Finite Element Analysis of Earth Pressures for Narrow Retaining Walls

High traffic demands have led to widening of existing highways to accommodate increased traffic volume. However, due to the high cost of additional right-of-way and limited space available at job sites, construction of earth retaining walls is often done under a constrained space. This leads to retaining walls that are narrower than in design guidelines. This type of walls is referred as ”Narrow” retaining walls. Various studies suggest the mechanics of narrow retaining walls differs from traditional walls and the lateral earth pressures in narrow retaining walls are no longer properly predicated by using conventional at-rest or active equations. This paper presents finite element analyses of earth pressures in narrow retaining walls for both at-rest and active conditions. The predicted data show a favorable agreement with measured data from centrifuge tests. The results indicate that, due to arching effects and boundary constraint, the earth pressures decrease as the decrease of the wall aspect ratio for both at-rest and active conditions. The results imply that earth pressure theories would overestimate the earth pressures and the design guideline based on the values of conventional earth pressure is somewhat overly conservative and uneconomical when applying to the design of narrow walls. A new design method especially for narrow wall is proposed by modifying the earth pressures in FHWA MSE wall design guidelines.