JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 H (地球人間圏科学) » H-TT 計測技術・研究手法

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

2017年5月23日(火) 10:45 〜 12:15 ポスター会場 (国際展示場 7ホール)

コンビーナ:早川 裕弌(東京大学空間情報科学研究センター)、佐藤 浩(日本大学文理学部)、楠本 成寿(富山大学大学院理工学研究部(理学))、内山 庄一郎(国立研究開発法人防災科学技術研究所)

[HTT19-P02] Making of a detailed DSM of a partially collapsed road embankment and correlation with 3D GPR data

★招待講演

*小河原 敬徳1木佐貫 寛1尾西 恭亮1稲崎 富士1 (1.国立研究開発法人土木研究所 地質・地盤研究グループ)

キーワード:Orthophoto, DSM, UAV, GPR, Near-surface Geophysics

We conducted an urgent but detailed field survey at a site where 8 m high road embankment slope had been partly collapsed by heavy rainfall along with strong motion of 2016 Kumamoto Earthquake 2 months before. The field measurements consisted of high-density surface photogrammetry and near-surface geophysical surveys. We employed a telescopic pole camera system and RICOH GR2 to take digital photographs in the air up to 6 meters. Finally, we made an orthophoto image and a DSM of a road surface which had escaped from collapsing at a spatial resolution of 2.86 mm using a commercial SfM-MVS (structure from motion and multi-view stereo) software package (Agisoft PhotoScan Professional). We used a total of 218 pole camera images and 7 GCPs to create the DSM. In addition, we processed UAV imagery taken on the day after the collapsing to generate a DSM of 2.5 cm spatial resolution of the site. The DSM, which covered 110 m x 90 m area, clearly imaged the embankment collapse and heaving of the ground in front of the failure caused by compression and thrusting. It was helpful to clarify the failure mechanism of road embankment and the role of geotextile-anchored concrete wall set at the foot part of the embankment to avoid entire collapsing of the embankment. Furthermore, we could identify non-tectonic structures from the road surface DSM. Number of cracks and small bulges were traced behind the failure crown, which indicated the co- or post-failure movement of the remained embankment. Then we conducted dense grid GPR survey on the road surface. As a result, cracks extended in the pavement up to 75 cm and the surface pavements were interpreted to be segmented and detached from the underlying road beds. Joint investigation and interpretation of the surface DSM and the near-surface geophysical data was capable to assess the safety conditions of remained road embankment. Namely, which types of restoration works were needed and what extent should be reinforced. In conclusion, combined analysis of surface DSM with the near-surface geophysical survey data is crucial to understand such surface deformation structures as slope failure.