호수내 인의 주요원으로 몬순 유입수

안광국 한국육수학회 2000 생태와 환경 Vol.33 No.3

Spatial and temporal variation of phosphorus in response to intensity of summer monsoon was evaluated in Taechung Reservoir during 1993∼1994. Total phosphorus (TP) averaged 31 ㎍/ℓ during the study and varied from 6 to 197 ㎍/ℓ. Concentrations of TP were highest in the headwaters during the monsoon of July∼August 1993, and these values were mainly made of particulate P and were closely associated (R²=0.74, p < 0.001) with high inorganic suspended solids (NVSS). In-lake TP in the headwaters was mainly influenced by the watershed runoff and declined toward the dam. Values of TP downlake was only one-fifth of the peak in the headwaters and had no correlation with NVSS. In 1994, inlake TP was markedly lower relative to 1993 and showed low spatial and temporal variation. Maximum TP during monsoon 1994 in the headwaters and mid-lake was 72% and 52% lower, respectively, than in those two zones in 1993 whereas TP downlake was similar between the two years. These results suggest that temporal variation downlake is much less influenced by seasonal inflow compared to the headwaters. In 1993, mean TP before fall overturn, based on average value for all sites, was significantly (t = 5.99, p < 0.001) greater than the mean after fall overturn, whereas in 1994 mean TP after fall overturn (32 ㎍/ℓ) was greater. This outcome indicates that in 1993 major P-input originated from the external source from the watershed during the intense monsoon, whereas in 1994 internal processes dominated during the weak monsoon. Overall data suggest that annual budget of inlake P is regulated by intensity of the summer monsoon, and phosphorus data measured at single site near the dam or headwater zone may not be represent seasonal trends of the system due to large spatial variation of Taechung Reservoir.

Group Effects in Pile Group under Lateral Loading

안광국,김홍택,Ahn Kwang Kuk,Kim Hong Taek Korean Geotechnical Society 2005 한국지반공학회논문집 Vol.21 No.2

본 연구에서는 점토지반에서 수평력을 받는 군말뚝과 단말뚝의 수평저항력을 파악하기 위하여 유한요소 해석프로그램인 ABAQUS를 이용하여 수치해석을 행하였다. 수치해석은 말뚝직경(1.0, 0.5m), 말뚝길이(7, 10m) 그리고 두부조건(두부자유와 말뚝캡을 적용한 두부구속조건)을 변수로 하여 실시하였다. 수평력 작용시 선말뚝(leading pile)의 캡에 의한 영향과,군말뚝내의 각각의 말뚝에 대한수평저항력의 크기와 분포를 평가하기 위하여 1$\times$3 군말뚝을 사용하였다. 점토지반은 Cam-clay 모델을 사용하였고, 말뚝은 원형의 콘크러트로 탄성모델을 사용하여 3차원 해석을 수행하였다. 해석결과 말뚝캡의 크기는 단말뚝의 수평저항력에 영향을 미치는 것으로 나타났으며, 군말뚝내의 선말뚝은 군말뚝의 효과에 의해 수평저항력이 증가하면서 Brown이 제안한p-multiplier 값이 1보다 크게 평가되었다. This paper describes the results for a numerical analysis of'single piles and pile oops in clayey soils subjected to monotonous lateral loading using the ABAQUS finite element software. The investigated variables in this study include free head and embedded capped single piles, pile diameter (1.0 m, 0.5 m), pile length (7.0 m, 10.0 m), and pile groups. The 1$\times$3 pile group was selected to investigate the individual pile and group lateral resistance, the distribution of the resistance among the piles, the effects of lateral stresses in front of and on the sides of the piles, and the effect of a cap on the lateral resistance of the leading pile. The soil was modeled using Cam-clay constitutive relationship and the pile was considered as a elastic circular concrete pile. The results show that the size of the cap influences lateral capacity of sin pile. The results also show in pile groups, the pile-soil-pile interaction and the cap effect the resistance in the leading pile, and the p-multiplier for the leading pile of greater than 1.0 was able to be obtained.

[박사학위 취득자 소개] PILE-SOIL-PILE INTERACTION IN PILE GROUPS UNDER LATERAL LOADING

안광국 한국지반환경공학회 2004 지반환경 Vol.5 No.1

원심모델링을 이용한 CSCP 및 SCP로 개량된 연약지반의 거동

안광국 한국지반공학회 2006 한국지반공학회논문집 Vol.22 No.4

In this study, centrifuge model tests were performed to investigate the stress concentration ratio, bearing capacity and deformation modes of piles in clay ground improved by granular piles with two types of pile (CSCP, SCP) and various replacement ratios (0, 20, 40, 60%). According to the results of tests, the load ratio of ground improved by SCP and CSCP proportionally increased as replacement ratio increased. It shows that average normalized load of ground improved by CSCP is higher by about 8~21% than by SCP. As a result of rigid loading tests, it was evaluated that average stress concentration ratio of CSCP is higher than that of SCP. Only expansion failure occurred in CSCP, whereas SCP showed the expansion and shear failure simultaneously.

변화의 시대를 맞이하는 우리 학회

안광국 한국지반환경공학회 2021 지반환경 Vol.22 No.4

금강 (錦江) 담수어의 (淡水魚) 대상분포와 (帶狀分布) 군집분석에 (群集分析) 관한 연구

안광국,홍영표,김재구,최신석 한국수생태학회(구 한국하천호수학회) 1992 생태와 환경 Vol.25 No.2

하절기 장마동안 용존산소의 역동적 변화

안광국 한국육수학회 2000 생태와 환경 Vol.33 No.3

Seasonal oxygen content and deficit rates were evaluated from 17 sites of Taechung Reservoir during 1993∼1994. In 1993, river inflows peaked during the monsoon in July∼August and disrupted thermal stratification and anoxic layers in the headwaters, thereby confining the anoxia to the mid-lake and downlake reach. The volume of anoxic water with < 4 mg/ℓ DO comprised only < 10% of the total lake volume in this period. In contrast, during monsoon 1994, 85% of total lake volume was subject to hypoxic conditions with oxygen concentrations < 30% saturation, resulting in massive fishkills(Hypomesus olidus). Relative areal oxygen deficit (RAOD) was -0.024 mg O₂ cm^(-2) d^(-1) during monsoon 1993, whereas it rapidly decreased at the rate of 0.080 mg O₂cm^(-2) d^(-1) during monsoon 1994. Anoxic factor (AF) showed a same interannual pattern as the RAOD and was greater > 50 d in 1994 (76.5 d) than 1993 (21.3 d). Thus, the reservoir showed a river-characteristics (6∼11 mg/ℓ DO) in 1993 while lacustrine conditions ( < 4 mg/ℓ DO) dominated in 1994. Regression analysis showed that the variation of summer DO was mostly determined (R²=0.99, p < 0.0001) by inflow. These findings suggest that the primary factor regulating the oxygen content in this system during summer is an intensity of the monsoon rain.

호수 지형 및 수리수문학적 변화에 대한 몬순 영향

안광국 한국육수학회 2000 생태와 환경 Vol.33 No.4

This paper demonstrates the influence of intensity of the monsoon on morpho-hydrological fluctuations in Taechung Reservoir during 1993∼1994. During the study, hydrological variables including rainfall, inflow, and discharge volume showed distinct contrast between 1993 and 1994. Interannaul differences in rainfall occurred during the monsoon in July∼August monsoon and influenced inflow, discharge, and water residence time (WRT). Total inflow in 1993 was four times greater than that of 1994, and summer inflow in 1993 was 8 times greater than summer 1994. Annual Mean WRT was 93.2 d in 1993 vs. 158.6 d in 1994 and the largest differences occurred between monsoons of 1993 and 1994. Morphometric variables reflected the interannual contrasts of hydrology, so that in 1993 surface area, total volume, shoreline development, and mean depth increased consistently from premonsoon to postmonsoon and over this same period in 1994 they decreased. This outcome indicates that the area of shallow littoral zones in 1993 was greater than in 1994. Also, the drainage area to surface area (D/L) at 80 m MSL was 60.7 which was much greater than values in Soyang and Andong reservoirs and natural lakes world-wide. The morpho-hydrodynamic conditions seemed to influence in-reservoir nutrient concentration which is one of the most important factors regulating the eutrophication processes. I believe, under the maximum hydrodynamic fluctuations in Korean waterbodies during the monsoon, applications of mass balance models to man-made lakes for assessments of external loading should be considered because the models can be used under the seasonally stable inflow and water residence time.

대형 인공호에서 무기 질소원에 대한 점오염원 및 유입수의 영향

안광국 한국육수학회 2000 생태와 환경 Vol.33 No.4

This paper evaluated the influence of point source and flow events on inorganic nitrogen fractions at 17 sites of Taechung Reservoir during 1993∼1994. Total nitrogen (TN) averaged 1.53 mg/L during the study and ranged between 0.70 and 2.56 mg/L. Dissolved inorganic nitrogen (DIN) accounted for > 90% of TN regardless of season and location, indicating a nitrogen-rich system showing eutrophic∼hypereutrophic conditions. Some 67∼94% of DIN was NO₃-N, whereas mean level of NH₄-N was less than 5% of DIN. During monsoon 1993, dilution of NO₃-N was evident in the headwaters as a result of mixing of lake water with rain water, while NH₄-N increased> 100% compared to the premonsoon. Values of NH₄-N had a positive correlation with rainfall (r = 0.85; p < 0.001) and negative correlations with theoretical water residence time (r = 0.90; p < 0.001) and conductivity (r = -0.78, p < 0.001), respectively. These outcomes suggest that NH₄-N came from external input from the watershed during the monsoon. In both years, mean TN was greater in the mid-lake sites than any other sites. A great amount of TN in the midlake was most pronounced in monsoon 1994 because of an accumulated influence of the point sources during low inflow. Overall data suggest that concentrations of TN in this system did not show large differences along the longitudinal gradients and its distributions is likely determined by point-sources rather than inflow regime.

대형 인공댐호이 효율적 수질 감시를 위한 적정 조사 빈도 설정 연구

안광국,홍욱희,최신석 ( Kwang Guk An,Wuk Hee Hong,Shin Suk Choi ) 한국하천호수학회 1995 생태와 환경 Vol.28 No.3

In water quality monitoring practices, frequent water sampling would promise data accuracy but may not be so cost effective. However, less frequent sampling would fail to provide accurate data which represents the exact quality of the water body. Hence, determining appropriate sampling frequencies will be enormously important in terms of data accuracy and cost saving, particularly when the sampled water bodies are of great importance as major water resources . In this study, such determination of sampling frequencies was carried out for the Lake Taechung. Total 13 water quality parameters sampled and analyzed every 2 to 3 days for a year were compared with the data sampled less frequently; once every 7 to 10 days, twice a month, and once a month. While general water quality parameters such as dissolved oxygen, pH, and turbidity were dynamically fluctuated throughout the year, the parameters related to the trophic state such as Secchi depths, total suspended solids, nutrients, and chlorophyll-a showed more distinctive fluctuations during the algal growth season. The effects of summer monsoon were remarkable in most water quality parameters. Based on these findings, it was suggested that during the algal growth season, June to September, at least weekly samplings should be carried out for VSS, total nitrogen, total phosphorus and chlorophyll-a. Nitrate- and ammonia-N, dissolved phosphorus, NVSS and other parameters may be measured twice a month during this season. During non-algal growth seasons, from October to May of the next year, bimonthly samplings were suggested for such parameters as total nitrogen, total phosphorus, and chlorophyll-a Monthly samplings would suffice for all other parameters.