Engineering geological and geomechanical assessments of the proposed Mezra dam site (Şanlıurfa, Turkey).

This paper discusses the results of the site investigations and rock mechanics studies carried out at the proposed Mezra dam site. Engineering geological properties of rock masses, such as strength, permeability along the dam axis, discontinuities, and stability of abutments, were investigated in order to determine probable problems prior to constructions. Mezra Dam is a sand-gravel filled dam with upstream concrete slab. The dam on the river Kızıl, a branch of Fırat river, is located about 83 km of west of Sanliurfa city in the southeastern of Turkey. The dam and its associated concrete structures are mainly founded on alluvium, talus, and limestone. Quaternary alluvium and talus at the dam site has a thickness of about 10 m and overlies the limestone of the Gaziantep formation of Eocene to Oligocene age. Studies were carried out both at the field and the laboratory. Field studies include engineering geological mapping, intensive discontinuity surveying, kinematical analyses, drilling, Lugeon permeability tests, and sampling for laboratory testing. Rock mass classifications, strength characteristics, and constants of rock masses were expressed by using Hoek-Brown empirical failure criteria, RMR, GSI, and UCS values. Finally, the deformation modulus of the limestones indirectly estimated using geomechanical quality. The results of the investigations indicate that the foundation rocks are suitable for designing the proposed Mezra dam, and the limestones exposed in the left bank are of higher quality rock masses when compared to those in the right bank. [ABSTRACT FROM AUTHOR]