6.4 Stability of clay slope

Slope failure tests were conducted at Osaka City University. Clay slope models were cut out from pre-consolidated alluvial clay deposit in Osaka Bay. The slope was 1 : 0.5 for all models, but the height ranges from 1 cm to 18 cm. Higher slope models of 18 cm, 12 cm, 7 cm, 5 cm and 4 cm were tested, using a centrifuge with nominal radius of 2.56 m, while lower slopes of 4 cm, 3 cm, 2 cm and 1 cm were tested by a 0.25 m-radius small centrifuge. Failure was caused by increasing centrifugal acceleration quickly so as to achieve undrained condition. In the cases of larger slopes, circular slip failures were observed as shown in Photo 1, whereas the shear zone was obscured for smaller slopes. This is because the width of shear bands are constant regardless of the model height. In Figure 1, heights at failure in prototype scale H_p are plotted to the model height H_m. Although H_p for the lower slope models were a bit smaller than those for the higher ones, H_p were almost same for various H_m. This shows the validity of similitude under undrained condition.

Takada, N. and Kusakabe, O. (1987) : Centrifuge model tests, 3. Principle, Tsuchi-to-kiso, Vol. 35, No. 12, pp. 89-94, (in Japanese).