**
4.1.7 Effect of rock bolts: **
when a rock bolt is**
**installed at angle β from the normal to the failure plane, it increases the
increase normal stress by *Tcosβ* and reduces the driving forces by *
Tsinβ* (figure 7), where T is the tension in the rock bolt.

**
**

Figure 7: Geometry of slope with tension crack in upper slope and its interaction with rock bolt

Therefore, the expression for factor of safety of the slope becomes

FOS =