• Tunnel and Underground Space
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• v.8 no.1
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• pp.53-66
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• 1998

Considering the mechanical cracking in the concrete lining of tunnels occurring in relatively short period of time after the construction, there is a need for the study on the mechanical behavior and the cracking characteristics of double lining support system(shotcrete and concrete lining). For the proposed study, downscaled lining models of Kyung-Bu High Speed Railway tunnels were tested. Most longitudinal cracks at about 93 percentage developed within 30 arch degree from the vault. Cracking load was about 30 percentage of the failure load and the deflection under the cracking load was 10 percentage of the deflection under the failure load. The overbreak around the vault contributed to the reduction of the capacity for cracking and failure by the percentage greater than the reduced effective depth. Of several rock block types considered in this research, the triangular block was the most critical, and the right triangular block under eccentric load was secondly critical for the stability of the tunnel lining system. The dimensionless support reaction curves were derived from the experimental results for single and double lining. The general equation to compute the designed flexural moment was modified.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.296-305
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• 1999

In ordinary back analysis it if hardly possible to obtain the mechanical properties of tunnel lining by using commonly measured displacements of tunnel lining, because only a few displacements could be measured at the site. Therefore, it is necessary to develop a new method which can evaluate the state of stresses of tunnel by using measured data. In this study, in order to assess tunnel lining stability by estimating its stresses with a few measured displacements, a formulation of back analysis method was proposed. The accuracy of results were investigated through the parametric study for several types of measurement model of two dimensional elastic lining. This new back analysis method to assess tunnel lining stresses and strains with a few numbers of measured displacements showed high accuracy and good applicability when compared to the results of numerical experiments by FEM. The method has been tested on subway tunnel and its applicability has been confirmed by comparing field and analytical data. It is verified that the stress on the tunnel lining can be obtained by only more than 3 point of input displacements without any condition of external loads.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.114-130
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• 1999

It is very important to study on the structural behaviors of structurally damaged tunnel linings. A series of centrifuge model tests were performed in order to investigate different behaviors of tunnel linings. A 1/100-scaled aluminum horseshoe tunnel linings with a radius 5 cm, height 8 cm were buried in a depth with dry Joomunjin standard sand, the relative density of which was 86%. Such sectional forces as bending moments and thrusts along the tunnel circumference were measured by twelve strain gages. Earth pressures in soil mass and on the outside of lining model were estimated by pressure transducers, ground surface settlements at a center and edges by using LVDTs.

• Journal of Industrial Technology
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• v.24 no.B
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• pp.107-116
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• 2004

This thesis is results of experimental works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Compared results model tests estimation with respect to displacements of the lining.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.146-156
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• 1998

Nemerical algorithms were developed to analyze the behavior of the double lining as well as ground mass separately or simultaneously. A lining interface element was especially developed, verified and applied to the study on the coupled interaction of shotcrete and the concrete lining. It could be known fro parameter studys on double lining support systems that as the contact surface between shotcrete and concrete lining was rougher, the more decreased bearing capacity against the cracking of the system. If the thickness of the shotcrete increased, the bearing capacity of the double lining also increased linearly with the thickness. If the thickness of the concrete lining increased, the bearing capacity of the double lining had the relationship of the characteristic S-shape of a sigmoid function with the thickness. When the thickness increased over a given value, it was not useful to increase more the thickness because bearing capacity had no remarkable change. It could be concluded that the behavior of the shotcrete and concrete lining was generally reversed before and after the ratio of horizontal to vertical earth preassure of 1.0 and 0.5 respectively. Therefore, we could guess that the movement which two shotcrete and concrete lining deflect toward each other around the crown caused a friction between two linings and thus this disadvantageous effect could contribute to reducing the bearing capacity against the cracking.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.227-238
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• 2004

This paper is results of experimental and nunerical works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Numerical analysis with the commercially available program of FLAC were performed to compare with results of centrifuge model experiment In numerical modelling. Mohr-Coulomb elasto-plastic constitutive model was used to simulaye the behavoor of Jumunjin Standard Sand and the interface element between the lining and the covered material was implemented to simulate the interaction between them. Compared results between model tests and numerical estimation with respect to displacement of the lining showed in good agreements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.675-683
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• 2015

The room-and-pillar construction method for underground space is adopted from the room-and-pillar mining method which is one of the most popular underground mining method in the world. Drainage system in the room-and-pillar underground construction method can be similar with the concept of single shell in tunnel because additional reinforcement except the TSL (thin spray-on liner) is not applied in the room-and-pillar construction method. That is, to decrease groundwater level and maintain safety in tunnel, the drainage pin hole inside lining (shotcrete) can be used. However, if total amount of outflow in the underground structure is relatively small or groundwater is not detected, such drainage system will not be useful and cause additional construction cost. In this study, outflow of conventional tunnels in South Korea was investigated and the criteria to determine whether the drainage pin hole is effective was suggested. And the guided drainage system was suggested when drainage pin hole was not applied in the room-and-pillar construction method.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.38-49
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• 2006

LNG storage in lined rock cavern demands various techniques concerned with rock mechanics, thermo-mechanics and hydrogeology in design, construction and maintenance stage. LNG pilot cavern was constructed in Daejeon in order to verify these techniques. In this paper, evaluation of drainage system and ice ring formation was studied by numerical simulation. By Modflow analysis in the viewpoint of aquifer and Seep/W analysis in the viewpoint of flow system, it was verified that the drainage system in the pilot cavern was efficiently operated. Since ice ring formation can be simulated by interactive relation between heat transfer and water flow, coupled analysis of those was performed. In this analysis, the position of ice ring was presumed and it was demonstrated that the formation is affected by velocity and direction of groundwater flow.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.434-445
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• 2010

Underground compressed air energy storage (CAES) system in a lined rock cavern is considered one of the promising large-scale energy storage technologies. In this study, permeabilities of concrete lining block and its construction joint, which are the major components of an air tightness system of the undeground CAES, were measured from a model experiment. From the experiment, it was found that intrinsic permeability of construction joint was larger than that of concrete block by the order scale of $10^1{\sim}10^4$, so that it would be very important to control the quality of construction joints in-situ in order to secure air tightness of storage system. And the permeability of construction joint could be decreased as low as that of the concrete block by pasting an acryl-type adhesive on bonding surfaces. Higher degrees of water saturation of the concrete block resulted in the lower permeability, which is more preferable in the viewpoint of air tightness of storage cavern.