Water pressure in propagating concrete cracks

Water pressure in propagating concrete cracks is experimentally and numerically investigated. Ultimate application of this study is the uplift pressure in a concrete gravity dam during and after an earthquake. Numerous tests were conducted on wedge splitting specimens with hydrostatic pressure along the crack. Relative velocities of water front versus crack front as well as the effect of sudden crack closure have been investigated. It was observed that, for the tested specimens, the crack opening rate has important consequences on the internal water pressure distribution. If the crack opening rate is slow enough, the water pressure has time to develop, whereas under fast crack openings the water front cannot keep up with the crack front. Furthermore, upon sudden crack closure the trapped water acts as a wedge causing tensile stresses in the specimen. Finally, on the basis of the experimental observations, a model for the conductivity of cracked concrete is developed. Such a model could then be used in the coupled transient finite-element analysis of a concrete dam subjected to an earthquake.