Piling Framed Concrete Retaining Wall: Design Pressures and Stability Evaluation

The piling framed retaining wall (PFRW) is an innovative earth-retention system applicable for soils underlain by rock, which is ideal for applications where only limited right-of-way is available or adjacent structures limit the use of tieback anchors. Two PFRWs were successfully built along the I-40/I-75 corridor in Knoxville, Tennessee, with significant cost savings over traditional retaining wall designs. Although the walls were designed using conventional earth pressure theories, the soil pressures and forces acting on the wall face are not fully understood, and a rational design method has not been fully developed. Traditional theories of lateral earth pressure assume rigid translations or rotations as the fundamental deformation mode, when in reality more complex mechanisms of deformation and earth pressure distributions may exist. A series of FEM analyses was used to evaluate the soil stresses on the face of the wall for various configurations of wall geometry, backfill slopes, and soil properties. From the results, simplified design equations were developed to predict the earth pressures on the wall face and the overturning moments for stability analyses. The proposed design equations were validated against traditional expressions and compared with earth pressures measured on the wall over a 3-year period. The measured stresses and the numerical results suggest that the typical earth pressure distribution of the PFRW is neither linear nor monotonically increasing, and the proposed design equations yield conservative results for practical combinations of geometry and soil properties. The proposed design methods offer a reliable way to predict wall pressures and overturning moments and eliminate the need to conduct extensive numerical analyses for each wall to be constructed.