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

Book Review of "The Story of Vaiont Told by the Geologist Who Discovered the Landslide"

THE STORY OF VAIONT TOLD BY THE GEOLOGIST WHO DISCOVERED THE LANDSLIDE, BY: E. SEMENDA, K-FLASH PUBLISHER, FERRARA, 205 PAGES, PRICE: 28.00 C, ISBN 978-88-89288-02-3 On 9 October 1963, at 10:39 p.m. local time, between 240 and 300 million cubic meters of sedimentary rocks detached from Mount Toc, in Veneto, northern Italy, and slid into the Vajont Lake. The falling rock mass acted like a huge piston, pushing the water of the lake against Casso and Erto, two small villages on the slope in front of the slope that failed, and then over an artificial dam 210m high. A large wave overtopped the dam and reached the town of Longarone at 10:46 p.m., destroying it. The dam did not fail and was only marginally damaged. However, the landslide and the resulting flash flood killed at least 1921 people: seven at San Martino, at least 151 at Frasegn, le Spesse, Cristo, Pineda, Ceva, Prada, Marzana, 54 at a construction camp near the dam, 109 in the town of Castellavazzo, and at least 1759 between the town of Longarone and the area downstream along the Piave River valley. News about the disaster went around the world; the Herald Tribune titled: "Vajont Dam: Warning Ignored". Before the catastrophic event, landslides had been identified in the Vajont valley by prominent investigators, but none had anticipated the size and potential dynamics of this event. This book is the story of the famous Vajont landslide, from the perspective of the geologist who was first to discover the landslide and who, following the disaster, spent most of his career to investigate one of the most significant landslide disasters ever experienced. The son of Carlo Semenza, the engineer who designed and built the Vajont dam, Edoardo Semenza, was the geologist who discovered the Va

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

ANALISI TEORICHE E PROVE SPERIMENTALI DI UN SISTEMA DIMONITORAGGIO DI FRANE CON EMISSIONE ACUSTICA

Viene illustrato un esperimento per valutare la fattibilità di un sistema di monitoraggio di frane in roccia tramite il rilevamento di emissioni acustiche e la individuazione della localizzazione spaziale delle sorgenti di emissione

ANALISI TEORICHE E PROVE SPERIMENTALI DI UN SISTEMA DIMONITORAGGIO DI FRANE CON EMISSIONE ACUSTICA

Viene illustrato un esperimento per valutare la fattibilità di un sistema di monitoraggio di frane in roccia tramite il rilevamento di emissioni acustiche e la individuazione della localizzazione spaziale delle sorgenti di emissione