Fill Dam의 漏水原因과 遮水에 關한 硏究

임희대,양재석 충남대학교 공업교육연구소 2001 論文集 Vol.24 No.1

In general, leakage of fill dam causes not only fall in economic field in problem of storage efficiency but also collapse of embankment dams. This leakage path can be embankment dams, joining part between embankment dams and foundation ground and foundation ground. Fissure which nearly happens in embankment dams, one of leakage causes of fill dam turned out that load transfer by differential settlement between different core and rip rap with each other is chief cause offerer. This phenomenon turned out to be so dangerous in early containing water. Futhermore, it induces hydraulic fracturing and has considerable influence on stability of embankment dams. Hydraulic fracturing is that fissure happens either in rock mass or internal embankment dams by hydraulic pressure and when dam is filled with water, means that core is torn horizontally by hydraulic pressure. Initial proposed mechanisms of hydraulic fracturing are for the most part supposed things in the process for investigating either leakage or cause of failure by internal erosion and are considerably qualitative but since finite element in moving analysis is used, have begun to be analyzed quantitatively. In this paper, the cause of leakage and the process of occurrence of leakage are examined, and measures which can predict and prevent leakage in advance is presented. Also a impervious method improved is presented after investigation of the methods which have been applied to fill dam to cut off leakage. As an impervious method, grouting after grasping the cause of leakage and flow channel with geophysical investigation is better efficient than only to reinforce part in which erosion or fissure happens.

국내 해안 연약지반의 점토광물 분포 및 공학적 특성

임희대,이상규 忠南大學校 産業技術硏究所 2002 산업기술연구논문집 Vol.17 No.2

These studies were carried out to investigate the characteristics of alluvial clay deposits distributed in the main coastal areas. Also we can use their outcomes which were analyzed from the soil test results surveyed during the latest for the purpose of design, construction and maintenance of civil engineering structures to be built in these areas in the future. Samples of clay minerals were analyzed using an X-ray diffraction test. Also, the geotechnical properties of the distribution of clay minerals were evaluated after collection physical and mechanical soil data. The results of Siroquant analysis though X-ray diffraction analysis show that natural water content, liquid limit., initial void ratio, compression index, and compression ratio are positively proportional th the amount of montmorillonite, whereas they are inversely proportional to those of illite and kaolinite. In addition, dry unit weight, unconfined compressive strength, and cohesion are inversely proportional to the amount of montmorillonite, and positively proportional to the amount of illite and kaolinite. In particular, the amount of montmorillonite is closely related to geotechnical characteirstics. However, it is considered that the relative composition ratio, physical and chemical characteristics of other clay minerals have influence on marine soil characteristics with montmorillonite, since the amount of montmorillonite is less than other clay minerals.

필댐 心壁材料의 分離 및 浸蝕에 關한 硏究

임희대,고부현 忠南大學校 産業技術硏究所 2001 산업기술연구논문집 Vol.16 No.2

Generally piping, or progressive erosion due to concentrated leaks, has caused a larger number of catastrophic failures than any other actions, except overtopping, and many modern techniques of earth dam design and construction have been developed to prevent it. Recent experience indicates that an effect of reservoir filling may lead to the formation of dangerous cracks, and hydraulic fracturing is considered to be a primary cause. The primary objective of this paper is to see the causes of damage, the mechanism of crack, piping or erosion and the possibility of hydraulic fracturing and load transfer in fill dams. The results of this study are summarized as follows: The tendency for dispersion piping is determined by a number of properties of the clay, and the most important properties are ESP and the content of dissolved salts in the seeping water. For the evaluation of a give soil, both the pinhole and pore water salts tests should be made. However, for soils that cannot be easily determined whether they are dispersive or not, only the pinhole test can reliably identify the state of dispersion. As a result of numerical analysis, this paper presents that possibility of hydraulic fracturing and load transfer is increased according to the decrease in wet unit weight, internal friction angle and cohesion. Besides, cracking can be caused by differential settlements or the arching of core material filling in the key trench. This cracking could also result in channels through the key trench fill which would permit rapid internal erosion.

UN과 韓國 : UN의 成立過程, 主權平等의 憲章原則및 그의 空文書化

임희대 충남대학교 교지편집위원회 1973 寶雲 - 충남대학교 Vol.- No.3

대청복합댐 접합면에 대한 토압 및 간극수압의 변동분석

임희대,김상규 한국지반공학회 1988 대한토질공학회지 Vol.4 No.2

The Taechong Dam completed in 1980 is a composite dam at which a junction was formed partly by butting the core against the end face of the concrete gravity section and partly by the core overlapping the upstream face of the concrete. In order to evaluate the performance of the junction, the interfaces between the concrete dam and core of the embankment dam were well instrumented with total pressure cells and piezometers. A nonlinear incremental finite element analysis simulating its construction behaviour was carried out under plane strain conditions. Material parameters for the core are determined from triaxial tests on the specimens, sampled in the quarry site and compacted to the field dry density at the field moisture content. Material parameters for the filter, transition materials and the rockfill are estimated from literature. When compared with the earth pressures measured at the interfaces, the analytical results show good agreement in the core, however, there are some discrepancy in the shell. A nonlinear model for pore pressure response is used successfully to predict the pore pressures at the interface in the core. 1980년에 완공된 대청댐은 콘크리트댐과 석괴댐으로 혼합된 복슴댐으로서 결합부에는 제체에서 가장 취약한 곳인 원합면이 존재하므로 댐 건설시 계측기를 매설하여 토려 및 간극수려을 계속 측 정하고 있다. 본연구에서는 해석적 방법으로 평면변형하에서 건설단계를 하중증분형태로 보는 비선형증가 유한 요소해석방법을 적용하였으며, 이에 대한 심벽재료의 파라미터들은 토취장에서 채취한 점토를 현장 밀도 및 함수비로 다진후 삼축압축시험을 실시하여 추정하였고 휠터 및 제각부의 파라미터들은 관계 문헌을 이용하여 추정하였다. 비교분석결과 심벽부의 토압은 대체적으로 예측치와 실측치가 일치하는 경향을 보였으나 제설부에서는 다소의 차이가 있었다. 또한 간선수압 모델은 심압부의 간선수압예측에 좋은 결과를 보여 주었다.

Wetting에 의한 필댐 상류측 shell의 거동특성

임희대,백장열,이영섭 충남대학교 산업기술연구소 1999 산업기술연구논문집 Vol.14 No.2

The primary objective of this paper is to see the behavior characteristics of rockfill dam due to wetting. There are many factors which affect the dam failure. One of them is the influence of reservoir filling. Differential movements in dam and foundation develop during reservoir filling, they induced cracking and consequent erosion, and sometimes caused dam failure. One of the major factors contributing to the development of differential movements during reservoir filling is the compression due to wetting which occurs in a wide variety of different types of soils including rockfill. To perform the numerical analysis of dam behavior adequately, the large-scaled triaxial test is needed to consider the effect of wetting on dry and wet rockfill material. But, As the large-scaled triaxial test is high capital cost and not available apparatus for a number of other experiment, it is not applied many case in the country. In this paper, the data of Oroville dam which performed the large-scaled triaxial test is referenced to find out stress-strain curve and hyperbolic parameters on wetting for modeled dam which is not performed the large-scaled triaxial test. So, effect of wetting on modeled dam can be considered for numerical analysis of dam behavior. As a result of numerical analysis, they estimate that horizontal and vertical displacement are increased with the rate of increasing wetting, and shear stress too. Because compression and shear strength is decreased with proceeding wetting. And results of analysis show that load transfer is not affect significantly by the wetting.

모래의 다짐율과 內部摩擦角에 대한 硏究

林熙大 충남대학교 공업교육연구소 1982 論文集 Vol.5 No.1

In many problems, such as the design of embankments the soil engineer must select the details of the compaction process to give the optimum combination of engineering properties. The objective of this paper is to confine the degree of compaction when sand is compacted by means of bulldozer. The following results are drawn from the study. 1) The maximum dry density and minimum dry density of representative samples of the insitu sand. 2) The relative density of the in-situ sand and sand compacted by means of a bulldozer. 3) The correlation between the relative density and the shear strength parameters. 4) The results obtained during laboratory tests and field tests show that the relative density of compacted sand is 70%, and the shear strength parameters are measured as: c=0.19 kg/㎠, ø=37°47', which are close to the experimental values of Peck.

다짐함수비 變化에 따른 필댐의 擧動分析

임희대,김태곤,이영섭,고근식 충남대학교 산업기술연구소 1999 산업기술연구논문집 Vol.14 No.2

Compaction water content is a key variable which controls fundamental properties of compacted clay (permeability, deformation and strength). There are three conditions in compaction water content (i.e. dry of optimum, optimum and wet of optimum). Actually, soil mass by compaction is unsaturated condition before seepage therefore, soil suction is the key which is able to explain properties of compacted clay. This paper used results from compacted Pittsburg sandy clay tested under UU test condition from Duncan and Seed in order to determine hyperbolic parameters and simulated behavior of Soyanggang dam as a example. As the results of analysis, dry of optimum presents higher strength and smaller displacement. Wet of optimum is sensitive to water content. Both dry and wet of optimum, any hydraulic fracturing potential does not appear. But dry of optimum is close to hydraulic fracturing.

$Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$(X=Cu, Mg, Mn)-Rubber Composite의 전파흡수특성에 관한 연구

임희대,윤국태,이찬규,Im, Hui-Dae,Yun, Guk-Tae,Lee, Chan-Gyu 한국재료학회 1999 한국재료학회지 Vol.9 No.12

Electromagnetic wave asorbing properties of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$, where X was replaced by substitution elements Cu, Mg, Mn, have been studied. The structure, shape, size and magnetic properties of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$ were analyzed by XRD, SEM, VSM. The relative complex permittivity, permeability, and electromagnetic wave absorbing properties were measured by Network Analyzer. The structure, shape, size and magnetization value of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$ were found to be similar in spite of substitution elements. The coercive force and hysteresis-loss showed maximum value when Mg was substituted for X. The dielectric loss(${\varepsilon}_r"/{\varepsilon}_r'$) was found to be maximum value when Mn was substituted for X. Also the magnetic loss(${\mu}_r"/{\mu}_r'$} was found to be maximum with Cu substitution. The electromagnetica wave absorbing property of the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber composite with 4mm thickness was excellent as over - 40dB at 9GHz, and the $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber composite with 8mm thickness was over-40dB at 2GHz. Those composites also showed superior microwave absorbing properties. $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$의 조성에서 X를 각각 Cu, Mg, Mn으로 치환시켜 치환원소에 따른 결정구조와 형상, 입도 및 자기적 성질을 비교 분석하여고, Network Analyzer을 이용하여 $Ni_{0.5}-Zn_{0.4}-X_{0.1}{\cdot}Fe_2O_4$-Rubber Composite의 재료정수 및 전파흡수특성에 대하여 비교 조사하였다. 치환원소에 관계없이 동일한 결정구조와 형상 및 입도를 나타냈고, VSM 분석결과 치환원소에 관계없이 동일한 자화값을 가지며, Mg로 치환된 경우 가장 큰 보자력과 자기이력손실을 나타냈다. 또한 Mn으로 치환된 경우 가장 높은 유전손실(${\varepsilon}_r"/{\varepsilon}_r'$)을, Cu로 치환된 경우에는 가장 큰 자기손실(${\mu}_r"/{\mu}_r'$)을 나타냈다. 4mm의 두께로 제조한 Compos-Composite에서는 Mg로 치환된 시료가 2GHz에서 -40dB이상의 가장 우수한 전파흡수특성을 나타내었다.

土木工學敎育科 學生의 現場實習 改善方案

林熙大,鄭海駿,金八圭,朴承範 충남대학교 공업교육연구소 1983 論文集 Vol.6 No.2(A)

Education is the process of acquiring or transferring knowledge from our existing body of tyeory and experience. The educational process must provide the Civil Engineers with ability to comprehend and adapt to the continuing changes in the practice of their profession. During the past several years, many practice-oriented educational programs and researchoriented programs have developed for students, but most of them are related to the improvement of curriculum. This paper deals exclusively with the spot-practice of civil engineering students. As the results of an analysis for the spot-practice, it is realized that the past spot-practice was somewhat isolated from outside environment and found too rigid to meet the changing requirements. The improvement of the spot-practice for civil engineering students is strongly recommended to produce qualified teachers, taking into account the changing social demands.