The equation that is used to calculate the total shear strength (s) of the material composing a slope, taking account of the pore-water pressure. The shear strength is then equal to the sum of the normal stress (σ) and cohesion (c). The Coulomb–Terzaghi equation is:s = c + σ.tan ϕwhere tan ϕ is the coefficient of plane sliding friction, which describes the packing, surface roughness, and hardness of the materials constituting the slope.
s = c + σ.tan ϕ
Subjects: Earth Sciences and Geography.