• Tunnel and Underground Space
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• v.8 no.4
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• pp.296-306
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• 1998

Ongoing huge Bakun Hydropower project is including the construction of a 210 m height hydroelectric rockfill dam with an installed capacity of 2,520 MW and a power transmission system connecting to the existing networks between Sarawak and peninsula Malaysia. In order to allow the main dam construction during the dry season, the Ballui river will have to be detoured through 3 concrete lined diversion tunnels with an internal diameter of 12 m and a length of 1,400 m each. The geology of Bakun site belongs to the several thousand meters thick Belaga formation deposited from the late Cteteceous to the early Teriary in the Northwest Borneo geosyncline. The orientation of the bedding plane, strike at N55$^{\circ}$E to N70$^{\circ}$E and dip at 50$^{\circ}$SE to 70$^{\circ}$SE, is developed uniformly in Bakun sedimentary rocks. Rock mechanical characteristics of Bakun site have been classified into 4 rock mass types(RMT) depending on the degree of weathering and the occurrence of rock jointing with RMR. Graywacke(Sandstone) as well as Shale can take place together in the same rock mass type if their rock mass properties are similar. It was summarized the rock support type and support system design of underground diversion tunnels in view of rock mechanics.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.359-359
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• 2016

본 연구에서는 최근 기후변화에 따른 가뭄으로 어려움을 겪고 있는 충청남도 서부권의 물 부족을 해결하기 위하여 금강 본류로부터 보령댐으로 일정 유량을 도수(diversion)하는 계획이 금강 본류에 미치는 수리적 영향을 검토하였으며 특히 금강 본류의 농공용수 취수에 제한을 초래할 수 도 있는 수위에 미치는 영향을 중심으로 분석하였다. 본 연구의 공간적 범위는 금강 하굿둑으로부터 하류 외해 방향으로 약 9km 지점에 위치한 금강 하구로부터 상류 방향으로는 금강 하굿둑으로부터 약 76km 지점에 위치한 공주시 반포면 검상동의 검상천 합류지점까지 총 85km에 이르는 구간에 대한 1차원 수리 모형을 구축하였으며, 시간적 범위는 보령댐으로의 도수가 갈수기에 이루어지는 것으로 가정하여 2015년 2월 1일부터 5월 31일까지 진두수위표의 시간별 유량과 8개 지천의 유입 유량, 장항검조소의 시간별 조위, 농공용수 취수시설 취수량 및 회귀수, 금강 배수갑문 운영 등을 고려하여 모형의 보정을 실시하였고, 유황분석에 따른 2016년 갈수기 예측 유량을 추정하여 보령댐으로의 도수에 따라 금강 본류 내 주요 구간의 수위에 미치는 영향을 분석하고자 하였으며, 서해안 조위에 따른 금강하굿둑 배수갑문의 운영에 직접적인 영향을 받는 배수위 구간임을 감안하여 비정상류 해석(unsteady flow analysis)을 수행하였다. 갈수기 예측 유량 추정 결과 2015년과 같은 가뭄이 지속될 경우, 2016년의 유황은 2015년 대비 21%로 분석되었으며 이는 보령댐 도수 여부에 관계없이 물 부족이 발생할 수 있는 상태인 것으로 분석되었고, 하천유지유량 정도의 유황이 유지되는 상태에서 보령댐으로 도수를 실시할 경우, 도수시 금강호 최저 수위는 각각 EL(+)0.94m와 EL(+)0.72m로 모의되어 농업용수를 비롯한 기존 취수시설 뿐만 아니라 보령댐 도수시설의 운영에도 어려움이 생길 것으로 예상되었다. 2016년 갈수기 동안 과업 대상 구간인 금강 하류부의 유황은 농업용수 취수가 본격화되기 이전인 2월에는 하천유지유량 정도의 유황을 유지하는데 별 어려움이 없지만 3월 이후농업용수 취수가 본격화되면 농업용수 취수시설이 집중된 입포수위표 ~ 금강 하굿둑 사이 구간은 하천유지유량 이하로 유량이 크게 감소할 것으로 예상되었다.

• Geotechnical Engineering
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• v.14 no.6
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• pp.17-32
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• 1998

The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia, The power station will consist of a 210m height concrete faced rockfill dam. During the construction of the dam and the power facilities the Balui river has to be diverted by three diversion tunnels with a length of some 1,400m each. The inner diameter of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet and outlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four. defined Rock Mass Types (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each 'global' slope without any rock support and shotcrete system. In the second stage, it is calculated for each 'local'slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• Magazine of korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.31-37
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• 2012

In the circumstances being continuous the unusual weather in the world, the city of Seoul has been devastating flood damage in July 2011, because of the heavy rainfalls. Along with expensive repairs to property, thousands of flood victims occurred; it is difficult to estimate the direct and indirect economic damages in city. Recently, as a part of the flood protecting measures, there are being discussed about the deep underground flood drainage tunnel, underground regulating reservoirs, permeable pavement, infiltration facility, river improvements, diversion channel, sewer pipe and ditch improvement and so on. Therefore, it is useful to make the plan of flood protecting measures more and more cost-effective and rational methods by considering the similar flood measures and constructions in the mega cities like Seoul.

• Tunnel and Underground Space
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• v.14 no.2
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• pp.79-85
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• 2004

수로터널은 일반적으로 상수 및 용수를 도수할 목적으로 설치하는 터널로서 기능상 여러가지로 분류할 수 있으나, 도로, 철도, 지하철 같은 교통터널(transportiontunnel)과는 달리 터널내에 수압의 작용이 반복되는 특징이 있으며, 이를 기본으로 하여 내수압의 작용 유무에 따라 자유수면(무압터널)터별과 압력터널로 분류된다(Fig. 1. 참조). 또한, 용도에 따라 상하수도 터널, 발전용 터널, 여수로(spillway) 터널, 가배수(diversion) 터널 및 방류(outlet) 터널로 분류되고 있다. 본 고에서는 이러한 수로터널 중 터널식 여수로에서 발생할 수 있는 공동현상(cavitation)에 대하여 발생원 인과 대처방안 및 피해사례에 대하여 정리하고자 한다.(중략)

• Proceedings of the Korean Geotechical Society Conference
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• 1990.10a
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• pp.35-50
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• 1990

This paper describes the importance of incorporating the titre-dependent deformation behaviour in the design and construction of tunnels in swelling rocks. Two tunnel projects, in which authors got involved in Canada, are chosen to demonstrate the importance. In diversion tunnels for Oldman River Dan Projects time-dependent deformation characteristics of the mudrocks obtained from teat tunnel program were neglected in the design and construction of the tunnels and several sectional of concrete lining in tunnels were cracked extensively. In SABNGS No.3 Projects an extensive experimental program was carried out to study time-dependent deformation behaviour of highly swelling Queenston shale, with the air of establishing the constitutional relationship for the rock-structure time interaction analysis.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.1-8
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• 2016

In 2008, 17, 596 dams and reservoirs are scattered across South Korea, and 17, 505 of them (99.5 %) are used for agriculture and 99.3 % are fill dam types. This study aimed to review literature related to the precise safety diagnosis system for agricultural reservoirs established by Korea Rural Community Corporation (KRCC) and analyze problems of its evaluation method. And then, it proposed ways to improve the system including a modified diagnosis system, which was applied to pilot districts in order to verify the utility. For assessment model development of agricultural reservoir, we reviewed status of precision safety inspections systems of agricultural reservoir. There are many problems such as assess agricultural reservoir not by sheet which used in fill dam but by block which used in concrete dam construction and diversion tunnel which main element in reservoir levee is treated as water intake facility. For considering diversion tunnel in reservoir levee, previous precision safety inspection systems which summed in separated phenomenon, separated element, separated site, separated facility was change to new systems which summed in site, phenomenon, element, and facility. Compared results of previous inspection system calculated total assessment index (Ec) with new system calculated total assessment index (Ec) are not show statistical difference.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.30-38
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• 2020

In order to construct a dam, the diversion facility such as cofferdam and a diversion tunnel should be installed in advance. And size of a cofferdam depends on type of a main dam. According to the Korea Dam Design Standard, if the main dam is a concrete dam, design flood of the cofferdam is 1~2 years flood frequency. This means that overflow of the cofferdam occurs one time for 1 or 2 years, therefore, stability of the cofferdam should be secured against any overflow problem. In this study, failure probability analysis for the concrete cofferdam is performed considering the overflow. First of all, limit state function of the concrete cofferdam is defined for overturning, sliding and base pressure, and upstream water levels are set as El. 501 m, El. 503 m, El. 505 m, El. 507 m. Also, after literature investigation research, probabilistic characteristics of various random variables are determined, the failure probability of the concrete cofferdam is calculated using the Monte Carlo Simulation. As a result of the analysis, when the upstream water level rises, it means overflow, the failure probability increases rapidly. In particular, the failure probability is largest in case of flood loading condition. It is considered that the high upstream water level causes increase of the upstream water pressure and the uplift pressure on the foundation. In addition, among the overturning, the sliding and the base pressure, the overturing is the major cause for the cofferdam failure considering the overflow.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.358-358
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• 2016

본 연구에 앞서 가뭄에 따른 충청남도 서부권의 물 부족을 해결하기 위하여 금강 본류로부터 보령댐으로 일정 유량을 도수(diversion)하는 계획이 금강 본류에 미치는 수리적 영향을 1차원 비정상류 해석(unsteady flow analysis)을 통하여 분석하였으며, 본 연구에서는 수리모형 결과와 연계하여 수질 모형을 구축하여 금강 본류 수질에 미치는 영향을 알아보고자 하였다. 조위 영향에 따른 염도의 역류 모의를 위하여 전자해도와 위성영상자료를 활용하여 금강 하굿둑에서 외해 방향으로 약 9km에 이르는 모의 구간을 확장하였으며, 상류단의 진두수위표를 포함한 8개 지천의 유입유량 및 수질, 하구의 조위와 염도, 농공용수 취수시설의 취수량 및 회귀수 수질, 금강 배수갑문 운영, 대상 구간에 인접한 기상대의 기상자료 등을 고려하고 금강 본류를 따라 9개 수질측정소의 수질자료를 이용하여 모형의 보정을 실시하였다. 또한 대상 구간 내 2015년의 갈수기 유황 분석을 토대로 비선형 회귀분석식을 도출하여 2016년 갈수기 예측 유량과 함께 수질-유량 관계식을 도출하여 대상 구간의 수온, 염도, 용존산소(DO), BOD, 조류 등 영향을 분석하였다. 수온 분석 결과, 지점에 따라 2015년 유황 대비 평균 수온 1.79~3.83도, 최고 수온 1.74~4.30도 상승할 것으로 모의되었으며, 염도는 2016년 갈수기 동안의 금강 하굿둑 외해 염도는 담수 방류량의 감소로 전년 동기 대비 평균 53% 증가하는 것으로 모의되어 기수역 생태계에 상당한 영향을 줄 것으로 분석되었으며, 갈수기 동안의 금강 하굿둑 내수의 염도는 배수갑문 개방 빈도, 개방 시간, 개방 정도의 감소에 따른 해수 역류의 감소로 전년 동기 대비 크게 감소할 것으로 모의되었다. 용존산소는 2016년 갈수기 동안의 용존산소 농도는 지점에 따라 전년 동기 대비 평균 4~11% 감소하는 것으로 모의되었으며, 2016년 갈수기 동안의 BOD 농도는 지점에 따라 전년 동기 대비 평균 30~57% 증가하는 것으로 분석되었다. 조류는 지점에 따라 전년 동기 대비 평균 29~67% 증가하는 것으로 모의되었다. 유량의 감소에 따른 수온 증가 및 수질 악화의 영향이 있을 것으로 분석되나, 도수에 따른 영향은 상대적으로 제한적인 것으로 분석되었다.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.63-71
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• 2020

Strength anisotropy is a typical feature of thin-bedded rock masses and their strength will be degraded subjected to water immersion effect. Such effect is crucial for the operation of hydropower plant because the impoundment lifts the water level of upstream reservoir and causes the rock mass of nearby slopes saturated. So far, researches regarding mechanical property of natural thin-bedded rock masses and their strength variation under water immersion based on field test method are rarely reported. This paper focuses on a thin-bedded stratified rock mass and carries out field test to investigate the mechanical property and strength variation characteristics. The field test is highlighted by samples which have a large shear dimension of 0.5 m*0.5 m, representing a more realistic in-situ situation than small size specimen. The test results confirm the anisotropic nature of the concerned rock mass, whose shear strength of host rocks is significantly larger than that of bedding planes. Further, the comparison of shear strength parameters of the thin-bedded rock mass under natural and saturated conditions show that for both host rocks and bedding planes, the decreasing extent of cohesion values are larger than friction values. The quantitative results are then adopted to analyze the influence of reservoir impoundment of a hydropower plant on the surrounding rock mass stability of diversion tunnels which are located in the nearby slope bank. It is evaluated that after reservoir impoundment, the strength degradation induced incremental deformations of surrounding rock mass of diversion tunnels are small and the stresses in lining structure are acceptable. It is therefore concluded that the influences of impoundment are small and the stability of diversion tunnels can be still achieved. The finings regarding field test method and its results, as well as the numerical evaluation conclusions are hoped to provide references for rock projects with similar concerns.