Evaluation of Engineering Properties of Rock Masses in Waste Dam Site: The Example of Gumushane

In this study, excavatability, bearing capacity and permeability characteristics of rock masses along the Gümüştaş Waste Storage Dam II site were evaluated. For the excavations to be carried out to increase the volume of the waste storage area, the excavation classes of the rock masses were determined as “Hammer” for andesitic breccia and “Hammer&Blasting” for andesite. The bearing capacity of andesite (bedrock) has been determined with the help of empirical equations and, allowable bearing capacity and ultimate bearing capacity were calculated as 10.44MPa and 31.07MPa, respectively. The permeability has been assessed by the Lugeon Tests conducted in the geotechnical drill holes located in the andesite and andesitic breccia rock masses and with the aid of the seepage analysis based on the finite element method the bedrock mass has been defined as low permeable. Low permeable rock masses would possibly cause the chemical wastes to be collected in the waste dam reservoir area to pollute the groundwater. To prevent the seepage, impermeable natural clay material of 35-40cm thickness should be laid and compressed along the dam axis and reservoir area. This suggestion was modeled with the aid of the finite element method, for the case that the reservoir area was completely filled with wastewater and, the permeability value was determined as 5x10-11m/s as a result of the seepage analysis. In addition, seepage values in the discharge section at a depth of 10m from the foundation vary between 1.69x10-17m3 /s and 3.44x10-16m3 /s. These values are quite low but, are indicators of a possible seepage. To eliminate this possible seepage, the geotextile materials (geosynthetic clay membrane, Geomembrane, and drainage geocomposite) should be laid over the compressed natural clay layer, and thus mixing of the chemical wastewater, which collected after flotation, into the groundwater will be prevented.