The matrix porosity and related properties of a leucocratic granite from the Krudum Massif, West Bohemia

This paper investigates the matrix porosity and related properties of a leucocratic granite from the Krudum Massif, West Bohemia. The required samples were obtained from the 30-year old core of borehole KZ-25 (Material Documentation Depositories). In total, nine sample sets were taken from different depth levels within the borehole ranging from 18 m to 108 m. The hydraulic conductivity of the granite matrix was measured using a pressure cell whilst standard methods were employed to determine the dry density, connected porosity and total porosity. The pore size distribution was analysed using mercury porosimetry. The ultrasonic velocities were measured using a pulse source and oscilloscope. Dynamic Young's modulus, dynamic shear modulus, Poisson's ratio, static Young's modulus, uniaxial compressive strength and moisture were determined according to measurements of ultrasonic velocities and deformability in uniaxial compression. The morphology and structure of the pore network was studied using high resolution scanning electron microscopy. The overall porosity values defined by the different porosimetry methods follow the same trends although the absolute values differ according to the specific method. A logarithmic relationship was found to exist between hydraulic conductivity and porosity within the granite matrix. In addition, a slight depth dependence was noted in the porosity, hydraulic conductivity, bulk density, and ultrasonic velocities of the granite matrix. The SEM images have allowed precise mapping and detailed description of the pore network. keywords: leucocratic granite; matrix porosity; geomechanical properties; hydraulic conductivity; ultrasonic velocities; scanning electron microscopy