The image above represents friction angle.

To compute for friction angle, two essential parameters are needed and these parameters are **Uniaxial Compressive Strength (σ _{c})** and

**cohesion (c).**

The formula for calculating the friction angle:

φ = 2tan^{-1}(^{σc – 2c} / _{σc + 2c})

Where;

φ = Friction Angle

σ_{c} = Uniaxial Compressive Strength

c = Cohesion

Let’s solve an example;

Find the friction angle when the uniaxial compressive strength is 11 and the cohesion is 22.

This implies that;

σ_{c} = Uniaxial Compressive Strength = 11

c = Cohesion = 22

φ = 2tan^{-1}(^{σc – 2c} / _{σc + 2c})

φ = 2tan^{-1}(^{11 – 2(22)} / _{11 + 2(22)})

φ = 2tan^{-1}(^{11 – 44} / _{11 + 44})

φ = 2tan^{-1}(^{-33} / _{55})

φ = 2tan^{-1}(-0.6)

φ = 2(-30.96°)

φ = -61.927

Therefore, the **friction angle **is **-61.927.**

Continue reading How to Calculate and Solve for Friction Angle | Rock Mechanics