Abstract

Temperature affects both the physical and structural properties of rocks and there may even cause chemical changes of minerals. Rocks are more or less inhomogeneous material, so that during testing the same rock samples taken from one location the measured values of physical properties can vary on large scattering between test specimens. To eliminate the influence of inhomogeneity of rock, we analyzed the effect of heat loading (up to 700° C) on the same specimens. For this reason we have used in our research particularly non-destructive testing methods – determination of bulk density, measuring of longitudinal ultrasonic wave propagation velocity, thermal conductivity and volumetric heat capacity. Besides the physical characteristics determined in the same specimen before and after tempering gas permeability and thermal expansion untempered and tempered test specimens was determined. Hg porosity and total porosity of untempered and tempered specimens were found, too. As model material was chosen so-called Silesian granite from Nový lom quarry (Žulová pluton, Czech Republic), which has been previously tested, and over macroscopically homogeneous character the variances in the measured parameters were found. Hg and total porosity and gas permeability increase with increasing temperature. The bulk density, the ultrasonic wave propagation velocity and thermal conductivity decrease with increasing temperature. The most sensitive parameters are ultrasonic wave velocity, thermal conductivity and permeability.

1. Introduction

A lot of experts [1–8] studied the effect of thermal loading on the rocks. Temperature affects the porosity, microcracking, ultrasonic wave velocities, thermal conductivity, strength and permeability of rocks and there cause rock expansion and even chemical changes.

Rock is usually more or less inhomogeneous material. To eliminate the influence of inhomogeneity of rocks, we analyzed the effect of heat stress on the same specimens. We have used in our research particularly non-destructive methods - determination of bulk density, measuring the longitudinal ultrasonic waves velocity, thermal conductivity and volumetric heat capacity.

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