• Tunnel and Underground Space
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• v.15 no.2 s.55
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• pp.102-110
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• 2005

○ ○ tunnel that is located at Iksan - Jangsu freeway ○ ○, has collapsed during construction at the valley with shallow depth. Although, the site investigations, such as TSP, drilling exploration and so of indicated the presence of discontinuities in this section. The RMR was upgraded and the construction were carried out because that not only actual rock qualities were relatively good during construction but also the tunnel foe was stabilized. However, the tunnel was collapsed at the same time blasting of full face, and surface and underground water was infiltrated due to the settlement of the upper part of the tunnel face. To restore the collapsed section, 3-d tunnel stability analysis was performed and suitable reinforcement methods were chosen. The cavity of the upper tunnel face was stabilized by means of UAM and ALC injection. And the settlement was restored using L.W grouting method.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.192-202
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• 2013

The domestic demand of natural gas has increased continuously due to the sudden rise of oil price and regulations on greenhouse gas to global warming. In order to improve the supply security of natural gas market in Korea, the agreement on supply of pipeline natural gas (PNG) in Russia was signed between Gazprom and Korea Gas Corporation in 2008. If the supply plan of Russian natural gas is realized, underground storage facilities would be required in order to balance supply and demand of natural gas because the gas demand is concentrated in the winter. This study investigated the safety of the storage facility in quantitative way considering several design parameters such as gas pressure, depth of the storage cavern, rock condition and in-situ horizontal stress ratio. Two dimensional stress analyses were conducted using axi- symmetry condition to examine the behavior of cavern depending upon suggested design parameters. Results showed that the factor of safety, defined as the ratio of 'shear strength'/'shear stress', was largely affected by the depth, rock class and gas pressure but was insensitive to the coefficient of lateral pressure(Ko).

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.229-242
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• 2009

Numerical analysis has been performed to estimate maximum settlement, maximum horizontal displacement and total settlement volume at the ground surface due to tunnel excavation varying ground condition, tunnel depth and diameter, and construction condition (volume loss at excavation face). The maximum surface settlement from the numerical analysis has been compared with the maximum settlement at tunnel crown considering ground condition, tunnel depth and diameter, and construction condition, and it has been also compared with the maximum horizontal displacement. In addition, the volume loss ($V_L$) at tunnel excavation face has been compared with the total surface settlement volume ($V_s$) with the variation of ground condition, tunnel depth, and tunnel diameter. The results from the numerical analysis have been compared with field measurements to confirm the applicability and validity of the results and by this comparison it is believed that the numerical results in this study can be utilized practically in analyzing the ground movements due to tunnel excavation.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.71-79
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• 2008

The underground conduit laid under different environments exhibits various behaviour according to the ground and external load as well as the loading time and conditions, so on. As the environmental conditions are usually different even within the same area, it is very difficult to correctly predict the stress conditions and behaviour of the underground conduit using currently available theoretical analysis. Especially, it is not yet satisfied in Korea for the evaluation of the underground conduit under the influence of the load of vehicles or unexpected loading conditions. Thus, in this study the assessment for the excavation depth and ground disturbance was carried out with a large box model test and numerical analysis. Numerical analysis was also performed for the assessment of dynamic loading conditions like railway load.

• Tunnel and Underground Space
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• v.10 no.4
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• pp.533-543
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• 2000

Deformation behavior and stability of vertical pipeline subjected to underground excavation have been studied by means of numerical analysis. Vortical ground displacements cause the pipe to be compressed, while horizontal ones cause it to be bent. In that region the vertical pipeline meets with the induced compressive stress and bending stress. In addition horizontal rock stress subjected to underground excavation may press the tube in its radial direction and it finally produces the tangential stress of pipe. In this study active gas well system is considered as an example of vertical pipelines. Factor analysis has been conducted which has great influence on the pipeline behavior. Three case studies are investigated which have the different pillar widths and gas well locations in pillar. For example, where overburden depth is 237.5 m and thickness of coal seam is 2.5 m, chain pillar of 45.8 m width in the 3-entry longwall system is proved to maintain safely the outer casing of gas welt which is made of API-55 steel, 10$\frac{3}{4}$ in. diameter and 0.4 in. thickness. Finally an active gas well which was broken by longwall mining is analyzed, where the induced shear stress turn out to exceed the allowable stress of steel.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.255-265
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• 2007

As the mechanism and effect range of subsidence are altered according to the various conditions (the ground condition, the earth pressure, the geometric condition of underground cavity and the structure load), the analysis and prediction of subsidence in abandoned mining area are very difficult. Also, as the geological characteristics and the mining methods are differed in each mines, the application of the pre-existing reinforcements without improvement has a lot of difficulties and limits. In this study, the various underground investigation such as long-depth core drilling, seismic tomography and BIPS (borehole image processing system) were performed, the distribution of underground cavity and coal seam and rock relaxation condition were analyzed. And we predicted the type of subsidence and estimated the subsidence by theories of mining subsidence. With these results, we analyzed the mechanism of subsidence occurrence in the research object area. Finally, we improved existing methods which were applied to the abandoned mining area and also we established the rational reinforcement for the ground and structure foundation against each subsidence cause.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.287-296
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• 2011

We performed a numerical modeling study of thermodynamic and multiphase fluid flow processes associated with underground compressed air energy storage (CAES) in a lined rock cavern (LRC). We investigated air tightness performance by calculating air leakage rate of the underground storage cavern with concrete linings at a comparatively shallow depth of 100 m. Our air-mass balance analysis showed that the key parameter to assure the long-term air tightness of such a system was the permeability of both concrete linings and surrounding rock mass. It was noted that concrete linings with a permeability of less than $1.0{\times}10^{-18}\;m^2$ would result in an acceptable air leakage rate of less than 1% with the operational pressure range between 5 and 8 MPa. We also found that air leakage could be effectively prevented and the air tightness performance of underground lined rock cavern is enhanced if the concrete lining is kept at a higher moisture content.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.9-16
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• 2016

During the 2004 Niigata-ken Chuetsu, Japan, earthquake, more than 1,450 underground structures, known as sewer manhole, were uplifted up to 1.5m in Nagaoka and Ojiya city. The uplift damage can be a serious matter because they not only hinder the flow of wastewater systems, as a part of lifeline systems, but also disturb traffic flows. For restoration works, an open-cut investigation of damaged wastewater system was conducted by the Nagaoka city government. The results from the investigation compiled valuable data sets for buried pipeline damage due to earthquakes. In the present study, the factors affecting the uplift amount of the underground structure is investigated by using the data sets which include locations of damaged sections and inclination of pipeline before and after the earthquake and the SPT borehole logs in the affected area. Correlation analysis between the underground structure uplift and the geological settings in the affected area revealed that ground water depth and original subsoil, including thickness of clay layer, SPT N-value and fill thickness are the key parameters for the uplift phenomenon.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.77-85
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• 2009

Flexible and lined segment air-tight tunnelling technology for Compressed Air Energy Storage-Gas Turbine(CAES-G/T) power generation was introduced. The distinguished characteristics of the air-tight tunnel system can be summarized by two facts. One is that the high inner pressure due to compressed air is sustained by surrounding rock mass with allowing sufficient displacement of lining segment. The other is that the air-tightness of storage tunnel was enhanced by adopting a specially designed rubber sheet. The flexible lined air-tight underground tunnel can be constructed at a comparatively shallow depth and near urban area so that the locally distributed CAES-G/T power generation can be accomplished. In addition, this air-tight tunnelling technology can be applied to a variety of energy underground storage tunnels such as Compressed Natural Gas(CNG), Liquifed Petroleum Gas(LPG), DeMethyl Ether(DME) etc.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.171-177
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• 2005

Fire in underground space may induce severe structural damage as well as heavy casualties. To protect underground structure and passengers from fire, it is very essential to characterize fire-induced damage on construction materials of underground structures. In this study, the high-temperature furnace was manufactured to evaluate fire-induced damage on underground structure materials. Especially, this study aimed at the evaluation of fire-induced damage on the shield TBM concrete segment. In the fire tests, furnace temperature was set to reach 1,200 degrees at five minutes after Ignition. The temperature of 1,200 degrees was kept during one hour, and the fire was extinguished after two hours elapsed. From the temperature measurement by thermocouples embedded in test specimens, the spatting was estimated to reach approximately 20 cm from the surface exposed to fire. After the fire tests, the alteration of physico-mechanical properties and microstructures of concrete segment was investigated from core specimens. The results showed that apart from spatting, the deterioration depth of the remaining concrete material amounted to approximately 10 cm from the spatting surface.