| 業 務 要 旨 | ||
| 落石対策においては，落石発生の予知と共に，斜面を落下する落石の運動および落石の衝突による防護工の応答を適切に予測することが重要である。 本業務は，斜面を落下する落石の速度および跳躍量の予測と，落石防護柵基礎の合理的な設計法の確立を目的とし，平成１３年度から平成１５年度にかけて実施したものである。 平成１３年度と平成１４年度においては幅0.6m，高さ1.0mで，長さが4.5m，7.5m，10.5mの３種類のコンクリート基礎に高さ1.5mのストンガードを設置した防護柵を製作し，0.5tの重錘を衝突させてストンガードの変形・破壊形態，吸収エネルギー，基礎の応答を観測した。さらに，ストンガードを構成するワイヤーロープの寸法や力学特性を考慮した基礎の応答解析法，および安定性照査法を提案した。 平成１５年度には高さ41m，傾斜角40度の自然斜面から0.12〜2.06tの自然石，加速度計を内蔵したコンクリート製の球(0.2t)および立方体(0.52t)を落下させ，落石の運動形態，落下速度，角速度，跳躍量を測定した。また，盛土斜面，岩盤切土斜面，および平坦地盤面に加速度計を内蔵したコンクリート球を自由落下させ，衝突後の運動のメカニズム，跳ね返り速度について観測した。さらに，落石速度，跳躍量の予測法を提案した。 |
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| While considering rock-fall countermeasures, along with the prediction
of rock-fall occurrence it is all important to appropriately predict the
response of prevention woks against the rock-fall collision and rock-fall
motion through the natural slopes. This is a work conducted in the year
2001 through 2003 with the objectives of predicting the velocity and jump
height of the falling rock boulder over the slopes and establishing a rationalized
design method for the foundation of protective fence. In 2001 and 2002, three concrete foundations measuring 0.6 meter wide and 1.0 meter deep with the lengths of 4.5 meter, 7.5 meter, and 10.5 meter supporting 1.5 meter high stone guards were constructed as the rock-fall preventive measures. Then, a model mass of 0.5 ton was let to collide with the preventive fence so as to measure the deformations, failure patterns, and response of the foundations and the energy absorbed by them. Moreover, a proposal was made for the methods of foundation response analysis and stability assessment considering the mechanics and dimensions of wire-ropes in the stone-guard. In 2003, on the other hand, field-scale rock-fall experiments were carried out. Naturally available rock boulders and two concrete masses were employed in the experiments, in which they were let to roll and fall over a natural slope of 40 degrees with 41 meter height. The masses of the natural boulders varied between 0.12 ton to 2.06 ton, while the concrete masses measured 0.2 ton and 0.52 ton with spherical and cubic shapes respectively. The concrete masses were so prepared that they consisted of in-built accelerometers. During the experiments, measurements were made for type of motion, linear falling velocity, angular velocity, and jump height. In addition, observations were made for the post-collision movement mechanism and rebound velocity of the concrete ball with in-built accelerometer during free fall over the fill-slope, rock base cut slope, and flat ground. Based on all this, proposals were made for the methods of predicting rock-fall velocity and jump height. |
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