The micromechanism accounting for wetting weakening of tertiary sandstones was studied. It was found that intragranular fracture prevails for all dry sandstones. However, when the sandstone is wet, intergranular fracture occurs for Type B sandstones. Therefore, one sandstone from Type A sandstones, MS1, and another from Type B, TK, were selected to further investigate the nature of the matrix. It was found that (1) for both sandstones, the major mineral components of the matrix are illite and kaolinite except that the MS1 sandstone has more chlorite; (2) leaching of matrix induced an increase of porosity and consequently results in leaching softening; and (3) among the mineral composition, chlorite is easiest to be dissolved and leached out and induces a more significant increase of porosity, which, in turn, results in a more significant leaching softening.
When geo-materials, such as soil, gravelly soil and soft rocks, are loaded by shear stress, they frequently exhibit volumetric deformation, either dilation or compression, that cannot be modeled by conventional elasticity of isotropic material. This study aims, using as few parameters as possible, to develop a material model designed to simulate the main deformation of geo-materials. A constitutive model based on the concept of shear-induced anisotropic degradation is proposed. The proposed constitutive model is characterized by the following features: (1) significant shear-induced volumetric deformation prior to failure, (2) modulus stiffening under hydrostatic loading and degradation under shearing; (3) stress-induced anisotropy; and (4) being versatile in representing many geo-materials and their behaviors under various stress paths.In the proposed model, the deformational moduli, E, G, and G′, vary according to stress state. The stiffening and degradation of these moduli render the deformational behavior of geo-materials. The proposed model needs only six material parameters, all of which possess physical meaning and can be easily obtained. Finally, the versatility of the proposed model is demonstrated by simulating various geo-materials such as sandstone, gravelly soil and shale loaded under different stress paths.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.