The image above represents mohr – coulomb criterion.

To compute for mohr – coulomb criterion, three essential parameters are needed and these parameters are **Cohesion (|τ _{o}), Co-efficient of Friction (μ) **and

**Normal Stress (σ**

_{n}).The formula for calculating the mohr – coulomb criterion:

|τ| = τ_{o} + μσ_{n}

Where;

|τ = Mohr – Coulomb Criterion

|τ_{o} = Cohesion

μ = Co-efficient of Friction

σ_{n} = Normal Stress

Let’s solve an example;

Find the mohr – coulomb criterion when the cohesion is 7, the co-efficient of friction is 30 and the normal stress is 28.

This implies that;

|τ_{o} = Cohesion = 7

μ = Co-efficient of Friction = 30

σ_{n} = Normal Stress = 28

|τ| = τ_{o} + μσ_{n}

|τ| = 7 + 30(28)

|τ| = 7 + 840

|τ| = 847

Therefore, the **mohr – coulomb criterion **is **847.**

**Calculating the Cohesion when the Mohr – Coulomb Criterion, the Co-efficient of Friction and the Normal Stress is Given.**

|τ_{o} = |τ| – μσ_{n}

Where;

|τ_{o} = Cohesion

|τ = Mohr – Coulomb Criterion

μ = Co-efficient of Friction

σ_{n} = Normal Stress

Let’s solve an example;

Find the cohesion when the mohr – coulomb criterion is 44, the co-efficient of friction is 10 and the normal stress is 4.

This implies that;

|τ = Mohr – Coulomb Criterion = 44

μ = Co-efficient of Friction = 10

σ_{n} = Normal Stress = 4

|τ_{o} = |τ| – μσ_{n}

|τ_{o} = 44 – 10(4)

|τ_{o} = 44 – 40

|τ_{o} = 4

Therefore, the **cohesion **is **4.**

Continue reading How to Calculate and Solve for Mohr – Coulomb Criterion | Rock Mechanics