Anisotropic Strength
The Anisotropic Strength model allows you to define Anisotropic strength properties for a soil or rock mass, by defining cohesion and friction angle along two perpendicular axes. The axes do NOT have to be oriented horizontally and vertically but can be specified at an arbitrary angle as shown in the figure below. Required Strength Parameters are:
- Cohesion 1 and Phi 1 (cohesion and friction angle in 1-direction)
- Cohesion 2 and Phi 2 (cohesion and friction angle in 2-direction, perpendicular to 1-direction)
- Angle (in degrees, measured counter-clockwise from the positive x-axis to the 1-direction)
The cohesion and friction angle for any arbitrary plane is given by:
where 
= angle between the plane and the 1-direction, as shown in the following figure:
The Anisotropic Strength model in Slide2 could also be referred to as "Transversely Isotropic" Strength.