Abstract
A new method to describe the regional characteristics on slope failure size-number distribution is proposed in terms of its Fractal properties.
The investigation area was 26.5km (N-S direction) long and 1km (E-W) wide through Misumi Town in Shimane Prefecture, in which psammitic and pelitic schists of Sangun Metamorphic Rocks are mainly distributed. Slope failures investigated occurred in the morning of the 23th in July 1983 by heavy rainfall concentrated in Misumi and Masuda areas. The relationships of the failure size (maximum width) -number distribution and the amount of rainfall, geographical, geological and botanical properties were investigated.
The results are summarized as follows.
1) The failure size (wider than 15m) -number distribution showed Fractal Distribution.
2) Coefficient D (Fractal Dimension, tangent of approximated line on the log-log graph.) is a parameter that indicates the ratio of the number of small/large failures. D in the whole investigated area was about 3.3 and varied with geology and vegetation; D was higher in the psammitic schist area than in the pelitic schist area, and was higher in the area of needle-leaf tree woods than in that of broad-leaf tree woods.
3) D and D′ (Fractal Dimension of the contour line in the investigated area) had positive correlation, but D was not influenced by the amount of rainfall that caused the investigated failures.
4) Coefficient α0 (number of failures wider than 1m per 1km2) is a parameter that indicates the slope in stability and was influenced by rainfall, geology, and vegetation.
5) The Fractal properties on slope failure size-number distribution could be used for the prevention of slope disasters, estimation of erosion volume, explanation of variety of failure type.
