Abstract
It has been observed in many cases that anelastic strain change on hemisphericalborehole bottom follows instantaneous elastic strain relief by overcoring and it lasts a couple of days depending on in-situ stress state rock type. Three dimensional principal strain orientations obtained from the time-dependent strains agreed with the one from the instantaneous elastic relief strains. In-situ measurement of both instantaneous and dependent strains on conical borehole bottom have indicated that the time-dependent maximum expansion core reflects the maximum stress state when the core was retrieved. The time-dependent strain variations, therefore, can not always be used to provide a reliable estimate of in-situ stress when the principal stress orientation at the poisson expansion behavior dose not agree with in-situ stress.
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