Terzaghi's Bearing capacity theory

Assumptions:
(i) Footing is shallow, i.e. Df<=B to 2B
(ii) Footing is continuous
(iii) Footing has a rough base
(iv) Soil above the base of the footing can be replaced by equivalent surcharge Y.Df and offer no shear resistance.
Terzaghi produced a general bearing capacity equation for footing,
     qf = c.Nc + Y.D.Nq + 0.5.Y.B.Ny
where,  qf = Ultimate bearing capacity of soil in kg or tonnes/m^2
             c= cohesion in kg or tonnes/m^2
            Y= Density of soil, kg or tonnes/m^3
    B and D = Width and depth of footing respectively in meters.
 Nc, Nq and Ny = Terzaghi's bearing capacity factors .

Ultimate and net ultimate bearing capacities of saturated clay(cohesive soils) is
  qf = 5.7.Cu + Y.D   ;    Qnf = 5.7.Cu
where Cu = Shear strength in un-drained  conditions.
Effect of water table:
(i) Water table lies below the failure zone:
   qf = Y.D.Nq + 0.5.Y'.B.Ny

(ii) Water table at the base of the footing
   qf = Y.D.Nq + 0.5[Y'+Ny]
                        Y' is submerged density
(iii) Water table at the ground surface
  qf = Y'.D.Nq + Yw.D + 0.5.Y'.B.Ny