In many works, it was tacitly assumed that Hill's  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
The geometric model was meshed in tetrahedral finite elements, C3D8 (154742 elements) and based on FEM simulation, one determined the Maximum Principal Stress
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
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
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