抄録
A quasi three dimensional model of slope stability is presented in this paper. The author treats three dimensional topographic features as solids of revolution, in which material distribution of slope is satisfied with symmetry to axis of rotation. As axisymmetric coordinates are introduced to a two dimensional (2-D) numerical model combined with both a transient finite element model of saturated and unsaturated seepage and a simplified method of Bishop's slope stability analysis, a quasi three dimensional (3-D) numerical model of rain-induced landslide is developed. Two numerical analyses of the three dimensional characteristics of slope feature under a constant 30mm/h rainfall on slopes with convergent and divergent horizontal cross sectional forms, but same longitudinal form, are compared with 2-D analyses. In consequence, the ratios of cumulative rainfall (R/Rst) at the time of landslide initiation for the 3-D model (R) compared to 2-D slope analysis (Rst) for convergent and divergent slopes are 0. 610 and 1. 112 respectively. Effects of the 3-D model can be strongly seen on the convergent slope, where an estimated unstable mass is located closer to the symmetric axis when compared to the divergent slope. A comparison between 2-D and quasi 3-D slope stability analyses on convergent and divergent slopes indicates that safety factors for the 3-D analysis exceed the 2-D result on the divergent slope, but are less on the convergent slope. It is concluded that a 3-D analysis is essential on convergent slope, because it provides more hazardous safety factor than 2-D analysis.
