Characterization of discrete fracture parameters – A case study of granites in eastern Taiwan

For granites, the interconnected water-conducting features tend to be the major groundwater flow paths. This study presents results analyzed from fracture data sampled from a single borehole for the granites in the Eastern Taiwan. Supporting data include geophysical well logging as well as measurements of brittle and brittle-ductile structures from borehole and outcrops. It is attempted to provide input data that are necessary for numerical simulations of discrete fracture network and groundwater flow. The rock in the vicinity of the borehole is highly fractured, with an average linear intensity of 8.84 m ^-1 and 5.76 m ^-1 in the upper and lower rock bodies, respectively. Rock cores retrieved from the upper rock body show evident slickensides caused by the shear zone. At present, the reactivation of fractures is controlled by the normal faulting stress regime. Features in the meta-granite cores mainly were developed along the (257°, 58°) and (341°, 37°) in the study area. The former set is perpendicular to the minimum principal stress direction. Although fractures of this set are mostly filled with calcite, it could be re-active in the future by the tectonic stress field.