If φ = nominal diameter of reinforcing bar, f_{s} = compressive stress in the bar and f_{bd}= design bond stress of concrete, the anchorage length, La of straight bar in compression is equal to :

For an anisotropic soil, permeabilities in x and y directions are k_{x} and k_{y} respectively in a two dimensional flow. The effective permeability k_{eq} for the soil is given by