Alemdaǧ, Selçuk; Cinoǧlu, Aslihan; Gacener, Elif

In this study, it is aimed to determine safe bearing capacity of soils, which are out cropped around Tamzi and Akcakale villages located in Gumushane, providing allowable settlement conditions for an optimum foundation design. To define the geotechnical properties of soils, three trenches were dug and two seismic refraction with two Multichannel Spectral Analysis of Surface Waves (MASW) were carried out in each research area. Sieve analyses, shear box tests, triaxial compression tests were carried out on disturbed and undisturbed samples taken from the trenches. Seismic velocities of the soils are determined by seismic refraction and MASW methods. While determining the safe bearing capacity; the equations proposed by Terzaghi, Meyerhof, Kurtuluş, Tezcan and Özdemir, Türker, Keçeli were used and the obtained safe bearing capacity values were compared to each other. After, the soils were modeled numerically by using finite elements method and safe bearing capacities providing allowable settlement conditions were determined. According to the results, safe bearing capacity values obtained from empirical equations are not satisfactory to have an optimum foundation design. For the optimum foundation design, safe bearing capacity should be accepted as 190 kN/m2 for clayey soil (CL) and 485 kN/m2 for the clayey sand (SC).

Kaya, Ayberk; Bulut, Fikri; Alemdaǧ, Selçuk

In this study, applicability of the excavatability classification systems in underground excavations is investigated. For this purpose, the entrance portal of the Konakönü (Arakli{dotless}-Trabzon) tunnel, excavated in volcanic rocks within the scope of Black Sea coastal highway project, is chosen as pilot study area. The entrance portal of tunnel is excavated through the rocks of Eocene-aged Kabaköy formation of basaltic-andesitic tuffs, aglomerate and basalt. In excavation, basaltic and andesitic tuffs were ripped by using hydraulic breaker; aglomerate and basalt were excavated by using explosives. Based on the results obtained from field and laboratory studies, rock masses are classified in terms of excavatability. According to Pettifer and Fookes (1994), basaltic and andesitic tuffs are included in "hard ripping", aglomerate and basalt in "blasting required" categories. With reference to Tsiambaos and Saroglou (2009), basaltic and andesitic tuffs fall in "ripping", agglomerate and basalt in "hammer and blasting" categories. It was found out that the classifications made according to these two methods are completely compatible with in-situ excavation works. Also, it is determined that the parameters give the best results for determining excavation class in underground excavations are GSI (Geological Strength Index), I s (50) (Point load strength index) and I f (Discontinuity spacing index).

Kaya, Ayberk; Bulut, Fikri; Alemdaǧ, Selçuk; Sayin, Aytuna

In this paper, engineering geological properties of the entrance portal section of Konakönü Tunnel, located on Black Sea Coastal Highway, Turkey, is studied. Moderately weathered basaltic and andesitic tuffs orderly to be driven by the entrance portal section. Tunnel portal design in weak rock presents some special challenges to the designers, since misjudgements in the design of tunnel can lead to very costly failures. The entrance portal was analyzed by empirical and numerical methods. Both field and laboratory studies were carried out during this study. Field studies involved geological mapping, detailed discontinuity surveying and sampling. Laboratory tests were carried out to determine the physico-mechanical and elastical properties of rock units. For this purpose, tunnel stability analyses were performed at the entrance portal section. The RMR (rock mass rating), Q (rock mass quality), RMi (rock mass index), NATM (new Austrian tunnelling method) and GSI (geological strength index) systems were employed for empirical rock mass quality determination and preliminary tunnel portal support design. The parameters calculated by the empirical methods were used as input parameters for the FEM (finite element method) analysis. The results from the two methods were compared and preliminary support designs were carried out. This comparison suggests that for more reliable support design, empirical and finite element methods should be combined.