Vedat Doyuran

Engineering geological properties and durability assessment of the Cappadocian tuff

Abstract Some of the unique landforms, the so-called “fairy chimneys”, which were formed within the Cappadocian tuff of central Turkey, were used as dwellings in the past and contain culturally valuable wall paintings. However, these structures are undergoing chemical and physical deterioration due to atmospheric effects. For conservation studies, an understanding of the engineering geological properties of the tuff is essential. In this study, emphasis is placed on both material and mass properties of the tuff. These properties are evaluated for the assessment of rock durability. This study shows that the Cappadocian tuff is almost fresh, with local discoloration, is moderately weak to very weak, and has low unit weight, very high porosity, and high deformability. Discontinuity surveys revealed two dominant joint sets, which not only controlled the formation but also control the structural stability of the fairy chimneys. Various methods used for the durability assessment of the Cappadocian tuff indicate poor to very poor durability. Due consideration must be given to strength reduction due to moisture, poor to very poor durability, and the adverse effects of joints on the structural stability of the fairy chimneys.

Municipal solid waste landfill site selection for the city of Şanliurfa-Turkey: an example using MCDA integrated with GIS

A municipal solid waste (MSW) management system needs solid waste management (SWM) techniques where the presence of a sanitary landfill is vital. One of the most important issues of sanitary landfilling is to locate the facility to an optimal location. Despite the versatility and case-dependent nature of conventional expert-based site selection procedures, the number of sites to be chosen increases with increased population forcing a number of constraints. Consequently, constraints and environmental regulations mechanically mask unsuitable areas, leaving very little areas to be assessed. This turns the situation into a challenging issue for a geographical information system (GIS) used with multi-criteria decision analysis (MCDA), to select optimal site. The study aims to apply MCDA integrated with GIS to select possible sites of a MSW landfill with the same expert and same cognitive parameters while compared with the already present one. Results of this study revealed that conventional expert-based methods could not always evaluate all constraints at the same time and map reproduction is limited when parameter maps are changing rapidly in time. In order to produce cognitive and reproducible analyses, GIS with MCDA integration offers a good solution for site selection issue and forms a good alternative for conventional methods.

Microzonation for earthquake hazards: Yenisehir settlement, Bursa, Turkey

Abstract Detailed geological, hydrogeological and geotechnical studies were performed for the assessment of the foundation conditions of the present and future settlement areas of Yenisehir. Yenisehir is located 50 km east of Bursa, Turkey, within an east–west trending elliptical sedimentary basin. The present and future development areas of Yenisehir cover 10 km 2 . The topography of the settled area is quite smooth and the slopes are generally less than 10°. Yenisehir is located within a First-Degree Earthquake Zone of Turkey according to the seismic design code. The seismicity of the town is mainly controlled by the Geyve-Iznik and Bursa fault zones. The study also involves trial pitting, drilling, in situ testing and laboratory testing. Borehole logs, index properties of soils, standard penetration test results and groundwater level measurements were used for activity and liquefaction assessments of the foundation material. Based on the evaluation of the data, two geotechnical zones were distinguished. The northern part of the area is characterized by cohesive soils of high expansion behaviour and the southern part by alternation of cohesive and non-cohesive soils showing high liquefaction potential.

Characterization of the Antalya (Turkey) tufa deposits

Carbonate rocks in Antalya (Turkey) which have previously been called travertine should, because of their biogenic origin and deposition in a cool-water regime, be termed tufa. Tufas in Antalya are the products of physico-chemical and biogenic precipitation. In the biogenic process, precipitation was caused by decreasing partial pressure of CO2 via photosynthesis of algae or bacteria. Following precipitation, the tufas underwent meteoric-vadose cementation and diagenesis. The Antalya tufa basin consists of horizontally-bedded carbonate sediments which are end products of a lacustrine depositional environment. However, a perched springline system has played an important role, serving as a starting point for calcium-carbonate precipitation. The morphology of tufa coastal cliffs is controlled by sea erosion. Thus, terraced morphology, except for small areas (e.g., Masadaği), should be considered a result of erosion. In this study, tufa deposits of Antalya were characterized with respect to mineralogy, sedimentology and surface morphology. In addition, for the future multidisciplinary needs (engineering and environmental) other aspects on tufa formation are discussed.

Characteristics of a multiple retrogressive failure in a coal mine in southwest Turkey

Abstract This paper describes the geotechnical investigations and the stability analysis of a multiple retrogressive circular failure developed through a few benches cut in deposits of a weak transition zone at a strip coal mining area, southwest Turkey. The instability was analyzed to understand the possible causes of failure and to determine mobilized shear strength at the time of failure through the use of back analysis. Geotechnical investigations comprised geological mapping, review of drill core and groundwater data, sampling and laboratory testing, and back analysis of the failure. The failed material is essentially composed of poorly consolidated claystone, which is a clay in engineering terms, and minor amounts of clayey silts. To evaluate the shear strength parameters mobilized during failure, drained soil shear tests were carried out on specimens taken from potential failure surface materials. Based on the results of the back analysis performed for various conditions and using the field observations, actual failure surfaces were defined by successive slip surfaces developing from the toe and advancing to the crest of the slope. The analysis also indicated that the instability was initiated by the construction of steep and high benches in the transition zone deposits. It was further noted that there is a good agreement between the laboratory-derived residual shear strength parameters and the results of back analysis. The results of the stability analyses performed to determine safe side slopes in the transition zone are also presented.

Engineering geological evaluation of the Of-Solakli hydropower development project (N.E. Turkey)

The Of-Solakli Hydropower Development Project (HDP) is designed to generate 380 MW of electricity through the diversion of six streams into a headrace tunnel and maintaining a head difference of 1 000 m above the underground power station. The tunnel system is located within felsic and mafic magmatic rocks, and volcanogenic flysch.In this paper an engineering geological evaluation of the HDP is introduced. The field investigations included geological strip mapping, core drilling, and intense discontinuity surveying. A portion of the headrace tunnel was re-located due to adverse foundation conditions. The rock mass qualities of various lithological units were determined and the necessary support systems are described.RésuméLe projet de construction d’une centrale hydraulique à Of-Solakli a pour objectif de produire 380 MW d’électricité par la diversion de six cours d’eau dans un tunnel principal en conservant une différence de charge hydraulique de 1000 m au-dessus de la station souterraine. Le système de tunnels se situe dans des roches magmatiques felsitiques et mafiques et dans un flysch d’origine volcanique.Cet article présente une évaluation géotechnique du projet. Les investigations sur le terrain inluent la préparation d’une carte géologique, des carottages, et un levé détaillé des discontinuités. Une partie du tunnel principal a été relocalisée en raison de mauvaises conditions de fondation. Les caractéristiques qualitatives des différentes unités lithologiques sont déterminées et les systèmes de support nécessaires sont décrits.

Landslide Investigation of a Residential Area in Göynüklü Village, Bursa (Turkey)

Landslide is a natural process of the earth’s surface, inevitably resulting from gravity with many triggering factors such as rainfalls, earthquakes, slope steepening, removal of vegetation, etc. The most frequent landslide-triggering mechanism is water from intense rainfall or human-based sources. The wide ranges of landslides and the complexity and variability of their interactions with the environment are the key points of a landslide investigation. The rate of the movement is the main factor of high property damages. On 16th of March in 2006, a rapid landslide occurred in Goynuklu village in Bursa, Turkey. The properties were inevitably damaged after the failure. The triggering factors of the failure mechanism and the properties of the landslide were investigated to specify proper remedial measures at the site. The geotechnical investigations including surface and subsurface studies were performed to determine the extent of the landslide and its sliding surface accurately. Within the framework of the geotechnical investigations, the inclinometer measurements were also recorded after drilling boreholes. Besides, a number of trial pits were excavated for evaluating the shallow sliding surfaces. Samples taken from the boreholes and trial pits were tested in the laboratory to obtain the soil class and the distribution of the grain size of the soil layers as well. The field tests including the hydraulic effect on the soil layers were also resolved by means of in situ permeability tests. Based on the data obtained, the characteristics and mechanism of the landslide were analyzed. The landslide occurred on a translational sliding surface in Neogene sediments including non-stratified sandstone-siltstone-claystone layers and a landfill site in a residential area. The shear strength characteristics of the sliding surface were calculated by back-analyses.

Hydrogeological and Hydrochemical Investigation for Below-Sea-Level Quarrying at Cement Raw Material Site (Kocaeli-Darica, Turkey)

Abstract A research has been carried out to investigate the effects of below sea level mining on the cement raw material quality of a limestone quarry located adjacent to the shoreline near Darica-Kocaeli-Turkey. Field studies involved rock mass characterization through discontinuity surveys performed at the working benches of the quarry as well as on the core samples, monitoring of groundwater levels, performance of water pressure tests, and in-situ hydrochemical measurements. Hydrogeological data suggest that the carbonate sequence forms a poor unconfined aquifer having hydraulic conductivity values ranging between 10−6 m/s and 10−8 m/s. In the quarry, water seepages can only be observed at the shear zones. Electrical conductivity profiles taken from the boreholes located at various distances from the shore line indicated the present position of the salt water wedge.

Seismic Source Regionalization

Seismic source regionalization problem entails the full use of geologic, tectonic, historical, instrumental macro-seismic records, and micro-earthquake survey findings. The seismic sources are usually delineated on the basis of the uniformity of tectonic features, homogeneity of earthquake occurrences, and the consistency of focal mechanisms.