Abstract:

Subcritical crack growth is one of the main causes of time-dependent behavior in rocks. Applied the constant displacement relaxation method, subcritical crack growth in specimens made of marble and granite which were in dry and water-saturated environments was studied in double torsion test. The relations of the stress intensity factor versus the subcritical crack growth velocity V were obtained under the two different environments. The behavior of subcritical crack growth was analyzed. The threshold values of subcritical crack growth in rocks were obtained under the two different environments —— dry environment: marble =1.365, granite =2.305; water-saturated environment: marble =1.118, granite =1.490. The results showed: the relations between and accorded with linear rules; but it were discrete because of inhomogenous mineral composition, etc, it was more discrete under water-saturated environment; water can accelerate the subcritical crack growth; the effect degree was different in different rocks; the threshold values were reduced by water; the reduction was different in different rocks.

Key words: constant displacement relaxation, double torsion specimen, subcritical crack growth, effects of water, relations between and threshold values