E.F.R. Bollaert - AquaVision Engineering Inc., FluvialTech Group, Lausanne, Switzerland

A new procedure to evaluate dynamic uplift of concrete slabs or rock blocks in plunge pools is presented. The procedure is based on near-prototype scaled measurements of transient pressure fluctuations over and under the slabs or blocks, and on appropriate assessment of the 2D pressure field at impact in the plunge pool. The pressures that occur at the surface of a slab or block (plunge pool bottom) are assessed by means of appropriate dynamic pressure coefficients. The pressures underneath the slabs or blocks are governed by transient pressure waves. Their assessment can be performed by two methods: (1) by investigating surface pressures that enter the joints and applying a maximum possible impulsion on the slab/block (taken from near-prototype scaled tests), and (2) by direct numerical modeling of the temporary and spatially distributed transient pressure field, based on known dynamic pressures that enter the joints. By relating the transient underpressures to the corresponding surface pressures, and by establishing appropriate correlations over the slab or block surface, extreme net uplift pressures can be deduced, defining so whether uplift will occur or not