Ground depression/cave-ins due to subsurface cavities have been occasionally occurred in urban area. To prevent the ground cave-ins, a ground penetrating radar (GPR) method was applied and more than 2,000 subsurface cavities were found in Seoul. For each cavity, excavation was carried out to investigate main cause of the cavity and then the site was restored permanently. It was found that this excavation-and-restoration method was not efficient to repair small size cavities. Instead, grouting methods was used to repair the small cavities temporarily. This study evaluated the field applicability of grouting methods on restoring small cavities. Three types of grouting materials were applied on 12 sections and two non-destructive tests were conducted in field. A falling weight deflectometer(FWD) test was conducted to assess the bearing capacity of the site before and after grouting. Ground penetrating radar (GPR) was used to evaluate the extent of the grouting materials to a cavity. From the FWD test results, the bearing capacity of the Section A and B was enhanced by 7.5% and 13.5% while the bearing capacity of the section C was reduced by 11.5%. It was found from the GPR tests that the grouting materials used in the Section B and C could fill the cavity well and also extended to surrounded area due to injection pressure or selfexpansion. In common, the small cavities could be restored quickly, less than 30 minutes per a cavity by the grouting methods. Hence it can be concluded that the grouting methods can be applicable to restore small cavities. However, it needs to consider the application of grouting methods carefully because the grouting methods can be lost through a pipe link to a cavity. Also, excavations can be conducted occasionally in urban roads so that the stiffness of grouting materials needs to soft enough to be excavated and strong enough to support traffic loads.

Oxidation of erythromycin, sulfamethazine and sulfathiazole by ozone was experimentally investigated to see the effects of background water quality such as ultrapure water, humic acid and biologically treated wastewater and water temperature on the removal rate, consequently to provide design information when the ozone treatment process is adopted. Initial concentration of the antibiotics was spiked to 10 μg/l and ozone dose was 1, 2, 3, 5, 8 mg/l. While the removal rate of erythromycin under ultrapure water background by ozone oxidation was over 99%, that under humic acid and biologically treated wastewater background was markedly reduced to the range of 59.8%~99% and 17.0%~99%, respectively. When water temperature is decreased from 20℃ to 4℃, the removal rate is reduced from the range of 17.0%~99% to the range of 9.4%~97.4% under biologically treated wastewater background. The effects of background and temperature on the removal rate of sulfamethazine and sulfathiazole were similar to erythromycin, but the degree was different. Therefore, it is concluded that the background of water to be treated as well as water temperature should be taken into consideration when the design factor such as ozone dose is determined to meet the treatment objective in the ozone treatment process.

Extreme low temperature has various effects on society. It has negative impacts on health, industry, agriculture, and transportation during winter season. Therefore, extreme low temperature is recognized as main factor that causing traffic accidents. This study analyzed the relationship between low temperature and traffic accidents from 2012 to 2018. This study also compared the differences in vulnerability to low temperature between urban and rural areas. Generalized Additive Model (GAM) and Poisson regression model are used to estimate the thresholds and the level of traffic accidents. The results show that the thresholds tend to be decreased gradually, but the level of traffic accidents are more likely to increase in both urban and rural areas Comparatively, rural areas are more vulnerable to traffic accident caused by drop in temperature than urban areas.

The aims of this research were to examine whether horticultural activity is appropriate for personality education to prevent reformatory students from redelinquency, to make use of it for developing educational programs and to take advantage of the research as based information. In order to accomplish the purposes, the researches and surveys were taken in four parts targeting 262 reformatory students from five different Youth Detention Centers out of ten centers in the country: simple mental health diagnostic inventory, general characteristics, preferences of personality programs that are currently underway to juvenile delinquents in juvenile protection education institution, and awareness and preference of the plants and horticultural activities. First of all, as a result of simple mental health diagnostic inventory, ‘depression’ appeared to be the highest while ‘hostility’, ‘somatization’, ‘obsessional thinking’, ‘interpersonal sensitivity’, ‘anxiety’ and ‘psychosis’ emerged in the order. Secondly, as a result of preferences of personality programs, ‘social work’ appeared relatively the highest, while ‘Do-dream program’, ‘art therapy’, ‘career exploration’, and ‘sex education’ showed in the order. Thirdly, 53.3% students responded that personality programs through horticultural activities is desirable and 84% appeared that they prefer it. The most preferred plant species were fruit trees (strawberries, apples), flowers (roses, herbs) and vegetables (Scatter cucumbers, tomatoes). The most interesting garden activities were ‘growing (cultivation)’, ‘decorating (decoration and craft)’ and ‘feeling plants (appreciating).’ Therefore, it is well ascertained that juvenile delinquents in juvenile protection education institution consider introducing horticultural programs into personality education positive. Based on these results, it is identified that more various and specialized horticulture programs to prevent reformatory students from redelinquency should be developed for practical use.