The Effect of Drying around Power Cables on the Vadose Zone Temperature

Core Ideas We show the impact of soil hydraulic properties on its critical temperature. Ambient conditions have a larger impact in some fields than local soil parameters. We introduce a parameter for optimizing cable backfill based on hydraulic properties. The effects of moisture migration away from power cables depend strongly in most soils on whether the soil has reached the so‐called critical conditions (e.g., critical temperature) for a dry‐out. However, research on how to estimate this critical temperature has been limited. We solved numerically a differential equation for the planar case of steady‐state coupled heat and mass transfer in porous media, using the van Genuchten–Mualem model for the hydraulic properties of the medium. The critical isotherm is assessed by the temperature at which the steepest change occurs in the moisture content with temperature. We considered the impact of the properties of the surrounding medium and of the ambient temperature and moisture content on the dry‐out temperature. We found that seasonal variations in ambient conditions in a field in Italy have a greater impact on the critical temperature than the variations in soil properties in that field (under the assumption of a nearly uniform moisture content with depth). However, our analysis shows that, under certain conditions, a change in the van Genuchten parameter n and in a specific combination of parameters that we call a dynamic parameter can have as large an effect on the critical temperature. This suggests a direction in the optimization of backfill materials.