著者

松川 瞬 板倉 賢一 早野 明 鈴木 幸司

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.11, pp.256-263, 2017-11-01 (Released:2017-11-16)

参考文献数

31

被引用文献数

1

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LIDAR (Laser Imaging Detection and Ranging) detects a rock mass surface as a point cloud, and threedimensional configurations of the rock mass can be obtained from the point cloud. In previous studies, algorithms to estimate discontinuities from a point cloud have been developed. In those algorithms, it is necessary to determine geological parameters in advance. DiAna(Discontinuity Analysis) is a Matlab tool which was developed for geostructural analysis of rock mass discontinuities. It is a semi-automatic tool. DiAna segments a point cloud into bounding boxes to estimate the surface of a rock mass. However, an expert's skills necessary to determine the appropriate size of the bounding boxes for DiAna. We developed the VBS (Variable-Box Segmentation) algorithm to determine the appropriate box size depending on the location of the point cloud and to estimate the surface of a rock mass. The VBS algorithm consists principally of three processes: large box segmentation, small box segmentation, and merging. The small boxes are merged to obtain an appropriate box size. The surface of the rock mass is estimated using the point cloud in the box. The performance of the VBS algorithms was evaluated using point clouds obtained by a geological survey. For evaluation, we estimated reference rock mass surfaces manually using the point cloud and geological sketches by geologists. Similarities among the respective reference surfaces and the surfaces estimated using the VBS algorithm were measured. Similarities among the respective reference surfaces and the surfaces estimated using the DiAna algorithm were also measured. The similarities among them were compared using standard competition ranking. The results of comparison showed that the VBS algorithm estimated planes more accurately for the reference planes than the DiAna algorithm. Therefore, the VBS algorithm determines appropriate box sizes automatically depending on the location of the point cloud and estimates the surface appropriately.

著者

早野 明 板倉 賢一

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ

巻号頁・発行日

vol.133, no.4, pp.76-86, 2017

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<p>Fracture mapping conducted during gallery excavation on construction projects of a large-scale underground facility is based on traditional geological techniques such as visible observations and simple measurements of fracture orientation using a clinometer. Therefore, some difficulties persist, such as securing data quality and worker safety. Three-dimensional (3D) laser scanning, which can instantly acquire point clouds representing the 3D shape of an object surface, is can be effective for resolving these difficulties. In order to confirm the applicability of the three-dimensional laser scanning to the fracture mapping on a gallery wall, this study proposes the method for obtaining attribute information from a point cloud, such as trace length and orientation, associated with the spatial distribution of fractures. In the proposed method, the two-dimensional image is generated from the point cloud to obtain the trace map. After the proposed method was applied to an approximately 50-m-long horizontal gallery excavated into the granitic rock, the reproducibility of the attribute information of fractures obtained solely from the point cloud was examined. Results show that the number of fractures extracted from the point cloud is approximately 80% of those extracted by traditional geological techniques. Although the trace length reproducibility ratio of fractures is approximately 70%, fracture orientations calculated from the point cloud compare favorably with those measured by an on-site researcher. Most fractures that were not extracted from the point cloud do not act as water-conducting fractures because they had short lengths and because they were bonded tightly. Even if the fracture data obtained from the point cloud were applied to modelling for hydrogeological analysis, the results would probably not be influenced strongly. Results of this study indicate the possibility of applying 3D laser scanning to fracture mapping.</p>

著者

早野 明 板倉 賢一

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.4, pp.76-86, 2017-04-01 (Released:2017-04-29)

参考文献数

27

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Fracture mapping conducted during gallery excavation on construction projects of a large-scale underground facility is based on traditional geological techniques such as visible observations and simple measurements of fracture orientation using a clinometer. Therefore, some difficulties persist, such as securing data quality and worker safety. Three-dimensional (3D) laser scanning, which can instantly acquire point clouds representing the 3D shape of an object surface, is can be effective for resolving these difficulties. In order to confirm the applicability of the three-dimensional laser scanning to the fracture mapping on a gallery wall, this study proposes the method for obtaining attribute information from a point cloud, such as trace length and orientation, associated with the spatial distribution of fractures. In the proposed method, the two-dimensional image is generated from the point cloud to obtain the trace map. After the proposed method was applied to an approximately 50-m-long horizontal gallery excavated into the granitic rock, the reproducibility of the attribute information of fractures obtained solely from the point cloud was examined. Results show that the number of fractures extracted from the point cloud is approximately 80% of those extracted by traditional geological techniques. Although the trace length reproducibility ratio of fractures is approximately 70%, fracture orientations calculated from the point cloud compare favorably with those measured by an on-site researcher. Most fractures that were not extracted from the point cloud do not act as water-conducting fractures because they had short lengths and because they were bonded tightly. Even if the fracture data obtained from the point cloud were applied to modelling for hydrogeological analysis, the results would probably not be influenced strongly. Results of this study indicate the possibility of applying 3D laser scanning to fracture mapping.