• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.485-488
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• 2008

Fire intensity in tunnel fire is very severe, which might cause the spalling on the surface of shotcrete and concrete lining exposed to the heat as well as rapidly-reducing stress due to heat transfer by steel material such as anchor embedded in tunnel which plays the critical role in securing the stability of the tunnel. In this study, a fire test to identity the heat intensity(Modifired Hydrocarbon Curve) and the fire resistance of steel materials embedded as parameters, was carried out. And the evaluation to identify the thermal damage, which was based on critical temperature range for thermal damage of steel materials determined according to the road tunnel fire resistance standard established by ITA(International Tunneling Association).

• Fire Science and Engineering
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• v.24 no.4
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• pp.86-91
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• 2010

In event of a tunnel fire, all kinds of equipment can be destroyed in high temperature that can exceed $1300^{\circ}C$, fatal structural demage can be caused by spalling of concrete structural elements. To make matters worse, there is a high possibility of the secondary damage which can lead to the collapse of the shear resisting structure. Accordingly, it is time that we developed the technology to counter fires in connection with the fire-resistant design of a tunnel structure. To secure the reliability of the fire-resistance performance of a tunnel structure, it is necessary to assess the fire's behavior on every structural element exposed to the fire as well as to calculate the tunnel fire intensity and the quantity of heat released. In this study, we drew out the fire damage range of each structural element of a tunnel and the minimum thickness of concrete cover for each fire-resistant material through some actual experiments of fire behavior on the structural elements of a tunnel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.219-228
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• 2006

In this study, a series of fire tests was carried out to evaluate fire-induced damage to structural members in tunnels. From the tests, the loss amount of concrete materials under the RWS scenario was slightly bigger than under the RABT fire scenario. Especially under the RWS fire scenario where the maximum temperature is over $1,200^{\circ}C$, the loss of concrete materials was mainly induced by melting. Generally, the loss of materials in reinforced concrete was slightly smaller than that in unreinforced concrete. Depending upon an applied fire scenario, fire-induced damage to shotcrete was quite different. From the realtime investigation of a specimen surface by a digital camcorder, it was proved that the material loss under the RABT fire scenario was mainly induced by spalling. However, it was also revealed that although fire-induced damage in the initial heating stage under the RWS was so close to that under the RABT, the material loss under the RWS at the later stage after 50 minutes elapsed since fire initiation was induced not by spalling but by melting.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.553-561
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• 2015

In this study, the performance assessment criterion for reasonable maintenance of shield TBM tunnel was presented. The performance assessment items such as crack, leakage, breakage, spalling, exfoliation/detachment, efflorescence, quality condition, exposure of steel, carbonation, faulting step, bolts condition, drainage condition, ground condition, contact section condition and conduit condition were selected by analyzing domestic and foreign performance assessment criterions and investigating segment lining deterioration cases through the site investigation and in-depth inspection analysis result on the shield TBM tunnel. In addition, the reasonable weight using AHP (Analytic Hierarchy Process) were estimated.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.194-200
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• 2010

Recently, a longitudinal tunnel construction has increased because of subway construction extension, geomorphological effect and the development of construction Technologies etc. When the fire occurs in a tunnel and an underground structure, the many damage of human life and the economic losses are caused. In Korea, fire resistance character study of a tunnel and an underground structure is proceeding. However, when a concrete is exposed to high temperature, study of load carrying capacity reduction and stability evaluation for spalling of a concrete is not enough. Therefore in this study, fire resistance character of a concrete evaluated according to time heating temperature curve(RABT and RWS) and a result compared on virtual fire accident in order to apply fire scenario. Also this study performed thermo-mechanical coupled analysis of a FEM-based numerical technique and estimated fire-induced damage of a tunnel and an underground structure.

• 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.13 no.3
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• pp.199-214
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• 2011

A crack is the main cause to affect the integrity of tunnel lining as well as leakage, spalling, exposed rebar, corrosion, carbonation and so on. Since the 1980, NATM has prevailed on excavation method and geotechnical philosophy in tunnel. Although the pattern of cracks has been reported by several engineers' effort, it was only focused on longitudinal cracks of lining. Eleven operational NATM tunnels have been conducted with the precise inspection for safety and diagnosis by KISTEC (Korea Infrastructure Safety and Technology Incorporation). With those results, the crack patterns by the spatial distribution and appearance for each tunnel have been analyzed and the cause of occurrence for seven common types of cracks in NATM tunnels was classified. Additionally, the longitudinal crack on lining above duct slab was figured out by numerical simulation and field inspection. Each crack has been analyzed by CCD (Charge-Coupled Device) scanner image with 3D configuration. Each type of cracks is also explained with output of experimental and condition of construction. Defined cracks on NATM tunnels will be good example for periodical inspection and precise inspection for safety and diagnosis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.1
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• pp.109-128
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• 2022

The precise inspection for safety and diagnosis (PISD) of tunnel has been conducted by the special act on safety control of public structures. However, the present assessment for the segmental lining of TBM tunnel has limitation such as: NDTs for integrity, segmental configuration for field inspection, and consideration for jacking system. Even if the number of TBM tunnel is less than 1% of enrolled facility in FMS, more attention to maintenance should be necessary due to its usage such as multi-use facility and national important facility. Compared to NATM tunnel, excavated by drilling and blasting and then installed lining by cast-in-place within 6~12 m, TBM tunnel is cut out ground by disk and cutter-bit and then assembled 7 pieces of precast segment, 1.2~1.4 m wide. Different features of design, construction, and maintenance should be considered to be more exact evaluation of TBM tunnel. The characteristics of defect is categorized and analyzed with 11 operational TBM tunnels in domestic subway. To be more comprehend various particular defects, foreign studies have been also adapted. Crack and leakage are categorized in 7 patterns. Breakage/spalling and corrosion are also grouped into 3 patterns. Patterned defects or damages are fed back in design, construction, and are useful guidelines for maintenance stage in future.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.469-479
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• 2021

As a material for preventing spalling of concrete, the effectiveness of PP fiber has already been confirmed. However, it is necessary to consider the maximum temperature that occurs during a fire, and to solve the mixing problem and the strength reduction problem that occur depending on the mixing amount. In this study, the fire resistance performance of tunnel segment linings according to the PP fiber content and air volume under the RABT fire scenario was investigated. As a result, no spalling or cross-sectional loss occurred in all test specimens, and when the PP fiber content was small, the maximum temperature was relatively high and the maximum temperature arrival time was also fast. On the other hand, no trend was found for the maximum temperature and arrival time according to the difference in air volume. In the internal temperature distribution results for the PP fiber mixing amount of 0.75, 1.0, 1.5, and 2.0 kg/m³, the results of 0.75 and 1.0 kg/m³ showed similar temperature distribution, and the results of 1.5 and 2.0 kg/m³ were similar. It was confirmed that the internal temperature distribution tends to decrease at the same depth when the amount of PP fiber mixed is large, and it was confirmed that a remarkable difference occurred from the results of 1.0 kg/m³ and 1.5 kg/m³ of PP fiber mixed amounts.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.397-400
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• 2006

The addition of polypropylene fibers is effective to avoid spalling of shotcrete and concrete adopted tunnel and underground structure under the fire. In this study, a cement based mortar for fire resistance of polypropylene fiber was developed and evaluated by experimentally. The geometry and amount of polypropylene fibers which are diameter, length and fiber dosage were significant factors in aspect of the response values of fire resistance.