Overview of Support Implementation

Before we describe the implementation of the different types of support in Slide, we will summarize the following general rules, which apply to all support types used in Slide.

Intersection with Slip Surface

First of all, in order for the support to have an effect on a given slip surface, the support must intersect the slip surface. If the support does NOT intersect a slip surface, then NO support force will be applied to the slip surface, and the support will have no effect on the safety factor of that slip surface.

image\support1a_new.gif

Support does NOT intersect slip surface – NO effect on safety factor.

image\support1b_new.gif

Support intersects slip surface – support force will be applied.

Location of Applied Support Force

When support intersects a slip surface, a force is applied at the point of intersection of the slip surface with the support (i.e. to the base of a single slice). The applied force is simply a line load, with units of FORCE per unit width of slope.

image\support2a_new.gif

Support force is applied at the point of intersection with slip surface.

Orientation of Applied Support Force

The orientation of the applied support force, will depend on the type of support which is used.

image\support_forceorientation2a_new.gif

Magnitude of Applied Support Force

The magnitude of the applied support force, will depend on the support properties entered in the Define Support Properties dialog. These are used to determine a Force Diagram for your support. A support Force Diagram simply represents the maximum available force which the support can apply to the sliding mass, at any point along the length of a support element.

For detailed information on how the Force Diagram is determined for each support type, see the individual support type topics.

image\support_nail2a_new.gif

 

       image\support_nail3b_new.gif

Soil Nail Force Diagrams

Interpretation of Support Force Diagrams

The user should appreciate that a support Force Diagram, as implemented in Slide, does not necessarily represent the true state of stress or loading mobilized by a given support element. The Force diagram simply represents the maximum available force, which a given support element can theoretically apply to the sliding mass, at any point along its length. This is based on the assumptions described for each support type in Slide.

Remember that the Slide analysis is a limit equilibrium analysis. Displacements and strains are not considered in such an analysis. In order to realistically model the interaction of support and slope, and to calculate actual strains and loading mobilized within the support, more sophisticated numerical analysis methods are required, such as finite element or finite difference methods.

The modeling of support in Slide is a simple but useful method, of accounting for the effect of the SUPPORT SYSTEM on the SLOPE, in a limit equilibrium slope stability analysis. It is not intended to model the effect of the SLOPE on the SUPPORT SYSTEM, and the support Force Diagrams should not be interpreted in this way.

Viewing the Support Force Diagram

The support force diagram for each support element in your model, can be viewed in the Slide Interpret program, with the Support Forces option. The diagram will be displayed directly on the model, as shown in the previous figure. See the Slide Interpret Help topics for information.