The Impact of Probability Density Functions Assessment on Model Performance for Slope Stability Analysis

Abstract

The development of forecasting models for the evaluation of potential slope instability after rainfall events represents an important issue for the scientific community. This topic has received considerable impetus due to the climate change effect on territories, as several studies demonstrate that an increase in global warming can significantly influence the landslide activity and stability conditions of natural and artificial slopes. A consolidated approach in evaluating rainfall-induced landslide hazard is based on the integration of rainfall forecasts and physically based (PB) predictive models through deterministic laws. However, considering the complex nature of the processes and the high variability of the random quantities involved, probabilistic approaches are recommended in order to obtain reliable predictions. A crucial aspect of the stochastic approach is represented by the definition of appropriate probability density functions (pdfs) to model the uncertainty of the input variables as this may have an important effect on the evaluation of the probability of failure (PoF). The role of the pdf definition on reliability analysis is discussed through a comparison of PoF maps generated using Monte Carlo (MC) simulations performed over a study area located in the Umbria region of central Italy. The study revealed that the use of uniform pdfs for the random input variables, often considered when a detailed geotechnical characterization for the soil is not available, could be inappropriate.

Expected Changes in Rainfall-Induced Landslide Activity in an Italian Archaeological Area

“…The physically based probabilistic model is constructed by coupling a simple hydraulic model for the analysis of the pore pressure evolution during rainfall, and a mechanical model for slope stability evolution due to pore pressure changes [27,47].…”

“…The probabilistic model, implemented in order to assess the impact of the pdf definition on the evaluation of the probability of failure (PoF), represents a probabilistic version [27] of the original TRIGRS code [48]. The probabilistic approach is able to work through the discretization of the study area on a regular grid, coupling a hydraulic model for the evolution of pore water pressure in time and a mechanical model for the assessment of the temporal slope stability conditions.…”

“…High confidence levels are required to ensure a good accuracy of the results. More details about the methodology are included in the works [25,27].…”

“…A probabilistic version [24,25] of the transient rainfall infiltration and grid-based slope-stability analysis code (TRIGRS) [26] was used. This version of the code has already been applied in an area located in the Umbria region [27]. The choice to adopt a probabilistic approach with a stochastic evaluation of the stability of the area was due to the impossibility to perform a wide geotechnical investigation campaign in the area (due to the presence of archaeological assets) and to the spatial variability of the mechanical characteristics of the soil.…”

A Heuristic Method to Evaluate the Effect of Soil Tillage on Slope Stability: A Pilot Case in Central Italy

“…Probabilistic approaches can provide a high level of reliability when a detailed description of the study area is available in terms of slope topography and physical, mechanical, and hydraulic soil properties. For landslide prediction, probabilistic approaches, which assume input data as random variables defined through their probability density functions, are more suitable than deterministic approaches, which assume the input data without uncertainty [47].…”