• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.95-105
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• 2014

Reinforced concrete (RC) shield tunnel lining must be designed for fireproof performance because the lining is sometimes exposed to very high temperature due to traffic accidents. Both experimental and numerical studies are carried out to evaluate fire resistance performance of precast RC tunnel lining systems. In the experimental studies, six full-scale precast RC tunnel segments are exposed to fire in order to examine the influence of various parameters on the fire resistance performance of precast RC tunnel lining. We used the temperature curve of the RABT criteria, which are severe conditions of fire temperatures. The fire test showed that the explosive spalling was not observed by substituting concrete to PP fiber reinforced concrete. A transient heat flow analysis was carried out in consideration of the material properties that change with temperature, and the results showed good agreement with the test results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.1
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• pp.1-11
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• 2013

Steel fiber-reinforced concrete (SFRC) is widely used for tunnel lining structure such as shot-crete in NATM tunnel and segment in TBM tunnel. In tunnel fire accidents, structural performance of a lining is very important because the lining is the structure that directly exposed to fire. In this study, the effects of high temperatures, mix ratios and types on failure pattern, DPT tensile strength and coefficient of variation were investigated through Double Punch Tests (DPT) of SFRC subjected to high temperatures. In the results, it is confirmed that the residual DPT tensile strength increases as for SFRC and this is more in SFRC with higher mix ratio. But, the equation for evaluation of DPT tensile strength does not involve the number of failure surfaces SFRC specimens subjected to high temperatures, therefore, it is required to investigate more fracture energy in DPT tests.

• Tunnel and Underground Space
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• v.20 no.6
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• pp.446-454
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• 2010

CAES-G/T (Compressed Air Energy Storage - Gas Turbine) power generation is a likely option for the buffer facility stabilizing the fluctuation of the renewable powers, such as wind and solar powers. Considering the geological conditions, the underground CAES facility is most probable if the CAES-G/T generation is planed in Korea. In this kind of facility, a concrete plug is installed to seal the compressed air in the container, so that the selection of the shape and dimension of concrete plug could be a critical design factor. The stability evaluation of two types of plug was carried out by investigating the distribution of the factor of safety in the plugs and the distribution of contact pressure over the contact surface. The analysis result shows that the taper-shaped plug is more structurally stable than the wedge-shaped plug for the given geological condition. Possible separation of the rock-concrete interface around the spring line of the wedge-shaped plug is anticipated, which means the possible leakage of compressed air through the side wall and also means the poor mobilization of frictional resistance on that area.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.175-186
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• 2013

Based on Model Code 2010, flexural and residual strength, flexural toughness of SFRC with design strength of 60 MPa are evaluated. For comparisons, SFRC with design strength 40 MPa was tested. Distribution of steel fibers in crack surface of specimens was evaluated by visual inspection. The used steel fibers were hooked fibers with aspect ratio of 64, 67 and 80. In all specimens, mix ratio of steel fibers was 0.5% Vol. In results, only SFRC with the highest aspect ratio satisfied requirements specified in Model Code 2010. The results demonstrated that the use of high aspect ratio will provide enough flexural toughness for high strength concrete. Also, it is found that low slump of high strength concrete can help to enhance isotropic fiber distribution.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.320-327
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• 2015

This study implicates a quality evaluation technique for lining concrete using the ultra-sonic technique and proposed a classification for quality evaluation. From the comparison of test results, an improved result comparable to the results by destructive test can be obtained by using averaged transmission velocity of velocities obtained at pure space and central space between two sensors of ultrasonic tester. It is also shown that strength evaluation by ultra-sonic method is not reliable and an evaluation according to the transmission velocities can be improved method for the strength evaluation of concrete.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.377-396
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• 2019

Explosion after penetration of a warhead in an underground structure generally causes considerable displacement, breakage and extensive damage to the target. Therefore, in order to reduce the damage effect, it is required to design an underground structure protection against penetration. In this study, major factors for improvement of penetration protection performance of reinforced concrete underground structures using applied element method are divided into strength (concrete UCS) and density (concrete thickness, reinforcement layers, reinforcement diameters, reinforcement spacings). Based on these major factors, this study performed numerical analysis of simulation of dynamic response by penetrators under various conditions and analyzed the results. The results of this study are expected to be used as basis materials to improve penetration protection performance of reinforced concrete underground structures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.2
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• pp.153-170
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• 2022

Waterjet has been comprehensively used in urban areas owing to a suitable technique for cutting concrete and rock, and low noise and vibration. Recently, the abrasive waterjet technique has been adopted and applied by the Korea Atomic Energy Research Institute to demolish concrete plugging without disturbing and damaging In-situ Demonstration of Engineered Barrier System in the disposal research tunnel. In this study, the use of abrasive waterjet in the tunnel was evaluated for practical applicability and the existing cutting model was compared with the experimental results. As a variable for waterjet cutting, multi-cutting, water flow rate, abrasive flow rate, and standoff distance were selected for the diversity of analysis. As regarding the practical application, the waterjet facilitated path selection for cutting the concrete plugging and prevented additional disturbances in the periphery. The pump's noise at idling was 64.9 dB which is satisfied with the noise regulatory standard, but it exceeded the standard at ejection to air and target concrete because the experiment was performed in the tunnel space. The experimental result showed that the error between the predicted and measured cutting volume was 12~13% for the first cut and 16% for second cut. The standoff distance had a significant influence on the cutting depth and width, and the error tended to decrease with decrement of standoff distance.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.1
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• pp.61-70
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• 2004

Precast Concrete Lining (PCL) is invented in order to resolve the problem of the cast-in-place concrete lining in Norway, However PCL could not consider the effect of earthquake because an earthquake rarely occurs in the region of Northern Europe, Consequently, the analysis of the effect of earthquake on PCL should be made before introducing PCL to Korea. The purpose of this research is to evaluate the stability of tunnel applying PCL in the case of earthquake. To evaluate the seismic performance of PCL, we used shaking table apparatus by 1/5 scale down model. The result of this research is as shows that deep tunnells satisfied for Korea seismic design criteria.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.149-158
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• 2011

Utilization of the fiber reinforced polymer (FRP) material has been increased as an alternative in a bid to supplement the problems with general construction materials such as long-term problems corrosion, etc. However, there are still many problems in using a linear-shaped FRP material for a tunnel lining structure which has arch-shape in general. In this study, the loading tests for the FRP-concrete composite member was carried out to evaluate their applicability as a tunnel reinforcement material, which are based on the results from preliminary numerical studies for identifying the behavioral characteristics of FRP-concrete composite member. Moreover, numerical analysis under the same condition as applied in the loading tests was again conducted for analysis of mechanical behavior of the composite member. As a result of the load test and numerical analysis, it appears that the FRP-concrete composite member is greatly subject to shear movement caused by bending tension acting on the interface between two constituent members.

• Fire Science and Engineering
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• v.23 no.3
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• pp.110-120
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• 2009

In tunnel, though the frequency of fire occurrence is relatively lower than other structures, the characteristics of sealed space tends to cause the temperature to rapidly rise to more than $1000^{\circ}C$ within 5minutes after fire, which might eventually lead to a large fire that usually results in a loss of lives and the damage to the properties, not to mention a huge cost necessary for repair and maintenance after fire. We have developed various conditions of the heating furnace and the method to install a thermo couple within the furnace based on EFNARC and KS F 2257-1. Referring to tunnel fire scenarios, it clarified the heat transfer characteristics of concrete PC panel lining depending on fire intensity (ISO, $1^{\circ}C$/SEC, MHC, RWS), and to identify the range of thermal damage, the evaluation was carried out using ITA standard. As a result, 30mm under ISO fire condition, 20mm under $1^{\circ}C$/SEC, 100mm under MHC and 50mm under RWS were measured. And when it comes to spalling, 30mm was measured under RWS and MHC.