Effects of sediment on the dynamic pressure of water and sediment on dams

After a reservoir has been in operation for a period of time, a sediment la yer is likely formed before the dam. Since studies of the effects of sedime nt layers on the hydrodynamic pressures of impounded water and the aseismic responses of dam are few, the dynamic effect of sediment may be applied ne ither in the seismic design of new dams nor in the assessment of earthquake safety of existing dams. However, a common practice of the action of sedim ent layers and foundation is based on a partial energy absorption boundary. It is shown that during a vertical harmonic ground motion, the sediment la yer could alter the natural frequencies of reservoir. The dynamic pressure on a rigid vertical dam face caused by the vertical ground motion is obtain ed through a computational model and an experimental test by using a shakin g table. With a change in the thickness of sediment, the frequency correspo nding to the inertia amplification effect appears to vary gradually. The re sults are useful for further study of seismic responses of dams.