An implementation of rock engineering system for ranking the instability potential of natural slopes in Greek territory. An application in Karditsa County

Abstract

This paper presents an application of rock engineering system (RES) in an attempt to reveal and assess the inherent instability potential of 388 sites where equivalent landslides have been manifested and recorded in the region of Karditsa County, Greece. The main objective has been defining the principal causative and triggering factors responsible for the manifestation of landslide phenomena, quantify their interactions, obtain their weighted coefficients, and calculate the instability index, which refers to the inherent potential instability of each natural slope of the examined region. From the statistical interpretation of the data reported in a well-documented database and concerning the examined failure sites, a clear correlation between the instability index and the area affected by a single landslide event has been revealed. Almost the entire failure sites, 98% of the examined slope sites, exhibit an instability index value over 55, a value which is thought to be a critical threshold for landslide manifestation concerning natural slopes in Karditsa County. It is argued that the presented RES methodology, engaging the selected set of parameters, could be considered as an effective expert's tool for ranking, in an objectively optimal and simple way, the instability potential of natural slopes in Karditsa County, and thus providing a tool for sound zoning landslide hazard.

Engineering-geological conditions of the formations in the Western Thessaly basin, Greece

“…Consequently, serious social, economic and technical problems arise, whichaffect the technical projects (transportation network, extensive engineering works, etc) with immediate impacts on urban development. These phenomena mainly concern zones of older activation due to geological factors, but also recent ones due to anthropogenic activity and incidents of peak precipitation [21,[23][24][25].…”

“…The interplay between the database system and Geographical Information System was established with the defined coordinates of the locations of existing landslide occurrences. After modifications, 979 landslide occurrences, which occurred between 1952 and 2012, were recorded and digitally stored [21,25,33,34,[45][46][47][48][49]. The spatial distribution of the recorded occurrences and the evaluation of the processed data led to the compilation of a landslide inventory map of Western Thessaly basin (Figure 4).…”

“…Rock formations that surround the basin are distributed between four geotectonic zones of the Alpine bedrock [25,[30][31][32][33][34][35][36]. The Pelagonian zone units consist of gneisses, crystalline schists, phylites, crystalline limestones, marbles and dolomites.…”

“…Post-Alpine formations that also contribute to the geological structure of the basin are: (a) Molassic formations of the Mesohellenic trench (sands, clays, marls, sandstones and conglomerates), (b) Neogene sediments (clays, silts, marls, sands, sandstones, conglomerates, breccias, grits and marly limestones) and (c) Quaternary deposits (alluvial and fluvial deposits, fluvial terraces, screes and talus cones) [25,33]. The major part of the Western Thessaly basin is comprised mainly of formations of Quaternary age (2,570.62 km 2 , or 42.19%).…”

“…In Western Thessaly basin, landslides occur very frequently. These natural catastrophic phenomena affect urban and cultivated areas, as well as technical infrastructure, various forms of transportation infrastructure, civil engineering work, etc., with disastrous socioeconomic implications [25].…”