Tamer Topal

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.

Deterioration mechanisms of tuffs in Midas monument

Slightly weathered white and pink tuffs of the Midas monument have deterioration problems. In this study, depths and characteristics of the weathering zones developed within the tuffs are investigated through optical microscopy, X-ray diffractometry (XRD), chemical analyses, scanning electron microscopy (SEM) and some index parameters. Accelerated weathering tests including wetting–drying, freezing–thawing and salt crystallization are performed, and durability assessment methods are used to predict the durabilities of the tuffs. The findings are compared with field observations. By examining quantitative weathering indices and comparing them with thin section studies, it is found that thin section analyses of the crystals, LoI, and WPI are good indicators to quantify the depth of weathering for the tuffs. However, thin section studies have limited value for fine-grained tuffaceous matrix. The chemical weathering of the tuffs produces weathered zones that are 4.5-cm thick within the white tuff and 2.5-cm thick within the pink tuff. Physical weathering causes scaling of outer layers of the tuffs and fracturing of feldspars along their cleavage planes. However, variations of the index properties of the tuffs due to weathering are not so significant to quantify the weathering depths in the tuffs. Among the accelerated weathering tests, salt crystallization is found to be the most destructive environmental condition. Pigeon droppings rich in NO3 are found to be the main source of soluble salt at the Midas monument. The salt transported up by capillary rise due to surface water causes spalling of the tuffs in the capillary zone. Surface water and salt of any kind in the close vicinity of the monument should be totally eliminated for the purpose of conservation. Field observations and the durability equations reveal that the white tuff is less durable than the pink tuff. Wet-to-dry strength ratio yields a better stone durability assessment among various durability methods used in this study. D 2002 Elsevier Science B.V. All rights reserved.

GIS-based landslide susceptibility mapping using bivariate statistical analysis in Devrek (Zonguldak-Turkey)

Devrek town with increasing population is located in a hillslope area where some landslides exist. Therefore, landslide susceptibility map of the area is required. The purpose of this study was to generate a landslide susceptibility map using a bivariate statistical index and evaluate and compare the results of the statistical analysis conducted with three different approaches in seed cell concept resulting in different data sets in Geographical Information Systems (GIS) based landslide susceptibility mapping applied to the Devrek region. The data sets are created from the seed cells of (a) crowns and flanks, (b) only crowns, and (c) only flanks of the landslides by using ten different causative parameters of the study area. To increase the data dependency of the analysis, all parameter maps are classified into equal frequency classes based directly on the percentile divisions of each corresponding seed cell data set. The resultant maps of the landslide susceptibility analysis indicate that all data sets produce fairly acceptable results. In each data set analysis, elevation, lithology, slope, aspect, and drainage density parameters are found to be the most contributing factors in landslide occurrences. The results of the three data sets are compared using Seed Cell Area Indexes (SCAI). This comparison shows that the crown data set produces the most accurate and successful landslide susceptibility map of the study area.

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.

Freeze-thaw resistance of the Yazilikaya tuffs

Publisher Summary Midas monument is an impressive cult facade carved with meander ornaments, pediment decorations, and inscriptions during Phrygian times. The monument is formed with Yazilikaya tuffs. In the monument, the Yazilikaya tuffs have two different units. These units are distinguished on the basis of color differentiation and strength. The lower part of the monument is formed with white tuff, whereas the upper part of the monument is formed with pink tuff. The monument shows some signs of deterioration in these tuffs. In this region, freeze-thaw processes are quite effective that can be the reason for deterioration of tuffs. This chapter focuses on free-thaw tests conducted to assess the freeze-thaw resistance of the tuffs. The assessment records the properties of both tuffs at different test cycles and compares with those of the fresh samples. The relative changes of the properties are used to assess the effects of the freeze-thaw tests on the tuffs. For the assessment, 20 fresh block samples were taken from the field and 50 tuffs (white and pink) were prepared in the laboratory. The samples were subjected to freeze-thaw tests in accordance with RILEM. Some physico-mechanical properties such as weight loss, effective porosity, dry unit weight, water absorption under atmospheric pressure, uniaxial compressive strength (UCS), and sonic velocity of both white and pink tuffs were recorded at different test cycles; and these were compared with results of the fresh samples. The test results reveal that the pink tuff is more resistant to freeze-thaw activity; but both white and pink tuffs are adversely affected from the freeze-thaw tests. Therefore, the Yazilikaya tuffs should be protected from freeze-thaw activity. The chapter provides tables and graphs to illustrate the test results of white and pink tuffs.

Rockfall hazard analysis for an historical Castle in Kastamonu (Turkey)

The Kastamonu Castle located on a sandstone hill with Eocene age is one of the most historical and touristic places in Kastamonu city center. The settlement of the city expanded towards the hill of the Kastamonu Castle and adversely affected by rockfalls in the past. The rockfall problems around the castle could be related to jointing, weathering, freezing-thawing and earthquake effects or a combination. In this study, the rockfall hazard at the castle is evaluated by two-dimensional rockfall analyses along 17 profiles selected in different orientations. Different size of rock blocks and various types of movements are taken into consideration in the analyses. Fall-out distance, bounce height, kinetic energy and velocity of the sandstone blocks are separately evaluated. The obtained data are used to define the possible rockfall hazard zones. Finally, the areas having potential rockfall risks are distinguished. Based on the evaluation of the data, rock bolting after removing of unstable blocks and supporting the area with the protective fences are suggested.

GIS-based microzonation of the Niksar settlement area for the purpose of urban planning (Tokat, Turkey)

Niksar (Tokat) is an urban area located in a seismically active zone of Turkey. The aim of this study is to prepare a GIS-based microzonation map of the Niksar settlement area for the purpose of urban planning. Liquefaction, activity, slope, aspect, fault proximity, ground amplification, and lithology are considered during the overlay analysis, using a multicriteria decision-making analysis of the analytical hierarchy process (AHP) and simple additive weighing (SAW) methods. Based on the resulting evaluations, the study area is divided into four different zones, namely (1) areas suitable for settlement, (2) provisional settlement areas, (3) areas requiring detailed geotechnical investigation, and (4) unsuitable areas. Maps prepared by the SAW and AHP methods are found to be consistent with each other. However, the microzonation map prepared by the AHP method is recommended for the purpose of urban planning because it is able to check its own consistency.

Decay of Limestone Statues at Mount Nemrut (Adiyaman, Turkey)

Mount Nemrut is a 2,206 m high mountain located in Adiyaman, Turkey. A number of monumental statues, a 50-m high tumulus, and a lion horoscope were constructed at the top of the mountain by King Antiochos I (69–36 bc) of the Commagene Kingdom. The site was included in the UNESCO World Heritage List in 1987 due to its unique character. However, the limestone statues located on both the east and the west terraces of the site are getting deteriorated. This study investigates the weathering of the limestone at Mount Nemrut based on field and laboratory studies. It is found that the dissolution occurs along microcracks developed in the limestone during geological time. It is more pronounced in the east terrace where freezing-thawing cycles are more than the west terrace. Furthermore, dissolution is more effective for the faces of the statues exposed to direct atmospheric contact. Due to harsh atmospheric conditions with dominant wetting-drying and freezing-thawing processes at the site, it is recommended that direct rain and snow contact with the statues should be minimized.

Assessment of deterioration and collapse mechanisms of dolomitic limestone at Hasankeyf Antique City before and after reservoir impounding (Turkey)

The Hasankeyf Antique City located in southeastern Anatolia (Turkey) includes several historical heritages and man-made caves. It is mainly located in dolomitic limestone. The city will be partly under water after reservoir impounding of the Ilısu dam, and the limestone will be subjected to cyclic processes such as wetting–drying and freezing–thawing. Although a new town is formed and part of the city is transported to a nearby area, this cannot be done for many existing historical and cultural values at the site. The behavior of the limestone under cyclic processes is not known. In this study, deterioration mechanisms of the limestone were investigated with field and laboratory studies. It is found that the rock is not durable. Very thin surficial deterioration zone exists on the rock surface. Discontinuity-controlled block failures associated with collapse of man-made caves occur at the site before reservoir impounding. Further discontinuity-controlled block failures are expected to occur after reservoir impounding by aggravated deterioration and surface erosion of the rock within the fluctuation zone of the reservoir.

Evaluation of the Rockfall Potential of Kastamonu Castle Using 3-D Analysis

The Kastamonu Castle is one of the magnificent monuments of the Kastamonu province (Turkey) located on a steep sandstone hill with Eocene age. The surrounding settlement around the castle suffered from numerous rockfall events in the past. Rockfalls after an initial block toppling are controlled by a bedding plane and two joint sets existing in the sandstone. The rockfall potential along the entire castle perimeter was evaluated by means of three-dimensional (3-D) rockfall analyses using the ROTOMAP software. Rockfall initiation was modelled along a detachment line situated just below the castle walls. The results indicate that the maximum run-out distances around the castle exceed the settlement boundary on the western, southern, and eastern sides. The northern part of the castle is less critical due to lower slope gradient. In order to protect the settlement from falling blocks, vital remedial measures are suggested.