Fluids in early stage hydrothermal alteration of high-sulfidation epithermal systems: A view from the Vulcano active hydrothermal system (Aeolian Island,Italy)     

Adrian J. Boyce  Paolo Fulignati  Alessandro Sbrana  Anthony E. Fallick 《Journal of Volcanology and Geothermal Research》2007

High-sulfidation (HS) epithermal systems have elements in common with passively degassing volcanoes associated with high T, acid fumarole fields or acid crater lakes. They are considered to form in two stages, the first of which involves advanced argillic alteration resulting from intense, strongly acidic fluid–rock interaction. The La Fossa hydrothermal system (Vulcano Island) represents a classic example of such an active HS system and can be considered as a modern analogue of this early stage of alteration, resulting in a core of intense silicic (90–95% pure SiO₂) alteration surrounded by alunitic alteration zones.  相似文献   

A robust empirical model to estimate earthquake-induced excess pore water pressure in saturated and non-saturated soils     

Mele  Lucia  Chiaradonna  Anna  Lirer  Stefania  Flora  Alessandro 《Bulletin of Earthquake Engineering》2021,19(10):3865-3893

In engineering practice, the liquefaction potential of a sandy soil is usually evaluated with a semi-empirical, stress-based approach computing a factor of safety in free field conditions, defined as the ratio between the liquefaction resistance (capacity) and the seismic demand. By so doing, an estimate of liquefaction potential is obtained, but nothing is known on the pore pressure increments (often expressed in the form of normalized pore pressure ratio r_u) generated by the seismic action when the safety factor is higher than 1. Even though r_u can be estimated using complex numerical analyses, it would be extremely useful to have a simplified procedure to estimate them consistent with the stress-based approach adopted to check the safety conditions. This paper proposes such a procedure with reference to both saturated and unsaturated soils, considering the latter as soils for which partial saturation has been artificially generated with some ground improvement technology to increase cyclic strength and thus tackle liquefaction risk. A simple relationship between the liquefaction free field safety factor FS, and r_u(S_r) is introduced, that generalizes a previous expression proposed by Chiaradonna and Flora (Geotech Lett, 2020. https://doi.org/10.1680/jgele.19.00032) for saturated soils. The new procedure has been successfully verified against some experimental data, coming from laboratory constant amplitude cyclic tests and from centrifuge tests with irregular acceleration time histories for soils having different gradings and densities.

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Dynamical downscaling of CMIP5 global circulation models over CORDEX-Africa with COSMO-CLM: evaluation over the present climate and analysis of the added value   总被引：2，自引：1，他引：1  

Alessandro Dosio  Hans-Jürgen Panitz  Martina Schubert-Frisius  Daniel Lüthi 《Climate Dynamics》2015,44(9-10):2637-2661

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Affluence drives the global displacement of land use   总被引：2，自引：0，他引：2  

Jan Weinzettel  Edgar G. Hertwich  Glen P. Peters  Kjartan Steen-Olsen  Alessandro Galli 《Global Environmental Change》2013,23(2):433-438

Increasing affluence is often postulated as a main driver for the human footprint on biologically productive areas, identified among the main causes of biodiversity loss, but causal relationships are obscured by international trade. Here, we trace the use of land and ocean area through international supply chains to final consumption, modeling agricultural, food, and forestry products on a high level of resolution while also including the land requirements of manufactured goods and services. In 2004, high-income countries required more biologically productive land per capita than low-income countries, but this connection could only be identified when land used to produce internationally traded products was taken into account, because higher-income countries tend to displace a larger fraction of land use. The equivalent land and ocean area footprint of nations increased by a third for each doubling of income, with all variables analyzed on a per capita basis. This increase came largely from imports, which increased proportionally to income. Export depended mostly on the capacity of countries to produce useful biomass, the biocapacity. Our analysis clearly shows that countries with a high biocapacity per capita tend to spare more land for nature. Biocapacity per capita can be increased through more intensive production or by reducing population density. The net displacement of land use from high-income to low-income countries amounted to 6% of the global land demand, even though high-income countries had more land available per capita than low-income countries. In particular, Europe and Japan placed high pressure on ecosystems in lower-income countries.  相似文献   

Role of vegetation in shaping Early Pennsylvanian braided rivers: Architecture of the Boss Point Formation,Atlantic Canada     

Alessandro Ielpi  Martin R. Gibling  Arden R. Bashforth  Corinne Lally  Michael C. Rygel  Saif Al‐Silwadi 《Sedimentology》2014,61(6):1659-1700

Vegetation is a major driver of fluvial dynamics in modern rivers, but few facies models incorporate its influence. This article partially fills that gap by documenting the stratigraphy, architecture and palaeobotany of the Lower Pennsylvanian Boss Point Formation of Atlantic Canada, which contains some of the Earth's earliest accumulations of large woody debris. Braided‐fluvial systems occupied channel belts of varied scale within valleys several tens of metres deep and more than 12 km wide, and their deposits predominantly consist of sandy and gravelly bedforms with subordinate accretionary macroforms, high flow‐strength sand sheets and rippled abandonment facies. Discrete accumulations of clastic detritus and woody debris are up to 6 m thick and constitute at least 18% of the in‐channel deposits; they represent lags at the base of large and small channels, fills of minor channels and sandy macroforms that developed in central positions in the upper parts of channel fills. Sandstones with roots and other remnants of in situ vegetation demonstrate that vegetated islands were present, and the abundance of discrete channel fills suggests that the formation represents an anabranching, island‐braided sandbed river, the earliest example documented to date. Although some sphenopsid and lycopsid remains are present, most woody fragments are derived from cordaitalean trees, and the evolution of this group late in the Mississippian is inferred to have exerted a significant influence on fluvial morphodynamic patterns. The formation records a landscape in which active channel belts alternated with well‐drained floodplains colonized by dense, mature forests and local patches of pioneering, disturbance‐tolerant vegetation. Lakes and poorly drained floodplains dominated by carbonate and organic deposition, respectively, were also present. A large supply of woody debris triggered channel blockage and avulsion, and active channel margins and islands within the channel belts were initially colonized by pioneer vegetation and subsequently stabilized by large trees. A similar alternation of stable and unstable conditions is observed in modern braided rivers actively influenced by vegetation.  相似文献   

Excavation of the Aica-Mules pilot tunnel for the Brenner base tunnel: information gained on water inflows in tunnels in granitic massifs   总被引：1，自引：1，他引：0  

Paolo Perello  Alessandro Baietto  Ulrich Burger  Stefan Skuk 《Rock Mechanics and Rock Engineering》2014,47(3):1049-1071

The construction of the Aica-Mules tunnel, completed in 2010, provides a relevant case history for improving the knowledge of hydrogeological issues related to the excavation of deep tunnels in granitic massifs. The Aica-Mules tunnel is a 10 km-long structure, forming part of the high-speed railway connection between Austria and Italy across the Alpine chain, located at an average depth of 500–1,000 m below the surface. Prior to and during the construction, intense hydrogeological monitoring was set up, allowing the collection of abundant data concerning: (1) the evolution of water inflows into the tunnel; (2) the chemistry and temperature of drained groundwater; and (3) the influence of tunnel drainage on springs. Based on detailed analysis of geological/hydrogeological data, this article provides an insight into the permeability distribution in granitic rocks affected by relevant brittle tectonic deformation, and the consequences of water inflow during excavation. The available time series from the principal water discharges in the tunnel have been used in order to test the reliability of some of the most commonly applied analytical methods for the forecast of water inflows into tunnels.  相似文献   

Asbestos and other fibrous minerals contained in the serpentinites of the Gimigliano-Mount Reventino Unit (Calabria,S-Italy)   总被引：1，自引：1，他引：0  

Andrea Bloise  Teresa Critelli  Manuela Catalano  Carmine Apollaro  Domenico Miriello  Alessandro Croce  Eugenio Barrese  Francesca Liberi  Eugenio Piluso  Caterina Rinaudo  Elena Belluso 《Environmental Earth Sciences》2014,71(8):3773-3786

Serpentinites are metamorphic rocks with good technological properties and valuable ornamental characteristics, which have been exploited since ancient times. Actually, their use is limited and monitored in several countries worldwide because they can contain fibrous asbestos minerals that may be carcinogenic. Furthermore, certain types of fibrous minerals can be confused with asbestos, and must therefore be carefully investigated. We have investigated the possible presence of the asbestos and non-asbestos fibrous phases contained in serpentinitic rocks in a meta-ophiolitic sequence from the Gimigliano-Mount Reventino Unit (Southern Italy), which had not been previously assessed. The detection and quantification of asbestos and the correct distinction of the fibrous non-asbestos minerals are very important not only from a scientific point of view, but also from a legislative one. This is especially the case for the administrative agencies that have to take decisions with regards to the implementation of public and occupational health protection measures (e.g., in road yards and quarry excavations). As a consequence of this, serpentinitic rock samples have been characterized in detail through X-ray powder diffraction, scanning and transmission electron microscopy combined with energy-dispersive spectrometry, analytical electron microscopy (SEM–EDS and TEM–AEM), differential scanning calorimetry, thermogravimetry and micro-Raman spectroscopy. Two kinds of asbestos and four kinds of non-asbestos fibrous silicates have been detected in the examined samples. In order of decreasing abundance these are polygonal serpentine, chrysotile, fibrous antigorite, tremolite, gedrite and magnesiohornblende. The size, morphology, crystallinity and chemical composition of the fibres were also discussed, in the light of the possible role these properties could play in the carcinogenic effect on human health.  相似文献   

A one-dimensional viscoelastic and viscoplastic constitutive approach to modeling the delayed behavior of clay and organic soils     

Aldo Madaschi  Alessandro Gajo 《Acta Geotechnica》2017,12(4):827-847

Accurate modeling of the time-dependent behavior of geomaterials is of great importance in a number of engineering structures interacting with soft, highly compressible clay layers or with organic clays and peats. In this work, a uniaxial constitutive model, based on Perzyna’s overstress theory and directly extendible to multiaxial stress conditions, is formulated and validated. The proposed constitutive approach essentially has three innovative aspects. The first concerns the implementation of two viscoplastic mechanisms within Perzyna’s theory in order to distinguish between short-term (quasi-instantaneous) and long-term plastic responses. Similarly, elastic response is simulated by combining an instantaneous and a long-term viscous deformation mechanism. The second innovative aspect concerns the use of a bespoke logarithmic law for viscous effects, which has never been used before to simulate delayed soil behavior (as far as the authors are aware). The third concerns the model’s extensive validation by simulating a number of different laboratory test results, including conventional and unconventional oedometer tests with small and large load increments/decrements and wide and narrow loading/unloading cycles, constant rates of stress and strain tests, and oedometer tests performed in a Rowe consolidation cell with measurement of pore pressure dissipation.  相似文献   

A quantitative approach to the influence of pyrite separation on Cu-processing tailings: a case study at Reps,Mirdita district,Albania     

Irene Fantone  Giovanni Grieco  Agim Sinojmeri  Alessandro Cavallo 《Environmental Earth Sciences》2017,76(22):774

Sulfide-rich tailings are a well-known environmental threat due to their production of acid drainage (AD) and release of potential toxic elements (PTE) to the local environment. The presence of heterogeneous materials produces complex environmental signatures and complicates the quantitative prediction of contamination. The present work provides a method of quantifying such heterogeneities, starting from mineral processing data of the Reps, Mirdita (Albania) site. A quantitative flow sheet (QF) method was applied to a selected dump site of the Mirdita copper mining district where secondary pyrite separation had been used in the past. The site is subject to long-lasting (10³ years) AD processes with significant release of PTE into the local environment. The tailings at the Reps site are divided into two classes based on the sulfide S content, respectively, represented by high-sulfide-content (S > 10 wt%) materials (hS) and low-sulfide-content (S < 3 wt%) material (lS). The reconstruction of the QF allowed us to identify the hS tailings as the discharge of single-flotation processing lines. This material accounts for about 82% of the total potential H₂SO₄ production, even though it represents < 20% of the entire tailing discard. The QF is a useful tool for the evaluation of heterogeneity and consequently for the modeling of waste management within abandoned sites and in working plants. Given a good quantification, heterogeneity can in fact support the setting of pyrite separation lines or the separate management of pyrite-rich tailing dumps.  相似文献   

A novel insight into vertical ground motion modelling in earthquake engineering     

Luca Prakash Argani  Alessandro Gajo 《国际地质力学数值与分析法杂志》2022,46(1):164-186

Recent observations of failure and damage of buildings and structures under seismic action has led to an increasing interest for an in-depth analysis of the vertical component of site ground motion. In particular, when dealing with saturated soils, the current engineering practice does not usually go beyond the simplified $u$–$p$ formulation of the Biot's equations describing the coupled hydro-mechanical behaviour, thus neglecting some terms of fluid inertial forces, despite the presence of more refined formulations, for example, the $u$–$U$ formulation. Therefore, a theoretical and numerical validation of the $u$–$p$ formulation as compared with the $u$–$U$ formulation is proposed in this work, where the numerical simulations are compared with the analytical solution for the $u$–$p$ formulation, which is also derived and illustrated in this text. The comparison between the two formulations and the analytical solution is provided for different levels of permeability and dynamic actions, which are representative of a wide scenario of site ground properties and seismic hazard in the vertical direction. In particular, the soil response is analysed in terms of acceleration and pore pressure time history, frequency content, acceleration response spectrum, and amplification ratio of acceleration. This study extends the discussion of the limits of applicability of the $u$–$p$ formulation with respect to the rigorous solution of Biot's equations (obtained here with $u$–$U$ formulation) to the context of a complex dynamic regime provided by the vertical components of real earthquake records, and paves the way for further investigations.  相似文献