# Micropile

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 *Slide3*, 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
*Slide3*, 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
*Slide3*, 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
*Slide3*, 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 *Slide3*.

## Pile Shear Strength

The **Pile Shear Strength**, is the shear FORCE necessary to cause shear failure THROUGH the pile. For illustration the diagram below is 2D however the actual implementation is 3-dimensional.

Shear failure mode for micro pile (2D diagram)

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.

## Force Application

By default, if Support Type = Micro Pile, the method of **Force Application** = Active. See the Force Application topic for a discussion of the significance of Active and Passive support force application in *Slide3*.

## Force Orientation

When a slip surface intersects a Micro Pile, the default **orientation** of the applied force (i.e. the Pile Shear Strength) is **Parallel to Surface**. For a given column base, this means that the force will be applied in the plane of the column base, **against the direction of sliding**. This is illustrated below in 2D; the actual implementation is 3D. This force orientation is consistent with the assumed failure mode of a Micro Pile. You can also choose **Perpendicular to Pile** as the force orientation if you want the applied force to be exactly perpendicular to the pile regardless of the slip surface orientation.

*Applied force orientation for micro pile, parallel (tangential) to surface (2D Diagram)*

## Implementation of Pile Support in Slide3

As discussed above, a **Pile** will apply a constant force (magnitude) to a slip surface, regardless of where it is intersected by a slip surface. The applied load is simply equal to the Pile Shear Strength:

F = P

where:

P = Pile Shear Strength (force units)

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.

*Force Diagram for Pile support*