四国における岩盤斜面安定解析の一試みと地質学的考察

抄録

The purpose of this study is to try an analysis for rock slope stability which is not well established and consider geological meanings of the results of analysis. The data of reck slope failures of road cuts in Shikoku are used for the investigation. Three thpes are distinquished as rock slope failures and roke slope stability is studied restrictedly based on the failure of " type 2" by the author's definition which is considered to reflect rock slope strength. He improves a kind of statistical slope stability analysis proposed by MURAKAMI and MIYAUCHI (1967), and an apparent shear strength and a critical slope height of weathered sedimentary and metamorphic rocks (ranging Paleozoic to Mesozoic in Shikoku) slope, are estimated respectively applying soil mechanics technique. The significance of estimation are confirmed comparing the results with the actual conditions of corresponding stable rock slopes and slope protection methods in Shikoku. As the case study to find geological meanings of slope stability analysis, Cretaseous Izumi Group which shows rather simple geological structures is minutely investigated the relation between the results of analysis and geological condition of rock slopes covering wide areas. Estimated shear strength of rock slopes seems to represent local characteristics of geological structure and sedimentary conditions and is affected considerably by the degree of crushing for Izumi Group caused by the Median tectonic line. Preliminary research for other Paleozonic and Mesozoic rock slope stability also indicates that these rock slope are effected by the inherent geologic developments characterized zonal strutures of Shikoku. Thus, engineering geology may contribute to study of geologic history, especialy to tectonic movements in this case.