Examination of influences of rainfall patterns on shallow landslides due to dissipation of matric suction

Abstract

The influences of rainfall patterns on shallow landslides due to the dissipation of matric suction are examined in this study. Four representative rainfall patterns including the uniform, advanced, intermediated, and delayed rainfalls are adopted. The results show that not only the occurrence of shallow landslides but also the failure depth and the time of failure are affected by the rainfall pattern. The different rainfall patterns seem to have the same minimum landslide-triggering rainfall amount. There is a rainfall duration threshold for landslide occurrence for a rainfall event with larger than the minimum landslide-triggering rainfall amount. For each rainfall pattern, the rainfall duration threshold for landslide occurrence decreases to constant with the increase of rainfall amount. The uniform rainfall has the least rainfall duration threshold for landslide occurrence, followed by the advanced rainfall, and then the intermediated rainfall. For each rainfall pattern, the failure depths and the times of failure from the same amount of rainfall with different durations could be largely different. In addition, the differences of the failure depths and the times of failure between various rainfall patterns with the same amount and duration of rainfall could be also significant. The failure depth and the time of failure, as compared with the occurrence of shallow landslides, are more sensitive to the rainfall condition. In other words, in comparison with the evaluation of the occurrence of shallow landslides, it needs more accurate rainfall prediction to achieve reliable estimations of the failure depth and the time of failure.

Probabilistic modeling of rainfall-induced shallow landslide using a point-estimate method

“…Infinite slope stability analysis, which is commonly used to evaluate shallow landslides because of simplicity and practicability (Montgomery and Dietrich 1994;Wu and Sidle 1995;Borga et al 1998;Iverson 2000;Morrissey et al 2001;Crosta and Frattini 2003;Collins and Znidarcic 2004;Tsai and Chen 2010;Tsai and Wang 2011), is suitable for evaluating landsides with depths that are smaller than the length and width of the landslide. This assumption is compatible with that used to perform hydrological modeling.…”

Threshold of Slope Instability Induced by Rainfall and Lateral Flow

“…The region above the upper bound in Figure 14 reveals that the slope remained stable because the outflow from the boundary and the pressure head decreased. Each rainfall threshold curve indicates a minimum rainfall duration and rainfall amount, different from the one-dimensional modeling results provided by [12]. Moreover, the results of [12] indicated the same minimum rainfall amount regardless of the rainfall duration or pattern, whereas the threshold curve in the one-dimensional model provides no upper bound.…”

“…Each rainfall threshold curve indicates a minimum rainfall duration and rainfall amount, different from the one-dimensional modeling results provided by [12]. Moreover, the results of [12] indicated the same minimum rainfall amount regardless of the rainfall duration or pattern, whereas the threshold curve in the one-dimensional model provides no upper bound. Slopes in which the duration is greater than the lower bound always slid, because FS < 1; in other words, one-dimensional modeling does not account for the dissipation of pore water pressure caused by the effect of outflow on the boundary.…”

“…When using Equation (12) together with the shear strength of unsaturated soil given by Equation (7), and assuming that the pore air pressure is atmospheric, the FS in Equation (15) can be expressed as…”

The study of the factors controlling rainfall-induced landslides at a failure-prone catchment area in Enugu, Southeastern Nigeria using remote sensing data

“…Consequently, matric suction and the stability of the slope decrease. The soil saturation leads to a reduction of the shear strength of the soil because of a rise in pore water pressure and the loss of the soil apparent cohesion (Fukuoka 1980;Gostelow 1991;Tsai and Chen 2010;Tsai and Wang 2011). These landslides have consistently occurred in the study area during intense, short duration rainfalls concentrated at the beginning of rainy season (Igwe and Fukuoka 2010).…”