ABSTRACT
The sinking of Zone I creates two zones of plastic equilibrium, II and III, on either side of the footing. Zone II is the radial shear zone whose remote boundaries bd and af meet the horizontal surface at angles (45 0 - ¢/2), whereas Zone III is a passive Rankine zone. The boundaries de andfg of these zones are straight lines and they meet the surface at angles of (45 0 - ¢/2). The curved parts cd and cf in Zone II are parts of logarithmic spirals whose centers are located at b and a respectively.
