The engineering properties of tufa in the Antalya area, SW Turkey

Abstract

Abstract This study aims to assess the engineering properties of tufa. The engineering behaviour of tufa is dependent on the depositional environment, diagenesis and weathering characteristics. An engineering classification of tufa should include primary fabric, post-depositional changes and strength. The rock mass features of tufa include sedimentary structures resulting from frequently changing sedimentary environments, lithological variation owing to depositional and post-depositional changes, and cavities of primary and karstic origin. The tufa mass is therefore heterogeneous and description of the rock mass requires specialist experience. When there is core loss during drilling, it is difficult to decide if the zone of zero core recovery is a weak clastic tufa, a palaeosol, a crushed phytohermal tufa or a cavity. Antalya tufa exhibits a wide range of behaviour, ranging from loess-like collapsible soil to limestone-like hard rock. The unconfined compressive strength of rock tufas varies between 1 and 100 MPa. Collapsible tufas may have collapse potential up to Cp = 14%. Typical geohazards associated with engineering works on tufa include flexural failure, punching shear, consolidation settlement and punch failure, cave collapse, differential settlement of footings and excavation collapse. Special foundation and drainage measures are required to overcome the geohazards posed by tufa.