Groundwater flow systems in turbidites of the Northern Apennines (Italy): natural discharge and high speed railway tunnel drainage

Turbidites crop out extensively in the Northern Apennine mountains (Italy). The huge amounts of groundwater drained by tunnels, built for the high speed railway connection between Bologna and Florence, demonstrate the aquifer-like behaviour of these units, up to now considered as aquitards. A conceptual model of groundwater flow systems (GFS) in fractured aquifers of turbidites is proposed, taking into account both system natural state and the perturbation induced by tunnel drainage. Analysis of hydrological data (springs, streams and tunnel discharge), collected over 10 years, was integrated with analysis of hydrochemical and isotopic data and a stream-tunnel tracer test. Hydrologic recession analysis of undisturbed conditions is a key tool in studying turbiditic aquifer hydrogeology, permitting the discrimination of GFS, the estimation of recharge relative to the upstream reach portion and the identification of springs most vulnerable to tunnel drainage impacts. The groundwater budgeting analysis provides evidence that the natural aquifer discharge was stream-focused through GFS, developed downslope or connected to main extensional tectonic lineaments intersecting stream beds; now tunnels drain mainly active recharge groundwater and so cause a relevant stream baseflow deplenishment (approximately two-thirds of the natural value), possibly resulting in adverse effects on local ecosystems.     

Heavy metals in marine sediments of Taranto Gulf (Ionian Sea, Southern Italy)

Al, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Ti and Zn concentrations have been determined in surface sediment samples collected in the Taranto Gulf (Ionian Sea, Southern Italy) in order to evaluate their levels and spatial distribution in this important area of the Mediterranean Sea. For various metals, the geoaccumulation index has been calculated as a criterion to assess if their concentrations represent contamination levels or can be considered as background levels. The results show that metals concentrations in sediments can be considered near the background levels found in the Mediterranean Sea.Analytical results have been elaborated by using a Geographical Information System (GIS) software to show metals accumulation areas. Using multivariate statistical analysis, we evaluate the possibility to distinguish the sampling stations, in relation to their geographical position. Results have showed metals distribution in the Taranto Gulf is principally influenced by industrial and urban wastes, located mostly in the northern coastal area of the Ionian Sea. Rivers in the Basilicata region and prevailing anticlockwise marine currents are further factors influencing metal accumulation in sediments.     

Numerical modelling of the transverse dynamic behaviour of circular tunnels in clayey soils

In this paper, different approaches aimed at investigating the dynamic behaviour of circular tunnels in the transverse direction are presented. The analysed cases refer to a shallow tunnel built in two different clayey deposits. The adopted approaches include 1D numerical analyses performed modelling the soil as a single-phase visco-elastic non-linear medium, the results of which are then used to evaluate the input data for selected analytical solutions proposed in the literature (uncoupled approach), and 2D fully coupled FE simulations adopting visco-elastic and visco-elasto-plastic effective stress models for the soil (coupled approach). The results are proposed in terms of seismic-induced loads in the transverse direction of the tunnel lining. The different constitutive hypotheses adopted in the coupled numerical approach prove to play a significant role on the results. In particular, the plasticity-based analyses indicate that a seismic event can produce a substantial modification of loads acting in the lining, leading to permanent increments of both hoop force and bending moment.     

About the relations between finite strain in non-cubic crystals and the related phenomenological P-V Equation of State

The notion of scalar strain in minerals is crucial for the formulation of P-V equations of state (EoS). A scalar strain, , holding for any crystal symmetry has been derived by a rigorous and general approach, and then used to develop the related phenomenological P-V EoS. , which depends on V and the trace of the G^* G⁰ matrix, can be split into two components, M and , where the former takes values close to those of the scalar strain according to Birch. M, providing the main contribution (often larger than 80%) to , is appropriate for the formulation of an EoS as M/V behaves regularly in the limit of an unstrained configuration. The phenomenological EoS based on M shows the same dependence on the elastic parameters (bulk modulus and derivatives versus pressure) of the usual Birch-Murnaghan EoS, and yields comparable results. Slight deviations occur for low symmetry minerals. This work is meant to contribute (1) to shed light on the relationships between scalar strain and related P-V EoSs, and (2) to provide a most general EoS which includes, as a particular case, the Birch-Murnaghan model and explains why this latter is reliable for crystal symmetry other than the cubic one, for which it was originally derived.     

Numerical modelling of the effects of foundation scour on the response of a bridge pier

Foundation scour can have a detrimental effect on the performance of bridge piers, inducing a significant reduction of the lateral capacity of the footing and accumulation of permanent settlement and rotation. Although the hydraulic processes responsible for foundation scour are nowadays well known, predicting their mechanical consequences is still challenging. Indeed, its impact on the failure mechanisms developing around the foundation has not been fully investigated. In this paper, numerical simulations are performed to study the vertical and lateral response of a scoured bridge pier founded on a cylindrical caisson foundation embedded in a layer of dense sand. The sand stress–strain behaviour is reproduced by employing the Severn-Trent model. The constitutive model is firstly calibrated on a set of soil element tests, including drained and undrained monotonic triaxial tests and resonant column tests. The calibration procedure is implemented considering the stress and strain nonuniformities within the samples, by simulating the laboratory tests as boundary value problems. The numerical model is then validated against the results of centrifuge tests. The results of the simulations are in good agreement with the experimental results in terms of foundation capacity and settlement accumulation. Moreover, the model can predict the effects of local and general scour. The numerical analyses also highlight the impact of scouring on the failure mechanisms, revealing that the soil resistance depends on the hydraulic scenario.

     

Decadal climate variability in the Mediterranean region: roles of large-scale forcings and regional processes

We analyze decadal climate variability in the Mediterranean region using observational datasets over the period 1850–2009 and a regional climate model simulation for the period 1960–2000, focusing in particular on the winter (DJF) and summer (JJA) seasons. Our results show that decadal variability associated with the winter and summer manifestations of the North Atlantic Oscillation (NAO and SNAO respectively) and the Atlantic Multidecadal Oscillation (AMO) significantly contribute to decadal climate anomalies over the Mediterranean region during these seasons. Over 30% of decadal variance in DJF and JJA precipitation in parts of the Mediterranean region can be explained by NAO and SNAO variability respectively. During JJA, the AMO explains over 30% of regional surface air temperature anomalies and Mediterranean Sea surface temperature anomalies, with significant influence also in the transition seasons. In DJF, only Mediterranean SST still significantly correlates with the AMO while regional surface air temperature does not. Also, there is no significant NAO influence on decadal Mediterranean surface air temperature anomalies during this season. A simulation with the PROTHEUS regional ocean–atmosphere coupled model is utilized to investigate processes determining regional decadal changes during the 1960–2000 period, specifically the wetter and cooler 1971–1985 conditions versus the drier and warmer 1986–2000 conditions. The simulation successfully captures the essence of observed decadal changes. Model set-up suggests that AMO variability is transmitted to the Mediterranean/European region and the Mediterranean Sea via atmospheric processes. Regional feedbacks involving cloud cover and soil moisture changes also appear to contribute to observed changes. If confirmed, the linkage between Mediterranean temperatures and the AMO may imply a certain degree of regional decadal climate predictability. The AMO and other decadal influences outlined here should be considered along with those from long-term increases in greenhouse gas forcings when making regional climate out-looks for the Mediterranean 10–20?years out.     

Ground deformation of the southern sector of the Aeolian islands volcanic arc from geodetic data

The deformation pattern and the dynamics of the southern sector of the Aeolian archipelago are investigated. A study on the ground deformation, measured over the last 20 years in the trilateration geodetic network between the islands of Vulcano and Lipari, has been conducted. Analysis of the relative displacements and the uniform strain tensor parameters, as well as the comparison between areal dilatation and the vertical variations deduced by precise levelling, allow distinguishing different phases associated both with the regional dynamics and the local volcanic context of the area. These phases, however, appear to be closely interrelated. The analysis of the deformation pattern allows to constrain the predominance of a roughly E–W trending extension and a N–S contraction at a regional scale. This regime is consistent with right-lateral movements along a NW–SE striking fault system.