Slope failure susceptibility due to fractures: an approach based on morpho-structural lineaments and brittle structural analysis

Abstract

This paper addresses the evaluation of slope failure susceptibility caused by fractures using morphostructural lineaments and brittle structural analysis. The study comprises the SP-98 and SP-55 highways in the northern coastal region of São Paulo State, which are highly susceptible to failures due to rugged topography and high rainfall rates. The main objective was to analyze how rock mass discontinuities affect slope stability along these highways based on macro-scale studies. The methodology correlates fracture data with morphostructural lineaments. We used various data sources, including Digital Elevation Models (DEMs), isobase maps, fracture data obtained from the literature, and field surveys. The analysis was performed within a Geographic Information System (GIS) environment, incorporating the strike and dip of discontinuities, which were assessed on a regional scale rather than locally. Slope failure analysis was based on the relationship between the geometry of discontinuities, and the road cut slopes represented by the highway alignment, evaluating planar, wedge, and toppling failures. The susceptibility maps showed high accuracy, with the best results achieved at a spatial resolution of 750 m, reaching 82,9% accuracy for SP-98 and 92,2% for SP-55. The study concludes that combining morphostructural lineaments and brittle tectonic data is a valuable way to evaluate slope failures and classify rock masses and soil formed by in-situ weathering that preserve preexisting discontinuities. Although the significance of discontinuities is recognized, their role is often underrepresented in most studies of this kind. This paper contributes to understanding relevant processes in susceptibility analysis for landslides.