So-Keul Chung

Innovative Method of LNG Storage in Underground Lined Rock Caverns

Today, the demand for LNG (Liquefied Natural Gas) in Korea is growing rapidly. However, it is difficult to solve problems regarding the adjustment of the demand and supply of LNG due to factors such as seasonal variations of the domestic demand for LNG, discordance among import patterns, limits of storage facilities, and so on. The supply of LNG can become unstable due to accidents at LNG producing areas. Furthermore, it is very important to secure large LNG storage facilities and to stabilize LNG supply management on a longterm basis (Chung et al, 2006).

Characterization of Complete Radial Displacement of Tunnel Using a Horizontal Inclinometer

ABSTRACT Measuring the displacement of a tunnel is prerequisite in evaluating the stability, which also makes it possible to understand the geological condition ahead of the tunnel face. In fact, the displacement of a tunnel occurs before, during and after the excavation. Generally, the measurement is undertaken only behind the face, which allows a certain amount of displacement, the so-called ‘pre-measurement-displacement’. The measured displacement is only a part of the total radial displacement. Therefore, the pre-measurement-displacement should be determined in order to characterize the complete radial displacement of the tunnel. A horizontal inclinometer was used to measure the degree of settlement ahead of the tunnel face at the study site, which was relatively easy to install from the other portal of the tunnel. The results from the measurement of the settlement ahead of the face enabled a complete radial displacement curve to be constructed using a nonlinear regression analysis. It was found that the crown displacement of the tunnel at the study site started to occur at a distance equivalent to three times of the tunnel diameter ahead of the tunnel face. Taking into consideration the complete displacement characteristics, the possible settlement could be about 40% of the total displacement of the tunnel. Based on the complete radial displacement, it was possible to determine the appropriate support characteristics and the time of installation.

Experience and challenge of underground oil/gas storage caverns in Korea

This paper reviews the current status of underground hydrocarbon storage in Korea and addresses technical aspects of the underground storage in rock caverns. Currently, Korea has a storage capacity equal to about 146 million barrels, and approximately 73% of the total, 106 million barrels, are stored in underground space. The key technologies in the underground storage of hydrocarbon products are the construction of the large rock cavern with a cross-sectional area ranging from 300 to 520 m2, the long-term structural stability of the cavern and the full containment of the product in rock caverns. Based on a 38-year experience in design, construction and operation of underground storage facilities, Korea has accumulated technical expertise in this field and achieved the position as one of the model countries holding stockpiles of strategic oil reserves. Also an innovative method of liquefied natural gas (LNG) storage in lined rock caverns has been developed to provide a safe and cost-effective solution. It consists of protecting the host rock against the extremely low temperature and providing a liquid and gas tight liner. From the construction and operation of Daejeon pilot plant, technical feasibility of the underground LNG storage system can be well proved.

Stability Assessment of Abandoned Gangway for Commercial Utilization of Services

Abstract The stability assessment of abandoned gangway for the purpose of services was performed. Among the many factors that affect the stability of openings, the span of the opening in a given rock mass condition provides an important element of design. In this paper, the stability of gangway was assessed by the critical span curves proposed by Lang, the modified Mathews’stability graph method and using support measures of the Q system. In the evaluation of stability as a whole the gangway is considered as stable. But the rockfalls of wedge-shaped blocks were expected in the area in which the horizontal joints of low angle appear. The support measures such as local rock bolts are required to use for commercial purposes of the abandoned gangway. And entrance section may require the particular attention as unstable section. Since there are so many spalling due to bad blasting in the roof and sidewall of gangway, the scaling operations should be followed primarily. Key words Rock mass classification, Abandoned gangway, Stability of opening, Critical span curve, Mathews’stability graph초 록 서비스업 목적을 위한 폐갱도에 대한 안정성 평가가 수행되었다. 공동의 안정성에 영향을 주는 많은 요소들 중 주어진 암반내의 공동폭이 하나의 중요한 설계요소가 된다. 이 논문에서는 폐갱도의 안정성 평가를 위해 갱도의 크기에 대해 Lang이 제안한 한계 공동폭 기준, Mathews’stability graph method 그리고 수정 제안된 한계 공동폭 기준과 Q 시스템의 지보대책을 이용하여 안정성 평가를 실시하였다. 전체적으로 안정성평가에서 안정한 것으로 판단되지만, 저각의 수평절리가 나타나는 구간에서는 쐐기형 블록의 낙석 위험이 예상된다. 또한 상용목적으로 폐갱도를 활용할려면 구역에 따라서는 록볼트와 같은 지보대책이 필요하다. 출입구 구간은 불안정구간으로 특히 주의가 필요한 구간이다. 과발파에 의한 갱도 천정 및 측벽에 많은 크고 작은 부석들이 존재하고 있어 부석들에 대한 제거작업이 선행되어야 한다.핵심어 암반분류, 폐갱도, 공동의 안정성, 한계 갱도폭 곡선, Mathews의 안정도표

Design Criteria for the Reinforcement of a Water Pressure Tunnel Driven by TBM

ABSTRACT In construction of domestic water pressure tunnels, concerns on the lining reinforcement is being increased with relation to the mechanical stability of the tunnel. In this study, the design of lining and unlining of a water pressure tunnel is carried out through the detailed estimation of rock mechanical and hydrological factors and the establishment of the design guideline. The field investigation for rock mass rating and joint pattern, laboratory rock test, numerical analysis on mechanical stability using UDEC, wedge analysis for the estimation of rock block falling according to joint pattern, and hydrological analysis for the lining and unlining conditions are carried out. The design criteria are evaluated for the factors such as support pattern related with RMR range, hydraulic jacking and leakage according to the condition of rock stress and inner/outer water pressure. With these guidelines, the lining and unlining sections are designed for the water pressure tunnel with the diameter of 2.6 m and the length of 5.35 km. This assessment technique and the design criterion can be used as a guideline in the design of lining reinforcement of the water pressure tunnel.