Physical experiments (at a scale of 1/20) are carried out using two different models: a vertical wall with cantilevering slab and a simple vertical wall. Tests are conducted for a range of values of water depth, wave period and wave height. The largest peak pressures were recorded at the SWL (82 * ρghs) on the vertical part and at the fixed corner of the cantilever slab (90 * ρghs. Pressure measurements and derived force calculations on the simple vertical wall were used to evaluate the existing prediction formulas. A significant effect of the cantilevering part is observed on the total horizontal force and overturning moment of a simple vertical wall. This is due to secondary impact occurring on the overhanging part by a jet climbing on the vertical part.
Vertical breakwaters and seawalls are frequently used to protect land from sea action such as high water levels and waves. To reduce the overtopping, coastal engineers provide the vertical walls with a return crown wall or even a horizontal cantilever slab. However, wave impacts on the horizontal structure introduce an important uplifting force. The lift forces consist of impact loads which one of high magnitude and short duration. It is reasonably impossible to substitute these impact effects by a static equivalent. A detailed description of the space and time distribution of the wave impacts thus becomes imperative. The Pier of Blankenberge which is located along the Belgian coast is an illustrative example of a vertical wall with cantilever surfaces (Verhaeghe et al., 2006). The qualitative and quantitative determination of wave loads on vertical walls has already been examined intensively in the past decades (e.g. Oumeraci et al., 2001; Allsop et al, 1996; Goda, 2000; Cuomo et al., 2009).