Creep strain was observed for specimens loaded to a stress difference greater than 70 MPa. The rate of strain accumulation increases with stress difference. Creep does not exhibit a constant strain rate, but decreases with increasing time. The effects of frequency, strain amplitude, and saturation on Young's modulus were measured on specimens of Berea sandstone, Gypsy sandstone, Devine limestone, granite, and welded tuff. The modulus of room dry samples remains relatively constant with frequency.
Dispersion is observed in the saturated samples and is attributed to fluid flow.
The moduli of sandstone, limestone, and granite decrease as strain increases. On several specimens, the higher confining pressure thermal cycles were first performed to inhibit possible thermal effects, such as cracking. The coefficient of thermal expansion for welded tuff increased with temperature. The effect of confining pressure on thermal expansion for tuff was small. In addition, for each specimen designated for unconfined compression, a CT scan was performed.