EXPERIMENTAL-VERIFICATION OF THE KAISER EFFECT IN ROCKS

The Kaiser effect is a measure of damage developed in rock. It was inv estigated using 63 core specimens of eight types of rocks under uniaxi al cyclic loading. The effects of the delay time between subsequent lo ading cycles and the holding time on the Kaiser effect were examined i n granite specimens. The characteristics of AE occurring during unload ing and holding were also studied. The experimental results showed tha t most of the rocks, with the exception of some iron ores, showed an o bvious Kaiser effect before the load was very near the level of the st rength. The delay and holding times did not strongly influence the Kai ser effect. Breakdown of the Kaiser effect was expressed by the felici ty ratio that may be taken as a measure of the quality of rock. The on set of the continuously increasing AE in the first loading cycle can b e taken as a measure of the damage in rock. The mechanism of the Kaise r effect was studied with the aid of a micromechanical model. An expre ssion for the damage surface in the stress space was derived from the model. The theoretical expression was compared with the results of the Kaiser effect tests, which showed a satisfactory consistence.