Along NS trending road cut between &Ccedil / ayyolu and incek, relatively thick tuffite layer of the Han&ccedil / ili formation has been exposed. It is alternating with other lacustrine deposits such as clayey limestone, marl, siltstone and mudstone. These units unconformably overlie the Mesozoic basement limestones of Akbayir formation. The illite rich tuffite consists of glass shards tridymite, biotite, quartz and plagioclase. It has a persistent areal extend and forms the foundation of the residential buildings at several localities. In this thesis, it is aimed to assess the engineering geological properties of the tuffite layer and to investigate its suitability as a foundation material. In order to accomplish this task, field studies and laboratory tests were conducted. Field studies involve detailed site geological observation. Laboratory studies include tests to investigate mechanical, physical and mineralogical properties of the tuffite. v Analyses revealed very weak nature of tuffite with strength values ranging between 0.1 MPa and 1.00 MPa. The tuffite is characterized with very high effective porosity (43.3%) and very low dry and saturated densities (1.19 Mg/m3 and 1.62 Mg/m3, respectively). The slake-durability tests yield medium durability. The durability index of tuffite is rated as very poor. Considering index properties and the durability assessment it is concluded that tuffite serves as a poor foundation material.

A landslide occurred during the construction of the Giresun &ndash / Espiye road between Km: 1+030 &ndash / 1+170 in April 2003. Investigating the causes and mechanism of this slope failure along with suggesting a proper stabilization technique is aimed in this study. For that purpose, a detailed site investigation study, including engineering geological mapping, drilling work, in situ and laboratory tests, was performed. Weathered tuffite, tuffite, flysch and dacitic tuffite, from top to bottom, are the major units in the study area. A &ldquo / translational slide&rdquo / occurred in completely weathered tuffite owing to the disturbance of the stability of the slope by the excavations performed at the toe of the slope / particularly the foundation excavation for the restaurant building and for the road cut for the Giresun &ndash / Espiye road. After establishing the model of the landslide in detail, shear strength parameters of the failure surface were determined by the back analysis method as &quot / cohesion&quot / =2.5 kN/m2 and &quot / friction angle&quot / =9&deg / . Toe buttressing, ground water and surface water drainage options were considered for stabilizing the slope. For the back analysis calculations, the Morgenstern-Price and Spencer methods were used with the aid of the SLOPE/W computer program.