Probabilistic study of rainfall-triggered instabilities in randomly heterogeneous unsaturated finite slopes

Le, T. M. H., Sanchez, M., Gallipoli, D. and Wheeler, S. (2019) Probabilistic study of rainfall-triggered instabilities in randomly heterogeneous unsaturated finite slopes. Transport in Porous Media, 126(1), pp. 199-222. (doi: 10.1007/s11242-018-1140-0)

Abstract

Water infiltration destabilises unsaturated soil slopes by reducing matric suction, which produces a decrease of material cohesion. If the porosity of the soil is spatially heterogeneous, a degree of uncertainty is added to the problem as water tends to follow preferential paths and produces an irregular spatial distribution of suction. This study employs the finite element method together with Monte Carlo simulations to quantify the effect of random porosity on the uncertainty of both the factor of safety and failure size of an unsaturated finite slope during and after a rainfall event. The random porosity is modelled using a univariate random field. Results show that, under partially saturated conditions, the random heterogeneity leads to a complex statistical variation of both factor of safety and failure size during the rainfall event. At any given time, the uncertainty about failure size is directly linked to the uncertainty about the position of the wetting front generated by infiltration. Interestingly, the statistical mean of the failed area is smallest when the mean of the factor of safety is lowest. In other words, the slope becomes more likely to fail, but the size of the failure mass tends to be limited. The study also investigates the sensitivity of failure uncertainty to external hydraulic parameters (i.e. initial water table depth, rainfall intensity) and internal soil parameters (i.e. permeability and water retention characteristics). In general, the sensitivity increases when the effect of these parameters on the spatial variation of suction is stronger.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gallipoli, Dr Domenico and Wheeler, Professor Simon
• Authors: Le, T. M. H., Sanchez, M., Gallipoli, D., and Wheeler, S.
• College/School: College of Science and Engineering > School of Engineering; College of Science and Engineering > School of Engineering > Infrastructure and Environment
• Journal Name: Transport in Porous Media
• Publisher: Springer
• ISSN: 0169-3913
• ISSN (Online): 1573-1634
• Published Online: 07 September 2018
• Copyright Holders: Copyright © 2018 Springer Nature B.V.
• First Published: First published in Transport in Porous Media 126(1): 199-222
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher