Longitudinal vibrations of tall concrete faced rockfill dams in narrow canyons

Longitudinal vibrations of concrete-faced rockfill dams may cause significant compressive stresses and joint openings in the slab panels. The behavior of such dams subjected to longitudinal and vertical vibrations is investigated, based on numerical simulation of the staged construction, reservoir impoundment and seismic shaking. The static analysis uses a hyperbolic model for the rockfill, whereas the seismic analysis uses a nonlinear hysteretic model which accounts for the dynamic properties. A damage plasticity model is used for the reinforced concrete and frictional contact behavior is considered at the base and vertical sides of the concrete panels. The seismic analysis takes into account the flexibility of the canyon rock and potential dynamic rockfill settlements. An existing 150m–high dam is used to investigate the effect of longitudinal vibrations on the compressive stresses near the slab-to-slab vertical interfaces and the opening of the joints. The effect of dynamic settlements is examined and comparisons are made to the response from upstream/downstream and combined vibrations. The effectiveness of introducing 5cm-wide cuts at selected vertical joints to reduce slab compression in existing CFRDs is demonstrated. The presented results offer useful insight into the effect of longitudinal vibrations on the seismic behavior of CFRDs. ► The seismic behavior of concrete faced rockfill dams to longitudinal vibrations is investigated. ► Compressive stresses in the slab are of similar magnitude to those from upstream–downstream vibrations. ► Dynamic rockfill settlements increase significantly compression in the concrete slab. ► Opening the slab joints may occur, but water leaks are unlikely, except at the side panels under very strong shaking with settlements. ► Use of few small gaps at selected slab joints allows significant compressive stress relief.