An experimental and numerical investigation of concrete dam joints

This communication summarises the results of a comprehensive investigation aimed at improving the understanding of the cyclic behaviour of concrete dam joints, covering both experimental and numerical aspects. In the laboratory work, a jointed concrete block is subjected to reversed cyclic slip at imposed normal stress. The specimen is intended to represent a portion of either a lift joint or the dam-foundation interface. Aspects of novelty can be found in the test setup and in the specimen size (90×70×30 cm). The tests performed so far, though limited in number, have allowed to assess and approximately quantify for concrete the characteristic influence of joint roughness on the observed shear strength and dilatancy. A generalised interface model is proposed in order to describe the joint behaviour, including all the phenomena commonly accounted for in mixed mode fracture of cohesive quasi-brittle materials and the effects of surface roughness. This result has been obtained by combining a fracture-mechanics based interface model for concrete with a cyclic one for rock joints. Simulations carried out so far evidence a good qualitative agreement with results available in literature