# Geometry Overview

In **C****pillar**, the pillar geometry can be modelled as either a:

- Rectangular Pillar
- Polygonal Pillar

## Rectangular Pillar

### Pillar Dimensions

A **Rectangular **pillar is defined by its **Length**, **Width**, and **Height**, or **x**, **y**, and **z** values. These are the first 3 items entered in the **Geometry **tab of the **Input Data** dialog for **Rigid**, **Elastic**, or **Voussoir **analysis methods.

**NOTE**: Depending on the relative magnitudes of x, y, and z, the term "pillar", "beam", or "plate" may be most applicable, as described at the end of this section. For convenience, the term "pillar" is used most often throughout the Help.

### Face Dip

For a **Voussoir Analysis**, the user can specify a **Face Dip **angle (degrees from horizontal) for the excavation face (>=0 and < 90). Specifying an angle > 0 has the effect of lowering the effective gravitational driving force by a factor of cos(dip angle). Other than this, the analysis procedure is the same as for a zero dip angle. See the Voussoir Analysis topic for more information.

## Polygonal Pillar

### Pillar Dimensions

A **Polygonal **pillar is defined by a at least three unique **vertices (x, y)**, and a **Height (z) **value. The polygon geometry can be viewed and defined in the **Stope Section** view.

To define the vertices of the Polygonal Pillar in the **Stope Section** view, you can:

- Select
**Add Stope Section**option from the**Boundaries**menu, or right-click menu. - Select
**Edit Coordinates**option from the**Edit**sub-menu of the**Boundaries**menu, or right-click menu.

See the Stope Section, and Stope Section View topics for more information.

### Abutment Orientation

Non-vertical abutments can also be specified by changing the **Abutment Trend** and **Abutment Plunge** under the **Geometry **tab in **Input Data** dialog.

**Polygon Pillar**option and non-vertical abutments are only available in

**Rigid Analysis**since in a Rigid Analysis only consider "plug" failure.

**Pillar Dimensions**will be reset to rectangular entries, and

**Abutment Orientation**will be reset to a

**Trend**of 0 degrees, and

**Plunge**of 90 degrees.

## Pillars, Beams, and Plates

Depending on the relative magnitudes of x, y, and z, the term **pillar**, **beam**, or **plate** will most correctly describe the geometric model:

- A
**pillar**refers to a model with a**low**span/depth ratio, the**span**being the shorter of the x and y dimensions. - A
**beam**refers to a model with one of the lateral dimensions substantially longer than the other, and a fairly high span/depth ratio (e.g. > 3). Note that the**beam span**is the**short**lateral dimension. - A
**plate**refers to a model where both lateral dimensions are of similar magnitude, and a fairly high span/depth ratio (e.g. > 3).

To model the roof of a long excavation (a **beam**), make one lateral dimension much longer than the other (e.g. x = 10, y = 100). A factor of 10 should suffice, although the user can specify any realistic dimensions (e.g. x = 10000, y = 10).