Experimental study on the evolutions of normal stiffness of fractured granites after different temperature treatments

This study experimentally investigated the evolutions of normal stiffness of fractured granites after different temperature treatments. The influences of normal displacement (delta(n)), initial aperture (b), temperature (T), and saturated condition on the closing behavior of specimens with different openings under normal stress are systematically investigated. The results show that the changing rate of normal stiffness increases gradually with the increment of normal displacement following a quadratic function. When the normal displacement is the same, the stiffness of the specimen with a larger initial opening is relatively smaller. For specimens with various initial openings, the stiffness of saturated specimens decreases with the increasing T (from 25 degrees C to 600 degrees C) by 48.18 % when the rotation angle (alpha) is 20 degrees and delta(n)= 1 mm. When T=25 degrees C and alpha=20 degrees, the stiffnesses of dry and saturated specimens are 27.31 GPa/m and 19.32 GPa/m, respectively. Finally, two empirical models are proposed to evaluate the variations in stiffness of specimens which are correlated to the parameters such as T, b, and normal strain, and the predicted results are in good agreement with the experimental results.