12.5 A square footing located at a depth of 5 ft below the ground surface in a cohesionless soil carries a column load of 130 tons. The soil is submerged having an effective unit weight of 73 lb/ft³ and an angle of shearing resistance of 30°. Determine the size of the footing for F₁ = 3 by Terzaghi's theory of general shear failure (Fig. Prob. 12.5). D₁=5ft, Sand BxB Figure Prob. 12.5 Q-130t Y = 73 lb/ft³ =30°