Investigation of Gümüşhane city and its near surrounding according to suitability for settlement

Investigation of Gümüşhane City and its Near Surrounding According to Suitability for Settlement Prior to the determination of settlement sites, it is necessary to investigate engineering geological properties of foundation rock units and also to understand behavior of these rock masses. The bearing capacity of foundation, strength of masses, slope trends, settlement properties, determination of horizontal ground acceleration during earthquake waves passing through foundation are the main data for the choice of structure type and number of the floor of buildings. In this study, earthquake, hydrogeology (flooding), rippability, topography, geotechnical, geophysical and geological features of beneath the settlement of Gümüşhane, a developing city, were investigated both in the field and in the laboratory, and suitable land units for new settlement were determined and data for the city planning and development were obtained. 1/10000 scale geological map of Gümüşhane was prepared and lithostratigraphic units of Gümüşhane Granitoid (Paleozoic), Zimonköy Formation (Liassic), Berdiga Formation (Malm-Lower Cretaceous), Kermutdere Formation (Upper Cretaceous), Alibaba Formation (Eocene), Kaçkar Granitoid II (late Eocene), alluvium and debris flows were mapped. Physico-mechanical properties of granitic, agglomerate and limestone masses from weathering profiles were obtained in the laboratory. Measurements, observations, and simple field tests in 87 locations were conducted in order to obtain RMR scores of rock masses forming foundation of urbanized area and these rock masses were classified based on geomechanical classification system (RMR). For describing the excavation circumstances well and thus choosing optimum excavators, degree of rippability were obtained from both using seismic reflection methods and geomechanical parameters. Flood frequency of Harşit River, which passes through the city, was calculated with the Gumbel distribution of probability. 10, 30, 50 and 100 years periods of maximum flood discharge rates of Harşit River were investigated and flooding probability of next 10, 20 and 50 years periods were calculated. Potential earthquake risks of the city were studied and magnitude-frequency relationship was established. Seismic risk values and reversal periods of earthquakes between years of 1900 to 2000 were calculated. The earthquake simulation models were produced and using directly field measured S-wave velocities in this simulation, horizontal ground acceleration values and soil expanded coefficients were determined. Strengths of fractured rock masses in the observation sites were determined using the Hoek-Brown empirical approach. Bearing capacity of the foundation units in settlement area were calculated via the seismic reflection method. The results obtained in this study were analyzed and evaluated in computer environment using Geographic Information System software and hardware tools. Finally, maps of engineering geology, slope zonation and flooding were produced. In addition, overlaying these maps, urban suitability map and 3-D digital topographic city map were obtained.Key words: Urban geology, weathering, mass strength, bearing capacity, earthquake study, flood, rippability. VIII