# Bolt Support Force

The **Bolt Support Force** that is ultimately applied to a wedge and the orientation of the applied force (**Tension** or **Shear**) depend on the following factors:

**Bolt Deformation Mode** - The mode in which a bolt intersects a wedge failure plane. The deformation mode depends on whether the failure plane is a shear (sliding) plane or a dilating (opening) plane, and also on the orientation of the bolt with respect to the plane and the sliding direction. There are six possibilities considered, as illustrated in the figure below.

Possible bolt deformation modes [Windsor, 1996]

**Bolt Tensile Capacity** - The maximum **Tensile Force** that can be supplied by the bolt is determined from the Bolt Force Diagram and the point at which a wedge plane intersects the bolt along its length. The **Bolt Force Diagram** is derived from the bolt properties (e.g., **Tensile Capacity**, **Plate Capacity**, **Bond Strength**) entered in the **Bolt Properties** dialog.

**Bolt Orientation Efficiency** - If considered, Bolt Orientation Efficiency is applied only to the **Tensile Force**. **Bolt Orientation Efficiency** can be toggled on or off, and there are three possible methods of computing the efficiency.

**Bolt Shear Strength** - Whether Shear Strength of the bolt is considered.

## Applied Bolt Support Force

The following table summarizes the possibilities of applied **Bolt Support Force** for all combinations of **Bolt Deformation Mode**, **Bolt Orientation Efficiency** (ON/OFF) and **Bolt Shear Strength** (ON/OFF).

Bolt Deformation Mode | Bolt Efficiency: Off Shear: Off | Bolt Efficiency: On Shear: Off | Bolt Efficiency: On Shear: On | Bolt Efficiency: Off Shear: On |

A | tensile | tensile * eff | tensile * eff | tensile |

B | tensile | tensile * eff | tensile * eff | tensile |

C | tensile | tensile * eff | tensile * eff | tensile |

D | tensile | tensile * eff | shear | shear |

E | tensile | zero force | shear | shear |

F | tensile | zero force | shear | shear |

Table 1: Summary of Bolt Support Force

#### NOTES:

**tensile**is the**Tensile Failure Capacity**(without applying**Bolt Orientation Efficiency**) determined from the Bolt Force Diagram.**eff**is the Bolt Orientation Efficiency factor.**shear**is the bolt shear capacity, if the Bolt Shear Strength option is used.**Modes A, B, C**- If a bolt is in mode A, B or C, only a**Tensile Force**is applied in the direction of the bolt. The**Tensile Force**is multiplied by the**Bolt Orientation Efficiency**factor if**Bolt Orientation Efficiency**is being used.**Mode D**- If a bolt is in mode D, it can use either**Tensile**or**Shear Force**. If the**Bolt Shear Strength**option is ON,**Shear Forc**e is used.**Shear Force**is applied opposite to the sliding direction of the wedge. If the**Bolt Shear Strength**option is OFF,**Tensile Force**is used.**Modes E, F**- If a bolt is in mode E or F, it can use either**Tensile**, zero, or**Shear Forc**e, depending on the selection of**Bolt Orientation Efficiency**and**Bolt Shear Strength**.- If both
**Bolt Orientation Efficiency**and**Bolt Shear Strength**are turned OFF, the full**Tensile Force**is applied in the direction of the bolt, regardless of how the bolt intersects the wedge (i.e., even if the bolt is in a**Shear Deformation Mode**).

## Direction of Bolt Support Force

There are two possibilities for the direction of the applied **Bolt Support Force** (referring to Table 1):

**Tensile -** For all cases marked as **tensile** or **tensile * eff**, the direction of the applied **Bolt Support Force** is *in the direction of the bolt*.

**NOTE:** The direction is not affected by the **Bolt Orientation Efficiency** factor. The direction is always exactly in the direction of the bolt, even if the **Bolt Orientation Efficiency** factor is applied.

**Shear -** For all cases marked as **shear** (**Bolt Shear Strength** option is toggled ON), the direction of the applied **Bolt Support Force** is *opposite to the sliding direction of the wedge*.

A bolt can never apply both **Tensile** and **Shear** **Support** at the same time. The two cases are completely exclusive in the **RocPlane** implementation.