Abstract. Liquefaction is one of the critical problems in geotechnical engineering. High ground water levels and alluvial soils have a high potential risk for damage due to liquefaction, especially in seismically active regions. Eskişehir urban area, studied in this article, is situated within the second degree earthquake region on the seismic hazard zonation map of Turkey and is surrounded by Eskişehir, North Anatolian, Kütahya and Simav Fault Zones. Geotechnical investigations are carried out in two stages: field and laboratory. In the first stage, 232 boreholes in different locations were drilled and Standard Penetration Test (SPT) was performed. Test pits at 106 different locations were also excavated to support geotechnical data obtained from field tests. In the second stage, experimental studies were performed to determine the Atterberg limits and physical properties of soils. Liquefaction potential was investigated by a simplified method based on SPT. A scenario earthquake of magnitude M = 6.4, produced by Eskişehir Fault Zone, was used in the calculations. Analyses were carried out for PGA levels at 0.19, 0.30 and 0.47 g. The results of the analyses indicate that presence of high ground water level and alluvial soil increase the liquefaction potential with the seismic features of the region. Following the analyses, liquefaction potential maps were produced for different depth intervals and can be used effectively for development plans and risk management practices in Eskişehir.
Abstract. The city of Eskişehir in inner-western Turkey has experienced a destructive earthquake with M s =6.4 in 1956 in addition to many events with magnitudes greater than 5. It is located in a wide basin having young sedimentary units and thick alluvium soils which also include liquefiable sand materials. There is also an active fault passing beneath the city center and the groundwater level is very close to the ground surface. Approximately 600 thousand people are living in the province of Eskişehir. Therefore, the city and its vicinity have a high risk, when earthquake hazard is considered. This paper summarizes the probabilistic seismic hazard analysis (PSHA) which was performed for the province of Eskişehir and introduces seismic hazard maps produced by considering earthquakes with magnitude M s ≥4.0 occurred during the last 100-years and a seismic model composed of four seismic sources. The results of PSHA show that the average peak ground acceleration (PGA) for the city center is 0.40 g for 10 percent probability of exceedance in 50 years, for rock site. The seismic hazard maps were obtained by means of a program of Geographic Information System.
Recently, geographic information system Software's are widely used in engineering geology applications. Such a study was performed in the Eskisehir urban area of about 30 km 2 via geo-engineering maps, crosssections and panel-block diagrams, which are formed to predict the properties of foundation soil. In order to determine the engineering geology properties of the region, physical and mechanical characteristics of the soil profile were tested on 1,011 disturbed and 383 undisturbed samples from a total of 170 boreholes. Topographic, lithological and geotechnical data of the region were compiled as a database in computer. Five geological cross-sections were drawn to decipher specifically the alluvial deposits in detail in densely populated areas. Hence, geological characteristics of the area were evaluated in a three-dimensional mode. Five standard penetration test (SPT) cross-sections at the same directions and SPT, uniaxial compressive strength (qu) and soil class Zonation maps were produced at different depths and panel-block diagrams were also created to define the geo-engineering properties of the investigation area. In this respect, the sub-surface of the study area is fully visualized and useful predictor maps, cross-sections and panel-block diagrams are performed to be used in further studies.
Cappadocia is one of the most important natural, historical and cultural heritages of Turkey. The region is seriously threatened by different instability problems, and several locations were accordingly closed to visit, mainly because of rockfalls. The aim of current study is to investigate the rockfall hazard potential near the Tatlarin Underground City. For this purpose, an extensive engineering geological investigation was performed and complemented with a set of rockfall simulations performed by means of the 3D numerical model HY-STONE. The investigation included: (1) mapping of the lithological units (tuffs and overlying basalts, talus deposits) and of unstable blocks along the cliff; (2) rock mass geomechanics and kinematic analysis of block stability; and (3) laboratory testing of tuff and basalt. These allowed to show that the instabilities are mainly controlled by different durability of tuffs and basalts. The weakness of tuffs facilitates a progressive undercutting of the basalt layer, the opening of subvertical joints and the consequent movement of large basaltic blocks. Two future potential rockfall scenarios have been produced by 3D rockfall modelling for hazard zonation and for suggesting risk management strategies. Model parameters were calibrated by back-analysis of both historical events and field tests. Different sets of parameters have been calibrated for different release volumes to consider different degrees of interaction with slope material of different size. The effect of roughness of the topography was investigated in terms of trajectories and lateral dispersion of blocks and its consequences on hazard zonation and risk management actions.
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