安定解析のc'ーφ'図に及ぼす地すべりの断面形状と土質強度の影響

摘要

地すべりの二次元安定解析においては，通常，安全率Fsを仮定してc'－tanφ'図を得る。一方，すべり形態を直接的に支配する最も重要な影響因子として，すべり面土の土質強度特性が挙げられる。土質強度定数を組み合わせたc'- φ'　図に及ぼす地すべりの断面形状と土質強度特性の影響を明らかにすることは重要であり，実務におけるc'-φ'　図の作成とその合理性確認の参考資料となる。%In this study, the c'- φ'diagram has been drawn up based on the stability analysis method, in which the residual factor is incorporated, concerning three landslides among which there are considerable variations in the cross section dimensions and soil strength. The characteristics of the c'- φ' diagram was extracted with an emphasis on the geometric elements and soil strength of the three landslides. Furthermore, the relationship between the c'- φ'diagram, the geometric elements of landslides and soil strength was clarified by means of various model landslides, which will be helpful in the creation and confirmation of the rationality of using the c'- φ' diagram in practice. Conclusions are drawn as follows :In the three landslides, the characteristics of the geometric elements and soil strength are reflected in the c'- φ' diagram having characteristic forms. The position of IP is decided by the movement of c'-tan φ' line controlled by the numerical value of Fs. The Influence of soil strength on the c'- φ'diagrams with the variation of groundwater level became obvious, and is reflected in the c'- φ' diagrams. The influence of length "L" is very minimal. Maximum thickness "D" has an effect on c' -intercept and inclination "β" of c'-tan φ' line, but has little impact on tan φ'-intercept whereas slope "α" has a significant impact on c' and tan φ , but does not seem to have any effect on β. Influence of groundwater level appears as a large rightward shift of tan φ' . The soil strength at slip surface govern the cross section dimensions of landslide and has an influence on the c' - tan φ' diagram.