The groutability of fissured rock masses is strongly dependent on fracture characteristics: degree of joint spacing, joint aperture, continuity, and presence of weathering in fill. Survey of the drill core boxes permits for estimating the degree of jointing spacing and joint aperture. Nonetheless, weathering in-fill and continuity cannot be detected. In this concept, the rock fracture groutability quality is defined by the Geological Groutability Index (GGI). A Geological Groutability Index (GGI), denoted as FGGI, may thus be defined as a numerical function of the components: joint spacing (BS) and joint hydraulic (JH), i.e., FGGI = f (BS, JH). The rock mass foundation with this index can be zoned according to different quality classes and each particularly improved zone. The proposed technique requires the interpretation of the results, from which the Lugeon (Lu) value effect in the section is certified, and the rock fracture classification criteria are applied. The GGI is an effective reference to foundation improvement design.

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