Abstract
Energy geo-structures are renewable energy solutions with a double role of structural support and heat exchangers. Some installations are recorded worldwide, but only limited information is available regarding the impact of thermal processes on the structural and geotechnical performance of energy geo-structures. A proper experimental campaign was conducted within the underground railway construction site of Piazza Municipio in Napoli (South Italy). An energy sheet pile wall was built and equipped with fibre optic sensors system allowing the evaluation of strains and temperature distributions along the piles, during geothermal processes. Results on a single energy pile and measurements undertaken during the field experiment are presented highlighting the effects of temperature variations on the mechanical behaviour of the soil‐structure system. From temperature measurements, it can be observed that, due to the excavation, there was a strong influence of the outside air temperature. Despite measurement uncertainties and some data gaps resulting from cut cables, the data presented makes a contribution to improving the available monitored case studies in the literature on energy structures.
Highlights
Over the years, numerous energy piles have been built in various structures and buildings and some as test piles
The instrumented piles during the heating test activities were three, this paper shows the results of the campaign related to one of them, the energy pile named EP2 (Fig.1a)
The experimental campaign on the energy piles of the retaining wall in Piazza Municipio was performed without any mechanical load applied on the energy geo-structure neither influencing construction site activities
Summary
Numerous energy piles have been built in various structures and buildings and some as test piles. The installed thermo-active elements provide additional insight into the geotechnical and energy performance of energy piles under coupled mechanical and thermal loading. You et al [8] investigated the effect heating modes on cement fly-ash gravel piles. Their findings discussed the axial stress distribution in the pile and creep rate of energy piles installed in stiff high plasticity clays due to associated effect of temperature increase. The influence of coupled thermo-mechanical load on the load redistribution, axial strain changes and induced vertical displacements in an energy pile were reported by Akrouch et al [9], McCartney and Murphy [10] and Santiago et al [11] respectively. Due to the good mechanical properties of the tuff, it was possible to excavate in a densely built environment to realize the station without significantly affecting any existing structures and infrastructures, even if the excavation level is well below the groundwater table
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