Failure Mechanism of Granular Soil Slopes under High Intensity Rainfalls

This study uses laboratory experiment to clarify the failure mechanism of granular soil slopes when subjected to high rainfall intensity. A rainfall simulator was employed to perform tests on slopes with convex and concave profiles; the slopes were non-homogeneous and had a dip stratum underneath. In addition, different fines contents (0 ~ 12%) and rainfall intensities (78 and 287 mm/hr) were considered as variables. During the experiment, the variations in pore water pressure and volumetric water content in the soil were measured. The characteristics of the failure mechanism and the responses of pore water pressure and water content in the model slopes are compared and discussed as functions of the variables. For samples with fines content of 12%, failure was more likely initiated by surface erosion. In contrast, for samples with fines content less than 10%, slope failures were initiated near the toe, where the soil was highly saturated. The profiles of total head above the impervious stratum were generally nonlinear and the pressure head near the toe of the slope could be even higher than the equivalent head of overburden pressure. Moreover, the initial failure in concave slopes occurred sooner than that in convex slopes; it was attributed to the thin soil layer near the toe of the slope, so that a high hydraulic gradient was induced to cause piping to be initiated. With regard to rainfall intensity (78 versus 287 mm/hr), less time to failure and longer failure surface were observed in the higher intensity condition; however, the length of failure surface and the runout distance were about the same irrespective of slope profiles.

並列關鍵字

Model test ； slope ； granular soil ； failure ； rainfalls

國際替代計量

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