Development of slope disaster prevention technique by the small-diameter spiral pile for effective use of slopes

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04678
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Hokkaido University
• Principal Investigator: Koichi Isobe 北海道大学, 工学研究院, 准教授 (70452084)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: スパイラル杭 / 支持力 / 斜面 / 深層学習 / 危険度評価 / 対策工 / 安定解析

Outline of Final Research Achievements

1) From the results of positive and negative alternating vertical loading experiments on a single small-diameter spiral pile considering the effect of rotational penetration, the penetration resistance decreased due to the increase in the number of turns of the spiral pile and the difference in the resistance mechanism between the straight pile and the spiral pile were found. The existence of the delay phenomenon of recovery of bearing capacity against repeated loads for the peculiar unsaturated ground were clarified, and points to be noted in the actual design were found.
2) A stability calculation method for a slope with a foundation structure that has multiple functions of supporting structures on the slope and slope stabilization work was established.
3) For landslide areas in Sapporo, Iwate and Niigata, a wide-area risk assessment method using deep learning while considering annual average　precipitation was realized to improve prediction accuracy and extract dangerous blocks.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

太陽光発電設備の建設急増は、発電事業の成立性確保のため、傾斜地上などの地盤や施工条件が悪い現場での施工事例を増加させ、結果として、豪雨を起因とした土砂流出による太陽光発電設備設置斜面の崩壊事例や強風被害が年々顕在化した。
本研究の成果である、小径スパイラル杭の複合荷重に対する支持力機構解明と、それに基づくた斜面上構造物の支持と斜面安定工の複数機能を有する構造形式の開発、さらに深層学習による斜面災害の広域危険度評価手法の構築により、傾斜地のより安全・安心な友好利用の可能性を見出し、豪雨災害の潜在的リスクを抱える斜面での施工を回避できる危険度評価手法の構築を実現した。