In general, granite has anisotropy due to the preferred orientation of pre-existing micro-cracks. It is possible to obtain the information of the preferred orientation of micro-cracks by the measurement of the P-wave velocity. Therefore, by measuring P-wave velocity in various directions, we can obtain the information of three-dimensional distribution of micro-cracks in granite. Assuming that the three-dimensional distribution of micro-cracks in granite was caused by the stress release during coring, it can be possible to assess the stress state at the location of coring in the underground considering the relationship between three-dimensional distribution of P-wave velocity and microcracks. Differential Strain Curve Analysis (DSCA) is one of the methods to assess the stress state in the underground using rock core samples based on the initiation of micro-cracks due to the stress release. Therefore, if the three-dimensional distribution of P-wave velocity can be related to the orientation of micro-cracks determined by DSCA, the stress state in the underground can be evaluate from the measurement of P-wave velocity. In this study, by conducting both P-wave velocity measurements in various directions with a polyhedral specimen and DSCA using granite samples obtained from the same location, the relationship between the three-dimensional distribution of P-wave velocity and that of the crack parameter determined from DSCA was investigated. In addition, we considered the possibility to assess the stress state in the underground from P-wave velocity measurement. From the above measurements, a negative correlation between the P-wave velocity and the crack parameter from DSCA was observed for granite. Additionally, by using the value of the P-wave velocity which is corresponding to the crack-free granite rock, we could show the possibility to assess the stress state in the underground.
