ABSTRACT
1.1 Origin of SMP
In order to understand the shear mechanism of granular materials such as sand and gravel from microscopic point of view, direct shear tests (Figs 1.1 and 1.2) and biaxial compression tests (Figs 1.3 and 1.4) have been performed using assemblies of aluminum rods and photoelastic rods. Here, the aluminum rods and photoelastic rods are used as two-dimensional models of granular materials. It can be seen from the particle movement in the figures that there is a special plane or a shear band which plays a dominant role in controlling the deformation and failure of the granular material during shearing. The potential slip plane is a plane between the upper and lower boxes in direct shear tests (Figs 1.1 and 1.2) and a plane inclined at 45° + ømo/2 (ømo = mobilized internal friction angle) to the major principal stress plane (usually horizontal plane). This plane is called the mobilized plane by Matsuoka (1974b). This mobilized plane becomes noticeable at failure (from peak to residual), and is usually called the slip plane. If the plane plays a dominant role in controlling the failure behavior of granular materials, it is natural to assume that the plane also plays a dominant role in controlling the deformation behavior up to failure. For example, as shown in Figure 1.2, the relative movement of the upper and lower particles along the central horizontal plane is largest within the specimen, and the plane can be considered to control the deformation and strength of the specimen. The shear resistance is the summation of the horizontal components of the contact forces between particles across the mobilized plane. Therefore, the shear resistance depends on the contact forces, the contact angles, and the mobilized friction angles between particles across the mobilized plane (Matsuoka 1974a).
