• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.2
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• pp.31-43
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• 1988

The Purpose of this study is to develop the rainfall-delayed response model (RDR Model) which influences the baseflow proportion of rivers as a result of the antecedent precipitation of the previous several months. The assesment of accurate baseflows in the rivers is one of the most important elements for the planning of seasonal water supply for agriculture, water resources development, hydrological studies for the availability of water and design criteria for various irrigation facilities. The Palukan river gauging site which is located in the Pulukan catchment on Bali Island, Indonesia was selected to develop this model. The basic data which has been used comprises the available historic flow records at 19 hydrologic gauging stations and 77 rainfall stations on Bali Island in the study. The methology adopted for the derivation of the RDR model was the water balance equation which is commonly used for any natural catcbment ie.P=R+(catchment losses) -R+(ET+DP+DSM+DGW). The catchment losses consist of evapotranspiration, deep percolation. change in soil moisture, and change in groundwater storage. The catchment areal rainfall has been generated by applying the combination method of Thiessen polygon and Isohyetal lines in the studies. The results obtained from the studies may be summarized as follows ; 1. The rainfall-runoff relationship derived from the water balance equation is as shown below, assuming a relationship of the form Y=AX+B. Finally these two equations for the annual runoff were derived ; ARO$_1$=0.855 ARF-821, ARF>=l,400mm ARO$_2$=0.290ARF- 33, ARF<1,400mm 2. It was found that the correction of observed precipitation by a combination of Thiessen polygons and Isohyetal lines gave good correlation. 3. Analysis of historic flow data and rainfall, shows that surface runoff and base flow are 52 % and 48% (equivalent to 59.4 mm) of the annual runoff, respectively. 4. Among the eight trial RDR models run, Model C provided the correlation with historic flow data. The number of months over which baseflow is distributed and the relative proportions of rainfall contributing in each month, were estimated by performing several trial runs using data for the Pulukan catchment These resulted in a value for N of 4 months with contributing proportions of 0.45, 0.50, 0.03 and 0.02. Thus the baseflow in any month is given by : P$_1$(n) =0.45 P(n) +0.50 P(n-I ) +0.03 P(n-$_2$) +0.02 P(n-$_3$) 5. The RDR model test gave estimated flows within +3.4 % and -1.0 % of the observed flows. 6. In the case of 3 consecutive no rain months, it was verified that 2.8 % of the dependable annual flow will be carried over the following year and 5.8 % of the potential annual baseflow will be transfered to the next year as a result of the rainfall-delayed response. The results of evaluating the pefformance of the RDR Model was generally satisfactory.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.343-350
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• 2017

Amid increasingly saturated ground space, development of underground space has been booming throughout the world and excavation has been underway near the structure above or under the ground level. But the ground subsidence caused by improper or poor construction technologies, underground water leakage, sudden changes of stratum and the problem with earth retaining system component has been emerged as hot social issue. To deal with such problems nationwide, establishment of preventive and proactive disaster management and rapid restoration system has been pushed now. In this study, collection of the data on technology development trend to secure the underground safety was made, taking into account of internal change elements (changing groundwater level, damage to underground utilities, etc) and external change elements (vehicle load, earthquake and ground excavation, etc) during excavation. Amid the growing need of ground behavior analysis, ground subsidence evaluation technology, safe excavation to prevent ground subsidence and reinforcement technology, improvement of rapid restoration technology in preparation for ground subsidence and development of independent capability, this study is intended to introduce the technology development in a bid to prevent the ground subsidence during excavation. It's categorized into prediction/evaluation technology, complex detect technology, waterproof reinforcement technology, rapid restoration technology and excavation technology which, in part, has been in process now.

• Journal of Korean Society of Forest Science
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• v.109 no.4
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• pp.429-437
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• 2020

In this study we quantified the long-term change in discharge against precipitation in a forested watershed and investigated how the growth of forest trees influences these changes. We found a proportional relationship between precipitation and discharge for each year, and discharge decreased gradually with time. Precipitation and discharge were highest in July and August, and the changes in precipitation, discharge, and runoff rate did not always coincide, given that high runoff rate was shown in August and September. The monthly coefficient of variation (CV) for discharge was larger than that for precipitation, and the deviation between precipitation and discharge increased gradually. From 2011 to 2017, the gradient of the trend line for the change of total discharge and direct runoff against precipitation decreased, whereas the gradient of the base flow increased in this same time period. A possible explanation is that the water holding capacity of soil deposits increased as the forest soil of the Palgong Mountain watershed developed and the increase of base flow rose with groundwater level together with that of outflow quantity. The coefficient of flood recession was lower in the period 2011 to 2017 than in 2003 to 2010; thus, the reduction of discharge was mitigated and remained steady as time progressed. We conclude from these results that the discharge of surface runoff decreased as tree growth and base flow increased; however, the water yield function of the forest increased gradually.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.5-13
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• 2007

Many construction projects adopt grouting technology to prevent the leakage of groundwater or to improve the shear strength of the ground. Recognition as a feasible field procedure dates back to 1925. Since then, developments and field use have increased rapidly. According to improvement of grout materials, theoretical study on grout penetration characteristics is demanded. Fluid of grout always tends to flow from higher hydraulic potential to lower one and the motion of grout is also a function of formation permeability. Viscosity of pout is changed by chemical action while grout moves through pores. Due to the increment of viscosity, permeability is decreased. Permeability is also reduced by grout particle deposits to the soil aggregates. In this paper, characteristics of new cement grout material that has been developed recently are studied: injectable volume of new grout material is tested in two different grain sizes of sands; and the method to calculate injectable volume of grout Is suggested with consideration of change in viscosity and clogging phenomena. The calculated values are compared with injection test results. Viscosity of new grout material is found to increase as an exponential function of time. And lumped parameter $\delta$ of new grout material to be used for assessing deposition characteristics is estimated by comparing deposit theory with injection test results considering different soil types and different injection pressures. Injection test results show that grout penetration rate is decreased by the increase of grout viscosity and clogging phenomena.

• Journal of the Korean Geotechnical Society
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• v.38 no.3
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• pp.17-26
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• 2022

Domestic district heating system needs safety management guidelines using the change of surface temperature to detect damages to buried heat pipes. This paper performed numerical analyses on the temperature change of ground surface due to the burial and leakage of heat pipes. Temperature difference between the ground surface above the buried heat pipes and the surrounding surface rises to a crescendo between 3 am and 8 am. It is more significant in winter rather than in summer. Low groundwater level magnifies the temperature increase of the ground surface by the heat pipe, which is smaller in the asphalt pavement than in the bare soil. Without leakage of the buried heat pipe, the temperature increment on the ground surface by the heat pipe is within 3.0℃ in the bare soil and 3.5℃ in the asphalt pavement. Leakage of the supply heat pipe in the bare soil increases the temperature on the ground surface gradually in the summer but rapidly in the winter. Asphalt pavement shows a lower increment and increasing rate of the temperature on the ground surface due to pipe leakage than bare soil surface. And leakage on both sides of the supply pipe takes 1-2 days for the temperature difference from the surrounding soil surface to reach 10℃.

• Journal of Korean Society of Rural Planning
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• v.24 no.3
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• pp.73-86
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• 2018

Agricultural or rural landscape provides various ecosystem services. However, the ecosystem services function is declining due to various environmental problems such as climate change, land use change, stream intensification, non-point pollution and garbage. The A1B scenario predicts that the mean air temperature of South Korea will rise $3.8^{\circ}C$ degrees celsius in 2100. Agricultural sector is very vulnerable to climate change, so it must be thoroughly predicted and managed. In Korea, the facility horticulture complex is 54,051ha in 2016 and is the 3rd largest in the world(MAFRA, 2014). Facilities of horticultural complexes are reported to cause problems such as groundwater decrease, vegetation and insects diversity reduction, landscapes damage and garbage increase, compared with the existing land use paddy fields. Heat island phenomenon associated with climate change is also accelerated by the high heat absorption of horticultural sites. Therefore, we analyzed the heat island phenomenon occurring in the facility of horticultural complex in Korea. As an improvement measurement, I examined how much air temperature is reduced by putting the channel and the open space. In the case of the Buyeo area, the Computational Fluid Dynamics (CFD) simulation was analyzed for the average summer temperature distribution in the current land use mode at $38.9^{\circ}C$. As an improvement measurement, CFD simulation after 10% of 6m water channel was found to have an effect of lowering the summer temperature of about $2.7^{\circ}C$ compared with the present average of $36.2^{\circ}C$. In addition, CFD simulations after analyzing 10% of the open space were analyzed at $34.7^{\circ}C$, which is $4.2^{\circ}C$ lower than the present. For the Jinju area, CFD simulations were analyzed for the average temperature of summer at $37.8^{\circ}C$ in the present land use pattern. As an improvement measure, CFD simulations after 10% of 6m water channel were found to have an effect of lowering the summer temperature of about $2.6^{\circ}C$ compared to the current average of $35.2^{\circ}C$. In addition, CFD simulations after analyzing 10% of the open space were analyzed at $33.9^{\circ}C$, which is $3.9^{\circ}C$ lower than the present. It can be said that the effect of summer temperature drop in open space and waterway has been proven. The results of this study are expected to be reflected in sustainable agriculture land use and used as basic data for government - level policy in land use planning for climate change.

• Proceedings of the KSEEG Conference
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• 2001.05b
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• pp.42-63
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• 2001

The detail survey on the Songsanri tomb site including the Muryong royal tomb was carried out during the period from May 1 , 1996 to April 30, 1997. A quantitative analysis was tried to find changes of tomb itself since the excavation. Main subjects of the survey are to find out the cause of infiltration of rain water and groundwater into the tomb and the tomb site, monitoring of the movement of tomb structure and safety, removal method of the algae inside the tomb, and air controlling system to solve high humidity condition and dew inside the tomb. For these purposes, detail survery inside and outside the tombs using a electronic distance meter and small airplane, monitoring of temperature and humidity, geophysical exploration including electrical resistivity, geomagnetic, gravity and georadar methods, drilling, measurement of physical and chemical properties of drill core and measurement of groundwater permeability were conducted. We found that the center of the subsurface tomb and the center of soil mound on ground are different 4.5 meter and 5 meter for the 5th tomb and 7th tomb, respectively. The fact has caused unequal stress on the tomb structure. In the 7th tomb (the Muryong royal tomb), 435 bricks were broken out of 6025 bricks in 1972, but 1072 bricks are broken in 1996. The break rate has been increased about 250% for just 24 years. The break rate increased about 290% in the 6th tomb. The situation in 1996 is the result for just 24 years while the situation in 1972 was the result for about 1450 years. Status of breaking of bircks represents that a severe problem is undergoing. The eastern wall of the Muryong royal tomb is moving toward inside the tomb with the rate of 2.95 mm/myr in rainy season and 1.52 mm/myr in dry season. The frontal wall shows biggest movement in the 7th tomb having a rate of 2.05 mm/myr toward the passage way. The 6th tomb shows biggest movement among the three tombs having the rate of 7.44mm/myr and 3.61mm/myr toward east for the high break rate of bricks in the 6th tomb. Georadar section of the shallow soil layer represents several faults in the top soil layer of the 5th tomb and 7th tomb. Raninwater flew through faults tnto the tomb and nearby ground and high water content in nearby ground resulted in low resistance and high humidity inside tombs. High humidity inside tomb made a good condition for algae living with high temperature and moderate light source. The 6th tomb is most severe situation and the 7th tomb is the second in terms of algae living. Artificial change of the tomb environment since the excavation, infiltration of rain water and groundwater into the tombsite and bad drainage system had resulted in dangerous status for the tomb structure. Main cause for many problems including breaking of bricks, movement of tomb walls and algae living is infiltration of rainwater and groundwater into the tomb site. Therefore, protection of the tomb site from high water content should be carried out at first. Waterproofing method includes a cover system over the tomvsith using geotextile, clay layer and geomembrane and a deep trench which is 2 meter down to the base of the 5th tomb at the north of the tomv site. Decrease and balancing of soil weight above the tomb are also needed for the sfety of tomb structures. For the algae living inside tombs, we recommend to spray K101 which developed in this study on the surface of wall and then, exposure to ultraviolet light sources for 24 hours. Air controlling system should be changed to a constant temperature and humidity system for the 6th tomb and the 7th tomb. It seems to much better to place the system at frontal room and to ciculate cold air inside tombs to solve dew problem. Above mentioned preservation methods are suggested to give least changes to tomb site and to solve the most fundmental problems. Repairing should be planned in order and some special cares are needed for the safety of tombs in reparing work. Finally, a monitoring system measuring tilting of tomb walls, water content, groundwater level, temperature and humidity is required to monitor and to evaluate the repairing work.

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.32-37
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• 2005

The soil properties of the royal tombs (managed by cultural properties administration) located in Seoul and suburban Gyonggi area were investigated to see the influence of the change in soil environment on the royal tomb s이I. To compare the soil chemical properties of four royal tombs soil of Changdeokgung, Jongmyo, Seooneung, and Dongguneung, pH, organic content, available phosphate, extractable calcium, extractable potassium, extractable magnesium, cation exchange capacity, degree of base saturation, and total nitrogen content were measured. The concentrations of Cd, Pb, and Cu measured as the degree of heavy metal contamination can be an indication of atmospheric pollution in the soil environment. To estimate the degree of soil compaction, soil hardness, pore space, porosity, bulk density, and soil atmosphere were analyzed. Through these studies, following conclusions were made: 1. The soil hardness and pore space which can be used as indexes of soil compaction, were worse in the soil of Seooneung than in those of Changdeokgung and Dongguneury. These phenomena seem to be the result of increase in visitors in Seooneung and Dongguneung better and soil management in Changdeokgung and Dongguneung. When three different regions of forest area, prohibited area, and soil compaction area in Seooneung soil were compared, the degree of compaction in the forest area was less than compaction area, indicating the need for the employment of soil resting period in the compaction area. 2. The pH measurements of all four royal tombs soil were higher in top soil than sub soil. The higher soil pH values in Jongmyo and Seooneung seem to result from the application of soil conditioner. In the case of Seooneung, the values for soil pH and organic content were higher in the forest area than those in compaction area. It is thought that active soil management was employed in the forest area through application of organic matters and soil conditioners. 3. The heavy metal contents from soil of Changdeokgung and Jongmyo were higher than that from soil of Dongguneung. Since Changdeokgung and Jongmyo are located inside Seoul, it is thought that the high level of heavy metal concentrations in these royal tomb soil is the result of accumulation of pollutants from the city.

• Journal of Soil and Groundwater Environment
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• v.7 no.4
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• pp.68-76
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• 2002

In this study, we have investigated the geochemical behavior and fate of heavy metals in acid rock drainage (ARD). The ARD was collected from the area of the former Dongrae pyrophyllite mine. The Dongrae Creek waters were strongly acidic (pH : 2.3~4.2) and contained high concentrations of $SO_4$, Al, Fe, Mn, Pb, Cu, Zn, and Cd, due to the influence of ARD generated from weathering of pyrite-rich pyrophyllite ores. However, the water quality gradually improved as the water flows downstream. In view of the change of mole fractions of dissolved Fe, Al and Mn, the generated ARD was initially both Fe- and AA-ich but progressively evolved to more Al-rich toward the confluence with the uncontaminated Suyoung River. As the AR3 (pH 2.3) mixed with the uncontaminated waters (pH 6.5), the pH increased up to 4.2, which caused precipitation of $SO_4$-rich Fe hydroxysulfate as a red-colored, massive ferricrete precipitate throughout the Dongrae Creek. Accompanying the precipitation of ferricrete, the Dongrae Creek water progressively changed to more Al-rich toward downstream sites. At the mouth of the Dongrae Creek, it (pH 3.4) mixed with the Suyoung River (pH 6.9), where pH increased to 5.7, causing precipitation of Al hydroxysulfate (white precipitates). Neutralization of the ARD-contaminated waters in the laboratory caused the successive formation of Fe precipitates at pH<3.5 and Al precipitates at higher pH (4~6). Manganese compounds were precipitated at pH>6. The removal of trace metals was dependent on the precipitation of these compounds, which acted as sorbents. The pHs for 50% sorption ($pH_{50}$) in Fe-rich and Al-rich waters were respectively 3.2 and 4.5 for Pb, 4.5 and 5.8 for Cu, 5.2 and 7.4 for Cd, and 5.8 and 7.0 for Zn. This indicates that the trace metals were sorbed preferentially with increasing pH in the general order of Pb, Cu, Cd, and Zn and that the sorption of trace metals in Al-rich water occurred at higher pH than those in Fe-rich water. The results of this study demonstrated that the partitioning of trace metals in ARD is not only a function of pH, but also depends on the chemical composition of the water.

• Journal of Soil and Groundwater Environment
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• v.11 no.5
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• pp.20-34
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• 2006

This study was undertaken to assess the anthropogenic impact on trace metal concentrations (Zn, Cu, Pb, Cr, Ni, and Cd) of roadside sediments (N = 70) from No.7 national road within the watershed of Hoidong Reservoir in Pusan City and to estimate the potential mobility of selected metals using sequential extraction. We generally found high concentrations of metals, especially Zn, Cu and Pb, affected by anthropogenic inputs. Compared to the trace metal concentrations of uncontaminated stream sediments, arithmetic mean concentrations of roadside sediments were about 7 times higher for Cu, 4 times higher for Zn, 3 times higher for Pb and Cr and, 2 times higher for Ni and As. Speciation data on the basis of sequential extraction indicate that most of the trace metals considered do not occur in significant quantities in the exchangeable fraction, except for Cd and Ni whose exchangeable fractions are appreciable (average 29.3 and 25.8%, respectively). Other metals such as Zn (51.4%) and Pb (45.2%) are preferentially bound to the reducible fraction, and therefore they can be potentially released by a pH decrease and/or redox change. Copper is mainly found in the organic fraction, while Cd is highest in the exchangeable fraction, and Cr and Ni in the residual fraction. Considering the proportion of metals bound to the exchangeable and carbonate fractions, the comparative mobility of metals probably decreases in the order of Cd>Ni>Pb>Zn>Cr>Cu. Although the total concentration data showed that Zn was typically present in potentially harmful concentration levels, the data on metal partitioning indicated that Cd, Ni and Pb pose the highest potential hazard for runoff water. As potential changes of redox state and pH may remobilize the metals bound to carbonates, amorphous oxides, and/or organic matter, and may release and flush them through drain networks into the watershed of Hoidong Reservoir, careful monitoring of environmental conditions appears to be very important.