Moravian greywacke – evaluation of fracture, strength and deformability properties

This contribution brings overview of mechanical properties of greywacke with focus on fracture mechanics parameters. Investigated rock type is clastic sediment, relatively widespread in Moravia region. The rock type is significantly utilized in construction industry. For purposes of this study, Kobeřice quarry was selected as sampling locality. Mechanical properties were investigated by deformation controlled 3-point bending test. Chevron notch was created on specimens in order to study fracture mechanics parameters. Moreover, deformation controlled uniaxial compression tests were carried out, as well. Specimens were equipped with strain gauges; thus, elastic modulus and the Poisson’s ratio could be determined. Splitting tensile test was employed in order to determine tensile strength. Mean value of fracture toughness K IC was determined to 1.85 MPa·m 0.5 . Mean value of uniaxial compressive strength was observed at level of 211 MPa and tensile strength reached 19.4 MPa. Hence, the tested greywacke was considered as high strength rock. Brittle type of failure occurred during the tests. The obtained results were compared with values reported for clastic sediments from several localities in the Czech Republic. Moravian greywacke reached significantly high strength in comparison to other clastic sedimentary rocks and can be considered as valuable raw material for purposes of construction industry.