Relationship between the deformation characteristics and microscopic properties of sandstone explored by the bonded-particle model

Previous research shows that the mechanical properties of sandstone are strongly influenced by porosity and grain area ratio (GAR). This study explores how these microscopic factors affect the elasto-plastic deformation of sandstone, and adopts a modified bonded-particle model to study the deformation behavior of sandstone under biaxial loading. Compared with the natural sandstone, the analysis model can effectively capture the elasto-plastic behavior of sandstone including non-linear elasticity and the variations of plastic flow. Furthermore, the simulated results of biaxial compressive tests show that the mechanical behavior of sandstone with different porosities and GARs possesses the following characteristics: The cohesion is significantly influenced by both GAR and porosity. Greater GAR and porosity values lead to a lesser cohesion. However, the influence of GAR on the friction angle is insignificant, and a lower porosity leads to a higher friction angle. For elastic deformation, the elastic shear and bulk modulus increase with decreasing porosity and increasing GAR. For plastic deformation, the influence of porosity and GAR on the variations of plastic angle Β under different shear stress ratios seems insignificant. On the other hand, the plastic strain trajectory ξ increases with increasing porosity, but the influence of GAR is insignificant.