Development of Hybrid Curtain Grouting Method for Dam Foundation with Inhomogeneous Geology

Abstract

Curtain grouting for dam foundation is one of the most crucial work items in dam construction to secure the impermeability of the foundation rock. Since some decades ago, the Grouting Intensity Number (GIN) Method developed in Europe has been frequently applied to relatively simple geology. On the other hand, the Conventional Method, which requires phased mix proportion and water pressure tests through a sequence of the works, is as yet reliable for inhomogeneous geology, which has complicated hydrogeological structure. This paper presents the development of a sophisticated curtain grouting method to meet with complicated hydrogeological structure, based on application to the Nam Ngiep 1 Hydropower Project in Lao PDR, which has inhomogeneous geology of sedimentary rock with low dip angle weak layers affected by fold movement. The method has been dubbed as “hybrid” because it garners both the economical superiority of the GIN Method in that it enables the use of a single mix proportion, and the technical superiority of the Conventional Method in that the individual design pressure in each stage is set based on critical pressures obtained by water pressure tests.