1,721,341 research outputs found
DEEP TUNNELS IN WEAK ROCK-MASSES: ANALYSIS OF TE GROUND-SHORT CONCRETE INTERACTION
No full textAnna Maria Ferrero, Francesco Silvestri, Claudio Scavi
Assessment of the stability conditions of a large-volume sandstone block in the northern sector of the Siq of Petra
No full textThe present paper describes a specific research performed in the framework of the project “Sustainable Monitoring Techniques for Assessing Instability of Slopes in the Siq of Petra, Jordan” carried out by ISPRA from July 2012 to May 2015. Focus is given to the stability conditions of a large-volume sandstone block located in the northern sector of the Siq, isolated from the rear rock-mass by a sub vertical, partially open, fracture and partially eroded at the base in correspondence of a softer sandstone layer. A limit equilibrium analysis for sliding and toppling failure mechanisms was performed in order to investigate the influence of geometrical and strength parameters and to assess the present stability conditions. These latter were also preliminary evaluated with the support of a numerical analysis, in which the influence of the real geometry and of progressive failure can be studied in detail. This knowledge, associated to the data provided by an integrated monitoring system realised with an automatic and wireless connected crack-gauge network, will help in identifying the most sustainable actions to be realised to mitigate the risk of collapse in such a vulnerable and complex context
Possibili impieghi applicativi della risorsa geotermica nell’ambito dei lavori di realizzazione e dell’esercizio della Galleria di Base del Brennero. Fase 1. Redazione di n°3 proposte di azioni preliminari da sottoporre al Progetto Trans-European Transport Network (TEN-T) “SWIFTLY GREEN - Sweden-Italy Freight Transport and Logistics Green Corridor”, come casi pratici di integrazione e armonizzazione dello studio e dello sfruttamento della risorsa geotermica all’interno del Corridoio Europeo Svezia – Italia, e loro potenziale replicabilità volta a favorire lo sviluppo di Corridoi Verdi Europei
No full textThe aim of the present work is to investigate the potential geothermal energy exploitation in the BBT Italian tunnel system.
In particular, the specific objectives of the work are:
• The evaluation of potential geothermal resource, exploitable from the entire mountain area interested by the infrastructure.
• The evaluation of potential geothermal reserve, in relation to its application as energy supply for the different energy users located in the nearby territories.
• The definition of the possible ways of energy extraction from the tunnels, and the associated preliminary quantification of power and energy exploitable, according also to environmental regulations and limits.
The work was developed in the months of June and July 2015; the data acquisition was divided in the following steps:
• Bibliographic study of similar energy geostructures projects and collection of related technical documentation.
• Acquisition of technical documentation about the current project of the BBT tunnel system.
• Acquisition of geographical, geological, hydrogeological and climate data of the interested zone.
• Acquisition of urban and energy plans of municipal areas and villages located in the area Bressanone – Fortezza – Val di Vizze.
• Collection of new temperature measurements on site, by the use of an infrared thermometer.
• On site visits and gathering information about local energy users located near the access tunnels portals.
The different activities included data analysis to evaluate the underground temperature values and the preliminary calculations on energy extraction potential from different geoenergy structures and natural geothermal sources. In particular:
• Geographical, geological, hydrogeological and climate data were used to create a 3D Temperature Mountain Mapping model of the investigated area. The geostatistical tool of the “Universal Kriging” was adopted for the temperature estimation and for the evaluation of the related precision.
• Technical documentation from BBT allowed a preliminary quantification of the effective possibilities of geothermal energy extraction, in both open loop (drainage water thermal utilisation) and closed loop (geothermal energy lining) configurations. The analytical design methods, defined in international technical norms, were adopted to calculate the preliminary values of needed piping length and related exploitable geothermal energy amount.
• Urban and energy plans of the investigated area were employed to illustrate the possible energy users, to identify the existent energy grids and to provide a preliminary idea of the heating infrastructure needed to link users to future BBT energy tunnel system.
Finally, the replicability and transferability potential of each solution identified for the BBT Italian tunnel system to other similar infrastructure projects was analysed in order to provide preliminary guidelines for stakeholders and partners of SWIFTLY GREEN EU Project.
The work led to the realisation of three factsheets, summarising three new solutions for evaluating and exploiting geothermal energy from tunnels
Concept, design and testing of an innovative geothermal heat exchanger installed at the Brenner Base Tunnel
No full textThe document briefly presents the design, installation and testing of a geoexchangers prototype, exploiting energy through drainage water of the Brenner Base Tunnel system. The prototype was developed by the joint efforts of BBT-SE and the University of Bologna, Department DICAM, employing the synergy of a Master’s thesis work (and working stage) hosted by BBT-SE during the period December 2020 – July 2021 (Spaggiari, 2021). The prototype was called “Smart Flowing” for the intrinsic type of heat exchange process occurring and for its simple design and ease of assembly. It consists in a modular horizontal closed-loop system located into the central drain formed by the invert elements of the exploratory tunnel’s lining. Modules were built outside the tunnel system and later on placed and assembled concurrently to the advancement of the Tunnel Boring Machine. Specific tests, simulating the work of a heat pump conditioning systems in heating and cooling mode, were carried out for a two-month period to prove the reliability and the efficiency of the system. The document is concluded by a preliminary economic and environmental potential assessment of the prototype and some insights about further evolution of the research
Possibili impieghi applicativi della risorsa geotermica nell’ambito dei lavori di realizzazione e dell’esercizio della Galleria di Base del Brennero. Fase 1. Redazione di n°3 proposte di azioni preliminari da sottoporre al Progetto Trans-European Transport Network (TEN-T) “SWIFTLY GREEN - Sweden-Italy Freight Transport and Logistics Green Corridor”, come casi pratici di integrazione e armonizzazione dello studio e dello sfruttamento della risorsa geotermica all’interno del Corridoio Europeo Svezia – Italia, e loro potenziale replicabilità volta a favorire lo sviluppo di Corridoi Verdi Europei.
No full textThe aim of the present work is to investigate the potential geothermal energy exploitation in the BBT Italian tunnel system.
In particular, the specific objectives of the work are:
• The evaluation of potential geothermal resource, exploitable from the entire mountain area interested by the infrastructure.
• The evaluation of potential geothermal reserve, in relation to its application as energy supply for the different energy users located in the nearby territories.
• The definition of the possible ways of energy extraction from the tunnels, and the associated preliminary quantification of power and energy exploitable, according also to environmental regulations and limits.
The work was developed in the months of June and July 2015; the data acquisition was divided in the following steps:
• Bibliographic study of similar energy geostructures projects and collection of related technical documentation.
• Acquisition of technical documentation about the current project of the BBT tunnel system.
• Acquisition of geographical, geological, hydrogeological and climate data of the interested zone.
• Acquisition of urban and energy plans of municipal areas and villages located in the area Bressanone – Fortezza – Val di Vizze.
• Collection of new temperature measurements on site, by the use of an infrared thermometer.
• On site visits and gathering information about local energy users located near the access tunnels portals.
The different activities included data analysis to evaluate the underground temperature values and the preliminary calculations on energy extraction potential from different geoenergy structures and natural geothermal sources. In particular:
• Geographical, geological, hydrogeological and climate data were used to create a 3D Temperature Mountain Mapping model of the investigated area. The geostatistical tool of the “Universal Kriging” was adopted for the temperature estimation and for the evaluation of the related precision.
• Technical documentation from BBT allowed a preliminary quantification of the effective possibilities of geothermal energy extraction, in both open loop (drainage water thermal utilisation) and closed loop (geothermal energy lining) configurations. The analytical design methods, defined in international technical norms, were adopted to calculate the preliminary values of needed piping length and related exploitable geothermal energy amount.
• Urban and energy plans of the investigated area were employed to illustrate the possible energy users, to identify the existent energy grids and to provide a preliminary idea of the heating infrastructure needed to link users to future BBT energy tunnel system.
Finally, the replicability and transferability potential of each solution identified for the BBT Italian tunnel system to other similar infrastructure projects was analysed in order to provide preliminary guidelines for stakeholders and partners of SWIFTLY GREEN EU Project.
The work led to the realisation of three factsheets, summarising three new solutions for evaluating and exploiting geothermal energy from tunnels
Modelling the instability phenomena on the NW flank of Stromboli Volcano (Italy) due to lateral dyke intrusion
No full textThe aim of the paper is to provide quantitative elements on the mechanisms that controlled the slope instabilities occurred after two major recent eruptions at Stromboli volcano (i.e. 2002–2003 and 2007). After a brief description of the geological setting and of the largest well documented instability phenomena on volcano flanks, the main objective is pursued using three-dimensional stress-strain analyses for modelling the effects of the magma intrusion on the stability of the volcano flank. Modelling is based on the results of an extensive geotechnical characterization of the volcaniclastic and lava materials. The numerical analyses investigate the influence of different paths and geometry of magma intrusion as well as the spatial variation of mechanical properties. As a result, favourable conditions for specific failure modes are identified. The stress-strain analyses show that magma intrusion can cause both a local failure of a wedge immediately downslope from the dyke or deep-seated movement involving large part of the slope; these two mechanisms were consistent with the deformative patterns observed during the 2007 and 2002–2003 eruptions, respectively. The magma thrust induces shear strains up to levels associated to appreciable grain crushing even below the sea level, where flow liquefaction can be invoked to explain the occurrence of past submarine slides. The submarine landslide is analysed by a combined finite element – limit equilibrium approach that demonstrates that instability conditions can develop if the loading exerted by the upper portion of the slope is sufficiently fast to produce undrained conditions. The analyses also support the hypothesis that at the 2002 subaerial failure occurred, due to combined effects of a magma mild thrust and the removal of the toe support caused by the preceding submarine slide
Implicit integration of a mixed isotropic-kinematic hardening plasticity model for structured clays
No full textIn recent years, a number of constitutive models have been proposed to describe mathematically the mechanical response of natural clays. Some of these models are characterized by complex formulations, often leading to non-trivial problems in their numerical integration in finite elements codes. The paper describes a fully implicit stress-point algorithm for the numerical integration of a single-surface mixed isotropic-kinematic hardening plasticity model for structured clays. The formulation of the model stems from a compromise between its capability of reproducing the larger number of features characterizing-the behaviour of structured clays and the possibility of developing a robust integration algorithm for its implementation in a finite elements code. The model is characterized by an ellipsoid-shaped yield function, inside which a stress-dependent reversible stiffness is accounted for by a non-linear hyperelastic formulation. The isotropic part of the hardening law extends the standard Cam-Clay one to include plastic strain-driven softening due to bond degradation, while the kinematic hardening part controls the evolution of the position of the yield surface in the stress space. The proposed algorithm allows the consistent linearization of the constitutive equations guaranteeing the quadratic rate of asymptotic convergence in the global-level Newton-Raphson iterative procedure. The accuracy and the convergence properties of the proposed algorithm are evaluated with reference to the numerical simulations of single element tests and the analysis of a typical geotechnical boundary value problem
In situ large size non conventional shear tests for the mechanical characterization of a bimrock in The Santa Barbara open pit mine (Italy)
No full textA high mine slope in the disused Santa Barbara open pit mine (Tuscany, Italy) is cut in the Shale-Limestone Chaotic Complex (SLCC), which is a typical bimrock made up of a scaly-fabric clayey matrix including heterometric calcareous blocks. The slope shows evidence of instability phenomena: mainly rotational landslides and toppling countercracks. In order to characterize the mechanical behaviour of the SLCC bimrock, in situ large size non conventional shear tests were performed. The aim of in situ tests is to overcome the size limitation of laboratory specimens and namely to take into account the influence of calcareous blocks on the strength of the bimrock. Bimrock’s strength parameters under natural conditions can be evaluated by means of a limit-equilibrium analysis taking into account shear test data and the geometry of the sliding surface
An equivalent beam approach for assessing tunnelling-induced distortions of frames with infills
No full textThis paper presents an approach to evaluate the response of low-and medium-rise frames with continuous foundations, either with or without infills, to tunnelling employing an equivalent beam with a behaviour dominated by shear deformations. Simplified soil-structure interaction models, consisting of a beam resting on an elastic continuum half-space, are compared against advanced three-dimensional analyses in which the tunnel, the soil, and the building are explicitly modelled. In the simplified approach, the frame is schematised as a Timoshenko beam and reliable procedures to estimate both bending and shear stiffness are discussed. In the refined modelling strategy, an advanced elastoplastic constitute law is employed, capable of reproducing fairly well the soil response to the excavation for increasing values of volume loss, while the full geometry of the structure is considered. First, the results of the proposed numerical approaches are compared in terms of tunnelling-induced foundation displacements, bay deformations and maximum tensile strains in the infills. Then, for the infill panels, the reliability of estimating the maximum tensile strain from the angular distortion of the frame bays is assessed. Finally, a meta-model is proposed to predict the maximum angular distortion based on greenfield settlements, eccentricity, and relative soil-structure stiffness
Rock Mass Properties and TBM Performance in the Central Gneiss Unit of the Brenner Base Exploratory Tunnel (Italy)
Full text linkRock mass characteristics, including uniaxial compressive strength and quartz content of the intact rock material, as well as the number, spacing, and orientation of joints, play a pivotal role in the performance of tunnel
boring machines (TBMs). Various researchers have proposed TBM performance prediction models that have gained widespread acceptance in the literature and have been extensively utilised over the years. This study aims to analyse data collected from the hard rock TBM excavation of the Northern Italian stretch of the Brenner Base Exploratory Tunnel within the Central Gneiss unit. To this end, statistical analyses were conducted to
explore relationships between intact rock and rock mass properties and the actual TBM data recorded during the excavation. Furthermore, the study compared penetration rates derived from performance prediction models based on rock and rock mass properties with actual penetration data, highlighting the extent to which the models align with real observations
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