Field Observation on the Behavior of Falling Rock. Study on the rock fall along a slope(1st Report).

It is considered that accumulation of data concerned with falling behavior of rocks along a slope is insufficient. Observational study for falling behavior of rocks was carried out at an open-shoot slope of a quarry by using video cameras. Linear velocity, rolling velocity, the ratio of the velocity after impact to the velocity before impact of a rock against a slope, and jumping height were analyzed from the video pictures, by using a personal computer with image processing board. From these video analyses, following points were clarified. 1) Falling velocity of the tabular rock is unexpectedly higher than the value considered generally. This shows the rock of tabular shape is not always safety. 2) Rolling velocity at optional distance from the top of a slope could be estimated reasonably by the equation(10)described in this text.3) There are cases that velocity ratios before and after the impact exceed 1.0. This means technical terms restitution coefficient and attainuation coefficient should not be used in the rock fall problem. 4) The value of 2m measured as jumping height is considered to be available when the height of protection fence is planned.