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Simulation of Ductile Failure of Granite Using DEM With Adjusted Bond Strengths Between Elements in ContactNormal access

Authors: H. Ohtani, H. Mikada and J. Takekawa
Event name: 81st EAGE Conference and Exhibition 2019
Session: Integrated Subsurface Studies - Geomechanics and Geo-Pressure Prediction
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201900940
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.44Mb )
Price: € 20

Summary:
The ductile behaviour at high confining pressure or temperature and the brittle behaviour at low confining pressure or temperature of granite is one of the most significant factors when considering the feasibility of enhanced geothermal system and disposal of high-level radioactive waste. The failure behaviour of rock mass may accelerate and might decelerate them. Therefore, laboratory testing and numerical analyses have been conducted to gain insight and replicate both brittle and ductile behavior of granite. On the other hand, numerical schemes using distinct element method (DEM), widely accepted as a conventional means of investigating rock failures, taking ductile behaviour depending on pressure and temperature conditions into consideration have not fully examined, though the numerical approach including their effects is essential for further investigations. In this study, two mechanical models for reproducing ductile behavior of granite are proposed: a bi-linear approximation model and a degradation model. The results of unconfined compression tests at different temperatures and bi-axial compression tests at different confining pressures are compared with those of laboratory experiments in terms of macroscopic failure patterns, stress-strain curves, and volumetric strain-axial strain curves. The results show that both models are valid enough to replicate semi-brittle and ductile behaviors.


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