Abstract (eng)
This master thesis deals with the assessment of the effective porosity of rocks of the Hauptdolomit Formation and the description of fault rocks cropping out in the quarry Grossau near Bad Vöslau. Effective porosity of rocks, which are categorized in different fracture density-, porosity- and fault rock classes, was determined using testing methods based on ÖNORM EN 1936 and ÖNORM B 3121, respectively.
Fault orientation and the distribution of fracture density classes and fault rock cate-gories were assessed along scanlines of different orientation to minimize scanline bias. Right angle distance equivalents of total scanline lengths and right-angle-dis-tances for faults within seven classes of sub parallel faults were determined and used to overcome scanline bias and describe the directional anisotropy of the rock mass. The approach uses the comparison between scanline length and right angle distance equivalent for each fault class. Data include the frequency and thickness of fault in the right-angle direction for each fault class.
The effective porosity of the bulk rock mass is assessed as a weighted mean by as-signing the values measured for each rock type to their proportion in a lithostrati-graphic profile (for the fracture density classes) and their proportion within the scan-lines (for the fault rocks). For cohesionless fault rocks a range of effective porosity values based on literature data for the effective porosity of loose sediments was used. The calculated porosity values for the bulk rock mass range between 1.7 and 2%.
The scanline data about orientation and thickness of fractures, faults, fault rocks and damage zones of faults allow calculations of the directional frequency of fractures and faults, and the dimension of fault rocks and damage zones. Three groups of steep NNW to WNW striking faults with occur with high frequency and well devel-oped uncemented damage zones penetrate the entire visible outcrop area and are likely to cause a higher permeability of the rock mass in this direction. Classification schemes for fault rocks and proposed mechanisms for their genesis from the literature are discussed based on observations from the field, samples and thin sections from Grossau.