Abstract
Weak layer, such as fault or fractured zone has great effects on stability of slope. These effects are divided into two types. One is the weakness of rock masses which consist natural slope or cutting slope, caused by the fault movement, and the another is decrease of slope stability due to forming the slip surface in fault or fractured zone.
As for the former types, one example is explained, which relates to the cutting slope along road, route 41.
As for the latter type, three examples are explained. For shigeto-landslide in Kochi prefecture, ground water ran into the sliding mass along the faults. Slightly weak zone compared to surrounding parts was found after slope failure occurred, and at that time, many field tests were carried out.
Concerning the slope failure which occurred in the fault zone located in the upper part of a cutting slope, stability analysis using finite element method is performed. In this case, distribution of point safety factor in slope, calculated by using computer, is considered in connection with four stages of slope, namely, natural slope, cutting slope for railway, cutting slope first designed for road, cutting slope designed for road with amendment. The change of safety factor by condition of faults by which rock mass forms a sliding wadge is discussed by using vector analysis.
