy rainfall due to the typhoon. CONCLUSION(s): For estimating sediment volume from watershed, long-term monitoring data on discharge and sediment is needed. This model will be able to apply to predict discharge and sediment yield simultaneously in ungauged area. This approach is more effective and less expensive method than the traditional method which needs a lot of data collection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.28-34
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• 2020

A reservoir is defined as an artificial facility that stores and controls water during floods and droughts. Korea has constructed and managed reservoirs all over the country to benefit farming communities. The importance of reservoirs has decreased gradually due to urbanization and the spread of tap water, but the importance of water is increasing because of the recent shortage of water and the resulting rise in the price of water resources. Therefore, this study suggests countermeasures through an analysis of the used threshold for agricultural reservoirs. To this end, the forecast of rainfall up to 2100 was first analyzed using flood estimates and RCP scenarios through rainwater data collection. The increase in the RCP 8.5 scenario, the largest increase in the probability rainfall, was calculated by adding it to the current probability rainfall, and it was predicted that the marginal height of Odong Dam would reach its limit in 2028. Therefore, as a countermeasure against this, the measures to secure effective water storage were suggested through measures, such as lowering the height of Yeosu and installing movable beams. Overall, it is expected that effective management of the reservoirs used for agriculture will be possible in the future.