Design of jet-grouting cut-offs

This paper deals with the design of jet-grouting cut-offs for dams. Available information from several cases is first reviewed, pointing out the differences between projects concerning dams under construction and operational ones. Various dam types and treatment schemes are considered; functions and requirements of jet-grouting cut-offs are defined; and possible solutions are proposed. Particular attention is devoted to the occurrence of discontinuities along the cut-offs, which may derive from two main factors: deviation of the treatment axes and variation of the jet-column's diameter. A probabilistic design method is developed in order to minimise the risk of such defects. Finally, the drawbacks and advantages of deterministic and probabilistic approaches are discussed.