Earth retaining walls with backfill possessing cohesion - Numerical analyses of seismic behavior

Abstract

Results of a parametric finite element study are presented regarding the seismic response of gravity earth retaining walls with backfill possessing cohesion (c-φ soil). The response of the “wall-backfill” system was studied for the cases of a 4.0 m and 7.5 m walls under both harmonic and actual (recorded) earthquake base excitations of varying intensities. The paper constitutes an extension of the Athanasopoulos-Zekkos et al. (2013) [2] study which provided a validation of the numerical model used in the analyses (based on comparisons to centrifuge testing results) and considered only cohesionless backfill material. The results indicate that the presence of backfill possessing a small to moderate amount of cohesion is beneficial regarding the kinematic response of the system: reduction of lateral wall displacements (up to 60%) and rotation (up to 40%) as well as reduction (or complete avertment) of the backfill settlements. On the other hand, the inertial response of the cohesion possessing system may range from beneficial (increase of phase difference between wall inertia and soil thrust, decrease of residual seismic earth thrust on the wall) through neutral (independence of seismic earth thrust magnitude from the presence of cohesion) to detrimental (aggravation of the backfill amplification of motion, movement of the point of application of resultant thrust towards the top of the wall). It is concluded that only low values of backfill cohesion (5 kN/m2 to 15 kN/m2) may be beneficial for the seismic response of the “wall-backfill” system.