<p>In closed-loop Ground Source Heat Pump system, the circulation of a heat-carrier fluid into the heat exchanger provides the thermal exchange with the underground.</p><p>In order to improve the heat extraction from the ground, the fluid temperature is often lowered down to subzero temperatures; as a consequence, the thermal alteration induced in the ground is more intense and can cause freezing processes in the surroundings. In sediments with significant clay fraction, the inner structure and the pore size distribution are irreversibly altered by freezing-thawing cycles.</p><p>A wide laboratory program has been performed in order to measure the induced deformations and the permeability variations under different conditions of mechanical loads/depth [1], interstitial water salinity [2] and soil plasticity [3]. In addition, vertical deformations and permeability variations induced by freeze-thaw cycles have been measured also in Over-Consolidated silty clays at different OCR [4].</p><p>The results suggest that, despite the induced frozen condition is quite confined close to the borehole [5], in Normal-Consolidated silty clay layers the freezing-thawing-cycles induce an irreversible settlement up to 16%, gathered cycle-after cycle depending on sediment plasticity, pore fluid salinity and applied load. In addition, despite the overall contraction of the soil, the vertical hydraulic conductivity may increase by about 8 times due to a remarkable modification of the soil fabric with increases in pore size, pores connectivity and orientation [6].</p><p>The OC silty-clays show an opposite behavior. Experimental results point out that, in case of OC deposits, higher the OCR lower the freeze-thaw induced settlement. In case of OCR > 15, the settlement turns to a slight expansion. Conversely, the observed augment in vertical permeability increases with the OCR degree [4].</p><p>These occurrences are significant and irreversible and could affect the functionality of the system as well as lead to environmental effects such as local settlements, negative friction on the borehole heat exchangers or interconnection among aquifers in the probe surroundings.</p><ul><li>[1]. Dalla Santa G*, Galgaro A, Tateo F, Cola S (2016). Modified compressibility of cohesive sediments induced by thermal anomalies due to a borehole heat exchanger. <strong>Engineering Geology</strong> 202, 143-152.</li> <li>[2]. Dalla Santa G*, Galgaro A, Tateo F, Cola S (2016). Induced thermal compaction in cohesive sediments around a borehole heat exchanger: laboratory tests on the effect of pore water salinity. <strong>Environmental Earth Sciences</strong>, 75(3), 1-11.</li> <li>[3]. Cola S, Dalla Santa G, Galgaro A (2020). Geotechnical hazards caused by freezing-thawing processes induced by borehole heat exchangers. <strong>Lecture Notes in Civil Engineering</strong>, 40, pp. 529&#8211;536</li> <li>[4]. Dalla Santa G, Cola S, Galgaro A (2021). Deformation and Vertical Permeability Variations Induced by Freeze-Thaw Cycles in Over-Consolidated Silty Clays. <strong>Challenges and Innovations in Geomechanics</strong>, 117</li> <li>[5]. Dalla Santa G*, Farina Z, Anbergen H, R&#252;haak W, Galgaro A (2019). A Comparative Study on the Relevance of Computing Freeze-Thaw Effects for Borehole Heat Exchanger Modelling. <strong>Geothermics</strong> 79, 164-175.</li> <li>[6]. Dalla Santa G*, Cola S, Secco M, Tateo F, Sassi R, Galgaro A (2019). Multiscale analysis of freeze-thaw effects induced by ground heat exchangers on permeability of silty-clays. <strong>Geotechnique</strong> 2019, 69(2).</li> </ul>
A terrestrial laser scanner (TLS) allows the generation of a detailed model of a landslide surface. In this way, when two or more georeferenced models obtained by multi‐temporal scans are available, the landslide displacement field can be computed. Nevertheless, such a computation is a relatively complex task because the recognition of correspondences among the multi‐temporal models is required. The Iterative Closest Point (ICP) algorithm allows the alignment of two 3D objects having a common part by iterative shape matching. A new method for the automatic calculation of a landslide displacement field is presented here. It is based on a piecewise application of the ICP algorithm and is made possible by the robustness of this algorithm against noise and small morphological modifications. After a series of numerical experimentations, this method was successfully applied to two test sites located in the North‐Eastern Italian Alps affected by high‐risk landslides of the slump type (Perarolo di Cadore and Lamosano) with very different observational conditions.
Propagation models can study the runout and deposit of potential flow-like landslides only if a reliable estimate of the shape and size of the volumes involved in the phenomenon is available. This aspect becomes critical when a collapse has not yet occurred and the estimation of the unstable volume is not uniquely predictable. This work proposes a strategy to overcome this problem, using two established analysis methods in sequence; first, a Strength Reduction Method (SRM)-based 3D FEM allows the estimate of the instable volume; then, this data becomes an input for a Smoothed Particle Hydrodynamics (SPH)-based model. This strategy is applied to predict the possible evolution of Sant’Andrea landslide (North-Eastern Italian Alps). Such a complex landslide, which affects anhydrite–gypsum rocks and is strongly subject to rainfall triggering, can be considered as a prototype for the use of this procedure. In this case, the FEM–SRM model is adopted, which calibrates using mapping, monitoring, geophysical and geotechnical data to estimate the volume involved in the potential detachment. This volume is subsequently used as the input of the SPH model. In this second phase, a sensitivity analysis is also performed to complete the evaluation of the most reliable final soil deposits. The performed analyses allow a satisfactory prediction of the post-collapse landslide evolution, delivering a reliable estimate of the volumes involved in the collapse and a reliable forecast of the landslide runout.
Weather plays an important role for energy uses in buildings. For this reason, it is required to define the proper boundary conditions in terms of the different parameters affecting energy and comfort in buildings. They are also the basis for determining the ground temperature in different locations, as well as for determining the potential for using geothermal energy. This paper presents a database for climates in Europe that has been used in a freeware tool developed as part of the H2020 research project named “Cheap-GSHPs”. The standard Köppen-Geiger climate classification has been matched with the weather data provided by the ENERGYPLUS and METEONORM software database. The Test Reference Years of more than 300 locations have been considered. These locations have been labelled according to the degree-days for heating and cooling, as well as by the Köppen-Geiger scale. A comprehensive data set of weather conditions in Europe has been created and used as input for a GSHP sizing software, helping the user in selecting the weather conditions closest to the location of interest. The proposed method is based on lapse rates and has been tested at two locations in Switzerland and Ireland. It has been demonstrated as quite valid for the project purposes, considering the spatial distribution and density of available data and the lower computing load, in particular for locations where altitude is the main factor controlling on the temperature variations.
