PSI - Issue 84

Arianna Lupattelli et al. / Procedia Structural Integrity 84 (2026) 845–851

848

Table 1. Material properties adopted in the analyses. Parameter Concrete

Beauchamp sand Unit

Density, ρ

2500

2100

Kg/m 3

Young’s modulus, E

18435

65

MPa

Poisson’s ratio, ν

0.25

0.3

-

Thermal expansion coeff., α

1∙10 -7

1∙10 -5 1140

1/K

Specific heat, C p

940

J/kg∙K W/m∙K

Thermal conductivity, λ

2

2.3

The model applies representative mechanical and thermal boundary conditions of the foundation–soil system: symmetry and fixed lateral and basal constraints, with a uniform 30 kPa load at foundation level to simulate superstructure and traffic via a substructure approach. Thermally, the soil is initialized at 15 °C with adiabatic boundaries, while heat transfer is controlled by a closed- loop geothermal system with an inlet fluid temperature of −1 °C for snow-melting conditions. 4. Results Numerical analyses were performed to assess the heat extraction efficiency of an EMP-based geothermal hydronic system under climatic conditions representative of Central Europe during winter scenario (Fig. 2a). Each simulation covered a period of 7 days, consistent with the typical operational use of such systems, which are intended to function only during limited time windows. The analyses focused on two representative micropiles within the foundation group (see Fig. 1): an edge pile (Micropile 1, P1) and a centrally located pile (Micropile 6, P6). The adopted sign convention considers compressive stresses and downward displacements as negative, and heat flux exchanged in absolute values.

4.1. Thermal behavior

The heat extraction process occurring during the snow-melting operational scenario is illustrated in Fig. 2a. In this condition, the circulating heat-transfer fluid absorbs heat from the ground through EMPs to warm the paved surface assuming a working hypothesis of a fixed snow-free area ratio, A r =0.5 (i.e., to melt at least 50% of the paved surface.

a

b

c

Fig. 2. (a) time evolution of conductive heat flux per-micropile for the edge ones (black line) and central ones (grey line) during snow-melting; temperature profiles over depth at selected time steps during snow-melting operation at the soil–pile interface: (b) edge pile; (c) central pile. Both P1 and P6 micropiles exhibit a pronounced initial peak in heat flux, reaching 92 W/m² and 86 W/m², respectively, followed by a progressive decline toward stabilized values. The results highlight the effect of thermal interference between adjacent micropiles over the 7-day operation period. Owing to the larger surrounding soil