ABSTRACT
Fault permeabilities can range over several orders of magnitude due to complex spatio-temporal heterogeneities and anisotropy. Investigation methods at field scale (packer tests) and laboratory scale (triaxial cell tests) were performed to characterise faulted crystalline rocks in the Semmering area, Eastern Alps (Austria). The analyses of more than 180 packer tests performed in boreholes with depths down to 700 m below ground surface allow a clear differentiation of the hydraulic properties of the four crystalline tectonic units present, even though they are composed of similar lithologies. In addition these tectonic units show a general decrease in hydraulic conductivity with depth following the correlation log10K = –2,49 log10(z) – 2,59 where (z) is the depth in metres. Two tectonic units show an increase of the hydraulic conductivity above the threshold of fault rock content of 15% within the test interval. Additional investigations of fault core domains at outcrop with a thickness of 10 to 15 m and of drill cores were performed at laboratory scale. Core samples (length of 15 cm, diameter 10 cm) were taken perpendicular and parallel to the fault foliation within a kinematic coordinate system. The samples were analysed hydraulically by triaxial permeability cell testing at a flow pressures of 36 kPa. The analyses show clear hydraulic anisotropies with an up to two orders of magnitude higher hydraulic conductivity parallel to the fault foliation than perpendicular within the core zone domains.
