Bearing capacity of two interfering footings

Abstract

SUMMARYBy 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 ( ) was determined, where 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 at S/B = 0 becomes equal to 2.0, and the maximum 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 for S/B>S cr /B.

Ultimate bearing capacity of equally spaced multiple strip footings on cohesionless soils without surcharge

“…Since the footing was assumed to be perfectly rough, no velocity discontinuity along the interface of footing and underlying soil mass was considered in the analysis. All the steps used in this paper for formulating the upper bound analysis as a linear programming problem and the associated computational procedure are described in the recent publications of the authors [4,14]. Linear optimization was carried out by using a linprog library program in MATLAB as was done in the previous analyses of authors [4,14].…”

“…The variations of the efficiency factor and nodal velocity patterns were examined by varying the ratio S/B. The values of N obtained from the present computations were found to be exactly the same as those computed earlier by the authors in their recent studies [4,14]; the numerical values of N are, therefore, not provided in this paper. The results only related to the interference of footings are presented herein.…”

“…In this study, the problem of finding the ultimate bearing capacity of a group of multiple strip rough footings, placed at equal spacing on the surface of a cohesionless medium, was dealt with the help of a rigorous upper bound limit analysis. This work is an extension of the previous work of the authors [4] for a group of two footings by using an upper bound limit analysis in combination with finite elements and linear programming. Following Sloan and Kleeman [10], velocity discontinuities were employed along all the interfaces of adjoining elements.…”

“…The existing solutions were obtained based on (i) the limit equilibrium method [1], (ii) the method of stress characteristics [2], and (iii) the upper bound limit analysis [3,4]. A few small-scale model tests have also been performed by different researchers 1418 K. M. KOUZER AND J. KUMAR to investigate the interference effect of two closely spaced footings [1,[5][6][7][8].…”

Soluciones de forma cerrada para la capacidad de carga de zapatas en suelos anisotrópicos cohesivos

“…With the advent of powerful computers and the development of modern computational methods the ability to analyze problems has, for the first time, outstripped our ability to describe the material (Drucker, 1991 (Chen and Davidson, 1973;Florkiewicz, 1989;Michalowski, 1997;Ukritchon et al, 1998, Kumar andKouzer, 2007;Kumar and Kouzer, 2008a;Kumar and Khatri, 2011) lateral earth pressure problems (Chen and Rosenfarb, 1973), stability of slopes (Chen and Giger, 1971;Izbicki, 1981), and vertical cuts (Drescher, 1983;Su et al, 1998;Kumar and Kouzer, 2008b). The theory provides upper and lower bounds that serve to bracket the limit load for rigid-perfectly plastic materials, and computations of the two bounds is generally referred to as limit analysis (Chen, 1975).…”