Riviste Online SApienza - R.O.SA - 2 (Sapienza University of Rome)
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Geophysical techniques for monitoring carbonate karstic rocks
Get PDFCarbonate aquifer in karst systems are very important water reservoir and are recognized as the most difficult to characterize. Then, the purpose of this article is to present a PhD project aimed to understand the circulation of fluids in carbonate reservoirs through innovative hydrogeophysical methodologies both in the laboratory and in the field. In order to achieve the research objective, two phases will be analyzed. One of these phases will be characterized by laboratory experiments where different carbonate samples and analogic karstic model (from cm3 to m3) will be observed by geophysical measurements. The other phase consists to transfer the laboratory experiences in a natural carbonate complex where it will be evaluated the effectiveness of a hydrogeophysical approach for monitoring carbonate karstic aquifer. The last phase will be applied in the carbonate karst area of Castel di Lepre (Marsico Nuovo, Basilicata, Italy)
Optimization of geostructural surveys in rock mass stability analyses using remote sensing techniques
Get PDFMost instability processes in carbonate rock masses, such as slides, falls and topples are related to the mobilization of discrete blocks delimited by discontinuities (i.e. bedding planes or joints) and, eventually, to the presence of caves of both natural and man-made origin. Currently, the most sophisticated methods for evaluating potential or on-going gravitational instability mechanisms are based on advanced numerical software, that are also able to consider their evolution over time. In this context, accurate geomechanical characterizations, that include quantitative descriptions of the rock masses and of on-site materials, are fundamental for an appropriate stability analysis. Field geomechanical and geostructural surveys are carried out with the aim of detecting discontinuity orientation, spacing, persistence, roughness, wall strength, aperture, filling, seepage, number of discontinuity sets, block sizes and shapes. In practice, this approach is expensive and time-consuming, with many drawbacks such as lack of significant data in areas inaccessible or with difficult logistics. The aim of this research activity is to improve the methods for the characterization of rock masses by integrating traditional field surveys with remote sensing techniques, such as Terrestrial Laser Scanning (TLS), Light Detection and Ranging (LiDAR) and, eventually, Unmanned Aerial Vehicles (UAV), in order to carry out practical and realistic discontinuous modelling. Adequate case studies will be investigated by means of traditional scanline/window mapping methods and remote sensing techniques, supported by Terrestrial Laser Scanning and, at places, high-resolution UAV (Unmanned Aerial Vehicle) data. The acquired point clouds will be processed and tested for automatic (through algorithms) and semi-automatic (through algorithms and manual control) extraction of the discontinuities and related properties, both on raw data and on meshes, with the aim of establishing the most reliable method. The comparison of the results will allow to evaluate the advantages and limits of each technique and properly combine them, in order to create accurate 3D models of the case studies. Potential instability processes and geometrically possible motion of rock blocks will be detected through kinematic analyses with the help of stereographic projections, on the basis of the geometrical relations between the slope and the discontinuities. Successively, the results will be used for numerical stability solutions, thus identifying the propensity of the case studies to gravitational processes. The choice of the most suitable software will strongly be influenced by thecalibrated geomechanical model and physical-mechanical behaviour of rock materials
First observation on the internal erodibility of some soil-like weathered rock by means of hole erosion tests
Get PDFConcentrated leak erosion involves the initiation and evolution of soil erosion along a pre-existing crack or micro-fissure due to seeping water and it can be often source of severe safety issues in man-made hydraulic infrastructures. In laboratory, this peculiar internal soil erosion mechanism can be simulated using the Hole Erosion Test (HET). The erodibility of highly weathered rock materials is poorly investigated in literature, although these materials often interact with embankment dams or levees. In this study, a series of HET tests were performed on some soil-like weathered rock specimens, coming from a project-site located in Africa, to investigate their susceptibility to develop internal erosion in concentrated leaks. Although affected by a certain degree of variability, the first outcomings have highlighted that some samples are potentially susceptible to be affected by internal erosion with rates from moderately to extremely rapid. The results of this research provide useful insights in the implication of weathering processes in modifying hydraulic properties of rock materials. Eventually, this study testifies that the Hole Erosion Test can be suited to study the progressive erosion of highly decomposed rocks
Slope analysis and rock fall assessment in the Khinis archaeological area (Kurdistan, northern Iraq)
No full textThis work assesses the conditions of slope instability in the Khinis archaeological area (northern Iraq), which threaten the integrity and conservation of the local cultural heritage. The site preserves traces of sculpturing activity produced during the reign of the Assyrian king Sennacherib (VIII-VII centuries BCE, i.e. before common era). Bas-reliefs were created to celebrate the realization of canalization works built to transport waters from the Zagros Mountains to Nineveh. Multidisciplinary analysis of the local rock slope highlights active rock fall processes of varying magnitude. A few large rock pillars (hundreds of m3) show different conditions of instability after a limit-equilibrium analysis. Meanwhile, potential falls of smaller rock blocks affect the entire Khinis slope as they can detach from mid-slope escarpments. Through probabilistic 3D modelling, the calculation of block trajectories, arrest areas and energy values involved allows the design of a remediation plan,in accordance with the preservation requirements of the landscape value of the site. Finally, some hypotheses are advanced concerning the possible relationships between rock fall processes and the accomplishment of some of the Assyrian sculptures. A reason for further interest in this archaeological site, that it will soon be proposed for inclusion in the UNESCO World Heritage List
New genera, species, and records of Trichogrammatidae (Hymenoptera: Chalcidoidea)
Get PDFThe following new genera and species are described: Adryas indica sp. nov., Chaetogramma (Chaetogrammina) asensillatum sp. nov., Chaetostricha brevifuniculata sp. nov., Chaetostricha huberi sp. nov., Haeckeliania africana sp. nov., Haeckeliania bicornis sp. nov., Haeckeliania brevimarginata sp. nov., Haeckeliania densiciliata sp. nov., Haeckeliania ipersensillata sp. nov., Haeckeliania longiterebrata sp.nov., Haeckeliania macrosensillata sp. nov., Haeckeliania malaysiana sp. nov., Haeckeliania pachivenata sp. nov., Haeckeliania trilongisensillata sp. nov., Hayatia longicornis sp. nov., Hydrophylita pacifica sp. nov., Indonesiagramma bistigmatum gen. nov., sp. nov., Masnerigramma sinicum gen. nov., sp. nov., Oligosita dolichogaster sp. nov., Oligosita kenyota sp.nov., Oligosita microciliata sp. nov., Probrachista biclavata sp. nov., Probrachista longiciliata sp. nov., Probrachista triclavata sp. nov., Pseudogrammina bifasciatipenne sp. nov., Pseudogrammina longifrangiata sp. nov., Pseudoligosita biclavata sp. nov., Pseudoligosita ipersensillata sp. nov., Pseudoligosita macrosensillata sp. nov., Trichogramma unicum sp. nov. New data and records are reported for Chaetogramma caudata (De Santis) and Probrachista nepalensis Viggiani
Preliminary results on the comparison between empirical and phisically-based rainfall thresholds for shallow landslides occurrence
No full textRainfall induced shallow landslides are hazardous phenomena causing significant damages all over the world. Rainfall thresholds are the most used tool to predict the occurrence of such instabilities over large areas. Most of these thresholds are empirical, basing on past rainfall events triggered landslides. These present several limitations, due to the amount and the uncertainty of available data and neglecting antecedent soil hydrological conditions. Physically-based thresholds could take into account also for soil hydrological responses towards rainfalls. Thus, this work aimed to compare both these typologies of thresholds, reconstructed for a 250 km2 area of northern Italian Apennines prone to shallow landsliding. Preliminary results of this research show the significant differences between thresholds reconstructed by means of different approaches. Empirical threshold estimates a lower triggering cumulated amount of rainfall than the values for physically-based thresholds, considering the same duration of rainfall event. Antecedent pore water pressure conditions have significant effects on reconstructed threshold, reducing the amount of rainfall leading to instabilities according to conditions approaching soil complete saturation. These preliminary results will be improved in order to create threshold useful for early warning strategies
Impact of territory management on urban flood: a test case
Get PDFThe maintenance of the territory, through the recovery of the water courses even at the scale of small canals, from any type of obstruction, in particular weeds, tree trunks, all kinds of debris that prevent the natural and correct drainage of rainwater, constitutes an important need for flood prevention, even for small urban scale located in small hydrological basins. For a correct evaluation of the actions to be implemented, the application of advanced computational tools, beside expert judgment, appear to be not only useful, but also necessary. For this purpose, different numerical tools have been proposed. Among these, the mathematical approach of the \u27Shallow water\u27, based on the Finite Element Method and the Godunov-Riemann technique, used in the commercial computational code, selected in this paper, is very popular within the international context. Moreover, the selected commercial software is based on the Graphical Processing Unit (GPU), which can reduce the calculation times even by 80 times. The case study used in this article concerns a rainy event that occurred between April 26th and May 2nd, 2014 that caused flooding between May 2nd and 3rd in the Pianello di Ostra district in the province of Ancona (Marche, Italy). After an opportune site inspection and the relative useful interview of the inhabitants of the place, a topographic high resolution survey (30 cm x 30 cm) was carried out by means of a drone. Then GIS and the available cartography were used, while the pluviometric data were taken from the available website, relating to the Corinaldo Station about 9.1 km from Pianello d’Ostra. The rainfall data were processed using the Curve-Number (CN) empirical method, developed by the USDA Natural Resources Conservation Service (SCS). The method allows to determine the approximate amount of runoff in small basins, consequent to a given precipitation, also considering the specific characteristics of the area concerned. Several parametric simulations have been carried out considering, in particular, the state of maintenance of the Fosso della Trocca that characterizes the basin under study, with and without the presence of debris. Furthermore, the effect of the presence of a small crossing bridge was also considered. The calibration of the model was obtained considering the pre-event state of the canal and of the small bridge, that was affected by debris, and confirming by a numerical point of view, the urban flood occurrence, with heights of the surface of the water comparable to that actually occurred. (15-50 cm). Finally, considering the current conditions of the channel and the removal of the small bridge, the numerical simulation predicts that, with the same rainfall conditions, the flooding would not have occurred
Multi-scale assessment of groundwater vulnerability to pollution: study cases from Campania region (Southern Italy)
Get PDFIn the Campania region (southern Italy), assessment of groundwater vulnerability is an important factor to be tackled for a proper management of risk to aquifer pollution, which is fostered by both high dependence of aqueduct systems on groundwater resources and the widespread agricultural and urbanized land uses of the territory. The different physiographic, geological and hydrogeological conditions of the region, coupled with high anthropic pressure, make such assessment complex to be dealt with, but at the same time mandatory to be accomplished. The proposed study has been developed into the framework of the “Campania Trasparente” project, which has been funded by the regional government to assess environmental factors controlling the quality of agricultural and livestock food productions. Specifically, it belongs to the research topic regarding the assessment of groundwater quality, with a special focus on the assessment of groundwater vulnerability. In this research a multi-scale approach for the assessment of groundwater vulnerability is carried out in order to propose suitable methods depending on extension of territory to be studied and related types and spatial density of available data. Scales considered were a) regional, including the whole Campania region; b) intermediate, identified with that of a single representative aquifer; c) site-specific, or local, related to a portion of aquifer for which a high spatial density of data is available.The applied methods were chosen among the many known in literature and adapted to the specific study cases. At the regional scale, the parametric SINTACS method (CIVITA & DE MAIO, 2000) has been applied to the whole region and adapted to types and spatial density of available data. At the intermediate scale, or aquifer scale, the Mt. Terminio karst aquifer was chosen as representative for the application of different parametric methods, also specifically designed for karst aquifers. At the site-specific scale, a representative sector of a shallow alluvial aquifer, located in the adjoining Casalnuovo di Napoli-Volla municipalities, in the Campania plain, at the eastern border of the city of Naples, has been studied by numerical modeling for the estimation of travel time of nitrate pollutant through the vadose zone. The obtained results can be conceived as useful for supporting a proper territorial planning aimed at the management of risk to pollution of groundwater resources
Apulian caves as natural hydrogeological laboratories
Get PDFIn Apulia (Southern Italy), there is a huge amount of freshwater resources stored within fractured limestone rocks. Being a karst region, Apulia presents over 2000 caves registered in the Regional Inventory; among these, only in two cases speleologists have physically reached the water table, namely at Inghiottitoio di Masseria Rotolo and at Vora Bosco. Thus, these two caves have become special and natural laboratories in which it is possible to directly study groundwater and its hydrogeological processes. The aim of this research is to assess Apulian groundwater quality and quantity starting from these two caves; for this, some actions have been performed inside the cave systems, and others have to be implemented in the next future. To evaluate groundwater quality, chemical and microbiological analyses have been conducted on groundwater samples, and bio-speleological sampling have been performed too. As regards groundwater quantity, the implementation of the mathematical groundwater flow model is needed. So far, modelers have used Equivalents Porous Media (EPM) approaches that are quite far from the real behavior of karst aquifers. Another purpose of this research is to reduce the existing gap between current models and the natural environment, merging two different approaches: the first implements the laminar flow within fractures and, the second, the turbulent flux inside karst conduits. At this aim, additional geological and hydrogeological data have to be collected. This phase of work will eventually result in getting a better knowledge of the natural dynamics and processes in karst, thus allowing identifying the best actions in order to safeguard and protect the underground freshwater resource
Hydrological features of endorheic areas in Southern Italy
Get PDFThis work focuses on hydrogeological behaviour of karst systems in southern Italy (Alburni, Matese, Termino and Cervialto massifs). The karst landform common to all areas analized is endorheic area, which may be considered the preferential vehicle for basal springs and groundwater recharge. A preliminary correlation was found between strata layout andm morphometric features of endorheic areas; this relationship helps to better understand the recharge processes of karst systems analyzed, particularly for some karst massifs of southern Apennines, affected by irregular orography and geomorphological features. The first step focused on a detailed analysis of endorheic areas, highlighting the etherogeneous size between the macro depressions of Terminio, Cervialto, Matese (polje) and minor-depressions of Alburni summit plateau typified by high density of sinkholes. The differences among endorheic karst landforms development can’t be explained only with various processes of karst rocks dissolution; otherwise the strata dip may be considered the main factor having a strong control on closed depressions evolution. Then Alburno, Matese and Picentini massifs have been split in several blocks homogeneous for strata dip. The analysis highlights that the steep slopes of strata do not allow the formation of the closed areas, whereas gentle dip of strata support endorheic areas development, especially minor-depressions. The closed depressions are especially developed on the summit areas, where most of the surface meteoric water are conveyed underground. Additionally the sinkholes detection allowed to define the kind of statistical distribution which better represent their spatial distribution