Evaluation of the mechanical properties of Inada granite under true triaxial conditions by discrete element method.

Uniaxial and triaxial compression tests are commonly used in rock engineering to achieve strength and shape variations parameters. However, loading conditions in real projects like excavation, underground reservoirs, and even high-magnitude earthquakes play a vital role in these experiments. Therefore, to represent the actual loading conditions on Earth, a true triaxial test ( σ 1 ≥ σ 2 ≥ σ 3 ) is performed on rock samples. In this regard, choosing the right shape of samples has significant effects on stress distribution. Cylindrical samples are more common in experimental tests because they represent better behaviour under stress and can compensate for some cubic drawbacks. Accordingly, this paper proposes a new simulation of a true triaxial test on cylindrical samples to present an efficient and economical procedure to understand the behaviour of rocks in a true triaxial state. Particle flow code in three dimensions (PFC3D) based on the discrete element method (DEM) and flat joint model were selected in this study. First, based on the data from experimental tests, a simulation of rock was performed in PFC3D software. Then, the micro-parameters were calibrated based on the macro-parameters of Inada granite test results, and the effect of those micro-parameters in this step was investigated. Next, the cylindrical true triaxial test machine was simulated in PFC3D, and loading conditions on the sample were simulated by applying various stresses in x-, y-, and z-directions. At last, the effect of unequal confinement pressure on the ultimate sample strength and failure has been investigated to predict the sample behaviour under true triaxial conditions. [ABSTRACT FROM AUTHOR]