Evaluation of long-term monitoring data of the energy foundations at metro station Taborstraße in Vienna

Abstract

Constructed in 2003 and subsequent years and opened in 2008, four underground stations of the extended metro line U2 in Vienna have been operating with their thermo-active ground-source energy systems for more than a decade by now. As it was the first full-size application of energy diaphragm walls and energy bottom slabs in underground stations, one of the locations, U2/2 Taborstraße, has been equipped with numerous sensors in order to allow for scientific evaluation. Some of the continuously measured data has unfortunately been lost due to technical malfunctions in recent years. Measurements have resumed manually since November 2020 on a monthly basis in order to regain knowledge of the yearly trend enabling long term comparisons and predictions. The paper presents an overview of the U2/2 Taborstraße station, focusing on the installed ground energy system and instrumentation. A comparison of the recorded energy output with the predicted heating and cooling demand are discussed in the scope of energy performance. Furthermore, this paper gives a first overview of the temperature-strain behavior of the diaphragm walls, utilizing the strain and temperature data collected over a period of roughly 13 years in operation.