| The major objective of this study has been to investigate experimentally the forces and overturning moments produced by tsunamis on vertical walls. The experimental results are compared with several analytical and numerical models. Several types of waves were used in a horizontal tank including solitary waves, undular bores, turbulent bores, and surges on a dry bed. Bores produced from breaking solitary waves in a tilting wave tank were also investigated. Various measurements were made, including the incident wave celerity, the wave profile, the runup, force, overturning moment, and pressure time histories. The impact process of the bores in the tilting wave tank were recorded with high-speed movies and the wave profiles in the horizontal tank were defined using a laser induced fluorescence system.;A boundary integral element model, which solves the potential flow problem subject to the full nonlinear free surface boundary conditions, predicted the loads imposed on the wall due to steep solitary waves quite well. A finite difference model of the Navier-Stokes equations also predicted the solitary wave loads quite well; however, it over-predicted the steepness of the incident bore profiles and produced a force-time history with a high amplitude and short-duration peak, which was not observed in the measurements.;Strong vertical accelerations were shown to occur during the reflection of bores and steep solitary waves at a vertical wall. These reduced the force on the wall relative to a hydrostatic force computed from the maximum runup height on the wall. For all cases, the maximum measured force and overturning moment were always less than computed from the maximum measured runup using hydrostatic considerations. At the transition from undular bores to turbulent bores, there was a discontinuity in the maximum water surface slope which corresponded with a rapid increase in the measured runup, force, and moment on the wall. The properly normalized force on a vertical wall due to the impingement of a bore on a midly sloping beach is shown to be equivalent to the force produced by a bore of constant volume on a horizontal bed. |
