MODELIRANJE KONTINUITETA I DISKONTINUITETA U TUNELSKOM INŽENJERSTVU

The paper discusses continuum and discontinuum modelling in tunnel engineering. A brief review of fundamentals is presented in connection with the use of closeg - form solutions and computer based numerical methods. a few remarks are derivedon the choice of either continuum or discontinuum modelling of rock mass behaviour at the design analysis stage. Consideration is given to the validation of discontinuum modelling in connection with rock mass classification methods and expected tunnel response to excavation. A case study of a TBM tunnel (4.75 m) in quartzitic micaschists is discussed in detail by paying attention to a comparison of modelling methods - including continuum and discontinuum modelling - applied at a fault zone.U članku je raspravljeno modeliranje kontinuiteta i diskontinuiteta u tuelskom inženjerstvu. Sažeto su opisane osnove zajedno s uporabom matematičkih rješenja i računalnih numeričkih metoda. Raspravljen je izbor modela kontinuuma i diskontinuuma stjenske mase u odnosu na analizu konstrukcije podgrađivanja. U obzir je uzeto potvrđivanje modela diskontinuiteta povezanog s metodama klasifikacije stjenskih masa i očekivane reakcije tunela pri iskopu. U detaljima je raspravljen prmjer studije TBM tunela (promjera 4,75 m) u kvarcitičnim mikašistima s posebnom pozornosti na uspoređivanje metoda modeliranja - uključujući modeliranje kontinuuma i diskontinuuma - uporabljenih u rasjednoj zoni

Tunnels in swelling ground: simulation of 3D stress paths by triaxial laboratory testing

The research is devoted to study the swelling behaviour in tunnels. A new triaxial testing procedure is developed, which is able to quantify the swelling behaviour of soft rocks and stiff soils. The Caneva Clay is tested both by conventional oedometer swelling tests and by the new triaxial test. The swelling parameters of the clay are quantified for predictive analyses of the swelling behaviour at the tunnel scale

INTERFEROMETRIA RADAR E MODELLAZIONE FDEM PER LO STUDIO DI FRANE IN ROCCIA: UN ESEMPIO DI APPLICAZIONE

Nella presente nota verrà illustrato un esempio di applicazione della tecnica interferometrica radar da terra (GBInSAR) e di modelli numerici avanzati di tipo combinato elementi finiti-elementi distinti (FDEM) per lo studio del cinematismo e della propagazione di una frana in roccia nell'Appennino umbro (Torgiovannetto di Assisi -PG). Con riferimento al caso di studio saranno mostrati i risultati del monitoraggio radar che hanno consentito di delimitare l'area interessata dagli spostamenti e di individuare nel cuneo in frana spostamenti differenziali non noti precedentemente. Al contempo saranno mostrati i risultati dell'analisi di scenario effettuata tramite i modelli numerici FDEM che, opportunamente tarati, hanno consentito di ricostruire i meccanismi di innesco, la possibile evoluzione e la distanza di propagazione dei fenomeni oggetto di studi

Development and testing of a novel geothermal wall system

Shallow geothermal energy systems have the potential to contribute to the decarbonization of heating and cooling demands of buildings. These systems typically present drawbacks as high initial investments and occupancy of wide areas. In this study, a novel energy wall system is proposed to overcome the limitations of conventional geothermal applications in urban areas. The system is characterized by ease of installation, low initial costs and applicability to existing buildings undergoing energy retrofitting. The paper illustrates the implementation of the prototype of such a system to an existing structure in Torino (Italy). An overview of the components is given together with the interpretation of an illustrative test carried out in heating mode. The data from both heating and cooling experimental campaigns allow us to highlight the potential of the proposed technology. The results suggest that an average thermal power of about 17 W per unit area can be exchanged with the ground in heating mode, while an average of 68 W per unit area is exchanged in cooling operations. The negligible impact on the stress–strain state of the wall and the surrounding soil thermal and hygrometric regime is also testified by the results collected. These aspects are associated with a reduced probability of interferences with other installations in highly urbanized areas, easiness of installation and affordable cost

Monitoring geotechnical structures by ground based radar interferometry

This paper describes two novel remote sensing techniques based on radar sensors, respectively the Synthetic Aperture Radar (SAR) and the Real Aperture Radar (RAR), and some applications to relevant geotechnical problems with the aim to demonstrate the outcomes these types of sensors can provide. The case studies here described show how the SAR technique can provide useful information to interpret landslides’ kinematics and how the RAR can be used to monitor dam displacements and tunnels’ convergences

MODELIRANJE KONTINUITETA I DISKONTINUITETA U TUNELSKOM INŽENJERSTVU

The paper discusses continuum and discontinuum modelling in tunnel engineering. A brief review of fundamentals is presented in connection with the use of closeg - form solutions and computer based numerical methods. a few remarks are derivedon the choice of either continuum or discontinuum modelling of rock mass behaviour at the design analysis stage. Consideration is given to the validation of discontinuum modelling in connection with rock mass classification methods and expected tunnel response to excavation. A case study of a TBM tunnel (4.75 m) in quartzitic micaschists is discussed in detail by paying attention to a comparison of modelling methods - including continuum and discontinuum modelling - applied at a fault zone.U članku je raspravljeno modeliranje kontinuiteta i diskontinuiteta u tuelskom inženjerstvu. Sažeto su opisane osnove zajedno s uporabom matematičkih rješenja i računalnih numeričkih metoda. Raspravljen je izbor modela kontinuuma i diskontinuuma stjenske mase u odnosu na analizu konstrukcije podgrađivanja. U obzir je uzeto potvrđivanje modela diskontinuiteta povezanog s metodama klasifikacije stjenskih masa i očekivane reakcije tunela pri iskopu. U detaljima je raspravljen prmjer studije TBM tunela (promjera 4,75 m) u kvarcitičnim mikašistima s posebnom pozornosti na uspoređivanje metoda modeliranja - uključujući modeliranje kontinuuma i diskontinuuma - uporabljenih u rasjednoj zoni

Evaluating borehole heat exchanger long term potential including the influence of advection and dispersion

Shallow geothermal energy (SGE) applications are gaining growing attention in the renewable energy sector because of high efficiency, worldwide availability and low environmental impact. Significant increase in the number of installations is envisaged as a result of energy policies and European Directives. Thus, the reliable evaluation of the available exchangeable energy, namely the geothermal potential, is of primary importance to support energy planning policies. A variety of factors influences the geothermal potential of a specific area, including ground properties, installation features, the presence of groundwater flows and the site temperature. Different approaches to assess the geothermal potential have been proposed, both with reference to the regional scale and to the city or district scale [1]. These are based either on numerical simulations or on analytical closed form solutions. The latter are particularly suitable to be adopted in Geographical Information Systems (GIS) for geothermal potential mapping purposes and are being used in practice. Most available methods consider heat conduction only. This may lead to a conservative evaluation of the potential and to a non-optimised installation planning. This is particularly true in urban areas, where space scarcity is a key factor. Furthermore, these areas may present high density of geothermal installations [2], leading to overexploitation or conflicting use of the resource. Assessment of the geothermal potential at the natural state [3] in these cases is of limited use and can lead to wrong estimation of the actual working load of a new installation. The need arises to develop methods able to capture real and actual geothermal potential which result from the cumulative effect of both natural and anthropogenic boundary conditions. This study was accomplished to implement advective and dispersive contribution and heterogeneous temperature boundary conditions in the existing analytical approach developed by [4]. This latter is considered very suitable for mapping borehole heat exchanger (BHE) potential both at regional and city scale. To consider the presence of groundwater flow and its influence on the heat exchange, a numerical parametric study was carried out. Conditions explored include temperature vertical heterogeneities and various groundwater flow velocities. It was found that, assuming depth-averaged mean parameters and a thermal conductivity equal to the first invariant of the thermal conductivities tensor, a multiplication factor Cgw, function of the ratio between advective and conductive contributions, should be added to the analytical formula [4] in order to provide improved evaluation of the BHE potential

Energy tunnels: concept and design aspects

Geotechnical structures are increasingly employed as energy geostructures in Europe and worldwide. Besides being constructed for their primary structural role, they are equipped to exchange heat with the ground and supply thermal energy for heating and cooling of buildings and de-icing of infrastructures. This technology can play a fundamental role in the current challenge of addressing the increasing need for clean and renewable sources of energy. This study investigates the possibility of thermal activation of tunnel linings. Particularly, attention will be paid on a new energy segment, which can be used together with tunnel boring machine tunneling to create so-called energy tunnels. Thermal and mechanical designs need to be developed by making effective use of computational methods to quantify the exploitable heat and assess the possible consequences on the surrounding ground and the structure itself. Guidance on how to proceed in this direction will be provided in this study, showing how thermo-hydro and thermo-mechanical numerical analyses can be used to achieve a proper and effective design of energy tunnels. Two examples of possible applications will also be presented. Keywords: Energy tunnel, Geothermal energy, Heating and cooling, Geotechnical desig

Analysis of jacking forces during pipe jacking in granular materials using particle methods

Trenchless technology is often used in congested urban areas or river crossings to install underground pipelines to minimize disturbance to surface traffic or other activities. Pipe jacking is a typical technique applied to jack pipe segments between two working shafts. However, the design of the jacking force is usually implemented using empirical methods. It should be emphasized that the jacking force will change for each site, depending on the magnitude of overcut, lubricants, work stoppages, geology and misalignment. A particle method is proposed to estimate the jacking force along the pipe. The microparameters are calibrated for sandy soils in Shenyang, so that the macroscale material behavior can be reproduced using the particle model. Hence, the normal force around the pipe circumference can be derived in the particle model, after which the interface friction coefficient is applied to evaluate the friction resistance mobilized at the soil-pipe interface. A modified Protodyakonov's arch model can be used to assess the magnitude of earth pressure acting on the shield face. In the end, the combination of friction resistance and face pressure provides the jacking force. The efficacy of the proposed particle method is demonstrated by comparing calculated jacking forces with those measured in the field for three types of jacking machines in sandy soils under the Hun River, Shenyang. Keywords: Pipe jacking, Jacking force, Particle methods, Distinct elemen