Riviste Online SApienza - R.O.SA - 2 (Sapienza University of Rome)
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Potential link between the Golde ratio and the At-Rest Earth pressure in normally consolidated soils
Get PDFThe paper deals with the prediction of the at-rest earth pressure coefficient K0 (≡ K0(NC)) for normally consolidated soils as a function of the mobilised proportion Φ’mob of the shearing resistance angle Φ’ in the one-dimensional virgin compression process. By carrying out a back analysis of a wealth of published experimental (K0(NC), Φ’) pairs, the author previously derived, with no assumptions and in a straightforward manner, an empirical equation for K0(NC) in terms of the mobilised angle Φ’mob of shearing resistance. Further focusing on the numerical value of the mobilising factor of Φ’ in the one-dimensional virgin compression process showed the possible emergence of the Golden Ratio τ = 1.618 as the ratio between the shearing resistance angle Φ’ and its mobilised proportion in the above process, i.e. Φ’/Φ’mob = 1.618 or Φ’mob = 0.618Φ’. The resulting empirical equation has the same basis, in terms of soil behaviour, as the previously obtained K0(NC) equation and a slightly better predictive capability for the full range of the Φ’ values considered; it is also better than several other K0(NC) equations, including Jaky’s approximate equation. The link between K0 and the Poisson’s ratio ν for elastic materials, combined with the connection between Φ’ and Φ’mob, suggests a correlation between ν and Φ’ for normally consolidated soils. However, this correlation is a borderline case for these soils, thus requiring experimental validation
An Integrated approach to elaborate 3-D geological and geotechnical models: a case study from the Daunia Sub-Apennine (Apulia, Southern Italy)
Get PDFIn the Daunia Sub-Apennine (Apulia, southern Italy) slope instability processes due to rainfalls and earthquakes are widespread and cause significant damage to buildings and other structures, and, in some cases, loss of life. A detailed slope stability assessment requires information on the predisposing and triggering factors, and a good knowledge of the geological and environmental conditions as well. As concerns seismic- induced landslides, conventional methods used for slope stability analysis can be divided in: i) force-based pseudo-static methods, ii) displacement-based methods, and iii) stress-strain methods. Detailed representations of geological and geotechnical units as well as static and dynamic geotechnical characterization of materials have to be considered for the correct choice of the method for slope stability analysis, since these are fundamental for slope behaviour prediction and modelling. The purpose of this paper was to present a methodological approach for elaborating detailed 3-D geological and geotechnical models for areas very heterogeneous in terms of geological and soil properties. In the southern portion of the eastern Daunia Sub-Apennine, the outermost formations of the chain domain crop out. These are represented by the Cretaceous-Miocene and Pliocene wedge-top basin units, followed upwards, in the easternmost portion, by the Plio-Pleistocene foredeep units and by Quaternary filling deposits. A high susceptibility to slope failures for the area is testified by the large number of slope movements consisting in mud flows, roto-translational and composite landslides, and soil slips. Field variability of the slope movements from site to site for mechanisms, velocity, depth of rupture surfaces and volume of materials involved is due to the presence of structurally complex formations, characterised by very poor mechanical properties and high variability of their lithological and structural features. The construction of geological and geotechnical models able to represent realistic information is conditioned by the efficacy of the methods used for assessing the spatial lithofacies distribution and parametrization. The case study of Deliceto is here presented, where the 3-D geological model was built based on the results of stratigraphic correlations between core logs and 2-D geological sections. In-situ surveys were performed by means of classical geological and geomorphological methods, and continuous coring boreholes. Silty-clayey sandstone materials (Conglomerates and Sandstones of Castello Schiavo) crop out along the slopes and rest on clayey silts and marls of turbidite origin (Flysch di Faeto). The Flysch di Faeto Fm. is a structurally complex geological unit which consists of three main lithofacies: 1) silty clays; 2) silty marly clays 3) marls and shales. A series of geotechnical laboratory tests, carried out in accordance with international standards for the static anddynamic characterization of materials, made it possible to obtain a detailed 3-D geotechnical model. In particular, resonant column (RC), cyclic torsional shear (CTS) and standard and cyclic triaxial (TXC) tests were performed on the silty clayey geotechnical unit of the Flysch di Faeto Fm., because it is highly susceptible to geotechnical fatigue resulting from cyclic stresses. The results of the laboratory tests confirmed a variable post-cyclic degradation in the range 40-80% and 12-36%, respectively for the secant shear modulus (G) and the undrained cohesion (cu) associated with an increase between 2.92% and 19.90% for the damping ratio (D), demonstrating the heterogeneity of the material in terms of geological and geotechnical characteristics
Hydrogeology and seawater intrusion proneness in the Metaponto plain aquifer (Basilicata, Italy)
Get PDFIn the Metaponto coastal plain (Basilicata region, southern Italy), the anthropogenic impact, mainly linked to agriculture and tourism, has significantly modified the land use and threatened the groundwater quality over the last century. Five protected sites located near the river mouths are included in the Natura 2000 network thanks to the high ecological value of their flora and fauna. The reduction of the groundwater flow, probably caused by the construction of dams and reservoirs for water storage, threatens the equilibrium of the coastal vegetated areas. Among the effects of groundwater quality modifications, the risk of salinity increase should be considered relevant. The purpose of this paper is to describe the approach, which is preliminary to the density-driven flow modeling, supporting the implementation of management criteria facing seawaterintrusion, climate change, and water demand in future scenarios. The definition of an accurate physically-based model is based on the geological and hydrogeological conceptualization and hydrochemical discussion
Phylogenetic placement of a new paleoendemic pill scarab (Coleoptera: Hybosoridae: Ceratocanthinae) from the Udzungwa Mountains, Tanzania, triggers biogeographic interpretations
No full textA new pill scarab with peculiar carinate apical halves of the elytra, Balleriodes sphaera gen. et sp. nov., is described and illustrated from the Udzungwa Mountains, Tanzania. A phylogenetic analysis of 73 terminals and 3118 aligned positions from three DNA fragments placed Balleriodes within a newly recognized and strongly supported clade herein informally named the Synarmostes group. The group includes three monophyletic species-rich genera: African Melanophilharmostes and Pseudopterorthochaetes, as well as Synarmostes from Madagascar and the Comoro Islands. The discovery of the monotypic genus Balleriodes gen. nov. in Udzungwa highlights the importance of the ancient and exceptionally biodiverse chain of the Eastern Arc Mountains in Tanzania and Kenya. Three cases of overseas dispersal by the members of the Synarmostes group are hypothesized: Africa to Madagascar, Madagascar to Comoros, and Africa to Annobón. Preliminary biogeographical interpretation of the increasingly more resolved pantropical subfamily Ceratocanthinae is presented
New explanatory variables to improve landslide susceptibility mapping: testing the effectiveness of soil sealing information and multi-criteria geological parametrization
Get PDFLandslide susceptibility maps (LSM) define the spatial probability of landslide occurrence based on the spatial distribution of predisposing factors. In this work, a LSM is produced for Norther Tuscany (3100 km2) with a Random Forest algorithm. The element of novelty is the use, besides 15 state-of-the-art parameters, of some newly proposed parameters. Starting from the national soil sealing map updated yearly by ISPRA, we derived a parameter accounting for the degree of human interference on hillslope systems. Soil sealing is the most intense form of land take, and it can be defined as the destruction (or covering) of soil by completely or partly impermeable artificial material. A multi-criteria approach was introduced to get a more complex and complete geological information into LSM. Usually, lithology is the only geological variable used, leaving the potential of geological maps largely unexploited. We used a 1:10,000 geological map to define a set of parameters based on lithological, genetic, structural, paleogeographic and chronological criteria, and found that the joint use of all the geology-derived parameters improved the susceptibility assessment. The outcomes of this study could be easily reproduced elsewhere in Italy, since the newly proposed parameters were generated from easily accessible datasets
The early stages of Miomantis binotata and their bearing on the question whether ant mimicry is a larval feature of first stage praying mantises (Mantodea: Mantidae)
Get PDFAnt mimicry, i.e., the mimicking of ant workers by another organism, is a widespread phenomenon among different groups of Euarthropoda, including spiders and different insect species. One example of ant mimicry occurs among praying mantises (Mantodea); here the first stage nymphs have been recorded to perform ant mimicry. In this study, we investigated different nymphal instars of Miomantis binotata for possible morphological similarities to ants. The different instars were compared as stages supposed to perform ant mimicry would differ morphologically from those stages not supposed to resemble ants. The specimens were investigated under different microscopic settings and measurements were performed. Our results do not show significant differences concerning morphological measurements or shape of structures between the different nymphal instars of M. binotata. One prominent difference between stage one nymphs and later stages occurs in the colouration of the body, which is very dark in the earliest nymph. This difference might explain why young nymphs of Miomantis binotata are interpreted as ant-mimicking, despite the apparent lack of other morphological resemblances
De Vincenzo D., Petrolio senza fine o fine del petrolio? Analisi, percorsi, strumenti, Libreriauniversitaria.it Edizioni, Cassino, 2020, pp. 176.
Get PDFRemote monitoring of natural slopes: insights from the first terrestrial Insar Campaign in Vietnam
Get PDFThe present work, realized in the framework of a research project funded by the Vietnamese Space Science & Technology Program, shows the first insights of remote monitoring at the Nam Dan landslide (Northern Vietnam). The Terrestrial SARInterferometry (TInSAR) technique was used for the first time in the Country. The activities were performed in Nam Dan village, where an active landslide with several geomorphological evidences as open cracks and scarps, severely damaged dwellings and public assets, constituting a serious hazard to the local inhabitants. The monitoring activities were carried out between August and December 2019 through a new TInSAR device called Phoenix which it was used for one of its first on-field applications. The Terrestrial SAR was aimed at creating displacement maps and related time series, providing detailed information on the location and deformation rate of the processes under investigation. The use of such a remote sensing technique, coupled with contact instrumentation (inclinometers, piezometers, rain gauge) and field surveys have contributed to improving the knowledge about the Nam Dan landslide and the understanding of its behaviour, with particular regard to the time evolution of deformations
New records of Orthoptera from Molise (Southern Italy) with an updated provisional checklist
Get PDFNew chorological data on some species of Orthoptera from the Italian region Molise are given, and 11 species are recorded as new for this area. Moreover, an updated checklist of the Orthoptera thus far recorded from Molise is provided
Extension of the univariate PC Prior
Get PDFIn the present paper, we describe and explore new methods for constructing joint penalised complexity prior distributions, PC priors hereafter, on the additive model components that build up a more flexible model starting from a base model which would not include those components. Although, an extension to the multivariate case has been already proposed, it is difficult to handle, especially in high-dimensional problems. So, we need something more manageable, particularly for computational purposes. We propose two different constructions of the multivariate PC prior, one based on the conditional PC prior distributions via the Hammersley-Clifford theorem, the other one based on the marginal PC prior distributions by means of a copula approach