GEOMECHANICAL PARAMETRES OF THE PODLESÍ GRANITES AND THEIR RELATIONSHIP TO SEISMIC VELOCITIES

We studied the geophysical, physical, and geomechanical parameters of the Podlesi granites in the western part of the Krusne hory Mts., near the village of Potůcky. The granites represent a fractionated intrusion within the Nejdecký Massif. In total, the studied borehole is about 300 m deep. The samples were collected at depths of between 35 and 105 metres. Seismic P-wave and S-wave velocities were measured using ultrasonic scanning. The samples were water-saturated, unsaturated, and dried. The ultrasonic scanning system consisted of four piezoelectric sensors and a digital oscilloscope recorder. The wave frequency was 1 MHz. P-wave velocities range from 4400 m.s -1 to 6500 m.s -1 while S-wave velocities range from 2800 m.s -1 to 3800 m.s -1 . These data were used to calculate dynamic Young's modulus, dynamic shear modulus, and Poisson's ratio. The deformational characteristics of the rock were specified from experimental loading of the sample with uniaxial strain. The shear and longitudinal deformation of each sample was measured using a resistive strain gauge fixed directly on the sample. Intermittent loading of the samples proceeded using a uniform gradient of axial stress of 1 MPa.s -1 . The samples were subjected to five separate loads. During the tests, following parameters were recorded: stress, longitudinal deformation, and shear deformation. These data were used to calculate static Young's and shear modulus, and Poisson's ratio.