Search

Groundwater sustainability is still an open question. Theoretical and practical approaches to the definition of groundwater sustainability were mainly developed on large scales, while few studies are available for its definition at a single well scale, especially in fractured aquifers. This study examines how much the sustainable yield of a well in fractured aquifers depends on the trend of drawdown over time. For this aim, pumping tests conducted in fractured rocks were considered and analytical models were applied to examine the long-term response of groundwater levels in some wells. To define the operational pumping flow of a well in these aquifers, results show that long constant flow rate pumping tests are preferred to step-drawdown tests. The late drawdown–time curve and residual drawdown segment-curves during the recovery, approximated by power, exponential or polynomial equations, represent the first step to extrapolating the long-term drawdown in the well. This prediction combined with the assessment of a drawdown limit in the well (as a function of the saturated thickness of the aquifer) are essential to plan the first operation of the well (flow rate and time of pumping). Subsequently, through the monitoring of this first operation step, the following operation phases can be updated and improved.

A modified incremental-iterative method for bulk carriers under alternate hold loading condition is outlined, focusing on the assessment of the local stress field, due to double bottom bending by t...

Hydrological properties of ignimbrites are known in detail only for some areas, although these rocks cover large areas with considerable thicknesses in many volcanic regions of the world. This study investigates hydrological properties of two ignimbrites of Latium (Central Italy), different in age, composition, and origin. The dual porosity of the ignimbrites was examined through laboratory tests, pumping tests, and outcrop surveys. The degree of welding, composition, and stratigraphy of the two ignimbrites are the main factors determining their hydrological properties. The two ignimbrites share a low matrix permeability, showing a different fracturing degree. The more welded ignimbrite is characterized by lower porosity of the matrix and higher fracturing degree, while the less welded ignimbrite is characterized by higher porosity of the matrix and lower fracturing degree. Hydraulic conductivity and storage capacity of the highly welded ignimbrite mainly depend on the denser network of discontinuities. The hydraulic conductivity of the younger ignimbrite, less welded, mainly depend on the sparser network of discontinuities and on the layer of unconsolidated coarse pyroclastic deposits at its base, while the storage capacity depends on the more porous matrix. Should the pyroclastic rocks be used as aquifer for water supplies, or, in other cases, as substratum of waste disposal sites, the dual porosity of the ignimbrites must necessarily include different scales of analysis in order to evaluate the role of matrix and fractures on the permeability of rock mass. In any case, the results of laboratory and on-site tests are to be interpreted taking into account the stratigraphy of the ignimbrite.

Groundwater sustainable yield is a concept widely treated theoretically in the literature. Moving from theoretical concepts to the definition of practical measures for groundwater management is not easy due to site-specific characteristics of the system. This study is aimed at identifying which factors influence the sustainable yield of the plain of Tivoli (Central Italy), where thermal springs with considerable flow (over 2 m3/s) emerge (or rather emerged) and supply a thermal plant. In the same plain, another profitable economic activity concerns the extraction of travertine; it caused a progressive decline in groundwater levels and in the discharge of the thermal springs. The hydrogeological history of the site and the data available in the literature and in new focused surveys are encapsulated in a simple flow model addressed to compare the pre- with the under-development conditions. The withdrawal of groundwater from the quarry area determined a significant impact on the water balance of the system. An increase in inflow from surrounding aquifers and a decrease in storage and in natural discharge of the travertine aquifer result in under-development conditions. Residual discharges towards the springs and river are very sensitive to the pumping flow rate of quarries, according to an inverse linear relationship; this hydrogeological feature may be adopted as an indicator of the sustainability of groundwater withdrawals from the plain. The residual discharge is most affected by the position of the pumping center in the groundwater flow net and its distance from boundaries to be captured, as well as on the depth and extent of the quarries. This lays the basis for developing sustainable management models of groundwater considering the economic and environmental aspects of the issue.

A parametric wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and significant wave height, based on the measurement and analysis of the heave and pitch motions of a vessel in a seaway, recorded by a smartphone located onboard the ship. The measurement system makes it possible to determine the heave and pitch acceleration spectra of the reference ship in the encounter frequency domain and, subsequently, the absolute sea spectra once the ship motion transfer functions are provided. The measurements have been carried out onboard the research ship &ldquo, Laura Bassi&rdquo, during the oceanographic campaign in the Antarctic Ocean carried out in January and February 2020. The resembled sea spectra are compared with the weather forecast data, provided by the global-WAM (GWAM) model, in order to validate the sea spectrum resembling procedure.

The paper focuses on the fatigue life assessment of mooring lines for floating offshore wind turbines, deployed on intermediate water depths. The nonlinear hydrodynamic model in the time-domain is preliminarily discussed. Subsequently, several spectrum estimation methods are outlined and embodied to carefully assess the low and high-frequency components of the stress process in the mooring lines and estimate the cumulative fatigue damage by the combined spectrum approach. The spectral reconstruction methods are applied to a reference case study, focusing on three different loading conditions. Current results are discussed and some suggestions are also provided to carefully assess the fatigue life of mooring lines for floating offshore wind turbines.

The paper focuses on the ultimate strength of perforated platings with circular openings and manholes, eventually reinforced by ringed or carling stiffeners, in order to develop a comprehensive and rationale format, useful to assess the ultimate capacity of perforated plate panels under uniaxial compression. In this respect, a large number of FE simulations is performed by Ansys Mechanical APDL, in order to provide new design formulas for the ultimate strength of platings with circular openings or manholes and, subsequently, for perforated plate panels reinforced by local stiffeners. The design formulas are developed by properly varying the opening size and the scantlings of ringed or carling stiffeners, in order to provide a comprehensive set of design curves. Hence, the incidence of the opening longitudinal position on the ultimate capacity of perforated platings, without and with local stiffeners, is also investigated. Finally, the proposed equations are applied in a straightforward design example. Based on current results, the new design formulas allow a reliable assessment of the ultimate capacity of platings with circular openings or manholes and the incidence of local stiffeners on the plating ultimate strength, so providing a rationale design format that could be easily embodied in current Rules and guidelines.

The parametric design of a resonant point absorber, equipped with a fully submerged toroidal shape and connected to a permanent magnet linear generator lying on the seabed, is performed to investigate the effectiveness of the new WEC device in terms of power production and cost of energy. After developing a non-linear time-domain model for the heave, surge and pitch motions of the floating buoy and the vertical motion of the Power Take-Off translator mass, a comparative analysis is performed among a reference WEC device and the new layout. The Annualised Energy Production of the WEC devices is assessed with reference to a candidate deployment site located in the western Mediterranean Sea. The scantling of the tensioned line, connecting the floating buoy to the Power Take-Off unit, is carried out based on both Ultimate and Fatigue Limit State design conditions. Subsequently, the Levelised Cost of Energy is determined and a sensitivity analysis is performed to detect a possible pathway to further reduce the power production costs. Based on current results, the new WEC device seems to be a promising layout to gain the EU target for the marine renewable energy sector that should be reached by 2025.

The thermal waters of the Island of Ischia, an active volcano located in Southern Italy, are widely used for supplying numerous spas. Groundwater withdrawals occur mainly through wells in the coastal strip. This study explores the impact of withdrawals on the quality of the waters used in thermal facilities, which is required to be constant in terms of composition and temperature by law. For this purpose, specific investigations were conducted including 155 pumping tests, 124 water temperature measurements during pumping tests, 31 temperature and electrical conductivity logs and periodic chemical analysis of the waters of 21 selected wells. By comparing the response to pumping of the aquifer and the quality of the water extracted from the wells, it turned out that the quality of groundwater supplying spas depends not only on natural phenomena (meteoric recharge, seawater intrusion, and rising of deep hydrothermal fluids) but also relies on the island sector where groundwater is pumped and on the pumping method. The distance of the wells from the coast, the type of aquifer formation intersected by the wells, and the field of groundwater temperature of the hydrothermal system strongly affect the aquifer pumping response, determining the quality of water extracted from wells and its variation over time. In Ischia, techniques and regimes of groundwater withdrawals should adapt to the local aquifer pumping response, more than in another hydrogeological context. The concomitant analysis of drawdown, water temperature, and salinity during pumping turned out to be a valuable tool to define the sustainable yield of the single well.

Very often, in-situ soil does not meet the requirements for landfill barriers, therefore, it is necessary to purchase the material from quarries. An increasing number of by-products have been proposed as alternative landfill barrier materials. The present study investigated the performance of two soils of Central Italy (alluvial and volcanic soils) with an organosolv lignin (sulfur-free lignin (SFL)), a widespread by-product in the world. Laboratory investigations indicated that the volcanic soil mixed with 10% in weight of lignin did not reach the permeability value required for landfill bottom liners, also showing high compressibility. On the contrary, the addition of 20% to 30% lignin to the alluvial soil reached the permeability value recommended for the top-sealing layer of landfills: scanning electron microscope analysis indicated that the improvement was due mainly to the physical binding. Large-scale investigations should be carried out to evaluate the long-term performance of the mixtures. The increasing production of organosolv lignin worldwide gives this by-product the opportunity to be used as an additive for the realization of the top-sealing layer. The approach can save the consumption of raw materials (clayey soils from quarries), giving lignin a potential new field of application and recovering in-situ soils.

This paper provides a new adaptive weather routing model, based on the Dijkstra shortest path algorithm, aiming to select the optimal route that maximizes the ship performances in a seaway. The model is based on a set of ship motion-limiting criteria and on the weather forecast maps, providing the sea state conditions the ship is expected to encounter along the scheduled route. The new adaptive weather routing model is applied to optimize the scheduled route in the Northern Atlantic Ocean of the S175 containership, assumed as a reference vessel, based on the weather forecast data provided by the Global WAve Model (GWAM). In the analysis, both wave and combined wind/swell wave conditions are embodied to investigate the incidence on the optimum route assessment. Furthermore, the effect of the vessel speed on the optimum route detection is also investigated. Current results clearly show that it is possible to achieve appreciable improvements, up to 50% of the ship seakeeping performances, without excessively increasing the route length and the voyage duration.

The monitoring of sea state conditions, either for weather forecasting or ship seakeeping analysis, requires the reliable assessment of the sea spectra encountered by the ship, either as a final result or intermediate step for the measurement of the relevant wave-motion parameters. In current analyses, different spectrum estimation methods, namely the Welch, Thomson and ARMA models, have been applied and compared based on a set of random wave signals, with different durations, representative of several sea state conditions. Subsequently, two sea spectrum reconstruction techniques were described and applied in order to detect the main sea state parameters, namely the significant wave height, the mean wave period and the spectrum peak enhancement factor. The performances of both spectral analysis and sea state reconstruction methods are discussed in order to provide some preliminary guidelines for practical application purposes. In this respect, based on current results, the Welch and Thomson methods seem to be the most promising techniques, combined with the nonlinear least-square reconstruction technique.

A new wave spectrum resembling procedure, based on two subsequent steps, is developed to detect the sea state parameters, namely the wave peak period, the significant wave height and the wave spectrum shape parameter, based on the analysis of heave and pitch motion time series, obtained by onboard measurements. The outlined procedure is applied to the S175 containership, assumed as reference vessel, and a set of basic conditions, with different vessel speeds, heading angles and sea state parameters, is preliminarily investigated. In this respect, heave and pitch motion time histories were obtained by time-domain simulations, based on theoretical wave spectra, in order to systematically investigate the reliability of the proposed procedure. Subsequently, a wide benchmark study is carried out, based on random generation of wave peak periods, significant wave heights and vessel speeds at four heading angles, equally spaced from head to following seas, in order to investigate the incidence of time duration on resembled sea state parameters. Finally, the statistics of errors on wave peak periods and significant wave heights are analysed to select the proper time duration of onboard measurements that allows balancing the reliability of resembled data with the need of an almost real-time sea state monitoring.

Groundwater flow in the Ischia volcanic island (Italy) and its implications for thermal water abstraction Hydrogeology Journal 28 (4): 1-23 This study improves knowledge on the hydrogeology of Ischia Island, an active volcano of southern Italy. Combining previous published and unpublished data with newly collected data, and through the results of simplified numerical models, the existing conceptual hydrogeological model of the volcanic island has been reviewed and the present impact of intensive withdrawals on the island’s groundwater resources has been examined. Two areas with different hydrogeological characteristics have been recognized: (1) the resurgent block of Mt. Epomeo, where an independent and uplifted basal groundwater circulation exists; (2) the external areas of Mt. Epomeo, where a continuous basal aquifer and local discontinuous perched aquifers have been distinguished. The marginal faults of the resurgent block of Mt. Epomeo represent the preferential pathways of ascending deep fluids. Innatural conditions, the island’s aquifersare recharged byrainfalland bydeepfluids frombeneath,dischargingtowards the sea and the springs. Since the start of activity at the spa facilities, involving intensive pumping from wells, a further and significant rechargeof the aquifershas come fromseawaterand fromincreased upwelling ofthe deepfluids. Althoughthisdoes notcompromisethesustainabilityofthegroundwater withdrawalsinquantitativeterms,thepumpingratesdeterminethequality ofthewater capturedbythewells.Thegreatvariabilityintemperatureandchemicalcompositionofgroundwater oftheislandis alsoinfluencedbylocalhydrogeologicalparametersandcharacteristicsofthewellsfromwhichthewatersamplesweretaken,as well as the phenomena of interaction among different end-members. &nbsp

Origin, yield and quality of the groundwater flows at high elevation in the Cimino volcano (central Italy) were examined. In this area, groundwater is geogenically contaminated by arsenic and fluoride, yet supplies drinking water for approximately 170,000 inhabitants. The origin of the high-elevation groundwater flows is strictly related to vertical and horizontal variability of the rock types (lava flows, lava domes and ignimbrite) in an area of limited size. In some cases, groundwater circuits are related to perched aquifers above noncontinuous aquitards; in other cases, they are due to flows in the highly fractured dome carapace, limited at the bottom by a low-permeability dome core. The high-elevation groundwater outflow represents about 30% of the total recharge of Cimino’s hydrogeological system, which has been estimated at 9.8 L/s/km2. Bicarbonate alkaline-earth, cold, neutral waters with low salinity, and notably with low arsenic and fluoride content, distinguish the high-elevation groundwaters from those of the basal aquifer. Given the quantity and quality of these resources, approaches in the capture and management of groundwater in this hydrogeological environment should be reconsidered. Appropriate tapping methods such as horizontal drains, could more efficiently capture the high-elevation groundwater resources, as opposed to the waters currently pumped from the basal aquifer which often require dearsenification treatments.

The paper focuses on the design and selection of mooring systems for Floating Offshore Wind Turbines, deployed on intermediate water depths, and provides a comparative analysis among non-redundant and redundant layouts, consisting of 3 and 9 lines, respectively. After developing the non-linear time-domain hydrodynamic model, the Ultimate, Accidental and Fatigue Limit State Design Conditions for mooring systems are briefly discussed. Subsequently, an improved optimization procedure, devoted to detect the minimum weight configuration of the mooring system, constrained to the fulfilment of several restraint criteria, is outlined and applied to a reference case study. The OC4-DeepCwind semisubmersible tri-floater platform, equipped with the 5 MW NREL wind turbine, is assumed to be deployed in the Northern North Sea. The optimization procedure is embodied to preliminarily detect a set of candidate configurations, satisfying the Ultimate and Accidental Limit State design conditions, that are subsequently checked to assess the expected fatigue life. The preliminarily design of anchor foundations is also performed. Finally, a cost analysis is carried out to investigate the impact of the line number on the total installation costs of the stationkeeping system. Some considerations, concerning the impact of line number on the expected cost due to maintenance operations, are also provided.

This study provides a review of the issues of occurrence, management and protection of mineral and thermal waters in volcanic areas of central and southern Italy. These waters have a great economic importance being widely used for therapeutic and water bottling purposes, although they have a limited influence on the total yield of hydrogeological systems (generally below 17%). The present study examines the hydrogeological environment where mineral and thermal waters originate, focusing on the hydrostratigraphic and structural conditions generating different hydrochemical facies. The complexity of the examined volcanic systems makes the interpretation of the hydrochemical facies and the building of reliable hydrogeological models often difficult. Mineral and thermal waters (up to 100 °C) originate from different flow paths and interactions among waters with different qualities. In this framework, current European, national and regional regulations do not specify the criteria of abstraction and management. The examined cases show how the management and protection of mineral and thermal waters are inseparable from the management of the other groundwater resources used for drinking, irrigation and industrial purposes, being the various hydrochemical facies related to different circuits within the same system. To maintain different water qualities and permit a sustainable multipurpose use of groundwater resources, a participatory and unitary management of the aquifer system seems to be the most appropriate approach.

The need for increasing the share of sea resources in the global renewable energy market requires a specialized design of wave energy converters and Power Take-Off units that, in turn, may be capable of maximising power production and minimizing extraction costs. In this respect, as optimization of wave energy converter performances, by properly tuning relevant hydrodynamic parameters and controlling the motion in waves, reveals a basic issue to reduce energy production charges, a new cost-based design procedure for heaving point absorber type devices is developed, with the main aim of accounting for wave climate at deployment site, reliable device operational profiles and design restraint criteria for both floating buoy and Power Take-Off unit. The newly proposed cost-based procedure is applied to detect the optimum configuration of heaving point absorber devices at several candidate deployment sites. Finally, the incidence of wave climate and available energy resources, on detecting the optimum device configuration and assessing relevant energy production costs, is investigated and fully discussed.

Estimationofrockmasspermeabilityusingvariationinhydraulic conductivity with depth: experiences in hard rocks of western Turkey Bull Eng Geol Environ (2018) 77:1663–1671 Determining permeability of fractured rocks is a focal point in engineering projects. Many methods have been developed for direct in situ determination of the hydraulic parameter; nevertheless, especially in the preliminary stages of rock mass characterization, empirical correlations are used to estimate the rock permeability. This study proposes a relationship between rock mass depth and permeability that may beusefulforinitialhydrauliccharacterizationoffracturedmedia. For this purpose, results of core drilling, injection tests, and geophysical prospecting carried out in fractured hard rocks—mainly andesites and secondly metamorphites—of western Turkey were considered. A decrease in rock mass permeabilitywithdepthisevidentfromtheresultsofinjection tests. Within the depth of investigation (the first 100 m), hydraulic conductivity shows an exponential declining trend with depth and depends on the surface value of the hydraulic parameter. No correlation is evident between discontinuity spacing and depth or rock quality designation (RQD) and depth. The applicability of the relationship found requires a hydrostructural homogeneity of the rock mass, which can be verified through inexpensive geological survey and geophysical prospecting.

Reliability analysis of an oil tanker in intact conditions is performed to investigate the incidence of load combination methods on hull girder sagging/hogging time-variant failure probability. Particularly, Turkstra rule, Ferry Borges and Castanheta method and Poisson square wave model are applied to evaluate the statistical distribution of bending moment, with reference to both one voyage and 1-year period. Statistical properties of time-variant ultimate strength are determined by Monte Carlo simulation, up to 25-year ship lifetime; bending capacity is determined by means of a modified incremental-iterative method, to account for corrosion wastage of structural members contributing to hull girder strength, welding residual stresses and material properties randomness. After determining the still water load combination factors, based on statistical properties of still water, wave and total vertical bending moments, with reference to 1-year time interval, reliability analysis is performed by Monte Carlo simulation, based on limit state formulations relative to different load combination methods. Finally, the VLCC double hull oil tanker, benchmarked in the 2012 ISSC report, is assumed as a reference ship and obtained results are fully discussed.

Time-variant sagging/hogging hull girder bending capacity of a corroded bulk carrier is determined by Monte Carlo simulation, in terms of mean values, variation coefficients and probability density functions; the incidence of welding residual stresses and steel mechanical properties is purposely investigated. Time-variant hull girder reliability is characterized, for both sagging and hogging conditions, by the annual failure probability and is determined by Second-Order Reliability Method. Sensitivity coefficients of all random variables at discrete points in time are also determined. Four different scenarios are considered and analysed, in order to separately and jointly investigate the incidence of welding residual stresses and material properties variability on hull girder capacity and annual failure probability and compare individual results with the reference case, which is relative to no welding stresses and material properties nominal values. The Capesize single side bulk-carrier, benchmarked in the last ISSC Report, is assumed as test case. Finally, obtained results of time-variant hull girder statistical properties and annual failure probabilities are discussed.

The paper focuses on hull girder reliability and sensitivity analysis of an oil tanker and a bulk carrier in intact condition. After a brief review of the theoretical background concerning the reliability analysis, Turkstra rule, Ferry-Borges and Castanheta, Moan and Jiao load models are applied and compared to investigate the incidence on hull girder reliability of different load combination methods for ships in full load (sagging) and ballast load (hogging) conditions. Subsequently, sensitivity analysis is carried out to investigate the incidence on the hull girder failure probability of the main parameters affecting the still-water and vertical wave bending moment stochastic processes, namely the maximum still-water bending moment reported in the loading manual, the ship voyage duration, the shape parameter of the long-term Weibull distribution of vertical wave bending moment and the mean wave period. Two reference ships, namely the ISSC oil tanker and bulk carrier, are assumed as test case for reliability and sensitivity analysis, that are performed by Monte Carlo simulation based on a dedicated programme developed in Matlab MathWorks. Obtained results are discussed and some suggestions are provided to improve the effectiveness of reliability analysis.