44 research outputs found
Flowmeter and Ground Penetrating Radar: comparison between hydrogeological and geophysical methods
We discuss a comparison between saturated hydraulic conductivity calculated with Electromagnetic Borehole Flowmeter (EBF) and water content obtained by Ground Penetrating Radar (GPR) Zero Offset Profile (ZOP
Application of a SPH depth-integrated model to landslide run-out analysis
Hazard and risk assessment of landslides with potentially long run-out is becoming more and more important. Numerical tools exploiting different constitutive models, initial data and numerical solution techniques are important for making the expert’s assessment more objective, even though they cannot substitute for the expert’s understanding of the site-specific conditions and the involved processes. This paper presents a depth-integrated model accounting for pore water pressure dissipation and applications both to real events and problems for which analytical solutions exist. The main ingredients are: (i) The mathematical model, which includes pore pressure dissipation as an additional equation. This makes possible to model flowslide problems with a high mobility at the beginning, the landslide mass coming to rest once pore water pressures dissipate. (ii) The rheological models describing basal friction: Bingham, frictional, Voellmy and cohesive-frictional viscous models. (iii) We have implemented simple erosion laws, providing a comparison between the approaches of Egashira, Hungr and Blanc. (iv) We propose a Lagrangian SPH model to discretize the equations, including pore water pressure information associated to the moving SPH node
Multiscale Analysis of Geo-Hazards Affecting the Alhambra Cultural Heritage
[EN] This paper presents a multiscale methodology to perform successful geo-hazards assessment in the context of Cultural Heritage. The methodology, defined in the European PROTHEGO project, has been applied to the Alhambra case study. Alhambra is an important Word Heritage site located in Andalusia, Spain. The site is prone to suffer flood, earthquake and landslide phenomena. The proposed multiscale methodology leans on new remote monitoring and modelling technics that not entail aesthetic and functional impacts on the site. For large-scale monitoring, satellite remote sensing technology enables to detect and characterize spatiotemporal ground and structure deformation as a whole, with up to millimeter precision. For very local phenomena analysis, small-scale monitoring based on Terrestrial Laser Scanner and airborne drone digital photogrammetry surveys enables to detect erosion processes that affect the slopes of the citadel. Furthermore, numerical modelling enables geo-mechanical instabilities to be quantified at different scales. Large-scale modelling shows that the most dangerous slope is located at the San Pedro cliff site. Small-scale stability analysis in the San Pedro cliff shows that a slope failure, triggered by a possible earthquake scenario, could reach the wall foundations of the Alhambra citadel located 22 m behind it. Finally, very detailed small-scale modelling, using very precise digital elevation models, enables to track local instabilities and erosion phenomena. Such a multiscale, interdisciplinary approach is the most effective way to identify, assess and monitor risks, strengthening disaster preparedness at heritage property.The research leading to these results has been supported by the PROTHEGO Project (Protection of European Cultural Heritage from Geo-hazards), funded through the framework of the Joint Programming Initiative on Cultural Heritage and Global Change (JPICH), and under ERA-NET Plus and the Seventh Framework Program (FP7) of the European CommissionPeer reviewe
An introductory review on gravitational-deformation induced structures, fabrics and modeling
Recent studies have pointed out a similarity between tectonics and
slope tectonic-induced structures. Numerous studies have demonstrated
that structures and fabrics previously interpreted as of purely geodynamical
origin are instead the result of large slope deformation, and this
led in the past to erroneous interpretations. Nevertheless, their
limit seems not clearly defined, but it is somehow transitional.
Some studies point out continuity between failures developing at
surface with upper crust movements.
In this contribution, the main studies which examine the link between
rock structures and slope movements are reviewed. The aspects regarding
model and scale of observation are discussed together with the role
of pre-existing weaknesses in the rock mass. As slope failures can
develop through progressive failure, structures and their changes
in time and space can be recognized. Furthermore, recognition of
the origin of these structures can help in avoiding misinterpretations
of regional geology. This also suggests the importance of integrating
different slope movement classifications based on distribution and
pattern of deformation and the application of structural geology
techniques. A structural geology approach in the landslide community
is a tool that can greatly support the hazard quantification and
related risks, because most of the physical parameters, which are
used for landslide modeling, are derived from geotechnical tests
or the emerging geophysical approaches
Regional-scale debris-flow risk assessment for an alpine valley
In this paper, we perform a societal and economic risk assessment
for debris flows at the regional scale, for lower Valtellina, Northern
Italy. We apply a simple empirical debris-flow model, FLOW-R, which
couples a probabilistic flow routing algorithm with an energy line
approach, providing the relative probability of transit, and the
maximum kinetic energy, for each cell. By assessing a vulnerability
to people and to other exposed elements (buildings, public facilities,
crops, woods, communication lines), and their economic value, we
calculated the expected annual losses both in terms of lives (societal
risk) and goods (direct economic risk). For societal risk assessment,
we distinguish for the day and night scenarios. The distribution
of people at different moments of the day was considered, accounting
for the occupational and recreational activities, to provide a more
realistic assessment of risk. Market studies were performed in order
to assess a realistic economic value to goods, structures, and lifelines.
As terrain unit, a 20 m x 20 m cell was used, in accordance with
data availability and the spatial resolution requested for a risk
assessment at this scale. Societal risk the whole area amounts to
1.98 and 4.22 deaths/year for the day and the night scenarios, respectively,
with a maximum of 0.013 deaths/year/cell. Economic risk for goods
amounts to 1,760,291 ?/year, with a maximum of 13,814 ?/year/cell
Coupling ground-penetrating radar and flowmeter investigations for the characterization of a fissured aquifer
We test the integration of ground-penetrating radar (GPR) borehole investigation and electromagnetic flowmeter surveys to characterize fissured or complex aquifers. Borehole GPR investigation allows assessment of the lateral continuity of the porous and permeable zones between closely spaced boreholes, whereas flowmeter tests are adopted to identify the inflow-outflow zones in the boreholes. We apply the coupled approach in a portion (between 10 and 20 m below ground surface) of a complex aquifer hosted in a calcareous-gypsiferous formation. The hydro-geophysical characterization was aimed to detect the most conductive levels and to estimate the hydrodynamic properties of the aquifer. The integration of single-hole flowmeters and GPR measurements accurately distinguished different productive levels of high porosity and permeability in the aquifer. Two aquifer systems characterized by a complex geometry of fissures and permeable layers have been recognized, establishing the role of the drilled boreholes in the short-circuiting of the two systems. Interpretation of the GPR survey in cross-hole configuration gave values of total porosity of the order of 0.35 and 0.5 in the two more productive levels, which were detected by the flowmeter investigatio