Index properties and strength variation controlled by microstructure for sedimentary rocks

A large number of laboratory tests were performed on intact chemical and clastic sedimentary rocks (marlstones, sandstones and limestones). Index properties such as total porosity, dry unit weight, Schmidt hammer value and point loading index as well as the strength under uniaxial and triaxial compression were determined. The material constant mi which constitutes an input parameter for Hoek and Brown failure criterion, was also estimated by analyzing the results from triaxial compression tests. From the statistical analysis of the data, regression equations were established among rock material parameters, while conversion factors relating index properties and strength were also determined. The petrographic characteristics of the studied rocks such as mineral composition and microstructure were analyzed in thin sections and their intrinsic influence on the measured strength parameters was also investigated.