Bearing Capacity of Footings in Plane Strain

The experimental program to study plane strain bearing capacities of 3-in. and 6-in. model footings on dense sand is described. It is found essential that plane strain conditions are maintained in the test box, as deflections of the walls can cause a significant reduction in the ultimate bearing capacity and lodging of sand grains between the footing and the walls. Results also show that the ultimate bearing capacities for tough footings are only 10% higher than those for smooth footings and thus Meyerhof's recommendation that 1/2 (Nγ) be used for smooth footings is not substantiated. Sokolovski's method of solving the plasticity problem, as illustrated through the scaling procedure developed by Ko and Scott, produces the most accurate estimate of the smooth footing bearing values and appears to give a slightly conservative estimate of rough footing bearing values.