Nail (LEM)

Define the Nail (LEM) element for Slope Stability Analysis.

Applicable Modules:

Stiffness

Reinforcement Spacing

Nail/Pile spacing in the (lateral) direction of the section thickness.

Initial Diffusion Width

Specify the width to account for the diffusion effect of Nail/Pile. Generally the width of bearing plate of Nail/Pile is used. In case of no bearing plate, the diameter of Nail/Pile may be specified.

Initial Diffusion Angle

Angle of stress distribution of Nail/Pile installation which is obtained from tests. Generally, a value in between 10-15 degrees are used.

Adjust Reinf. Effect by F.S.

During iteration to calculate slice forces, reinforcing force can be divided by safety factor resulted from each iteration.

      Independent : Input value for reinforcing force is used in the equilibrium equation. It is suitable to simulate
     reinforcing effect such as reducing driving force and increasing resisting force right after applying
     reinforcements.

     Dependent : Reinforcing force divided by safety factor calculated in the previous iteration is used in the
    equilibrium equation for the next iteration. It is suitable to simulate reinforcing effect like increasing resisting
    force after deformation occurs rather than reducing driving force.

Tension Force

Maximum tension strength (material) of Nail/Pile.

Tension/Shear Application Method

Nail

The smaller of the tension force (input) and the pull-out force (calculated from qs or input) is applied as the reinforcing force in the axial direction. Shear force can be applied by specifying a value or defining by a function.

RCS calculation from qs

Equivalent Radius

Converted equivalent radius to calculate the pull-out force resisted by Nail and the surrounding ground  

Pull-out Force = qs x π x 2R x Lin ,   R: Equivalent radius, Lin: Length embedded beyond the failure surface

Shear Force Change

If checked on , shear distribution changing from the Nail head can be entered.

Shear Force

Enter a value for shear force based on the length.

Shear Force Function

Enter a function expressing the change in shear force over the length.  

Pile

The Shear force is calculated from the plastic moment and the flexural stiffness. Tension force is used only for the upper bound of the shear force (shear force not exceeding 50% of the tension force based on Tresca) and is not used for calculating axial reinforcing force.

Minimum Applied Length

If the embedded length of Pile beyond the failure surface is shorter than the minimum applied length, then the reinforcing force for the corresponding Pile is not considered.

Equivalent Radius

Converted equivalent radius to calculate the pull-out force resisted by Pile and the surrounding ground, which is generally the radius of the bored hole.

Pull-out Force = qs x π x 2R x Lin ,   R: Equivalent radius, Lin: Length embedded beyond the failure surface

Plastic Moment

Plastic moment (Mp) of Pile.

Flexural Stiffness

Flexural stiffness (EI) of Pile.   

Nail/Pile

Reinforcing force is calculated using the critical angle (θcr) by assessing shear governed (Pile), tension governed (Nail) or tension+shear governed (Nail/Pile).   

Minimum Applied Length

If the embedded length of Pile beyond the failure surface is shorter than the minimum applied length, then the reinforcing force for the corresponding Pile is not considered.

Equivalent Radius

Converted equivalent radius to calculate the pull-out force resisted by Pile and the surrounding ground, which is generally the radius of the bored hole.

Pull-out Force = qs x π x 2R x Lin ,   R: Equivalent radius, Lin: Length embedded beyond the failure surface

Plastic Moment

Plastic moment (Mp) of Nail/Pile.

Flexural Stiffness

Flexural stiffness (EI) of Nail/Pile.

Critical Angle

Enter the critical angle (θcr) to identify shear governed (Pile), tension governed (Nail) and tension+shear governed (Nail/Pile) when calculating the reinforcing force. If the angle (θ) formed by the failure arc tangent and Nail/Pile is greater than π/2-θcr, then it is shear governed. If the angle is smaller than θcr, then it is tension governed. If the angle is greater than θcr and smaller than π/2-θcr, then it is tension+shear governed.  

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Critical angle is specified to find if Nail/Pile is shear governed, tension governed or governed by both without having to user-define it. The critical angle of 5 degrees or less is generally used.