Micro Pile

The Micro Pile support type can be used to model a micro pile or pile type of support system. Due to the nature of pile support, this type of support behaves differently from other types of support in SLIDE, since resistance to movement is assumed to be provided by loading transverse to the support direction, rather than parallel to the support direction. Note:

Like all other support types in SLIDE, it is necessary for a slip surface to intersect a Micro Pile, in order for the support to have an effect on the safety factor of the slip surface.
However, unlike other support types in SLIDE, the only failure mode for a Micro Pile, is by Shear, transversely through the pile (this is illustrated below).
Tension or pullout are NOT considered as failure modes for a Micro Pile in SLIDE, regardless of the pile orientation. Only transverse shear through the pile is considered.

NOTE: make sure that you have read the Overview of Support Implementation topic, for important information which applies to all support models in Slide.

Pile Shear Strength

The Pile Shear Strength, is the shear FORCE necessary to cause shear failure THROUGH the pile, as illustrated below.

Shear failure mode for micro pile

NOTE that the Pile Shear Strength is entered as a FORCE. The user must calculate the total shear force capacity of a pile, based on the pile cross-sectional dimensions, and the pile shear strength per unit area of cross-section.

Out of Plane Spacing

The spacing between piles in the out-of-plane direction (i.e. along the slope).

Force Application

By default, if Support Type = Micro Pile, the method of Force Application = Passive. See the Force Application topic for a discussion of the significance of Active and Passive support force application in SLIDE.

Force Orientation

When a slip surface intersects a Micro Pile, the orientation of the applied force (i.e. the Pile Shear Strength) is always TANGENTIAL to the slip surface. This is illustrated below. This force orientation is consistent with the assumed failure mode of a Micro Pile.

$image\pile3.gif$

Applied force orientation for micro pile

Implementation of Pile Support in SLIDE

As discussed above, a Pile will apply a constant force to a slip surface, regardless of where it is intersected by a slip surface. The applied load, PER UNIT WIDTH OF SLOPE, is simply equal to the Pile Shear Strength divided by the Out of Plane Spacing. i.e.

F = P / S

where:

P = Pile Shear Strength (force units)

S = Out of Plane Spacing

The Force Diagram for a Pile support type, is therefore a horizontal line, representing a constant value of applied force, regardless of where a slip surface intersects the pile.

$image\support_pile1.gif$

Force diagram for Pile support