GATE Civil Engineering (CE) 2014 Shift 2 Solved Paper

An infinitely long slope is made up of a c-φ soil having the properties: cohesion, C = 20 kPa, and dry unit weight, γ_d = 16 kN/m³ . The angle of inclination and critical height of the slope are 40° and 5 m, respectively. To maintain the limiting equilibrium, the angle of internal friction of the soil (in degrees) is _________________