Geotechnical assessment of a landslide along a natural gas pipeline for possible remediations (Karacabey-Turkey)

A new natural gas pipeline with a 0.90-m diameter is under construction to provide a gas connection between Turkey and Greece as well as to create a gas ring for southern Europe. The new pipeline route lies next to an existing small diameter gas pipeline broken by a landslide that occurred in February 2006 near Karacabey (Bursa). Although the existing pipeline has been temporarily repaired, either the pipeline route should be relocated or the landslide should be stabilized. The geological survey conducted in the study area reveals that relocation is not feasible due to the existence of other landslides in close vicinity to the site. In order to investigate the causes of the landslide and to suggest possible remedial measures, geotechnical investigations including surface geological mapping, trial pitting, drilling with field tests, inclinometer measurements, laboratory testing, and limit equilibrium analyses were conducted. The investigation revealed that the unconsolidated clayey soil slid on claystone along a non-circular failure surface. Based on the gathered data, possible remedial measures including partial removal of landslide material and construction of toe buttresses, slope flattening, lowering the pipeline, and surface drainage systems were evaluated. These are suggested to prevent the reactivation of the landslide, and thus to establish a safe route for both the existing and the new pipelines.     

Landslide susceptibility mapping: A comparison of logistic regression and neural networks methods in a medium scale study, Hendek region (Turkey)

Landslide susceptibility mapping is one of the most critical issues in Turkey. At present, geotechnical models appear to be useful only in areas of limited extent, because it is difficult to collect geotechnical data with appropriate resolution over larger regions. In addition, many of the physical variables that are necessary for running these models are not usually available, and their acquisition is often very costly. Conversely, statistical approaches are currently pursued to assess landslide hazard over large regions. However, these approaches cannot effectively model complicated landslide hazard problems, since there is a non-linear relationship between nature-based problems and their triggering factors. Most of the statistical methods are distribution-based and cannot handle multisource data that are commonly collected from nature. In this respect, logistic regression and neural networks provide the potential to overcome drawbacks and to satisfy more rigorous landslide susceptibility mapping requirements. In the Hendek region of Turkey, a segment of natural gas pipeline was damaged due to landslide. Re-routing of the pipeline is planned but it requires preparation of landslide susceptibility map. For this purpose, logistic regression analysis and neural networks are applied to prepare landslide susceptibility map of the problematic segment of the pipeline. At the end, comparative analysis is conducted on the strengths and weaknesses of both techniques. Based on the higher percentages of landslide bodies predicted in very high and high landslide susceptibility zones, and compatibility between field observations and the important factors obtained in the analyses, the result found by neural network is more realistic.     

Real Option Identification Framework for Mine Operational Decision-Making

Natural Resources Research - Identification of opportunities for applying real options (RO) in mining operations is a major challenge to decision-makers. In order to make optimal decisions in...     

Lichenic growth as a factor in the physical deterioration or protection of Cappadocian monuments

Cappadocian monuments that are within tuff have serious deterioration problems. Understanding the effects of lichens on the tuffs is of utmost importance. In this paper, interactions between lichen-coated surfaces of Cappadocian monuments and the rock substratum have been studied. Thin sections and freshly cut sections were investigated by light and scanning electron microscopy. The presence of clay minerals and zeolites as weathering by-products produced by alteration and hydrolysis of glass and feldspars was assessed by XRD patterns. Furthermore, some physical properties of the tuff coated by and free of lichens were measured and compared. Analysis of mineralogical data has shown that the main weathering mechanism can be identified as hydrolysis of some of the rock-forming minerals. The lichenic coat reduces the presence of water inside the rock, thus protecting the rock material from physical decay and disintegration.     

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 NO₃¹⁻ 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.     

Effect of weathering on the geomechanical properties of andesite, Ankara – Turkey

Andesite exposed in different parts of Ankara has different weathering categories varying from fresh to residual soil. The geomechanical properties of the andesite are significantly affected by weathering. Buildings constructed especially in completely weathered and residual soil levels of the andesite have some geotechnical problems. In this study, the variation of the geomechanical properties of the andesite due to weathering is investigated in three selected sites of Ankara, through optical microscope, X-ray diffraction analyses, major element analyses, pressuremeter tests, physicomechanical tests, and seismic refraction method. The data gathered from the field and laboratory studies were used to assess the characteristics of the weathering zones. Based on the data obtained from this study, an idealized weathering profile is assessed. No bearing capacity and consolidation settlement problems exist in the area. However, care should be taken for immediate settlement of the buildings. Slopes with heights less than 8 m are not expected to cause any significant problems for buildings. There exists a ground amplification problem in the study area. The natural period of the building should not match that of the weathered rock. The ground response analyses reveal that the buildings with four to seven stories may be adversely affected from earthquakes due to resonance phenomenon. Therefore, this has to be taken into account when designing new buildings.     

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.     

2005 Photometric observations and multiple frequencies of the <Emphasis Type="Italic">δ</Emphasis> Scuti variable V350 Peg

We present the V light curves of δ Scuti type variable V350 Peg, obtained between August and October 2005 at the Ankara University Observatory (AUG) and the TüBíTAK National Observatory (TUG). By application of multiple-frequency analyses using Period04 to 7878 photometric V measurements (which are consist of our 747 V data and 7131 V data obtained at Monegrillo Observatory) of V350 Peg, a five-frequency solution was found to be fitted well to the data. In accordance with the computed Q values for V350 Peg, it was found that this star has probably radial mode with l=0 and g-mode oscillations.