The Povoação County, located in São Miguel Island (Azores), is an area that throughout the history has been frequently affected by important landslide events, which caused tens of deaths and damages that ascended to tens of millions of Euros. The Furnas-Ribeira Quente road, located in Povoação County, chosen as study area to this project, is the only terrestrial way to Ribeira Quente village. This road is flanked by huge steep slopes, sometimes with more than 400 m high, composed by volcanic materials of crumbly nature, in which numerous landslides occurred, triggered mainly by heavy rainfall episodes, causing risk to humans, cars and houses, and blocking sometimes the road, obstructing the access by land to the village. This fact has important consequences in what concerns rescuing procedures in emergency situations.
The slope stability quantitative assessment it is only possible having very rigorous and detailed knowledge of the geotechnical properties of the materials, which compose the slopes. Through laboratorial and in-situ tests, using specific equipments, it is possible to calculate the values of different parameters of the materials, namely the cohesion and the internal friction angle. In this way, it will be possible to simulate the answer of the soils to different types of triggering factors, like heavy rainfall episodes and earthquakes.
The specificity of the physical parameters that characterize recent volcanic soils, and the tiny geographical area that they occupy in the world, as well as their variability from area to area, justify the few available scientific works that exist in the literature, and also the impossibility of their extrapolation for other areas to carry out landslide hazard assessment. In this way, the knowledge of the geotechnical soil properties that this project intends to focus is a crucial step for landslide hazard evaluation. For a slope in a certain geomorphologic and hydrologic context, it can be determined which are the most favorable scenarios for landsliding activity, allowing the development of slope stability numerical models, crucial for landslide forecast and risk mitigation.
This project represents a significant contribution not only for volcanic soils geotechnical knowledge but also to identify which are the favorable conditions for triggering landslides, through the creation and adaptation of numerical models. The results will contribute for landslide hazard assessment and risk mitigation in the Azores, making possible to improve land-use policies and emergency planning.