AMPLITUDE-FREQUENCY ANALYSIS OF SIGNALS OF ACOUSTIC EMISSION FROM GRANITE FRACTURED AT ELEVATED TEMPERATURES

The problem of stability of underground structures serving to store radioactive waste, to gasify carbon, and to utilize geothermal energy is associated with the action of elevated temperatures and pressures. The acoustic-emission method makes it possible to monitor the accumulation of microcracks arising in stress fi elds of both thermal and mechanical origin. In this report, the authors give results of a laboratory investigation into the acoustic emission from granite subjected to impact fracture at temperatures of up to 600^oC. An amplitude-frequency analysis of acousticemission signals has enabled the authors to evaluate the dimension of the arising microcracks and to determine their character (intergranular or intragranular). It has been shown that intergranular faults on the boundaries between identical minerals predominate at room temperature (purely mechanical action); at a temperature of 300^o C (impact plus thermoelastic stresses), there also appear cracks on the quartz–feldspar boundaries; fi nally, at temperatures of 500–600^o C, it is intragranular faults that predominate in feldspar. The dimensions of the above three types of microcracks are approximately 2, 0.8, and 0.3 mm respectively
   
Author:  I. P. Shcherbakov and A. E. Chmel′
Keywords:  granite, impact fracture, thermal action, acoustic emission, microcracks
Page:  786