Quartz-sand compressibility at high stresses and temperatures

The effects of temperature on the degree of grain crushing and the stress-strain response of a granular soil subjected to high stresses are a matter of interest for unconventional geomechanical projects. As a part of a research program on the thermo-hydro-mechanical-chemical compressibility of quartz sand from a heavy oil reservoir, we have conducted a series of oedometric tests under dry conditions, high stresses (up to 50 MPa) and constant temperatures, ranging from 25 to 250°C. Acoustic emissions were recorded throughout the tests, and SEM photomicrographs of sieved grain-size fractions before and after the experiments were analysed. The results show that the temperature has a negligible effect on the macroscopic compressibility, with similar oedometric curves for all the tests. Conversely, the acoustic-emission counts drop off, and changes in the particle size distribution are minor, though grains subjected at high temperature show incipient fractures attributed to subcritical cracking through stress-corrosion. Miriam Martín-Ruiz Universidad Politécnica de Madrid, UPM, Department of Continuum Mechanics and Structuress