Correct Answer - Option 1 : tan ϕ = 0.1 and c = 95 kN/m

^{2}
__Concept:__

**Coulomb's equation,**

τ = C + σ tan ϕ

Where,

τ = Shear strength of soil

C = Apparent cohesion

σ = Normal stress on the plane of rupture

ϕ = Angle of internal friction

__Calculation:__

Given,

σ_{1} = 150 kN/m^{2} , σ_{2} = 250 kN/m2

τ_{1 }= 110 kN/m2 , τ_{2} = 120 kN/m^{2}

We know,

τ = C + σ tan ϕ

**When, σ1 = 150 kN/m**^{2} and τ1 = 110 kN/m2

110 = C + 150 tan ϕ........(1)

**When, σ1 = 250 kN/m2 and τ1 = 120 kN/m2**

120 = C + 250 tan ϕ........(2)

Equation (2) - (1)

10 = 100 tan ϕ

**tan ϕ = 0.1**

Put tan ϕ in equation (1),

110 = C + 150 × 0.1

**C = 95 kN/m**^{2}.