THE EFFECT OF CHEMICAL-WEATHERING ON THE ENGINEERING PROPERTIES OF EOCENE BASALTS IN NORTHEASTERN TURKEY

Eocene-aged basalts, north of Niksar (Tokat-Turkey), are quickly affec ted by chemical weathering, as well as physical and biological weather ing. In order to assess the influence of chemical weathering on the en gineering properties of these basalts, a study was performed in some p rofiles from the study area, The results of chemical analyses were use d in various weathering indexes, These chemical indexes were compared with the petrographical weathering index and the microfracture density in order to find the most suitable chemical index of weathering, appl icable to basaltic rocks. The results suggest that the Parker Index an d the loss on ignition can be used to find variations of the degree of chemical weathering in the basaltic rocks. In addition, physical and mechanical properties of the basalts were compared with the Parker Ind ex and loss on ignition, and it was found that the dry density and the compressive strength decrease with weathering, while the porosity inc reases.