Geotechnical characteristics of clays in diversion tunnel of 4 Eylül dam (Sivas, Turkey)

This study aims to determine the geotechnical characteristics of clays in the diversion tunnel of the 4 Eylül dam which will provide the water supply of Sivas city. Index properties and geotechnical parameters were obtained by laboratory tests on disturbed and undisturbed samples collected from the soils of study area. According to XRD analysis, dominant clay mineral appears to be a smectite. Soils are generally classified as CH group soils and reveal high swelling potential. In the light of the data obtained, soils were determined as swelling clays for tunnel design, lateral pressures and floor swelling will occur during excavation. Circular ribs are required and yielding support must be used in extreme cases. © 1996 International Association of Engineering Geology.