Toshiyuki Katada

Failure Mechanism of Anchored Retaining Wall Due to the Breakage of Anchor Head

In this research, a case history of temporary earth support collapse is first illustrated briefly and the mechanisms of accident occurrences are introduced, with the results showing that the shallow penetration of piles mainly caused the sequences of collapse. In order to understand these failure characteristics and mechanisms, centrifuge model tests using an in-flight excavator were carried out. The failure mechanism of the retaining wall in this labour accident was first demonstrated using centrifuge model tests by Toyosawa et al. Failure mechanism of anchored retaining wall, 667–672 (1996). In this paper, we added some viewpoints regarding the mechanism of the retaining wall and it was thus clarified that the active and passive earth pressures in the retaining wall increased during excavation and then the anchor head exceeded the capacity with respect to tensile stress. As a result, the retaining wall and ground behind the wall collapsed suddenly.

INSTABILITY OF MOBILE CRANES DUE TO THE GROUND PENETRATION OF OUTRIGGERS CAUSED BY BRITTLE FAILURE OF THE GROUND

ホイールクレーンなどの移動式クレーンは, アウトリガによって作業中の機体を安定させる. しかし, これが地盤に沈下したことによる転倒災害が多く発生している. 本研究では支持地盤の破壊によるアウトリガの沈下挙動に着目し, その破壊沈下特性の違いが移動式クレーンの転倒に与える影響を遠心模型実験と数値計算によって検討した. その結果, 表層が固結した2層地盤ではその脆性的な破壊によって, アウトリガが急激に沈下するために移動式クレーンは動的に不安定化し, 静的転倒角に比べて少ない機体傾斜でも転倒することがわかった. そのため移動式クレーンの転倒危険度を, 地盤破壊危険度と運動学的沈下危険度の最大値によって評価することを提案し, 地盤工学的な使用限界を示した.