Influence of microstructure on geotechnical properties of clays

Clays are geomaterials which are used in various applications in ur society. The mor common geotechnical applicatio s are: waterproof cores of dams, barriers to contain waste, slurry walls etc. But even if clays are not used as construction materials the geotechnical engineer encounters them frequently during construction of e.g. foundations and tunnels. Within the group of clay minerals we find individual clay species that possess geotechnical properties that vary enermously. These differences in geotechnical pr perties can b related directly to the differences in microstructure of the clay minerals. In this contribution it is shown how the knowledge of clay microstructure from X ray diffraction analysis, thus knowledge of the clay mineralogy, can be used to assess the geotechnical behavior of the clay. When mineralogy alteration processes of the clay are know from appropriate geological analogues, the geotechnical characteristics of the engineered clay structure can be estimated on the basis of these processes (e.g. containment of hazardous waste, infiltration of permeates in dams etc.). This implies however that the clay used as construction material is well characterised. A method to prepare such a clay atlas and how to use it is presented in this contribution.