Evaluation of fracturing process of soft rocks at great depth by AE measurement and DEM simulation

Mito, Yoshitada*; Chang, C. S.*; Aoki, Kenji*; Matsui, Hiroya ; Niunoya, Sumio; Minami, Masayuki*

In order to examine the relationship between AE, stress change and rock failure, the authors conducted the high stiffness triaxial compression tests including AE measurements, and its simulations by DEM (Distinct Element Method) using the bonded particle model. As the result, it is clarified that predominant AE frequency is a significant AE parameters to monitor the stress change in fracturing process of soft sedimentary rocks. After that, the DEM simulation of the triaxial compression test using the bonded particles model is conducted to visualize the fracturing process in the rock specimen. As the results, the relationship between AE, stress change and rock failure is clarified. Furthermore the three-dimensional DEM simulation under the in-situ stress condition provides a successful result to examine the borehole breakout observed in the actual deep borehole in the soft sedimentary rock, and the applicability of the simulation to the actual field is verified.