1 Abstract—Allowable-bearing capacity is the competency of soil to safely carries the pressure from the superstructure without experiencing a shear failure with accompanying excessive settlements. Ensuring a safe bearing pressure with respect to failure does not tolerate settlement of the foundation will be within acceptable limits. Therefore, settlement analysis should always be performed since most structures are settlement sensitive. When visualising the movement of a soil wedge in the bearing capacity criterion, both vertically and horizontally, it becomes clear that by confining the soil surrounding the foundation, both the bearing capacity and settlement values improve. In this study, two sizes of spread foundation were considered; (2×4) m and (3×5) m. These represent two real problem case studies of an existing building. The foundations were analysed in terms of dimension as well as position with respect to a confining wall (i.e., sheet piles on both sides). Assuming B is the least foundation dimension, the study comprised the analyses of three distances; (0.1 B), (0.5 B), and (0.75 B) between the sheet piles and foundations alongside three depths of confinement (0.5 B), (1 B), and (1.5 B). Nonlinear three-dimensional finite element analysis (ANSYS) was adopted to perform an analytical investigation on the behaviour of the two foundations contained by the case study. Results showed that confinement of foundations reduced the overall stresses near the foundation by 65% and reduced the vertical displacement by 90%. Moreover, the most effective distance between the confinement wall and the foundation was found to be 0.5 B. Keywords—Bearing capacity, cohesionless soils, spread footings, soil confinement, soil modelling. I. INTRODUCTION NY foundation when designed should satisfy two essential requirements; first, it must have at least a certain specified safety against bearing capacity failure, and second, the settlement under working load must not exceed the tolerable limits for the superstructure. In any specific case, one of these criteria will determine the necessary dimensions of the foundation, but it may be difficult to say in advance, which one it will be. Therefore, it is usually necessary to investigate both. The study of ultimate bearing capacity has the purpose of determining the load under which a foundation with given shape, dimensions, and depth sinks indefinitely into the soil. The study of the limit of deformation has the purpose of determining load movements of the structure are at the limit of what is still allowable for the stability. Fig. 1 shows the pattern of particle motion at failure for a Tahsin Toma Sabbagh is with the School of Computing, Science and Engineering, University of Salford, UK (e-mail: t.toma@salford.ac.uk). Ihsan Al-Abboodi and Ali Al-Jazaairry are with the School of Computing, Science and Engineering, University of Salford, UK. shallow foundation. This provides the basis for understanding the development of failure in granular soil. When the soil fails, the particles move downward and move in the horizontal direction at the same time. Hence, the soil is pushed out from beneath the footing and the surface of the surrounding soil heaves. Fig. 1 Failure Zones under Footing (after [1]) By observing the behaviour of shallow foundations subjected to vertical loads, it is a well-established fact that the bearing capacity failure occurs usually as a shear failure of the soil supporting the footing. The problem formulated, as shown in Fig. 2, has been solved by Al-Aghbari [3] using the theory of plasticity. Fig. 2 Failure Wedge (after [2]) The basic solution available indicated that the failure pattern should consist of three zones; (I, II, III), where zone (I) is an active Rankin zone, which pushed the radial Prandtl zone (II) sideways and the passive Rankin zone (III) in an upward direction. The lower boundary (ACDE) of the displaced soil mass is composed of two straight lines AC and DE, inclined at 45+ϕ/2 and 45-ϕ/2 respectively, to the horizontal. The shape of the connected curve CD depends on the angle ϕ and on the ratio γB/q. When γB/q approaches 0 (weightless soil) the curve becomes a logarithmic spiral, which for γ = 0 degenerates into a circle. In the general case (γB ≠ 0), the curve lies between a spiral and circle as long as (ϕ ≠ 0). For frictionless soil (ϕ = 0), the curve is always a circle. All these finding have been Effect of Confinement on the Bearing Capacity and Settlement of Spread Foundations Tahsin Toma Sabbagh, Ihsan Al-Abboodi, Ali Al-Jazaairry A World Academy of Science, Engineering and Technology International Journal of Geotechnical and Geological Engineering Vol:12, No:11, 2018 686 International Scholarly and Scientific Research & Innovation 12(11) 2018 Digital Open Science Index, Geotechnical and Geological Engineering Vol:12, No:11, 2018 waset.org/Publication/10009792