GEOLOGICAL FEATURES, PERMEABILITY AND GROUTABILITY CHARACTERISTICS OFTHE ZIMAPAN DAM FOUNDATION, HIDALGO STATE, MEXICO

The geology of the Zimapan Dam foundation has a significant influence on the permeability and groutability characteristics. The dam foundati on is composed of a sequence of dolomitic limestones and dolomitic bre ccia of the late Jurassic period. Karst phenomena contribute the main structural features. In this paper the relationships between the karst ic features and the permeability characteristics of the Zimapan Dam fo undation have been evaluated. A modification of the low pressure test (Foyo and Cerda, 1990) for analyzing the permeability characteristics was carried out. This type of permeability test permits the determinat ion of the critical pressure and the analysis of the differences betwe en the critical manometric pressures and the real critical pressures i nduced during the test performance. Permeability and hydrofracture tes ts results were used in the foundation for the design of the grouting programme, and the karstic features of the formation were grouted usin g a special treatment process. The relationships between the permeabil ity and the grouting results have been analyzed.