Hyperbolic

A Hyperbolic shear strength envelope is defined by the following equation:

It is important to note the definition of the parameters and in the Hyperbolic shear strength equation. The following figure illustrates a hyperbolic shear strength envelope.

Hyperbolic shear strength envelope

Cohesion is defined as the shear strength at .

Friction angle is defined as the friction angle at .

NOTE the definitions of Cohesion and Friction Angle for the Hyperbolic shear strength model. The Cohesion for a Hyperbolic shear strength envelope is actually the limiting, maximum shear strength, for high normal stress.

The Hyperbolic shear strength model has been found to characterize the shear strength of soil / geo-synthetic interfaces, and other types of interfaces [ Esterhuizen, Filz & Duncan (2001) ]. For example, it could be used to model the shear strength of:

• a concrete / soil interface
• a geotextile / soil interface

You may wish to use Hyperbolic strength to model the failure mode of "direct sliding" along a GeoTextile / Soil interface. In this case, you will have to define a narrow layer of soil along the geotextile, and assign a material type which uses the Hyperbolic shear strength model.