For the further development of shallow geothermal energy, geological boundary conditions shall also be considered for the assessment of the actual properties and condition of the backfill material in the subsurface, among other things.
In the QEWS+ research project, this is being investigated in order to develop a better knowledge and understanding of the geological aspects in the construction of borehole heat exchanger systems.
Therefor, a test rig was developed to simulate boreholes for borehole heat exchangers, which allows water to be released from the borehole. The pressure regime measured in real boreholes during backfilling is transferred to the test rig. Thereby, the pressure causes a filtration of the backfill material during backfilling. After curing, the backfill column is uncovered and analysed both optically and in the laboratory. The results are presented and their transfer to real boreholes is discussed.