1,721,098 research outputs found
Satellite based radar interferometry to mapping and monitoring swelling/shrinking clay soils
No full textA methodology for the study of swelling/shrinkage through the satellite radar images acquired from 1992 to 2010 by different sensors (ERS, RADARSAT) and processed by means of the SqueeSARTM technique is proposed. The methodology aimed at improving the understanding of the kinematical behavior of swelling/shrinking processes, mapping these soils, monitoring the soil volume change and enabling also non-expert users to handle DInSAR data. The methodology has been applied and validated in an area of the Northern Italy where swelling/shrinking soils are frequent. The map of the ground displacements was compared with the geological model of the subsurface and with the distribution of the damaged buildings. The obtained results are helpful in land use planning to identify and quantify the swelling/ shrinkage of clay soils
ANIONIC POLYACRYLAMIDE AS AN ADDITIVE TO PREVENT SOIL PRONENESS TOWARDS LAND DEGRADATION LEADING TO SLOPE INSTABILITIES
No full textClimate change and the intensification of extreme weather events constantly pose new threats to all human activities, damaging roads and communication networks, as well as economical activities and threatening human lives. Recently new materials are being considered as potentially useful tools in the prevention of land degradation leading to slope instabilities; among them polymers such as anionic polyacrylamide (PAM) are gaining more and more interest. PAM is known and employed as an additive in agriculture, in the prevention of irrigation -connected erosion, to maximize irrigation and fertilization efficiency and to enhance agricultural yield. Samples were reconstructed in laboratory using kaolin clay and silty sand, respectively, without mixing them to observe the effects of application of anionic polyacrylamide (PAM) on their physical, volumetric, mechanical, and hydrological properties. Fixed values were dry density (1.2 g/ cm 3 for kaolin clay and 1.4 g/cm 3 for silty sand), initial water content (20% and 25% respectively) and polymer application rates (moving from the original 0%, 0.003%, 0.03%, 0.3%, 1% by weight for both "parent materials" to 0.01%, 0.03% and 0.05% for kaolin clay and 0.1%, 0.3% and 0.5% for silty sand, based on the results of previous analysis). Additional samples consisting of kaolin clay and quartz powder and polyacrylamide (with a concentration of 5% and 50%) were reconstituted specifically for ESEM analysis. The polymer, a granular anionic polyacrylamide provided by Micronizzazione Innovativa Srl, has been manually applied and mixed with the samples, reconstituted in pvc cylinders with a diameter of 9.5 cm and 5 cm high (although some were reconstituted in different cases for specific tests). Samples were then submitted to Atterberg limits with different curing times, hyprop and filter paper tests, WP4C, shear tests, and the record of volumetric characteristics. Results showed that the increase of PAM percentage in samples generally coincided with a widening of samples plasticity range, as well as with the increase of liquid limit and plasticity index; PAM influence was also a matter of time, being more relevant few days after the treatment and then slowly decreasing. Rise in PAM percentage coincided with an increase in samples porosity, and with a higher water retention, although it was impossible to identify a polymer characteristic structure with SEM analysis. These results can shed light on the potential application of polymers such as anionic polyacrylamide as a useful additive for the improvement of soil characteristics that impact on soil stability, in a frame of sustainable solutions for reduction of landslides hazard and risk
Reconstruction of lithotechnical terrain units for the assessment of shallow landslides hazard in Oltrepò Pavese (northern Italy)
No full textThe prediction of the areas prone to rainfall-induced shallow landslides needs of terrain units which represent
the basis for the susceptibility and the hazard zonation of the territory. Terrain units correspond generally to
sub-sections of catchments, distinguishes each other by slope angle, altitude and hydrological parameters.
Instead, the proneness of a hillslope towards shallow landsliding is strictly related also to the lithotechnical
features of the superficial soils, which are affected by these slope instabilities. Thus, the distinction of the
terrain units across a catchment should consider also these soil properties. This work has the objective to
develop and apply a methodology for the definition of the main litho-technical terrain units across a particular
area, aiming to represent an input predictor for the assessment of shallow landslides susceptibility and hazard.
The methodology was tested in the Oltrepò Pavese area (Lombardy region, northern Italy), that corresponds to
the northern termination of the Italian Apennines and is characterized by a significant predisposition towards
shallow failures events as a consequence of severe rainfalls. The following parameters are measured as basic
input for defining the terrain units: 1) soil lithotechnical profile, determined through the field evaluation of soil
density, porosity, carbonate content, resistance to the penetration; 2) grain size distibution and Atterberg limits
of the levels identified in a soil profile; 3) thickness of the soil profile. These parameters were measured in more
than 200 points, corresponding to field surveys realized in an area of about 250 km2. Soil profiles with similar
features were, then, grouped through a cluster analysis, which allowed to identify soil groups characterized
by similar lithotechnical properties. A map of distribution of these lithotechnical terrain units were obtained,
linking the features of the soil profiles with the distribution of the bedrock materials with geological features
similar to those ones of the reconstructed terrain units. The terrain unit distribution were compared with the
shallow landslides inventory map of Oltrepò Pavese area, in order to identify the most prone lithotechnical
terrain units by means of a knowledge-driven technique based on the Frequency Ratio methodology. These
results could represent the basis for a future implementation of other methodologies (deterministic or datadriven
models) for the assessment of shallow landslides susceptibility and hazard at regional scale, that could
take into account also for this terrain units. This work was made in the frame of the ANDROMEDA project,
funded by Fondazione Cariplo
Temporal prediction of shallow landslides exploiting soil saturation degree derived by ERA5-Land products
No full textERA5-Land service has been released recently as an integral and operational component of Copernicus Climate Change Service. Within its set of climatological and atmospheric parameters, it provides soil moisture estimates at different soil depths, represeting an important tool for retrieving saturation degree for predicting natural hazards as shallow landslides. This paper represents an innovative attempt aiming to exploit the use of saturation degree derived from ERA5-Land soil moisture products in a data-driven model to predict the daily probability of occurence of shallow landslides. The study was carried out by investigating a multi-temporal inventory of shallow landslides occurred in Oltrepo Pavese (northern Italy). The achieved results follow: (i) ERA5-Land-derived saturation degree reconstructs well field trends measured in the study area until 1 m from ground; (ii) in agreement with the typical sliding surfaces depth, saturation degree values obtained since ERA5-Land 28-100 cm layer represent a significant predictor for the estimation of temporal probability of occurrence of shallow landslides, able especially to reduce overestimation of triggering events; (iii) saturation degree estimated by ERA5-Land 28-100 cm layer allows to detect soil hydrological conditions leading to triggering in the study area, represented by saturation degree in this layer close to complete saturation. Even if other works of research are required in different geological and geomorphological settings, this study demonstrates that ERA5-Land-derived saturation degree could be implemented to identify triggering conditions and to develop prediction methods of shallow landslides, thanks also to its free availability and constantly updating with a delay of 5 days
USE OF ANIONIC POLYACRYLAMIDE TO CHALLENGE LAND DEGRADATION THAT LED TO SLOPE INSTABILITIES: PRELIMINARY RESULTS
No full textA novel method for landslides investigation through A-DINSAR time series
No full textIn recent years, Advanced Differential Interferometric Synthetic-Aperture
Radar A-DInSAR technique has advanced rapidly for detecting and
monitoring ground surface deformations due to landslides. Identification
of the areas affected by ground motion through A-DInSAR data is generally
based on visual inspection and hotspot or cluster analysis of average
displacement rates. However, interpreting A-DInSAR time series of a
particular area provides a better indication of the real trend of displacement
of a landslide, while identifying the possible moment of acceleration of the
deformation process as well. A novel methodology is then proposed for
identifying different typologies of ground motion areas mainly related to
landslide phenomena at a regional scale, by means of A-DinSAR data at high
spatial and temporal resolutions. This methodological approach was tested
and validated in Piedmont region northern Italy, by means of RADARSAT
and COSMO-SkyMed satellite data, in both ascending and descending
modes. Linear constant in time displacement and non-linear acceleration
or deceleration in the displacement rate trends were recognised, allowing
characterisation of the kinematic pattern of a landslide or a portion of it. Local
and site-specific scale analyses, performed in an Alpine valley and in two
hillslopes representative of the main geological/geomorphological contexts
of the study area, validated the results obtained at the regional scale. This
supported the interpretation of the driving mechanism for such known
landslides, or other geological processes which can cause ground motion
along slopes. The developed procedure can allow one to specify priority
areas for prevention activities, in order to optimise the costs and benefits
of designing a plan to monitor instability phenomena at regional and sitespecific
scales. Moreover, ground motion areas identified by different sensors
in the same landslide help in the characterization of the state of activity of
this phenomenon, identifying also possible moments of re-activation
PSI-based methodology to land subsidence mechanism recognition
No full textA methodology based on Persistent Scatterer Interferometry (PSI) is proposed in order to disentangle the contribution of different processes that act at different spatio-temporal scales in land subsidence (i.e. vadose zone processes as swelling/shrinkage of clay soils, soil consolidation and fluid extraction). The methodology was applied in different Italian geological contexts characterized by natural and anthropic processes (i.e. a Prealpine valley and the Po Plain in northern Italy)
ERT-based experimental integrated approach for soil hydrological characterization in rainfall-induced shallow landslides prone areas
No full textDetailed analysis of soil-atmosphere interactions in two sample sites in Oltrepò Pavese
No full textLarge-scale quantitative assessment of water resources is generally carried out using models that take into
account the soil-atmosphere interaction and hydraulic behaviour of an unsaturated soil.
Volumetric water content and pore water pressure are the main basic characteristics to be considered when
assessing the hydraulic behaviour of the soil in relation to rainfall events. These quantities are very useful
because they constitute input data in different types of water balance models.
Some models require knowledge of water retention curves that indicate a sort of “biunivocal” link between
water content and pore water pressure. Most of these models include a single hysteresis, due to in situ wettingdrying
processes to which soils are subjected under natural conditions (Bordoni et al., 2017).
Experimental evidence shows that the “biunivocal” relationship between the quantities considered does not
allow to adequately reproduce the real behaviour of un saturated soils. In the modelling chain, this mismatch
can lead to an inappropriate estimate of water resources, in relation to the amount of rain.
This note reports a detailed description of the interaction between soil and atmosphere in a specific area in
Northern Italy. Data from continuous monitoring of two sample sites in Oltrepò Pavese, namely Montuè and
Costa Cavalieri, representing two different geological contexts, were used (Bordoni et al., 2015). Different
time spans have been considered, even those including single rainy events. Field measurements of both water
content and pore pressure allow to clearly identify not only the seasonal fluctuations of the hydraulic properties
of the soil, but also the hysteresis cycles that characterize the hydraulic behaviour of the unsaturated soil in
correspondence of single rain events. In order to achieve this objective, the data recorded over a long period of
time were processed and graphs representing the link between pore pressure and water content were obtained.
The trends were also compared with the data on precipitation and air temperature.
Analysis of the data shows that the dynamics characterising variations in water content and pore pressure
at both test sites are closely linked to the alternation of wet and dry periods. However, the response is different
in the two sample sites because it depends on the geological context and on the type of shallow soil. It seems
that the response is also affected by the presence of preferential flow paths, especially in cracked clayey soil.
In general, it can be observed that in winter and spring months, after rain events followed by a prolonged
drying period, the response of soil layers up to 0.6 m from ground level is faster than that of the underlying
layers. In fact, by increasing depth, the interaction between soil and atmosphere is delayed. Moreover, it is
evident that the soil behaviour is not characterized by a single wetting-drying hysteresis, but by numerous
cycles that correspond to different isolated rainy events
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