Influence of Buildings on the Subsurface Thermal Field of the City of Yekaterinburg

The influence of buildings on an urban subsurface thermal field has been analyzed based on borehole temperature data obtained in observational boreholes in Yekaterinburg and the surroundings. It has been established that the subsurface thermal field under and around buildings is characterized by a negative geothermal gradient (–0.13 to –0.05 K/m) and a positive mean annual temperature anomaly (up to 7 K at a depth of 10 m and 3.5 K at 50 m) relative to undisturbed natural value of 5.3°С. The magnitude of the temperature anomaly and its penetration depth depend on the size of the building and the time of its operation. Heat fluxes and heat contents of rocks associated with the operation of buildings have been quantified. It has been established that the excess amount of heat accumulated in the subsurface environment under and around buildings due to leaks from building basements in the range of 0–50 m reaches 500 MJ/m2, which is 10–50 times greater than the contribution associated with climate change. At the same time, this value is only hundredths of a percent of thermal energy spent on heating. The mathematical models describe well the temperature field directly under buildings and are worse at describing the near-surface temperature distribution around them due to heat leaks from the side walls of basements, the influence of heating mains and supply lines, and the contrast in the thermal properties of covering surfaces near buildings.