Heat resultant of uniaxial stress field in rock

Abstract

Laboratory experiments on cylindrical samples of sandstone and bituminous coal were undertaken dealing with precise measurements of temperature change during uniaxial compression of test pieces until failure occured. Temperature gradients are quoted as a function of stress, and the internal stress field is defined. Effect of the rate of stress and heat dissipation in time under steady load were determined experimentally. Thermal stress concentration factor at the gage insert holes was calculated to facilitate conversion of apparent thermal gradients into real internal heat values. The internal energy balance based on measurements of modulus of elasticity, strain hysteresis, and thermal properties of rocks, and calculated heat flow, is submitted. A rheologic interpretation of the measured effects based on the results of previous rheology-of-rock investigations, and Burgers' body strain energy calculation, is quoted. Satisfactory agreement of theoretical and experimental results was obtained.