Correct Answer - Option 4 : Elevated cohesion soil
Concept:
On the basis of Shear strength, the soil is classified into three types as specified below:
1. Cohesion-less Soils: They are purely granular soils and possess no cohesion at all. Examples are: Sand.
The shear strength of such soils is given as:
τ = σ’ tanϕ
Where
σ' is effective normal stress and ϕ is the angle of internal friction
2. Cohesive Soils: Soils such as clay possess cohesion but no friction at all. The shear strength of such soils is given as:
τ = c ; c is cohesion
3. Cohesive frictional Soils: Soils that possess both cohesion and friction are called c-ϕ soils. Example: silt. The shear strength of such soils is given as:
τ = c + σ’ tanϕ
Where
c is cohesion
σ' is effective normal stress and ϕ is angle of internal friction