This project is designed to study the thermal energy flow in the rock environment built of granitic rocks, both in terms of efficiency as well as safety. In the frame of an in-situ experiment a study of heat stress of rock is carried out in underground laboratory Josef (central Europe). Relative stress changes in granitic rock environment induced by cyclic thermal loading at c. 120 m depth are being continuously monitored in order to evaluate the influence of the thermal load increments. The rock massif is monitored in c. 10m perimeter around a heating borehole, being built by faulted/fractured granitic rocks crosscut by a swarm of quartz veinlets. The main objective of the laboratory and field experiments and related studies is to confirm or eliminate any possible changes in physical and chemical parameters of granitic rocks exposed to thermal load of maximum 95°C. Appropriate attention is also paid to variations in the flow and circulation of groundwater and to the deformation of the rock massif caused by heating – cooling cycles. These are the key parameters necessary for the safe design and construction of underground facilities proposed for the storage of thermal energy or for waste disposal of materials that produce heat (e.g. nuclear waste).
Geotechnical monitoring is focused on stress and strain changes in rock matrix (stressmeters and strain gages), pore pressure (piezometers) and displacements induced along fractures (micro and 3D crackmeters). Present results indicate very rapid reaction of the rock massif to fluctuations in rock heating intensity and large extent of these artificially induced stress changes. The changes appear without any observable hysteresis, i.e. they behave as fully reversible in respect to irregular experimental heat supply modifications.
