[SIT26-P04] Applications of DCDA method for in-situ crustal stress measurement using recovered core samples
Keywords:DCDA method, in-sitsu crustal stress, rock core
We used recovered hard rock cores of active fault drillings by NIED (more than 10 years ago) from the depth about 200m - 2000m. The circumferential core diameter variation was measured by an especially designed apparatus at Kyoto Univ. that consists of an optical micrometer, a pair of motor-driven rollers and a data processing system (Funato and Ito, 2017, IJRMMS). We estimated stress magnitude from a theoretical elastic relationship between the in-situ stresses and the core diameters (Funato and Ito, 2017, IJRMMS). The elastic constants (Young's modulus and Poisson's ratio) included in the theoretical relationship were already measured by standard laboratory rock tests just after the drilling. The estimated stress magnitudes were consistent to those estimated by another independent methods, such as, hydraulic fracturing and borehole breakout method conducted in the same borehole at the depth next to the recovered cores. This confirmed consistency between DCDA method and another method suggests that the stress magnitudes can be estimated reliably at many core drilling sites where the in-situ stress measurements were not yet performed.