Slide Model > Support > Define Support Properties
The Soil Nail support type can be used to model soil nail slope reinforcement. Note:
A Soil Nail is assumed to be fully bonded along its entire length
The Soil Nail support type in SLIDE is equivalent to Grouted Tieback support with Bond Length = 100%.
The Soil Nail support type in SLIDE is differentiated from the Grouted Tieback for user convenience. However, the user should be aware that, as far as the SLIDE implementation is concerned, a Grouted Tieback with Bond Length = 100% would behave exactly the same as a Soil Nail, all other parameters being equal.
A Soil Nail is NOT equivalent to the Grouted Tieback with Friction support type in SLIDE.
NOTE: make sure that you have read the Overview of Support Implementation topic, for important information which applies to all support models in Slide.
Tensile Capacity
The Tensile Capacity entered for a Soil Nail, represents the maximum tensile capacity of an individual soil nail. This is the capacity of the soil nail itself (e.g. steel tensile capacity), independent of the plate capacity or the bond capacity. Units are Force.
Plate Capacity
The Plate Capacity is the maximum load which can be sustained by the plate assembly which connects the soil nail to the slope. Units are Force.
Out of Plane Spacing
The spacing between soil nails in the out-of-plane direction (i.e. along the slope).
Force Application
For Soil Nail support, the default method of Force Application = Passive, since there is normally no initial loading or tensioning of a soil nail. See the Force Application topic for a discussion of the significance of Active and Passive support force application in SLIDE.
Force Orientation
For Soil Nail support, the orientation of the applied force is always PARALLEL to the orientation of the soil nail.
Pullout Strength
For a Soil Nail, the Pullout Strength is expressed as a Force per unit Length. NOTE that the length units in this case, refer to the length along the soil nail. The Bond Strength determines the pullout and / or stripping force which can be generated by a soil nail.
Material Dependent Pullout Strength
See the Grouted Tieback topic for details, as the procedure is the same.
Implementation of Soil Nail Support in SLIDE
Consider a soil nail which intersects a slip surface, as shown below.
Li = length of soil nail within sliding mass
Lo = length of soil nail embedded beyond slip surface
Soil Nail Parameters
B = Bond Strength (force / unit length of soil nail)
S = Out of Plane Spacing
T = Tensile Capacity (force)
P = Plate Capacity (force)
At any point along the length of the soil nail, there are 3 possible failure modes which are considered:
Pullout (force required to pull the length Lo of the nail out of the slope)
Tensile Failure (maximum axial capacity of the soil nail)
Stripping (slope failure occurs, but nail remains embedded in slope)
The maximum force which can be mobilized by each failure mode, PER UNIT WIDTH OF SLOPE, is given by the following equations:
Pullout: 
Eqn.1
Tensile: 
Eqn.2
Stripping: 
Eqn.3
At any point along the length of a soil nail, the force which is applied to the slip surface by the soil nail, is given by the MINIMUM of these three forces.
Applied Force = min (F1, F2, F3) Eqn.4
NOTE:
in order for stripping to occur, the Plate Capacity must be exceeded. The Plate Capacity is included in the stripping force equation, and added to the shear capacity along the length Li.
if the Soil Nail Pullout Strength is specified as Material Dependent, then the Pullout Force and Stripping force, are determined by integrating along the lengths Lo and Li, to determine the force contributed by each segment of the soil nail which passes through different materials.
A typical Soil Nail Force diagram, which exhibits all three failure modes, is shown below. In this case, the Plate Capacity is less than the Tensile Capacity, and therefore "stripping" is a possible failure mode. If the Plate Capacity is greater than or equal to the Tensile Capacity, then stripping cannot occur, and the Soil Nail Force diagram will be determined only by the Tensile and Pullout failure modes.
Soil Nail Force Diagram