DCDA is a new method for evaluating the in-situ stress of rocks based on the elliptical deformation of boring cores with stress relief. When a rock core sample is carved out by drilling, it becomes free from in-situ stress, and the expansion should occur elastically. If the condition of in-situ stress is anisotropic, the core must deform in an asymmetric manner. With the precise measurement of core diameters in each directions, the deviatoric stress SHmax-Shmin and azimuths of SHmax and Shmin could be determined from the circumferential variation of the measured diameter. In order to confirm the reliability of DCDA, laboratory verifications were conducted. The estimated stresses by DCDA agreed well with the applied stresses, and the directions of dmax coincide to the directions of the applied stresses. From these results, the effectiveness of DCDA was confirmed.
The measurement methods of in-situ rock stress are classified into two types, (i) the method upon in-situ tests such as over-coring and hydraulic fracturing and (ii) the core-based method such as ASR (Anelastic Strain Recovery), DSCA (Differential Strain Curve Analysis), DRA (Deformation Rate Analysis) and AE (Acoustic Emission). The latter methods allow us to estimate the state of in-situ stress from laboratory tests using rock core samples retrieved from a depth by drilling Compared with this method, the core-based method is understood to be inexpensive but less reliable because of the lack of scientific understanding of the mechanisms behind the methods. Funato and Chen [1] have proposed recently a new core-based method based on a simple elastic model, which is called the Diametrical Core Deformation Analysis (DCDA). In the present paper, we introduce the concept of DCDA and present the results of field application and laboratory experiments carried out to verify the method.
