Numerical Prediction of Thermo-Mechanical Behavior of Energy Pile in Pyroclastic Soil

Abstract

The use of the ground as heat source or heat sink to manage the thermal loads within buildings through foundation is a well-established technology known as Energy Geostructures (EGS). The application of heat exchange via piles foundation known as Energy Piles (EP) are becoming increasingly popular in many European countries in the last few years. Field scale and small-scale laboratory tests represent a useful tool to get an insight in the mechanism governing pile-soil interaction under thermo-mechanical loading. In situ testing provides more realistic thermo-hydro-mechanical behavior of piles but is costly and time consuming. For these reasons laboratory small scale tests are often preferred. In such a case known stress-strain histories and controlled boundary conditions are more easily obtained. In this paper, class A predictions of small-scale laboratory tests are presented and discussed. The predictions are based on fully coupled thermo-mechanical 2D FEM simulations; these refer to a prototype cubical box made of PMMA designed to minimize boundary effects. The EP is embedded in a continuous homogeneous layer of a pyroclastic sandy soil and equipped with heat exchange pipes with circulating heat carrier fluid. Heating and cooling cycles are simulated under operational head axial load. The results of the numerical simulations are used for a proper design of the physical modeling that will be set up at laboratory and for calibration of the sensors to be installed.