In many works, it was tacitly assumed that Hill's [11] suggestion of having the orthotropic directions aligned with the principal plastic stretch directions is valid, and this is indeed the case when loading maintains fixed

principal stress directions from the onset of plastic deformation.

The arch is the path of the major

principal stress, and the direction perpendicular to direction of the plane which the minor

principal stress acts.

The geometric model was meshed in tetrahedral finite elements, C3D8 (154742 elements) and based on FEM simulation, one determined the Maximum

Principal Stress (Fig.

In the case of isothermal flow, a profile of

principal stress difference from the surface to the core shows a V-shape, so molecular orientation is directly related to fountain flow (9).

Because the reservoir extends normal to the minimum

principal stress direction in theory, it was expected that hydraulic fracturing creates the reservoir extending horizontally.

Many result quantities from finite element analysis contain directionality as well as value, and, in fact, there is an inherent directionality in most analysis data such as

principal stress and deformation.

However, the experimental results show that the intermediate

principal stress is the important characteristic of rock and soil mass.

In the case of

principal stress, applying simplified von Mises yield criterion at axle point K , we get

The DP model is a smooth circular cone along the hydrostatic axis in

principal stress space (Fig.

in the non-cracked component the maximum

principal stress reaches at a point the material strength [sigma]([I.

The direction of the tensile opening calculated by the moment tensor evaluation coincides very well with the direction of the minimum

principal stress.