Fundamental investigation of constant stress simple shear test using DEM

DEM and experimental study of bi-directional simple shear

“…With increasing shear strain, the non-coaxiality becomes smaller, and eventually they almost approach the same orientation at the end of shearing. This is consistent with the principle of non-coaxiality for the shearing along one direction as was observed in previous studies (Yang and Yu 2006;Thornton and Zhang 2006;Ai et al 2014;Asadzadeh and Soroush 2016). The reason may be that the second shearing along only the x-direction is dominant during the whole loading process.…”

“…For instance, in Fig. 9(a), the strong contact forces projected on the xz plane approach a notable diagonal distribution, similar to the distribution under unidirectional shear obtained by Thornton and Zhang (2006), Shen et al (2011) and Asadzadeh and Soroush (2016). In Fig.…”

“…Similar contact models have been introduced or validated by many researcher for cohesionless materials including glass beads and sand (Iwashita and Oda 1998;Tordesillas and Walsh 2002;Zhou et al 2002). The DEM parameters used in the study are shown in Table 1, by referring to micromechanical parameters for glass beads or similar materials determined by Härtl and Ooi (2008) and other researchers (Ni et al 2000;Shen et al 2011;Dabeet et al 2015;Asadzadeh and Soroush 2016;Li et al 2017).…”

“…The values of all parameters except for the final friction coefficient are set and added in the model before the equilibrium calculation is launched. The final friction coefficient is used after the equilibrium process is finished, which has been a well established way to simulate dense samples because a very small sliding coefficient can speed up the equilibrium calculation The measurement sphere has long been used and well accepted by other researchers to obtain quantities such as stresses or strains (Asadzadeh and Soroush 2016). It is a sphere in three-dimensional model or a circle in two-dimensional model located in the DEM model.…”

“…Another method to study the PSR impact is the discrete element method (DEM), which is able to reflect the discrete characteristics of granular materials (Cundall and Strack 1979). The 2D and 3D DEM have been employed to model simple shear tests and hollow cylinder tests (Jiang et al 2015;Thornton and Zhang 2006;Dabeet et al 2015;Adhikari and You 2016;Asadzadeh and Soroush 2016;Farhang and Mirghasemi 2017). While the numerical results are generally in good agreement with experimental results, it can also study particle interactions such as the development of fabric.…”