Geotechnical Hazards in Rocky Slopes (Northern Portugal): Focused on Methodology

Abstract

Interdisciplinary studies of rocky slopes stability have been performed on Northern Portugal, that allowed to establish a design methodology. This approach carries together the use of more traditional techniques, with the application of more recent technologies, such as unmanned aerial vehicles. This work presents a set of procedures that have been applied successfully in several case studies, describing the different stages, with an emphasis on the production of a ground threedimensional model. This model is generated from photographs obtained with successive drone flights, with overlapping. It is the support for the development of subsequent stages, especially for the characterisation of the trajectories of rockfalls and modelling, the development of susceptibility mapping and of rock slope hazard. In this context, the Natural Slope Quality Index (N-SQI ), an adaptation of the Slope Quality Index (SQI), orientated to natural slopes, is presented. The Block Gravity Number (BGN), created in order to hierarchise rock blocks, selecting them for modelling, is also proposed.

Risk assessment on landslides focused on the role of the water: examples from model regions (Rio de Janeiro State and Hong Kong)

“…Natural or built slopes are defined as sloping surfaces on rock masses, earthy or mixed masses, originated from geological, geomorphological processes and anthropic actions. The slope design involves the collection of geological and geotechnical information, the evaluation of the strength properties of the formations and discontinuities, and of the presence of water with emphasis on the pluviometry regime (e.g., [2,9,17,33,54,70,74,76,81,92,96].…”

“…The hydrologic response of a slope to rainfall depends on a great number of factors, on both local and catchment basin scales [54]. In fact, the percolation of water into the discontinuities induces a pressure increase on the adjacent rock surfaces and promotes the decrease of the shear strength of these surfaces [41,92]. The hydrologic response of a slope to rainfall is a complex phenomenon.…”