Failure of infrastructure embankments induced by flooding and seepage: a neglected source of hazard

The risk of failure of transportation embankments due to seepage induced by temporary and occasional impoundments taking place on the upstream side as a consequence of exceptional rainfalls is frequently underestimated. These failure events result from a combination of three main factors, i.e. the flooding event, the hydraulic weakness and the geotechnical weakness of the embankment. Based on the case study of a railway embankment in Southern Italy that collapsed in 2005 due to an upstream impoundment that occurred after few hours of a very intense rainfall, the paper describes a methodological approach aimed at assessing hazard of failure of transportation embankments induced by flooding and seepage. In particular, ccording to hydrological, hydraulic and geotechnical studies performed to define the factors affecting the process of the embankment failure, three subsequent activities are proposed: the historical analysis of flood damages at the watershed scale; and the assessment of the upstream peak impoundment based on hydrological analysis and the embankment stability analysis, these latter to be carried out at the site specific scale. The approach here proposed is planned to be further validated and improved by means of the application to other case studies, characterised by different contexts and embankment structures

Time response of a landslide to meteorological events

International audienceA landslide affecting two small villages located on the Northwestern Italian Apennines has been investigated since the year 2000 through the use of different equipment. A complex monitoring system has been installed in the area. The system includes several inclinometers, piezometers and a raingauge. An Automatic Inclinometric System (AIS) has been also installed that automatically performs measurements, twice a day, along the entire length of a pipe that is 45 m deep. This monitoring system has been set up to identify a methodology that allowed to deal with landslides, trying to predict their behaviour beforehand for warning purposes. Previous researches carried out in the same area for a period of about 7 months, in the year 2000, have allowed to identify a correlation between deep slope movements and rainfalls. In particular, it has been possible to determine the time lag needed for a rainfall peak to produce a corresponding peak of the landslide movements; this time lag was of 9 days. This result was possible because the AIS allows to obtain, as mentioned, daily inclinometric measurements that can be correlated with the recorded rainfalls. In the present report we have extended the analysis of the correlation between deep slope movements and rainfalls to a greater period of observation (2 years) to verify over this period the consistency of the time lag mentioned above. The time lag previously found has been confirmed. We have also examined the possibility to extend to the entire landslide body the correlation that has been found locally, analyzing the results of the remaining inclinometric tubes with traditional reading installed on the landslide and comparing them with the results of the AIS. The output of the tubes equipped with piezometric cells has also been analyzed. The relations existing among rainfalls, ground water level oscillations and the related slope movements have been explore

Preliminary 3-D finite element analysis of the triggering mechanism of an occasional reactivation of a large landslide in stiff clays

In December 2013 a large landslide occurred along a clay slope located at the south-western outskirts of the Montescaglioso village (Basilicata, Southern Italy) as a consequence of intense and prolonged rainfalls that presumably caused a significant increment of the pore water pressures in the slope. The slope is formed of stiff clays belonging to the formation of the Subappennine Blue Clays, which are over-consolidated and characterized by medium plasticity. According to aerial photos dating back to 1950s, the slope was already affected by previous landslide processes, so that the examined landslide process can be classified as an occasional reactivation according to the well-known classification of Cruden & Varnes (1996). Also, during the last decades several man-made actions in the area resulted in strong changes in the original water surface network that could have played some role in the slope reactivation. Based on displacement data, obtained from a monitoring system installed few days after the phenomenon, and still in function, at present the landslide does not show relevant signs of activity. Preliminary 2-D and 3-D finite element analyses have been carried out to investigate the factors that controlled the mechanism of reactivation of the landslide. The numerical model has been setup based on the available topographical, geological and geomorphological information, the geotechnical properties of the involved soils and the information concerning the piezometric regime in the slope. The results indicate that the mobilized shear strength of the clays ranges between the typical post-peak and residual values for this type of material and confirmed that the strong increment of the pore water pressures in the slope induced by the exceptional rainfalls occurred in the previous days can be identified as the main triggering factor of the reactivation

Anthropogenic sinkholes in the Marsala area (western Sicily) linked to underground quarries

Marsala territory (western Sicily) is characterized by the presence of a Lower Pleistocene (Calabrian) calcarenite succession (Marsala Calcarenite Fm). It can be divided into three lithofacies that show the regressive evolution of the depositional system: a) coarse to fine yellow bio- and lithoclastic calcarenites, b) sands, and c) gray sandy clays. At least 80 m-thick, this succession gently dips (5-10) towards the south and the south-west. At some locations the Marsala Calcarenite is covered by Middle and Upper Pleistocene marine terraced deposits. Since the Roman period, due to the great abundance of calcarenite rocks, and to the facility of extraction, the Marsala area has been characterized by a high number of quarries for the extraction of this building materials. Many of them were excavated underground, at depth varying from a few meters to about 25 m, and are arranged in one or two levels, following the galleries and pillars excavation technique. With time, the underground quarries have been progressively abandoned for the decay of the physical and mechanical properties of the calcarenite rock mass, the interaction with the groundwater, the high costs of extraction, and the dangers and difficulties encountered in working underground. Since the 1960’s the quarries have been affected by instability processes, visible through collapses and deformations of vaults and pillars. These phenomena often propagate upward reaching the topographic surface and forming sinkholes which affect and severely damage the built-up area. In particular, two case studies of sinkholes related to different underground quarries will be analyzed in this paper. The aim is to provide a description of the most significant processes and factors responsible of the instability processes based on field surveys, as well as to understand the generation mechanisms of these anthropogenic sinkholes by means of numerical modeling, based on rock laboratory testing data, that represents in these cases a remarkable tool for the investigation of the cause-effect relationships, as already performed in other areas of Italy

Three-dimensional modelling of artificial caves for geomechanical analysis

Accurate cave surveying is crucial for understanding their genesis, current state, and potential hazards, especially in challenging environments marked by limited accessibility and poor visibility. This study applies geomatics techniques, including Terrestrial Laser Scanning (TLS), SLAM-based Mobile Mapping Systems (MMS), and digital photogrammetry, to create three-dimensional models of artificial caves in Gravina in Puglia, Apulia region, southern Italy. The research aims to assess these methodologies' accuracy, reliability, and performance for structural monitoring and hazard assessment. Despite challenges such as rough conditions, limited accessibility and poor visibility, the study reveals promising insights into the capabilities of these techniques for efficient surveying in complex underground environments. While highlighting the potential of MMS for cost-effective and rapid data acquisition, digital photogrammetry using spherical cameras also emerges as a viable alternative, offering comprehensive data collection capabilities with minimal capture time. Further research is warranted to optimize these techniques for enhanced hazard assessment and structural monitoring in challenging underground environments