Relaxation of rock after removal from in situ state consists of an elastic (instantaneous) component and an anelastic (time-dependent) component. Technique using anelastic strain recovery (ASR) have been aimed to determine the direction and magnitude of in situ principal stresses by measuring changes in geometry of recovered core with time immediately after retrieved from deep boreholes. Timedependent microcrack growth has been suggested as a possible mechanism for the strain recovery process, although it has been modeled by using viscoelastic theories. Time-dependent microcrack growth driven by the tensile residual stress as well as an instantaneous microcracking by the relaxation of the stresses was modeled by considering an homogeneous inclusion containing mocrocracks that grow due to subcritical crack growth. The inclusion having circular cross section was embedded in coaxial himogeneous matrix which was less stiffer than the inclusion. The model was able to predict the dependence of the time-strain curve of the inclusion on the initial stress level and agreed with the observed ASR data.
