Modeling the Post-construction Deformation of Spillways over Concrete-Faced Rockfill Dams

Customarily, spillways are constructed outside the embankments of concrete-faced rockfill dams (CFRD) on account of well-known problems associated with the long-term deformation of the embankments. Construction of a spillway outside the dam’s body is costly; hence, locating the spillway over the dam embankment itself is a promising alternative. However, this requires a more profound and accurate knowledge of the mechanisms involved in the post-construction behavior of the rockfill embankment. In this work, the goal is to study displacement patterns of CFRDs, particularly displacements experienced by the overlying spillway after construction and during the first 50 years of operation, and to explore the suitable conditions under which the on-body construction of the spillway is feasible. To this end, CFRDs are modeled in three dimensions, with their on-body spillway considering various factors and modeling the rockfill creep phenomenon vital for post-construction behavior. Next, a comprehensive sensitivity analysis is performed to investigate the influence of parameters affecting the dam behavior, and a mathematical relationship is proposed to estimate the creep displacements under the spillway. Finally, CFRDs are classified into three categories based on predefined limits for the maximum creep displacement of the spillway.