JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Oral

H (Human Geosciences) » H-TT Technology & Techniques

[H-TT19] [EE] GEOSCIENTIFIC APPLICATIONS OF HIGH-DEFINITION TOPOGRAPHY AND GEOPHYSICAL MEASUREMENTS

Tue. May 23, 2017 3:30 PM - 5:00 PM 103 (International Conference Hall 1F)

convener:Yuichi S.Hayakawa(Center for Spatial Information Science, The University of Tokyo), Hiroshi, P. Sato(College of Humanities and Sciences, Nihon University), Shigekazu Kusumoto(Graduate School of Science and Engineering for Research, University of Toyama), Shoichiro Uchiyama(National Research Institute for Earth Science and Disaster Prevention), Chairperson:Shigekazu Kusumoto(Graduate School of Science and Engineering for Research, University of Toyama), Chairperson:Hiroshi Sato(College of Humanities and Sciences, Nihon University), Chairperson:Yuichi Hayakawa(Center for Spatial Information Science, The University of Tokyo), Chairperson:Shoichiro Uchiyama(National Research Institute for Earth Science and Disaster Prevention)

4:00 PM - 4:20 PM

[HTT19-08] 3D modeling of a damaged Sabo dam with a combination of a DSM and near-surface geophysical survey data

★Invited papers

*Tomio INAZAKI1, Kunio Aoike2, Takanori Ogahara1, Hiroshi Kisanuki1, Hideki Saito2, Takeshi Shimizu1, Hiroaki Izumiyama3, Naoki Fujimura1 (1.Public Works Research Institute, Tsukuba Central Institute, 2.OYO Corporation, 3. National Institute for Land and Infrastructure Management)

Keywords: Orthophoto, DSM, Sabo dam, GPR, Fracture Imaging

We conducted an integrated analysis of high-resolution digital surface model (DSM) and detailed geophysical survey data obtained on the rear wall of a sabo dam, which had been damaged by a huge debris flow occurred in July 9, 2014. An orthophotograph and a DSM of the rear wall of the dam were reconstructed from a set of surface digital photo images at a spatial resolution of 1.2 cm using commercial multi-view stereo (MVS) software (Agisoft Photoscan). The debris flow swept away the top 5 m part of the dam, and segmented the dam body into several blocks associated with horizontal cracks. Estimated surface dislocation was at most 20 cm. Our DSM covered the right half surface of the dam (left bank side), about 30 m wide and 20 m high. We also carried out GPR measurements on the surface, 10 m wide and 15m high, by hanging and moving up the tool along the surface from the top of the dam. A total of 50 lines was scanned at 20 cm intervals. In addition, high-resolution seismic measurements were conducted along 5 survey lines set horizontally on the surface. Piezoelectric type accelerometers were pasted on the surface at 20 cm intervals, and manual hit using rock hammer was employed for generating high-frequency signals.
Because the dam surface was too steep and too high to place a number of GCPs by hand, only 3 points were set on the surface at reachable distances. Then we built a DSM projected on the inclined plane defined by these 3 points. Detailed GPR measurements successfully imaged fractures at the shallow depths up to 1 m, and high-resolution seismic survey detected dipping fractures extending into the deeper portion in the body up to 8m. In addition, photogrammetric analysis clearly mapped blocked deformation. Finally, we combined these planes to create a 3D model with aid of a 3D modeling tool named Voxler provided by Golden Software. In conclusion, joint interpretation of geophysical survey results with the photogrammetric analysis was quite helpful to interpret the dislocation process of the dam body. GPR and high-resolution seismic survey results also demonstrated their applicability for the delineation of internal fracture in large concrete structures.