Engineering geology of the Foca tuff

Tuffs occur widely around Foca town and Izmir city in western Turkey. Tuffs generally have pumice texture. Main engineering structures are being built in around the Foca town and different places in Aegean region, which are partially on tuffs. Tuffs with respect to the strength are being generally in the limit between weak rock and hard soil. Additionaly, tuffs slake on exposure to the atmosphere. In this reason weathered tuffs caused some problems in many respect of engineering practice. Weathering grade of tuffs have been established macroscobicy and the following further investigations have been caried out on the weathering grade determined samples to check the applicability of observational weathering grade determinations in this study.a)Petrographic study of the rock samples were carried out and modal analysistables were prefered for each weathering grade.b)Main element and oxides ratio?s for each weathering grade were determinedfrom the chemical analysis and x-ray difractograms.c)Engineering properties and P - Wave velocities of tuffs with differentweathering grades were determined.Key Words: Foca, Engineering properties, P - Wave velocities, Weathering grade, Tuff