Theoretical and Numerical Comparison of Lateral Pressures Imposed by Surcharge on Retaining Walls (Technical Note)

The elasticity theory and numerical method has been used to determine the lateral earth pressures on retaining walls due to surcharge. Initially, Boussinesq (1876) presented a relationship based on the elasticity theory to estimate the lateral pressure induced from point load. This was then extended for line, strip, uniform, …, surcharges. Experimental results showed that there exists difference between Boussinesq equation and experimental results. For example, Spangler (1936) performed large scale experiments and recorded the lateral stresses. He found stresses twice the lateral stress estimated by Boussinesq equation. Mindlin (1936) related this phenomenon to “mirror effect” but some of researchers such as Bowels does not agree with this. In this paper, PLAXIS software has been used for calculating lateral earth pressure exerted on retaining walls from line and strip surcharges. Three values of 0.3, 0.40, and 0.45 have been used for the soil Poisson ratio. The numerical results have been compared with those obtained from Boussinesq equation. The horizontal distance between surcharge and retaining wall has been taken as a variable. At a given depth, the ratio of lateral pressure determined from PLAXIS divided by that obtained from Boussinesq equation has been drawn. The results show that the horizontal distance between surcharge and retaining wall has a negligible effect on results. In addition, the ratio of PLAXIS result to that given from Boussinesq equation for line and strip surcharges is about 1.5. Moreover, the Poisson ratio has a negligible effect on results. While only line and strip surcharges are considered in this paper, the extension of analysis to other surcharges is straightforward.