• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.457-463
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• 2012

Changing the environment around detecting areas may lower the performance of a video-based accident detection system. Region of interest(ROI) and background information changing constantly on account of the car headlights at night and a sudden changes in the weather are the biggest factors to increase the ratio of wrong results. Thus, we proposed and implemented the integrated accident detection system combined the video-based system and the laser-based imaging system. In this paper, we were able to overcome the majority problem of video-based system and it was a meaningful results that it can improve the reliability for the system.

• 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 Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.239-245
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• 2010

The present study is about an efficient extraction of tunnel cross sections from huge point cloud achieved by a terrestrial laser scanner. A method, using a hash-based data structure, is introduced, by which point clouds, potentially composing cross sections, are extracted along a tunnel center line. The center line is estimated by linking points which are drawn in the middle of pseudo cross sections based on the hash-based data structure. Point clouds of a same thickness are extracted at a same interval along the center line. In result, it took less than 3 seconds and 124 MB of memory to extract, out of the 7.5 million points, the point clouds of 1 m interval and 0.1 m thickness. A manual operation, however, was needed to fix the outliers on the center line and to select both start and end points on it.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.165-174
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• 2007

The technique, which reproduces the figures of objects from measured data of the objects using 3-D laser scanner, is called reverse engineering. Recently, research studies into applications of reverse engineering to rock engineering are increasing in number, in the discontinuity surveys for rock slopes out of man's reach, or rapid discontinuity surveys for wide range areas. For analysis of discontinuity using reverse engineering, a program for processing point clouds data from the 3-D laser scanner, for sampling from these point clouds data, and finally analyzing the discontinuity is needed. However, existing programs rarely have sufficient functions to properly analyze the discontinuities. In this study, a program was developed, which can automatically sample discontinuities from the point clouds data which measured in a rock slope using a 3-D laser scanner, and which can also undertake statistical analysis of the discontinuities. This developed program was verified by the application of discontinuity surveys in a rock slope and a tunnel. By undertaking the discontinuity survey using a 3-D laser scanner and the developed program, the feasibility and rapidity of such surveys is expected to improve in areas out of man's reach in geotechnical surveys. Taking into consideration the fact that the international level of related techniques is at a rudimentary stage, the possibility of prior occupation of a broad market is also expected.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.227-235
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• 2015

In recent years, owing to the frequent occurrence of natural disasters, the inspection and maintenance of structures have become increasingly important on a national scale. However, because most structural inspections are carried out manually, and due to the lack of objectivity in data acquisition, quantitative data are not always available. As a result, researchers are seeking ways to collect and standardize survey data using terrestrial laser scanning, thereby bypassing the limitations associated with visual investigations. However, field data acquired using a laser scanner have been required to measure changes in structure geometry resulting from passive deterioration. In this study, we demonstrate that it is possible to identify the processes of structural deterioration (e.g., efflorescence, leakage, delamination) using intensity data from terrestrial laser scanning. Additionally, we confirm the viability of automated classification of alteration type and objectification of the polygon area by establishing intensity characteristics. Finally, we show that our method is effective for structural inspection and maintenance.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.1
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• pp.90-104
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• 2008

Laser scanning technology with high positional accuracy and high density will be widely applied to vast range of fields including geomatics. Especially, the development of laser scanning technology enabling long range information extraction is increasing its full use in civil engineering. This study taps into the strengths of a terrestrial laser scanning technique to develop a tunnel cross section management system that can be practically employed for determining the cross section of tunnels more promptly and accurately. Three dimensional data with high density were obtained in a prompt and accurate manner using a terrestrial laser scanner. Data processing was then conducted to promptly determine arbitrary cross sections at 0.1meter, 0.5meter and 1.0meter intervals. A laser scanning technique was also used to quickly and accurately calculate the overbreak and underbreak of both each cross section and the entire tunnel section. As the developed system utilizes vast amounts of data, it was possible to promptly determine the shape of arbitrary cross section and to calculate the overbreak and underbreak more accurately with higher area precision. It is expected, therefore, that the system will not only enable more efficient and cost effective tunnel drilling management and monitoring but also will provide a basis for future construction and management of tunnel cross section.

• Tunnel and Underground Space
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• v.32 no.4
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• pp.272-284
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• 2022

This study conducted tunnel blasting to evaluate the blasting effect of a shear thickening fluid-based blasting stemming material and a sealed plug device under development. STF single stemming and STF stemming materials were combined with plugs to a tunnel blasting to which the SAV-Cut method was applied, and the advanced rate and fragmentation of tunnel blasting muck pile were compared when sand stemming was used. Tunnel advanced rate was evaluated using a 3D laser scanner. When the STF stemming material and STF stemming material with the plug were compared to the sand stemming material, it increased by 5.7 and 5.36%, respectively. As a result of evaluation of the fragmentation of tunnel blasting muck pile, it was the best when the STF stemming material was applied, and it decreased by about 61% compared to the case of sand stemming blasting. However, no significant improvement in blasting effect was observed with the application of plug devices.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.342-350
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• 1998

In this study, fracture network in rock mass was interpreted using borehole wall images obtained by televiewer. The orientation and JRC value of major joint set were evaluated adopting image analysis techniques, of which process were written in macro-program code. As linking JRC to joint stiffness using Barton-Bandis model, fracture network map was produced for application to jointed rock modelling in numerical analysis of underground structure.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.183-196
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• 2006

Rock joint roughness obtained from the camera-type 3D scanner was classified into waviness and unevenness. The classification criteria were established in the previous study; digital filtering was used to distinguish one from another. The classified and original profiles were used to produce metal moulds. For accurate machining of the moulds, the WEDM(Wire-cut Electric Discharge Machining) was adopted. Specimens were cast using high strength gypsum, and joint shear tests were performed by varying normal stress from low value to high one. Roughness mobilization characteristics depending on the asperity scale and the applied normal stress were investigated. A new equation was proposed to predict shear strength of rock joint, which can consider the characteristics of roughness mobilization and roughness parameters. The roughness quantification composed of waviness and unevenness was found to be a useful method to predict the joint shear strength.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.269-283
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• 2005

To figure out the cause of underestimating the roughness and shear strength of rock joints suggested by numerous researchers, we analyzed roughness mobilization characteristics, characteristics of roughness parameters, effects of sampling interval, and waviness for roughness parameters. It was found out that lack of understanding of the roughness mobilization characteristics, inappropriate applications of roughness parameters, and effect of aliasing provide a main reasons for those problems. Several practical alternatives for improving those problems were suggested. As far as digitizing methods are concerned, we can find that using a 3D scanner can give a relatively effective result. To avoid aliasing, sampling interval should be less than one-quarter of the minimum asperities. As for the quantification of roughness, it was analyzed that the roughness parameter should be classified into two components depending on the scale of roughness to apply the shear strength model. For classifying the roughness, a framework of the criterion was suggested based on the plastic flow concept for the asperity failure, and the basis for proposing a new alternative shear strength model was established.