2,365 research outputs found
Influenza della cementazione sulla compressibilità di depositi pelitici lacustri pliocenici dell'Italia centrale
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Remote monitoring of deformation using Satellite SAR interferometry
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Revisiting the February 6th 1783 Scilla (Calabria, Italy) landslide and tsunami by numerical simulation
No full textOn February 6th, 1783, a landslide of about 5 x 10(6) m(3) triggered by a 5.8 M earthquake occurred near the village of Scilla (Southern Calabria, Italy). The rock mass fell into the sea as a rock avalanche, producing a tsunami with a run-up as high as 16 m. The tsunami killed about 1,500 people, making it one of the most catastrophic tsunamis in Italian history. A combined landslide-tsunami simulation is proposed in this paper. It is based on an already performed reconstruction of the landslide, derived from subaerial and submarine investigation by means of geomorphological, geological and geomechanical surveys. The DAN3D model is used to simulate the landslide propagation both in the subaerial and in the submerged parts of the slope, while a simple linear shallow water model is applied for both tsunami generation and propagation. A satisfying back-analysis of the landslide propagation has been achieved in terms of run-out, areal distribution and thickness of the final deposit. Moreover, landslide velocities comparable to similar events reported in the literature are achieved. Output data from numerical simulation of the landslide are used as input parameters for tsunami modelling. It is worth noting that locations affected by recordable waves according to the simulation correspond to those ones recorded by historical documents. With regard to run-up heights a good agreement is achieved at some locations (Messina, Catona, Punta del Faro) between computed and real values, while in other places modelled heights are overestimated. The discrepancies, which were most significant at locations characterized by a very low slope gradient in the vicinity of the landslide, were probably caused by effects such as wave breaking, for which the adopted tsunami model does not account, as well as by uncertainties in the historical data
An equivalent fluid/equivalent medium approach for the numerical simulation of coastal landslides propagation: theory and case studies
No full textCoastal and subaqueous landslides can be very dangerous phenomena since they are characterised by the additional risk of induced tsunamis, unlike their completely-subaerial counterparts. Numerical modelling of landslides propagation is a key step in forecasting the consequences of landslides. In this paper, a novel approach named Equivalent Fluid/Equivalent Medium (EFEM) has been developed. It adapts common numerical models and software that were originally designed for subaerial landslides in order to simulate the propagation of combined subaerial-subaqueous and completely-subaqueous landslides. Drag and buoyancy forces, the loss of energy at the landslide-water impact and peculiar mechanisms like hydroplaning can be suitably simulated by this approach; furthermore, the change in properties of the landslide's mass, which is encountered at the transition from the subaerial to the submerged environment, can be taken into account. The approach has been tested by modelling two documented coastal landslides (a debris flow and a rock slide at Lake Albano) using the DAN-W code. The results, which were achieved from the back-analyses, demonstrate the efficacy of the approach to simulate the propagation of different types of coastal landslides
Evaluation of landslide reactivation: a modified rainfall threshold model based on historical records of rainfall and landslides
No full textThis study proposes a modification of the conventional threshold model for assessing the probability of rainfall-induced landslide reactivation. The modification is based on the consideration that exceedance of a pre-determined rainfall threshold is a necessary but not sufficient condition to reactivate a landslide. The proposed method calculates the probability of reactivation as a function of the probability of exceedance of a pre-determined rainfall threshold, as well as the probability of occurrence of a landslide after such exceedance. The data for the calculation were obtained from historical records of landslides and rainfall.
The method was applied to two complex landslides (“San Donato” and “La Salsa”) involving fine-grained debris in the southern section of the Apennine foredeep. The minimumrainfall threshold triggering landslide reactivation on the two slopes was determined by examining rainfall patterns during the 180 days preceding the slide events. For the San Donato and La Salsa landslides, the minimum triggering threshold consists of rainfall events lasting 15 days,with cumulated rainfall exceeding 150 and 180mm, respectively. Based on hydrological and statistical analyses, the annual probabilities of exceeding the thresholds were estimated to be 0.38 and 0.25, respectively. During the period from 1950 to 1987, the minimum threshold was exceeded 14 times, and four reactivations occurred at San Donato; whereas, the threshold was exceeded 10 times and three reactivations occurred at La Salsa. Hence, the probabilities of landsliding after exceedance of theminimumrainfall threshold are 4/14 and 3/10, respectively. Finally, annual reactivation probabilitieswere calculated to be 0.11 and 0.08, respectively. The reliability of the minimumrainfall threshold was tested by: i) simulating variations in the stress–strain behavior of the slopes as a result of fluctuations in the water table from normal to extreme values; and ii) analyzing the results of continuous multi-year monitoring of pore pressure and rainfall variations on a slope composed of dominantly fine-grained debris
New insights into the temporal prediction of landslides by a terrestrial SAR interferometry monitoring case study
No full textTen small rock slides (with a volume ranging from 101 to 103 m3) on a slope affected by working activities were detected, located, and timed using pictures collected by an automatic camera during 40 months of continuous monitoring with terrestrial SAR interferometry (TInSAR). These landslides were analyzed in detail by examining their pre-failure time series of displacement inferred from high-sampling frequency (approximately 5 min) TInSAR monitoring. In most of these cases, a typical creep behavior was observed with the displacement starting 370 to 12 h before the collapse. Additionally, an evident acceleration decrease of the displacement a few hours before the failure was observed in some rock/debris slides, thus suggesting the possibility of a mechanical feature of the slope that differs from the classical creep theory. The efficacy of the linear Fukuzono approach for the prediction of time of failure was tested by back-analyzing the ten landslides. Furthermore, a modified Fukuzono approach named average data Fukuzono (ADF) was implemented and applied to our dataset. Such an approach is able to improve forecasting effectiveness by reducing the error due to anomalies in the time series of displacement, like the acceleration decrease before failure. A prediction with a temporal accuracy of at least 2 h was obtained for all the analyzed rock/debris slides. © 2014 The Author(s)
Digital image correlation (DIC) analysis of the 3 December 2013 Montescaglioso landslide (Basilicata, Southern Italy). Results from a multi-dataset investigation
No full textImage correlation remote sensing monitoring techniques are becoming key tools for
providing effective qualitative and quantitative information suitable for natural hazard assessments,
specifically for landslide investigation and monitoring. In recent years, these techniques have
been successfully integrated and shown to be complementary and competitive with more standard
remote sensing techniques, such as satellite or terrestrial Synthetic Aperture Radar interferometry.
The objective of this article is to apply the proposed in-depth calibration and validation analysis,
referred to as the Digital Image Correlation technique, to measure landslide displacement.
The availability of a multi-dataset for the 3 December 2013 Montescaglioso landslide, characterized
by different types of imagery, such as LANDSAT 8 OLI (Operational Land Imager) and TIRS
(Thermal Infrared Sensor), high-resolution airborne optical orthophotos, Digital Terrain Models
and COSMO-SkyMed Synthetic Aperture Radar, allows for the retrieval of the actual landslide
displacement field at values ranging from a few meters (2–3 m in the north-eastern sector of the
landslide) to 20–21 m (local peaks on the central body of the landslide). Furthermore, comprehensive
sensitivity analyses and statistics-based processing approaches are used to identify the role of the
background noise that affects the whole dataset. This noise has a directly proportional relationship to
the different geometric and temporal resolutions of the processed imagery. Moreover, the accuracy
of the environmental-instrumental background noise evaluation allowed the actual displacement
measurements to be correctly calibrated and validated, thereby leading to a better definition of
the threshold values of the maximum Digital Image Correlation sub-pixel accuracy and reliability
(ranging from 1/10 to 8/10 pixel) for each processed dataset
The underground cavity network of south-eastern Rome (Italy): an evolutionary geological model oriented to hazard assessment
No full textThere are many abandoned underground mines beneath the city of Rome, created in the Pleistocene pyroclastic deposits over thousands of years. These pose a serious public safety risk hence the study was undertaken to better assess the stability of the underground workings. The Villa de Sanctis public park was selected as a suitable test site, as in this area the cavity network can be inspected and the different steps of the progressive migration of voids toward the surface can be identified. In addition to an underground geological survey, geophysical investigations were undertaken to elucidate some key characteristics of the involved lithological units, including elastic stiffness and layer thickness. Recommendations are made for further studies of the accessible and inaccessible areas
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