Balázs Vásárhelyi

Brittle-Ductile Transition Of Anisotropic Rocks During Three-Point Bending Test

Firstly Kármán (1910, 1911), after Griggs (1936) later many other researchers (e.g. Handin and Hager 1957, Paterson 1958, Heard 1960, Byerlee 1968, Edmond and Paterson 1972, Rutter 1972, Gowd and Rummel 1980, Scott and Nielsen 1991, etc.) observed the influence of confining pressure on the behaviour of rocks which were brittle at zero and low confining pressure. At high confining pressure, however, the same rocks may be ductile. That means they may fault or otherwise deform without loss of compressive strength. The amount of ductile deformation and the strength increase progressively with increasing confining pressure until fully ductile deformation occurred with apparent work-hardening.The aim of this paper is to show the influence of confining pressure during a three- point bending test. An anisotropic gneiss was investigated in 5 different directions of the foliation under 4 different confining pressures. The function of the tensile stress vs. hydrostatic pressure was determined, as well.

Comparison of Mechanical Properties of Dry, Saturated and Frozen Porous Rocks

The mechanical properties of frozen rocks are very different from the properties of the same lithologies under ambient temperature. The goal of this paper is to describe the changes in the physical parameters of rocks caused by freezing. In addition, estimations are given on how these parameters are influenced by the intrinsic properties of rocks. For the tests, cylindrical specimens were made from highly porous Miocene limestone and porous rhyolite tuff. The samples were tested in air dry, water saturated, and frozen (−20 °C) conditions. Besides the porous stones, ice specimens were also made and used for the same tests. The laboratory tests included the determination of density, ultrasound speed propagation, porosity, capillary water absorption and strength parameters. The test results obtained under the three conditions were compared. The data set of measured physical parameters was analyzed by using regression analyses. Correlations were calculated for the measured physical parameters of air-dry, saturated, and frozen conditions. The results suggest that a stronger correlation exists between the strength and density of frozen specimens than between the strength and density of air-dry specimens. Equations were also found that describe the relationships between the density and uniaxial strength of ice and various porous rocks.

Image processing for fractal geometry-based discrete fracture network modeling input data: A methodological approach

With the intent of making data acquisition for fractal geometry-based discrete fracture network (DFN) modeling time-efficient and automatized, a new method was established. For the automation of da...