Stability of strip footings adjacent to concrete sheetpile walls

In urban areas, earth retaining structures, such as retaining walls and sheetpile walls, are often used to enhance the utility of open space by eliminating ground slopes. After the slopes are eliminated and the ground behind the retaining structures is leveled, buildings are constructed on the backfill. Such a case scenario also appears in suburban and rural areas. When the building foundations are not far behind the walls, the foundations and walls may interact resulting in an adverse effect on the stability of either the foundation or the wall or both. As an example, the foundation-induced forces on the wall may cause excessive lateral wall deflection or displacement which may then affect foundation stability. For such problems of foundation and wall interaction, considerable attentions have been directed toward the effect of foundation on the wall stability. In the analysis, the foundation-induced forces on the wall are first determined using the theory of elasticity, these forces are then considered in the stability analysis of the wall. A more reasonable approach is to analyze the foundation and wall together with due considerations of the stress-strain and strength behaviors of foundation soil and wall.; This field study presents the method and results of analysis of the stability of concrete strip footings which are located near and parallel with concrete sheetpile walls. The foundation soil studied are a compacted kaolin and a silty clay. In the analysis the stability of strip footings was analyzed for various conditions including footing location, loading intensity, and wall thickness. The analysis was made using the finite element method based on the theory of elasto-plasticity.; According to the results of analysis, it seems that a strip footing should be located from a wall of over 6 in. thickness (152.4 mm) a distance of at least five times the footing width to avoid significant adverse effect of the wall on the ultimate bearing capacity of the footing. The minimum distances, at which the influence of wall diminishes, are estimated for the various wall thicknesses. For the kaolin backfill, the minimum distances are approximately 9, 15, 16.5 ft (2.7, 4.5, and 5.0 m) for wall thicknesses of 6, 4, and 2 in. (152.4, 101.6, and 50.8 mm), respectively. For the silty clay backfill, the minimum distances are approximately 15 ft (4.5 m) for 6 in. (152.4 mm) thick wall, 18 ft (5.5 m) for 4 in. (101.6 mm) thick wall and much greater than 18 ft (5.5 m) for 2 in. (50.8 mm) thick wall.