Abstract: Big difficulty normally appears in lab terrestrial stress measurement by conventional differential strain method. This paper firstly introduces the theory about anisotropy of core wave velocity vs. in-situ stress direction into differential strain analysis (DSA), and proposes a new simple and practicable method for lab in-situ stress measurement-principal direction differential strain analysis (PDDSA). The principle of this method is using anisotropy of core wave velocity to measure horizontal principal stress by which prepares samples for DSA experiment. The results by PDDSA are consistent with relatively high-accuracy hydraulic fracturing measures, indicating that PDDSA is better than DSA in accuracy, lab experimental difficulty and work requirement.

Key words: in-situ stress, measurement, anisotropy, strain, method