• Journal of Korea Water Resources Association
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• v.38 no.7 s.156
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• pp.537-544
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• 2005

For the proper management of high pressurized gas storage caverns, analysis of groundwater flow field and inflow quantity according to the groundwater head, gas storage pressure and water curtain head should be performed. The finite element method has been widely used for the groundwater flow analysis surrounding underground storage cavern because it can reflect the exact shape of cavern. But the various simulations according to the change of design factors such as the width of water curtain, shape of cavern etc. are not easy when elements were set up. To overcome these limitations, two dimensional groundwater flow model is established based on the boundary element method which compute the unknown variable by using only the boundary shape and condition. For the exact computation of drainage rate into cavern, the model test is performed by using the exact solution and pre-developed finite element model. The test result shows that the model could be used as an alternative to finite element model when various flow simulations are needed to determine the optimizing cavern shape and arrangement of water curtain holes and so forth.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.381-391
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• 2008

The eigenvalue technique is introduced to overcome the problem of truncation errors caused by temporal discretization of numerical analysis. The eigenvalue technique is different from simulation in that only the space is discretized. The spatially discretized equation is diagonized and the linear dynamic system is then decoupled. The time integration can be done independently and continuously for any nodal point at any time. The results of eigenvalue technique are compared with the exact solution and FEM numerical solution. The eigenvalue technique is more efficient than the FEM to the computation time and the computer storage in the same conditions. This technique is applied to the solute transport analysis in nonuniform flow fields around underground storage caverns. This method can be very useful for time consuming simulations. So, a sensitivity analysis is carried out by using this method to analyze the safety of caverns from nearly located contaminant sources. According to the simulations, the reaching time from source to the nearest cavern may takes 50 years with longitudinal dispersivity of 50 m and transversal dispersivity of 5 m, respectively.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.238-243
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• 2003

As there are many advantages on underground caverns, such as safety and operation, they can also be used for gas storage purpose. When liquefied gas is stored underground, the cryogenic temperature of the gas will affect the stability of the storage cavern. In order to store the liquefied gas successfully, it is essential to estimate the exact temperature distribution of the rock mass around the cavern. In this study, an analytic solution and a conceptual model that can estimate three-dimensional temperature distribution around the storage cavern are suggested. When calculating the heat transfer within a solid, it is likely to consider the solid as the intersection of two or more infinite or semi-infinite geometries. Therefore heat transfer solution for the solid is expressed by the product of the dimensionless temperatures of the geometries, which are used to form the combined solid. Based on the multi-dimensional transient heat transfer theory, the analytic solution is successfully derived by assuming the cavern shape to be of simplified geometry. Also, a conceptual model is developed by using the analytic solution of this study. By performing numerical experiments of this multi-dimensional model, the temperature distribution of the analytic solution is compared with that of numerical analysis and theoretical solutions.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.450-459
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• 2011

For the purpose of evaluating the safety of rock structures such as underground caverns, tunnels and slopes, rock displacement measurement is carried out to identify the behavior of rock masses. Tapes, levels, and total stations are usually applied to the displacement measurement. These tools, however, are weighed down by many disadvantages. In this study, a new displacement measurement system by precise vision metrology was proposed for the observational design and construction method of rock structures, and then applied to a tunnel under construction. Comparisons and investigations of the measurement of the tunnel have confirmed the effectiveness and applicability of the developed measurement system.

• Tunnel and Underground Space
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• v.27 no.4
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• pp.185-194
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• 2017

This technical paper is a study on the unique displacements of Shotcrete Lining at the mined tunnel during excavation period through deep consideration with real time data from monitoring instrumentations correlation with the numerical analysis to identify the rock stresses and the rock spring points at the working face of the Conventional tunnelling by the Drill and Blast, based on the geological face mapping results of the project NS2, Transmission cable tunnel project in Singapore. The created geometry of numerical model was prepared to the real mined tunnel construction site including, vertical shaft, construction adit, tunnel junction area, and 2 enlargement caverns. The convergence measurements by the monitoring instrumentation were performed during the tunnel excavation and shaft sinking construction stages to guarantee the safety of complicated underground structures.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.91-97
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• 2008

In this paper, in-situ technique for measuring hydraulic conductivity of Excavation Disturbed Zone (EDZ) in a direct way and its application to an Underground Research Laboratory (URL) site were introduced. It was understood that both the EDZ oriented test equipment as a hardware and analysis/evaluation technique as a software should be integrated for upgrading a quality of estimated EDZ hydraulic conductivity. The well-estimated EDZ hydraulic conductivity is expected to enhance a reliability of stability evaluation for caverns under groundwater table and design of a waterproof or drainage system as well as a grout system.

• Structural Engineering and Mechanics
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• v.53 no.3
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• pp.481-495
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• 2015

Many hydropower stations in southwest China are located in regions of brittle rock mass with high geo-stresses. Under these conditions deep fractured zones often occur in the sidewalls of the underground caverns of a power station. The theory and methods of fracture and damage mechanics are therefore adopted to study the phenomena. First a flexibility matrix is developed to describe initial geometric imperfections of a jointed rock mass. This model takes into account the area and orientation of the fractured surfaces of multiple joint sets, as well as spacing and density of joints. Using the assumption of the equivalent strain principle, a damage constitutive model is established based on the brittle fracture criterion. In addition the theory of fracture mechanics is applied to analyze the occurrence of secondary cracks during a cavern excavation. The failure criterion, for rock bridge coalescence and the damage evolution equation, has been derived and a new sub-program integrated into the FLAC-3D software. The model has then been applied to the stability analysis of an underground cavern group of a hydropower station in Sichuan province, China. The results of this method are compared with those obtained by using a conventional elasto-plastic model and splitting depth calculated by the splitting failure criterion proposed in a previous study. The results are also compared with the depth of the relaxation and fracture zone in the surrounding rock measured by field monitoring. The distribution of the splitting zone obtained both by the proposed model and by the field monitoring measurements are consistent to the validity of the theory developed herein.

• The Journal of the Petrological Society of Korea
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• v.16 no.2 s.48
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• pp.47-58
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• 2007

This study examines the distribution of basement rocks in Gyochon-ri, Muan-eup, Muan-gun, Jeonnam where ground subsidence occurred in June 2005, and traces corrosion of limestone. Mica schist and rhyolite are distributed in the surface of the study area, but thick limestone layer with large and small caverns are distributed underground. A horizon of limestone with maximum width of 300 m and 4 km of length was found along the detour which is in the north of pound subsidence. Such identification of limestone presence would be very useful to predict potential ground subsidence. Limestone in this area was disturbed by fold and fault due to severe shearing deformation. Small caverns were frequently found in anticline part of folds formed in limestone layer. Schists with different thicknesses were intercalated in the limestone with shearing deformation and consist of sheet silicate minerals (chlorite and mica) and quartz. In sections of weathered specimen, it is shown that biotite of schist part was altered into chlorite and corrosion of calcite around the schist followed. This suggest that ground water permeated between intercalated sheet silicate minerals and corrosion of limestone began. And small caverns were generated where active corrosion occurred. This study suggests that because of many reasons (for instance, reclamation of the Bulmu reservior and excess pumping), cavern water level was lowered and cave sediments were removed, and it caused ground subsidence to occur.

• The Journal of Engineering Geology
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• v.7 no.3
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• pp.229-245
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• 1997

There are Common aspects between the underground oil storage cavern and the radioactive waste disposal facility. Both facilities use appropriately the intrinsic natural berrier characteristics of the rock mass and additionally the engineered barrier system for the long term safety. The geological structures and their hydrogeological characteristics in a faactured rock mass act a major role in the safety and performance of the underground oil storage facility through the design, construction and the operation stages. Because the fracture system distributed in a fractured rock block is complicated owing to their own geometrical and hydrogeological attributes, the hydrogeological perforrmrnce of the facility would depend mainly upon the understandings of their characteristics. This study reviews the uncertainties and key issues which have to be considered to analyse the groundwater flow system in a fractured rock mass and proposes the techniques applicable to characterize the hydrogeological parameter.

• Journal of the Korean Society of Groundwater Environment
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• v.4 no.2
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• pp.61-72
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• 1997

With increasing activities for groundwater withdrawal and for the construction of underground cavern in the coastal areas, the seaward flow of groundwater has been disturbed or even reversed, resulting in seawater intrusion in aquifers. This phenomenon would be attributed to the freshwater contamination and the corrosion of steel materials. The hydrogeological and geochemical investigations have performed to characterize the seawater intrusion into the underground caverns located in the coastal area. Assumimg the inland aquifer as unconfined one, we have found out that the theoretical interface of freshwater-seawater is far different from the pathways identified. In the study site, the main pathways of seawater intrusion into the underground cavern are characterized as the sub-horizontal fractures (zones). The seawater intrusion in granitic terrane would depend mainly on the characteristics of conductive fracture system developed along the coastal area.