The influence of horizontal confinement on the bearing capacity factor Nγ of smooth strip footing

We studied the upper-bound ultimate bearing capacity of smooth strip shallow footings with symmetrical and asymmetrical horizontal confinements on purely frictional sand within the framework of upper-bound limit analysis. The subsoil follows the associated flow rule, and no surcharge on the soil surface is assumed. The contact between the soil and the horizontal confinement walls is assumed to be perfectly rough. The upper-bound solutions for the objective functions are obtained using nonlinear sequential quadratic programming. The results for the different internal friction angles phi are provided in terms of the variation of two parameters, namely, the bearing capacity factor N-gamma and the correction factor of bearing capacity K-gamma, with respect to the change in the clear spacing between the edge of smooth footing and the rigid vertical walls. The values of N-gamma and K-gamma increase with phi and decrease with the clear spacing between the edge of the smooth footing and the rigid vertical walls. N-gamma and K-gamma are more sensitive to this confining effect as phi increases. The numerical results, a comparative analysis with the results from previous studies, and design charts are also included. (C) 2014 Elsevier Ltd. All rights reserved.