Journal of Natural Disaster Science

FAILURE OF GRANITE SLOPES IN CHUGOKU DISTRICT UNDER HEAVY RAIN : SHEARING STRENGTH AT FAILURE*

Hisao ABOSHI
Professor, Department of Civil Engineering, University of Hiroshima, Hiroshima

(Received 18 November, 1979 and in revised form 30 December, 1979)

Abstract

Characteristics of slope failures of decomposed granite in heavy rain in the Chugoku Distrct, Japan, are analysed, utilizing the experience of many disasters. One of the worst disasters which occurred in the city of Kure near Hiroshima in 1967, is investigated in detail. It is concluded that a representative value of the strength of decomposed granite at failure is 33 degree with internal friction angle and 0.2-0.5 ton force per square meters with cohesion, which is obtained after stability calculations for several hundred cases in the above-mentioned disasters. The critical depth of decomposed soil for given slope angle is proposed, and a curve for the critical rainfall which causes slope disasters is presented.

Key words

decomposed granite, slope failure, disaster under heavy rain, shearing strength