• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.5-14
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• 2017

The hazard maps for predicting collapse on natural slopes consist of a combination of topographic, hydrological, and geological factors. Topographic factors are extracted from DEM, including aspect, slope, curvature, and topographic index. Hydrological factors, such as soil drainage, stream-power index, and wetness index are most important factors for slope instability. However, most of the urban areas are located on the plains and it is difficult to apply the hazard map using the topography and hydrological factors. In order to evaluate the risk of subsidence of flat and low slope areas, soil depth and groundwater level data were collected and used as a factor for interpretation. In addition, the reliability of the hazard map was compared with the disaster history of the study area (Gangnam-gu and Yeouido district). In the disaster map of the disaster prevention agency, the urban area was mostly classified as the stable area and did not reflect the collapse history. Soil depth, drainage conditions and groundwater level obtained from boreholes were added as input data of hazard map, and disaster vulnerability increased at the location where the actual subsidence points. In the study area where damage occurred, the moderate and low grades of the vulnerability of previous hazard map were 12% and 88%, respectively. While, the improved map showed 2% high grade, moderate grade 29%, low grade 66% and very low grade 2%. These results were similar to actual damage.

• Journal of the Korean Geotechnical Society
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• v.33 no.7
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• pp.55-64
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• 2017

A geological repository has been considered one of the most adequate options for the disposal of high-level radioactive waste. A geological repository will be constructed in a host rock at a depth of 500~1,000 meters below the ground surface. The geological repository system consists of a disposal canister with packed spent fuel, buffer material, backfill material, and intact rock. The buffer is very important to assure the disposal safety of high-level radioactive waste. It can restrain the release of radionuclide and protect the canister from the inflow of groundwater. High temperature in a disposal canister is released into the surrounding buffer material, and thus the thermal transfer behavior of the buffer material is very important to analyze the entire disposal safety. Therefore, this paper presents a thermal conductivity prediction model for the Kyungju compacted bentonite buffer material which is the only bentonite produced in Korea. Thermal conductivity of Kyungju bentonite was measured using a hot wire method according to various water contents and dry densities. With 39 data obtained by the hot wire method, a regression model to predict the thermal conductivity of Kyungju bentonite was suggested.

• Journal of the Korean Geotechnical Society
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• v.37 no.4
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• pp.19-26
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• 2021

The high-level radioactive waste (HLW) produced from nuclear power plants is disposed in a rock-mass at a depth of hundreds meters below the ground level. Since HLW is very dangerous to human being, it must be disposed of safely by the engineered barrier system (EBS). The EBS consists of a disposal canister, backfill material, buffer material, and so on. When the components of EBS are installed, gaps inevitably exist not only between the rock-mass and buffer material but also between the canister and buffer material. The gap can reduce water-retarding capacity and heat release efficiency of the buffer material, so it is necessary to investigate properties of gap-filling materials and to analyze gap spacing effect. Furthermore, there has been few researches considering domestic disposal system compared to overseas researches. In this reason, this research derived the peak temperature of the bentonite buffer material considering domestic disposal system based on the numerical analysis. The gap between the canister and buffer material had a minor effect on the peak temperature of the bentonite buffer material, but there was 40% difference of the peak temperature of the bentonite buffer material because of the gap existence between the buffer material and rock mass.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.1
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• pp.90-98
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• 2009

The aim of this study was to evaluate the effect of a milling by-product diet and two sugar cane diets on the local Creole pig breed (CR). A total of 48 CR pigs (24 females and 24 castrated males) were randomly assigned to four different groups of 12 animals. Pigs were allotted to one of 4 dietary treatments: fed with a control soya-bean meal-corn diet containing 19.1% crude protein (CP) and 15.4 MJ DE/kg (diet 1), with an experimental milling by-product diet (soya-bean meal and wheat by-products) containing 19.4% CP and 13.0 MJ DE/kg (diet 2), with ground cane stalks (GCS) or with fresh sugar cane juice (SCJ). Both GCS and SCJ were supplemented with soya-bean meal complement (400 g/d of a 48.7% CP and 16.1 MJ DE/kg diet) in order to obtain diets 3 and 4, respectively. Pigs were fed close to ad libitum level and had free access to water. All the pigs were slaughtered at 65 kg BW. Between 30 and 65 kg BW, growth performance was significantly (p<0.001) affected by dietary treatments: average daily BW gain was 657, 530, 546 and 200 g/d for diets 1, 2, 4, and 3, respectively. Average daily DM intake was 1.8, 1.9, 2.5 and 1.4 kg/d for diets 1, 2, 4, and 3, respectively. Fat cuts (backfat+leaf fat) and backfat thickness were significantly lower on diet 3 than for other treatments (127 vs. 192, 166 g/kg of left half-carcass weight and 24.6 vs. 39.0, 35.3 mm for diet 3 vs. diets 1 and 4, and diet 2, respectively; p<0.001). The dressing weight was significantly lower on diets 2 (82.7 vs. 84.0%; p<0.001). The entire empty digestive tract (DT) weight was higher on diet 2 (73.1 vs. 66.7 g/kg empty BW). However, stomach and large intestine were more developed on diet 3: 12.8 vs. 9.3 g/100 g empty DT (p<0.001) and 26.4 vs. 23.8 g/100 g empty DT (p<0.05), respectively. In conclusion, this study suggests the CR pig has the ability to reach rather good growth and carcass performance with a well-formulated sugar cane meal and/or with a milling by-product diet refined according to its low requirements.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.71-81
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• 2020

The large circular steel pipe for a marine bridge foundation has been developed as a construction method capable of performing the role of the working platform and cofferdam. The objective of this study is to demonstrate the wireless remote sensing system for monitoring the stability of the large circular steel pipe during construction and operation through field tests. The artificial seabed ground with an water level of 4 m is constructed for field tests. The large circular steel pipe with a diameter of 5 m and height of 9.5 m is installed into the ground by suction, and the embedded depth is 5 m. The inclinometer and strain gauges are installed on different surfaces of the upper module, and the tilt angle and stress are monitored throughout the entire construction process. As results, tilt angles are measured to be constant during the suction penetration. However, the tilt angle is larger in the x-axis direction. In addition, even when installed on different surfaces, the tilt angle in the same axial direction is measured to be almost the same. The stresses measured by strain gauges increase during suction penetration and decrease during pull-out. Based on measured stresses, it is found that the eccentricity is acting on the large circular steel pipe. This study shows that a wireless remote sensing system built with an inclinometer and strain gauge can be a useful tool for the stability monitoring of the large circular steel pipe.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.4
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• pp.1-14
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• 2012

A river is defined as the watercourse flowing through its channel, and the mapping tasks of a river plays an important role for the research on the topographic changes in the riparian zones and the research on the monitoring of flooding in its floodplain. However, the utilization of the ground surveying technologies is not efficient for the mapping tasks of a river due to the irregular surfaces of the riparian zones and the dynamic changes of water level of a river. Recently, the spatial information data sets are widely used for the coastal mapping tasks due to the acquisition of the topographic information without human accessibility. In this research, we tried to extract a river from the RapidEye imagery by using the ISODATA(Iterative Self_Organizing Data Analysis) classification algorithm with the two different parameters(NIR (Near Infra-Red) band and NDVI(Normalized Difference Vegetation Index)). First, the two different images(the NIR band image and the NDVI image) were generated from the RapidEye imagery. Second, the ISODATA algorithm were applied to each image and each river was generated in each image through the post-processing steps. River boundaries were also extracted from each classified image using the Sobel edge detection algorithm. Ground truths determined by the experienced expert are used for the assessment of the accuracy of an each generated river. Statistical results show that the extracted river using the NIR band has higher accuracies than the extracted river using the NDVI.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.2
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• pp.61-69
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• 2005

The coastal erosion and the look of a heap which are mainly occurred in the district along the coast are found for various forms such as the estuary closing, the estuary sand bar the development of the coast sand bar, and the modification of coastline. Recently, due to the coastal development, these transformations have been intensified. The change of coast, which has been made slow progress is required long-term study on a searching examination of the root cause and a suggestion of a counter measure. In this research, ortho aerial photos were produced to analyze volumes of topographical alternations that have been progressed fer the long run, by 10s cycle from 1940s through 1990s, to compute accurate volumes of coastline variation, through a datum point and G.C.P (Ground Control Point). Also in this study, without respect to water level, the coastline variation was analyzed by using comparatively analyzed a Idlest land map, a cadastral map. And to analyze topographical variation volumes, the tidal station's materials was used under consideration f3r tide. Finally, topographical variation volumes are comparatively analyzed through surveying and sounding and a point of fine of aviation photographing was calculated and revised. After this research, by using ortho aerial photos, We can understand efficiency of these in computing volumes of variations of coastline by analyzing quantitatively erosion and look of a heap. Besides, in the future, these will be used for information gathering of the coastline integration control system.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.142-151
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• 2007

The rock excavation work on the sea is planned as underwater process if the elevation of the rock is lower than the M.S.L.(Mean Sea Level). However, in case of West and South sea which are largely different between the rise and fall of the tide, the earth work can be performed on the ground while the work surface is exposed above the sea according to the tide cycle. Thus, it may a good substitute to make up for shortcomings of underwater construction works such as safety problems of workers, loss of efficiency and increasement of construction costs. But the difference between the height of the rock excavation surface and the water surface changed by the tide makes the exposure time of work surface, that is the possible working hours be changed. Also, it may cause the changes of construction cost. Thus, this study analyzes the economical efficiency of the construction method using the difference between the rise and fall of the tide in comparison with the construction method which is performed under the sea, and it also suggests the way to analyze the economical working hours by estimating the possible working hours on the ground. We also try to find out the application possibility of the way like the rock excavation work on the sea using the difference between rise and fall of the tide.

• Journal of Radiation Protection and Research
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• v.37 no.2
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• pp.84-89
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• 2012

The purpose of this study was to compare radiation dose and image quality between low-dose (LDP) and standard-dose protocol (SDP). LDP (120 kVp, 30 mAs, 2-mm thickness) and SDP (120 kVp, 180 mAs, 1.2-mm thickness) images obtained from 61 subjects were retrospectively evaluated at level of carina bifurcation, using multi-detector CT (Brilliance 16, Philips Medical Systems). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated at ascending aorta and infraspinatus muscle, from CT number and back-ground noise. Radiation dose from two protocols measured at 5-point using acrylic-phantom, and CT number and noise measured at 4-point using water-phantom. All statistical analysis were performed using SPSS 19.0 program. LDP images showed significantly more noise and a significantly lower SNR and CNR than did SDP images at ascending aorta and infraspinatus muscle. Noise, SNR and CNR were significantly correlated with body mass index (p<0.001). Radiation dose, SNR and CNR from phantom were significant differences between two protocols. LDP showed a significant reduction of radiation dose with a significant change in SNR and CNR compared with SDP. Therefore, exposure dose on LDP in clinical applications needs resetting highly more considering image quality.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.183-194
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• 2004

It's essential process to study non-linear material function related to characteristics of compressibility and permeability when we predict the consolidation behavior of soft clay ground. In this study, laboratory tests were conducted to find out the material function using marine clay. Standard oedometer test and Rowe cell test were performed with conditions, which were classified into vertical drainage only, radial drainage only and vertical-radial drainage case. Modified oedometer test equipment was developed to find out the material function and special extrusion device was originated to minimize the sample disturbance effect. Reliability of the results in modified oedometer test could be confirmed by comparing with the Rowe cell's one. Effective stress - void ratio - permeability relations were analyzed using all testing results. As a result, void ratio with effective stress level could be expressed by the power function and permeability with void ratio could be expressed by exponential function. In soft clay with high initial water content and low shear strength, non-linear characteristics related to compressibility and permeability varied with wide range by the effective stress levels. It's important to note that non-linearity of the material function should be considered at prediction of the consolidation behavior.