1,721,072 research outputs found
Experimental and numerical investigations on the energy performance of a thermo-active tunnel
Full text linkThe paper illustrates the experimental and numerical study performed to assess the energy performance of a thermo-active tunnel lining. The experimental data from the real-scale energy tunnel prototype tested in the tunnel of the Turin Metro Line 1 South Extension are considered, by presenting the results of the tests performed in heating and cooling mode through both the ground and air configurations of the novel Enertun layout. Thanks to the availability of the original experimental data collected, it was possible to calibrate and corroborate a thermo-hydraulic numerical model, then used to extend the results to different ground and environmental conditions. Understanding of the role of some of the most important design parameters is illustrated in the form of parametric design charts, that update to the Enertun configuration those already existing in literature. A simple method for preliminary evaluation of the potential of energy tunnels, accounting for the investigated design parameters, is formulated
Analysis of jacking forces during pipe jacking in granular materials using particle methods
Full text linkTrenchless 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
Assessing the interaction of an energy tunnel with the underground thermal conditions in an urban area
Full text linkIn the very shallow depths of urban areas it is difficult to find natural undisturbed underground thermal conditions because of anthropic interventions. Moreover, these areas are being increasingly used for energy purposes, for example implementing the technology of shallow geothermal systems to provide clean thermal energy and supply the thermal demand of buildings in both winter and summer seasons. The heat exchanged by these types of renewable energy technologies, in particular ground source heat pump systems such as open loop and closed loop ones, in combination with further anthropogenic activities, results in altered thermal regimes in the subsurface. Energy tunnels, which are achieved by thermally activating the tunnel lining, have recently gained attention among closed loop geothermal systems. Therefore, when planning an urban energy tunnel, attention has to be devoted to the initial underground thermal conditions and to the interactions the pre-existing thermal regime will have with the energy tunnel itself. To this aim, the paper outlines a methodological approach which is then applied to a case study in Turin, Italy, where a new metro line is planned. Thermo-hydraulic numerical modelling is adopted to reproduce the thermally disturbed subsurface environment in the study area prior to the energy tunnel’s thermal activation, due to the presence of multiple heat sources (open loop and closed loop systems, underground buildings, car parks and infrastructures), as well as after its commissioning. Results are illustrated in terms of temperature maps and cross sections where the thermally affected zones due to open loop, mainly, and closed loop systems are depicted depending on the operational mode of the shallow geothermal systems. Those results highlight that, when the installation of a new energy tunnel is envisaged, it is necessary to consider the current geothermal exploitation of the area and the operation of neighbouring similar systems
Sensitivity analysis for the design optimisation of an energy tunnel based hydronic heated pavement
Full text linkTo cope with road safety management during cold seasons, chemical agents such as sodium, magnesium and calcium chlorides are usually chosen for their effectiveness and rapidity of action. However, besides accelerating road pavement degradation, these may also induce several environmental damages, such as altering the chemical composition of aquifers. For this reason, electric- or hydronic-based solutions have been explored, developed and tested successfully. The paper investigates the performance of a hydronic heated pavement supplied by an energy tunnel as a function of geometrical, operational and environmental factors. Thermo-hydraulic numerical analyses are adopted to guide the realisation of a full-scale prototype of an anti-icing system in an existing tunnel in the North-West of Italy. An economic assessment is then presented
A novel real-scale experimental prototype of energy tunnel
No full textThe paper illustrates the realization of an experimental real-scale energy tunnel prototype in the tunnel under construction of the Turin Metro Line 1 South Extension.
The aim is to test a new concept of energy segment (Enertun) that will be here described by outlining advantages, possible configurations and applications. A
comprehensive view of the different phases needed for the installation of the prototype will be given together with the description of its main components. An
illustrative test performed at the site is also described and discussed by showing the amount of heat that can be exploited from the ground
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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