Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Study of rock matrix properties in granitoid rocks using in situ dye experiment and mathematical modeling

 

Jan Holeček, Libor Gvoždík, Lenka Rukavičková, Jiří Záruba

Geoscience Research Reports 45, 2012 (GRR for 2011), pages 239–242

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Abstract

A new in situ dye experiment was designed and successfully performed on MEV-1 borehole at Melechov study locality in 2011. Athin borehole with diameterof 20 mm and length of 75 cm was drilled at the bottom of the MEV-1 borehole (0 76 mm) in the depth 100 m. The solution of Ostazin VG dye was injected to the thin borehole and the bottom part was isolated by inflatable packer from the rest of the borehole. The dye migrated through rock matrix in fresh granite under lithostatical pressure for 81 days. Subsequently, the borehole bottom was redrilled by original diameter 76 mm and dyed rock core was excavated. The dried core was sliced lengthwise by air-cooled diamond saw. The dye penetration length of 40 mm (i.e. 0,49 mm/day) was determined by optical observation. Mathematical modeling was used to simulate the field experiment and to determine the importance of diffusion and advection processes. The experimental measured values of dye consumption and penetration length were used to calibrate model scenarios. The model shows, that the field consumption of dye (4.6 l) is higher than the simulated value (0.12 l) for the model calibrated against the penetration length. This difference can be explained by presence of some inhomogeneities in host rock and the scale effect of the measurements. According to the model results the advection process predominates over simple diffusion in the performed field experiment.