4.2   Impenetrable Materials

  • Circular slip surfaces are generally associated with homogenous soil conditions. However, in the field, soil conditions are rarely uniform and there exist regions of significantly different shear strength, along with discontinuities such as fissures and pre-exsting slips. Therefore, most slip surface shapes observed in slope failures are of a non-circular type, and it is a common task for the slope stability analyst to model non-circular slip surfaces.
  • MacSlope provides two ways to model non-circular slip surfaces:
  • Specified Surfaces
  • Impenetable Materials

  • The use of specified surfaces is discussed in more detail in the Search Types section. To quickly recap:
  • An unlimited number of specified surfaces may be drawn.
  • The only restriction to the shape of specified surfaces is that they do not "overhang". It is the responsibility of the user to draw valid, permissible slip surface shapes.

Impenetrable Materials

  • To create an impenetrable material, use the material editor tool as discussed in the Materials section, and select the material type to be Impenetrable. All strength, unit weight, and pore pressure paramaters are ignored.
  • Impenetrable materials, when applied to a drawing region, do not allow slip surfaces to pass through them. Slip surfaces will pass along the top of them, as depicted in the figure below.
  • The material at the slice base where impenetrable materials are encountered will be the material just above the the impenetrable material.

Impenetrable material used with specified surface