Effect of Unsaturated Soil Properties on the Intensity-Duration Threshold for Rainfall Triggered Landslides

Year 2019, Volume: 30 Issue: 2, 9009 - 9027, 01.03.2019

Melih Birhan Kenanoğlu Mohammad Ahmadı-adlı Nabi Kartal Toker , Nejan Huvaj

https://doi.org/10.18400/tekderg.414884

Cited By: 2

Abstract

Rainfall triggered landslides are one of the most common
natural hazards in many countries all around the world, as well as in Turkey. This
study investigates the effect of unsaturated soil properties on landslide-triggering
rainfall intensity-duration threshold. In addition to the time to failure, the suction
(negative pore water pressure) distribution in the slope, the shape and depth
of the failure surface are also evaluated. Properties of soil-water
characteristic curve which affect the distribution of suction in the soil in
response to changes in water content are varied in a parametric study. Effects
of air entry value (relates to particle size), de-saturation rate (relates to
uniformity of particle size distribution), saturated volumetric water content
(relates to void ratio) and residual volumetric water content (relates to fines
content and characteristics) are evaluated by determining the intensity-duration
threshold numerically by carrying out infiltration and slope stability
calculations. The variation of unsaturated soil properties is found to
significantly alter the landslide mechanism (ranging from mere surface erosion
to groundwater level rise in response to complete infiltration) and consequent intensity-duration
thresholds for the same slope geometry. Among the parameters considered, air
entry value appears to be the most influential parameter. The effects of the slope
angle and initial moisture condition on threshold rainfall intensity-duration are
also investigated. This study could be useful for creating the basis and
mechanical understanding for future research on early warning systems.

Keywords

rainfall triggered landslide, intensity-duration threshold, soil water characteristic function, suction

Effect of Unsaturated Soil Properties on the Intensity-Duration Threshold for Rainfall Triggered Landslides

Abstract

Rainfall triggered landslides are one of the most common natural hazards in many countries all around the world, as well as in Turkey. This study investigates the effect of unsaturated soil properties on landslide-triggering rainfall intensity-duration threshold. In addition to the time to failure, the suction (negative pore water pressure) distribution in the slope, the shape and depth of the failure surface are also evaluated. Properties of soil-water characteristic curve which affect the distribution of suction in the soil in response to changes in water content are varied in a parametric study. Effects of air entry value (relates to particle size), de-saturation rate (relates to uniformity of particle size distribution), saturated volumetric water content (relates to void ratio) and residual volumetric water content (relates to fines content and characteristics) are evaluated by determining the intensity-duration threshold numerically by carrying out infiltration and slope stability calculations. The variation of unsaturated soil properties is found to significantly alter the landslide mechanism (ranging from mere surface erosion to groundwater level rise in response to complete infiltration) and consequent intensity-duration thresholds for the same slope geometry. Among the parameters considered, air entry value appears to be the most influential parameter. The effects of the slope angle and initial moisture condition on threshold rainfall intensity-duration are also investigated. This study could be useful for creating the basis and mechanical understanding for future research on early warning systems.

Keywords

Unsaturated soil, rainfall triggered landslide, intensity-duration threshold, soil water characteristic curve, suction

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