Active vs Passive Support

Many users ask whether Active or Passive support should be used, and what capacities should be used.  First it is important to identify the main difference between Active and Passive support implementation in Slide.  Basically, active support forces work to reduce the driving forces in the factor of safety calculations, while passive support forces work to increase the resisting forces. 

 In terms of convergence properties, it has been found that active support is generally better.  However, in the end, it is up to the user to determine what type of support makes the most sense in each situation.

For a more detailed discussion comparing the two support types, one can refer to the "Active or Passive Support Modeling in Slide" developer's tip.  There is also an Active/Passive Force Application section in the Online Help.  Another good reference for support in slope stability analyses can be found in Duncan and Wrights Soil Strength and Slope Stability Text, the reference for which is provided below:

Duncan, J.M. and Wright, S.G. (2005). Soil Strength and Slope Stability, John Wiley and Sons Inc.

In particular, Chapter 8 deals with support.  In Chapter 8 of the Duncan and Wright text, Method A is the same as Slide’s Active support model, while their Method B is the same as Slide’s Passive support model. 

Related Discussions: 

  1. With respect to active and passive support capacities used in limit equilibrium slope stability analysis, Duncan and Wright (2005) offer the following guidelines:

  2. In the case of active support, how are the normal and shear components proportioned when they get to the base of the slices?