• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.245-259
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• 2023

The purpose of this paper is to examine the most recent tunnel scanning systems to obtain insights for the development of non-contact mobile inspection system. Tunnel scanning systems are mostly being developed by adapting two main technologies, namely laser scanning and image scanning systems. Laser scanning system has the advantage of accurately recreating the geometric characteristics of tunnel linings from point cloud. On the other hand, image scanning system employs computer vision to effortlessly identify damage, such as fine cracks and leaks on the tunnel lining surface. The analysis suggests that image scanning system is more suitable for detecting damage on tunnel linings. A camera-based tunnel scanning system under development should include components such as lighting, data storage, power supply, and image-capturing controller synchronized with vehicle speed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.19-28
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• 2007

Tunnel management is a time-consuming and expensive task. In particular, visual analysis of tunnel inspection often requires extended time and cost and shows problems on data gathering, storage and analysis. This study proposes a new approach to extract information for tunnel management by using a laser scanning technology. A prototype tunnel laser scanner developed was used to obtain point clouds of a railway tunnel surface. Initial processing of laser scanning data was to separate those laser pulses returned from the installations attached to tunnel liner using radiometric and geometric characteristics of laser returns. Once the laser returns from the installations were separated and removed, physically damaged parts on tunnel lining are detected. Based on the plane formed by laser scanner data, damaged parts are detected by analysis of proximity. The algorithms presented in this study successfully detect the physically damaged parts which can be verified by the digital photography of the corresponding location on the tunnel surface.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.3
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• pp.159-164
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• 2006

Mobile communication with wireless modem can be powerful tool in web-based structural health monitoring system in which power and communication method are crucial points. In this study, the major reasons of side cracks in tunnel lining are studied by FEM analysis. In addition, a web-based monitoring system using mobile communication with wireless modem is applied to the tunnel structure to monitor the long term behavior of the side cracks. The field application shows that CDMA is useful method for structural health monitoring system which installed long distance away.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.30-42
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• 2022

Due to the increase in construction of tunnels, the burdens of maintenance works for tunnel structures have been increasing in Korea. In addition, the increase of traffic volume and aging of materials also threatens the safety of tunnel facilities, therefore, maintenance costs are expected to increase significantly in the future. Accordingly, automated condition assessment technologies like image-based tunnel scanning system for inspection and diagnosis of tunnel facilities have been proposed. For image-based tunnel scanning system, it is key to create a planar image through stitching of multiple images captured by tunnel scanning system. In this study, performance of feature-based stitching algorithms suitable for stitching tunnel scanning images was evaluated. In order to find a suitable algorithm SIFT, ORB, and BRISK are compared. The performance of the proposed algorithm was determined by the number of feature extraction, calculation speed, accuracy of feature matching, and image stitching result. As for stitching performance, SIFT algorithm was the best in all parts of tunnel image. ORB and BRISK also showed satisfactory performance and short calculation time. SIFT can be used to generate precise planar images. ORB and BRISK also showed satisfactory stitching results, confirming the possibility of being used when real-time stitching is required.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.160-166
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• 2006

Optical Fiber Bragg Grating sensor has a good performance to measure microscopic displacement which can measure strain of lining concrete and cylindrical structure like high intensity containment building and it can present many advantages like a corrosion resistance from the durability point of view. Then it can measure plane geometrical displacement of cylindrical structures with two-way displacement FBG sensor module. According to the test result, measurement of FBG sensor is better performance than other electric sensor system and 2D-level measurement. As a test result, Resolution of the two-way displacement sensor module with FBG sensors are more 10 times than other LVDT or 2D surveying.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.5
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• pp.345-355
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• 2023

An analysis of covariance and Pearson correlation coefficient were performed to identify the relationship between both variables: traffic volume and crack. For this, it was carried out to analyse 216 tunnel inspection/diagnosis results with respect to the traffic. As a result, it has been proven that traffic volume and cracks in concrete linings are highly correlated. Therefore, it is recommended to consider traffic volume in planning of preemptive maintenance such as crack repair, etc.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.4
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• pp.35-55
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• 2001

Recently, as tunnel structures are getting older and decrepit, many tunnel inspections are carried out for evaluating the tunnel state and safety. But, because there is no exact standard for tunnel state and safety, depending on subjective decision, the new standard to assess the tunnel state is required. The existing standard including mainly the assessment of the state of tunnel lining is not considered the characteristics of tunnel as underground structures. Also, the item of assessment and process of grading and classifying the state of tunnel is not objective and systemetic. In this study, new standard for assessment of tunnel state is presented for improving the problems in evaluating the tunnel state and safety. In the new standard, the new items of assessment including geotechnical condition were selected and graded, the process in classifying the tunnel state is quantitative for objective assessment for tunnel state. This new standard and method is practically used in effective safety inspection and diagnosis and tunnel maintenance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.95-104
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• 2006

The presence of cavitations under pavements or behind tunnel linings of concrete is likely to result in collapse. One method of detecting such voids by non-destructive means is low frequency type radar(GPR). By the way, the size and thickness of small cavitation can't be detected by the present radar technology with low frequency and low resolution when it apply to civil structures like that. To overcome these problems and limitations, this study aims to develope and propose a new analysis method for estimating the depth, cross-sectional size and thickness of cavitations using low frequency radar. A new proposed method is based on the experiments that are carried out for analyzing the correlation between the measurement values(the amplitudes of radar return) of low frequency radar and various type of cavitations. In this process, the threshold value for radar image processing which aims to represent only cavitations to be fitted size can be obtained. As the results, it is clarified that a proposed method has a possibility of estimating cavitation depth, size and thickness with good accuracy in laboratory scale.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.193-204
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• 2008

This paper describes laboratory experiments modelling multiple tunnel construction in soft ground. A series of small-scale model tests have been conducted at approximately 1/50 scale in order to investigate the behaviours of existing tunnels in response to the construction of new tunnels in close proximity. The model tunnels were constructed in a consolidated Speswhite Kaolin clay using a tunnelling device involving an auger type cutter within a shield. Strain gauges and LVDTs were used for instrumenting the existing tunnels. The findings obtained from the analyses of these tests were compared to the field measurements involving the reconstruction of the Northern Line London Underground Ltd. tunnels at Old street, United Kingdom. The results were also compared to the ground movement measurements obtained from a separate set of tests undertaken using the same apparatus and experimental procedures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.192-203
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• 2009

In the new Seoul-Busan high speed railroad construction specially in area of city center passage the roadbed establishment is recommended the staibility for the existing subway tunnel segments of Busan subway 1st and 2nd lines regarding the appearance condition, a quality condition and the durability of the objective facility, and it evaluates the numerical analysis using MIDAS/GTS which leads the stability of the objective facility and investigatesd tunnels. Fundamental issues in tunneling under high groundwater table are discussed and the effect of groundwater on tunnel excavation was examined using a 3D stress-pore pressure coupled Finite-Element Method. Based on the results the interaction mechanism between the tunnelling and groundwater is identified. In the both of 1st and 2nd Line the maximum sinkage, unequal sinkage and the lining stress from numerical analysis are within permission and the damage degree is appearing to be disregarded. But it enforces necessary Pre-grouting in order to minimize an actual tunnel face conduct and when the tunnel is excavated it is also necessary to minimize the outflow possibility.