İzmir șehir merkezinde yüzeyleyen andezit lavlarının dayanımlarının anizotropiye baǧlı değişimlerinin belirlenmesi

The northwestern part of the city of Izmir majorly lies on andesite lavas. The major formation features are basaltic, pink and grey andesite that are adversely prone to weathering. The andesite rocks of the region are characterized by self-organized directional cooling joints and flow bands features that entail possibilities of inherent anisotropy that pose a challenge to geotechnical design such as tunneling, excavation and construction. The study area has become evident with these projects, therefore investigating the properties of andesite type of rocks is now even more important. This study investigates the anisotropic characteristics of andesite lavas outcrop of Bornova the northern part of İzmir city (Turkey). The study principally investigates the influence of anisotropy on pink and grey andesite rock strength in other words strength anisotropy. A detailed anisotropy analysis was conducted by field work study and laboratory tests. Field work included geological mapping and sample collection. To evaluate the changes in rock strength depending on the direction, in the laboratory fresh intact block samples of pink and grey andesite were cored at 0°, 30°,45°,60°and 90° angles in respective to the lava flow direction. Firstly, the samples were subsequently subjected to microscopical analysis, whole rock geochemistry analysis, X-ray diffractometer studies, porosity and unit weight tests, ultrasonic p-wave velocity tests (Vp), Uniaxial Compressive Strength (UCS) test, Brazilian Tensile Strength (BTS), Point Load Index (I50) tests and Bohme abrasive resistance test. The major findings of the study in relation to anisotropy dependence indicated that the rock's strength is maximum when the anisotropy angles is close to 0° and 90° while minimum between 30° and 45° respectively in both rocks further classifying the anisotropy exhibited as "weak anisotropy" after UCS, BTS, I50 and Vp anisotropy quantification indices results. The rock's UCS in grey andesite was classified as "high strength" and pink andesite "high-medium strength". Primarily other factors that may negatively influence the performance of andesite were also investigated. The samples were exposed to corrosive environments under accelerated weathering physical and chemical, thus wetting-drying and freezing-thawing, sodium sulphate and magnesium sulphate soundness tests. Finally, the quality and durability of the rock was evaluated by using rock quality indicators i.e. saturation coefficient, wet to dry strength ratio and Static Rock Durability Index (RDIs). These quality indicators classified the quality and durability of the rock as "good". Keywords: Material properties, strength anisotropy, andesite, RDIs