Bearing capacity of two interfering footings

By using an upper bound limit analysis in conjunction with finite elements and linear programming, the ultimate bearing capacity of two interfering rough strip footings, resting on a cohesionless medium, was computed. Along all the interfaces of the chosen triangular elements, velocity discontinuities were employed. The plastic strains were incorporated using an associated flow rule. For different clear spacing (S) between the two footings, the efficiency factor (xi(gamma)) was determined, where xi(gamma) is defined as the ratio of the failure load for a strip footing of given width in the presence of the other footing to that of a single isolated strip footing having the same width. The value of xi(gamma) at S/B = 0 becomes equal to 2.0, and the maximum xi(gamma) occurs at S/B = S-cr/B. For S/B <= S-cr/B, the ultimate failure load for a footing becomes almost half that of an isolated footing having width (2B + S), and the soil mass below and in between the two footings deforms mainly in the downward direction. In contrast, for S/B>S-cr/B, ground heave was noticed along both the sides of the footing. As compared to the available theories, the analysis provides generally lower values of xi(gamma) for S/B> S-cr/B. Copyright (c) 2007 John Wiley & Sons, Ltd.