Question

The effective stress friction angle of a saturated cohesloniess soil is 38° The ratio of shear stress to normal effective stress on the failure plane is
1. 0.781
2. 0.616
3. 0.488
4. 0.438

Answer 1

Correct Answer - Option 1 : 0.781

Concept:

we use the following equation to find out the applied shear stress;

τ = C + σ tanϕ 

Where, τ = Shear stress;  σ = normal stress

C = cohession of soil; ϕ = angle of internal friction or failure plane;

Calculation:

Given:

ϕ = 38∘ 

As the given soil is cohessionless, hence C = 0

Now, let's put the values into the equation.

∴ τ = 0 + σ × tan 38∘ 

⇒ τ/σ = tan 38∘

∴ τ/σ = 0.781