• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.595-606
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• 2009

This paper presents the characteristics of stress transfer around carven due to cavern size and rock joint properties by laboratory model test. In order to perform this study, eight different scaled model tests were carried out according to excavation stage. The limited numerical analysis were also performed to verify the model test results. The amount of stress transfer around the cavern is increased and then decreased by longitudinal arching effect according to tunnel excavation. It is founded that the stress developed around the cavern during excavation is increased when the cavern size and joint orientation are increased. It is also investigated that shear behaviour (such as stress, deformation) developed around cavern is considerably depended on the characteristic of fill material, dip and direction of joints. It is suggested that the behaviour will be verified throughout the 3D numerical prediction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.84-92
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• 2010

This paper presents the influence of the underground structure (such as cavern and tunnels) behavior according to the rock joint orientation and underground cavern size. In order to perform this research, numerical and experimental studies are carried out. Stress aspect was assessed by quantitative according two kind of factor. In the experimental study, the laboratory model tests are performed in the several ground conditions with different underground cavern size. The results obtained from the model tests are also verified and evaluated using the numerical analysis. Due to the underground cavern, it is found from this study that the stresses developed in archcrown, side wall of underground are increased with increasing the underground cavern size. It is also investigated that the rock joint direction is one of main influence factor as risk factor, to maintain the underground cavern stability. It may be expected that this research will provide the very useful information to evaluate the underground cavern stability.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.193-205
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• 2008

The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.

• Geomechanics and Engineering
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• v.10 no.2
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• pp.175-188
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• 2016

The construction of a new cavern modifies the state of stresses and displacements in a zone around the existing cavern. For multiple caverns, the size of this influence zone depends on the ground type, the in situ stress, the cavern span and shape, the width of the pillar separating the caverns, and the excavation sequence. Performances of underground twin caverns can be unsatisfactory as a result of either instability (collapse) or excessive displacements. These two distinct failures should be prevented in design. This study simulated the ultimate and serviceability performances of underground twin rock caverns of various sizes and shapes. The global factor of safety is used as the criterion for determining the ultimate limit state and the calculated maximum displacement around the cavern opening is adopted as the serviceability limit state criterion. Based on the results of a series of numerical simulations, simple regression models were developed for estimating the global factor of safety and the maximum displacement, respectively. It was proposed that a proper pillar width can be determined based on the threshold influence factor value. In addition, design charts with regard to the selection of the pillar width for underground twin rock caverns under similar ground conditions were also developed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.189-198
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• 2009

Recently the concern about the construction of underground structures such as oil and food storage caverns is increasing in Korea and abroad. The stability of those underground caverns is greatly influenced by shape factor and the size of excavation area as well as the joint conditions. In this study, therefore, the effect of the shape factor of an underground cavern on its stability was analyzed in terms of safety factor. To this end, four different shape factors of a cavern excavated in good rock conditions were investigated and sensitivity analyses were performed based on overburden, lateral earth pressure coefficient, joint spacing, properties, and orientation. The stability of a cavern is evaluated in terms of safety factor estimated numerically based on the shear strength reduction technique. In future, this study is expected to be helpful in designing and evaluating the stability of caverns excavated in discontinuous rock masses.

• The Journal of Engineering Geology
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• v.5 no.2
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• pp.155-165
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• 1995

Fluid flow studies of fractured rocks require three-dimensional modeling of the fracture system. The stochastic discrete fracture models constructed by Monte Carlo simulation technique were applied to the analysis of groundwater flow and mass transport in fractured rock for the assessment of tightness criteria of underground LPG storage cavern. The parameters that most affect the conceptual discrete fracture modeling proved either fracture orientation or size and on the fract'lre flow interpretation proved conductive fracture intensity. The fracture transmissivity played important role in solute transport in fractured rock simulated by particle tracking approach. It was partly recognized that the calibrated stochastic discrete fracture model can be used for the tightness criteria of underground LPG storage cavern.

• Tunnel and Underground Space
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• v.19 no.3
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• pp.167-173
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• 2009

Underground storage cavern is known as the most complicated underground project because of the complexity of construction schedule, tunnel size, and geological problems. In order to optimize the construction schedule of underground storage cavern, two up-to-date technologies were applied. The first technology was 3 dimensional visualization of complicated underground structures, and the second was 4 dimensional simulation considering construction resources, geological conditions and construction schedule. This application case shows that we can achieve optimized construction schedule in the ways to optimize the number of work teams, fleets, the sequence of tunnel excavation, the commencement time of excavation and the hauling route of materials and excavated rocks. 3 dimensional modeling can help designer being able to understand the status of complicated underground structures and to investigate the geological data in the exact 3 dimensional space. Moreover, using 4 dimensional simulation, designer is able to determine the bottle neck point which appear during hauling of excavated rocks and to investigate the daily fluctuation in cost.

• The Journal of Engineering Geology
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• v.14 no.1
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• pp.93-104
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• 2004

This paper intended to assess the hydro-structure characteristics of volcanic rocks based on the hydrogeological data obtained from the underground storage cavern during construction. The variation of groundwater levels was periodically measured from the 28 surface monitoring holes(NX size) and the hydraulic pressures and injection rates were daily monitored from the water curtain holes(95 horizontal holes and 63 vertical holes). The hydraulic interference tests were performed in whole water curtain holes. The distribution patterns of hydraulic pressure are closely related to the dip angles of fracture intersected to the water curtain holes. Three domains can be grouped by the distribution of hydraulic pressures in the horizontal water curtain holes. The initial hydraulic pressures measured immediately after drilling of water crutain holes are high in ascending order of the cavern C-2, C-1, and C-3. The priliminary hydrochemical data also indicate that the portions of the deep groundwater composition is relatively great in the cavern C-3 area. Some of the horizontal water curtain holes in the cavern C-3 show a steady higher groundwater pressure with the composition of shallow groundwater indicating the outer boundary as constant hydraulic boundary. The water curtain holes in the cavern C-2 is characterized as low initial hydraulic pressure and less injection rates, suggesting poor hydraulic connectivity to a shallow groundwater system. The results of the study can help to understand a hydraulic compartment concept in a fracture hydro-geology and be utilized during the surface investigation for a groundwater system.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.449-458
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• 2001

In order to verify the numerical model, which was developed to simulate the behavior of the two-phase fluid flow in a single fracture, the characteristic equation of relative permeability was incorporated into the developed numerical model, and the computed results were compared with the experimental results of the model test. As results of the sensitivity analysis on the roughness and the aperture size of fracture, the gas velocity was inversely proportional to the fracture roughness, and not proportional to the square of aperture size which is usually observed in single phase flow in a single fracture. The numerical model was applied to the underground LPG storage terminal in order to check the field applicability. The simultaneous flow of water and gas in accordance with the operation pressures in a single fracture near cavern was simulated by the model. It was shown that the leaked gas was able to be controlled in a single fracture neither by the pressure of operation nor by that of groundwater in case the fracture became smoother in roughness and smaller in aperture size.

• The Journal of Engineering Geology
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• v.8 no.1
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• pp.1-12
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• 1998

The fracture size among geometric parameters of the fracture system is treated as one of the most important factors in the geotechnical and hydrogeological analysis. However, several uncertainties in data acquisition and analysis pmcess about the fracture size are not clear yet. This study presents the current status on the estimation of the fracture size and verifies the estimating method using forward modeling approach. The factors considered are the variation of fracture intersection probabilities with different assumptions on the orientation of sampling planes and fracture size by using a simulated tleee dimensional fracture network model. If it is possible to analyze precisely the fracture intersection probabilities and the characteristics of probabilistic distnbution fiom cavern walls, outcrops or boreholes,the actual fracture size developed in rock rnass can be estimated confidently.