The Degree of Alteration and Geomechanical Properties of Diabase in the Ankara Ophiolitic Melange, Turkey

Abstract

The ophiolitic melange of Ankara, located in Central Anatolia, is composed of a mixture of several types of rocks. They are ultramafic and mafic rocks such as dunite, harzburgite and pyroxenite; gabbro and diabases; basalt and pillow lavas; and pelagic sedimentary rocks. Geomechanical properties and micropetrographic index studies for the diabase were performed as a larger part of a study focused on investigating potential dam sites. A new classification is proposed, based on a concept called the “unified alteration index,” which is the multiplication of loss percentage during uniaxial compression tests and the compression wave velocity of diabase determined in the laboratory. Diabase is classified into five classes based on this proposed classification system. A statistical analysis was used in examining the relationships between the unified alteration index and the geomechanical properties of diabase. A relationship was established between the unified alteration index (K vc ) and the compression wave velocity (C p ) in the form of: K vc = 1.18 − 3.00e − 4C p + 1.84e − 8C p 2 (r 2 = 0.91). The relationship between the unified alteration index and unconfined compressive strength is in the form of: K vc = 0.9*10 (−0.00188σ c ) (r 2 = 0.69).