Kamil Kayabali

Engineering aspects of a novel landfill liner material: bentonite-amended natural zeolite

This study aims at investigating certain features of a novel material proposed to serve as an impervious liner in sanitary landfills. The natural zeolites of Gordes (Turkey) and the commercial powdered bentonite were used in various experiments, such as compaction, hydraulic conductivity, and strength. Various ratios of bentonites and zeolites (B/Z) compacted at the optimum water content (wopt) were tested to determine the strength parameters. The laboratory samples compacted underwopt and slightly higher water contents were tested for hydraulic conductivity (k). For the bentonite content > 5%, the resulting averagek values ranged from 2 × 10−8 to 4 × 10−8 cm s−1. Cation exchange capacity, an important chemical property of a liner material, of bentonite and natural zeolite were found to be 60 and 95 meq/100 g, respectively. AB/Z ratio of 0.05–0.10 was found to be an ideal landfill liner material regarding its low hydraulic conductivity and high cation exchange capacity. The use ofB/Z mixtures as an alternative to clay liners would significantly reduce the thickness of base liner for sanitary landfills.

Seismic hazard map of Turkey using the deterministic approach

Abstract Because the instrumental records of Turkey are far from being satisfactory for modeling the seismic hazard using the probabilistic approach, an attempt was made in this study to accomplish it through the deterministic way. In this regard, all active faults of Turkey, small and large, were evaluated together to obtain major fault systems. Then, the procedure suggested by Wells and Coppersmith [Bull. Seismol. Soc. Am. 4 (1994) 975] applied to those faults to obtain the maximum magnitude earthquake that they can generate. To do this, it was assumed that 1/3 of the total fault length would rupture to yield the maximum earthquake. Following that, seven different attenuation relationships of the strong ground motion were utilized to calculate the maximum horizontal ground accelerations for the whole Turkey at 0.2° intervals using the computer model TUMDES written in BASIC programming language. The computed peak ground acceleration (pga) values were contoured and the iso-acceleration map based on Sadigh et al. [Seismol. Res. Lett. 1 (1997) 180] relationship was selected as the new seismic hazard map of Turkey on which the seismic zonations were determined as following: pga>0.3 g Zone 1; 0.3 g

Modeling of seismic hazard for Turkey using the recent neotectonic data

Abstract Recent developments in the neotectonic framework of Turkey introduced new tectonic elements necessitating the reconstruction of Turkeys seismic hazard map. In this regard, 14 seismic source zones were delineated. Maximum earthquake magnitudes for each seismic zones were determined using the fault rupture length approximation. Regression coefficients of the earthquake magnitude–frequency relationships for the seismic zones were compiled mostly from earlier works. Along with these data, a strong ground motion attenuation relationship developed by Joyner and Boore [Joyner, W.B., Boore, D.M., 1988. Measurement, characterization, and prediction of strong ground motion. Earthquake Engineering and Soil Dynamics, 2. Recent Advances Ground Motion Evaluation, pp. 43–102.] was utilized to model the seismic hazard for Turkey using the probabilistic approach. For the modeling, the “earthquake location uncertainty” concept was employed. A grid of 5106 points with 0.2° intervals was constituted for the area encompassed by the 25–46°E longitudes and 35–43°N latitudes. For the return periods of 100 and 475 years, the peak horizontal ground acceleration (pga) in bedrock was computed for each grid point. Isoacceleration maps for the return periods of 100 and 475 years were constructed by contouring the pga values at each node.

Soil liquefaction evaluation using shear wave velocity

Abstract A reasonably good relationship between shear wave velocity (SWV) and standard penetration resistance (SPT) of granular soils in agreement with previous studies was obtained from field tests. A similar correlation between SWV and cone penetration resistance of granular soils was also obtained. Using Seeds Standard Penetration Test (SPT)-based soil liquefaction charts, new charts of soil liquefaction evaluation based on SWV data were developed for various magnitude earthquakes.

Measurement of swelling pressure: direct method versus indirect methods

Light structures including highways and railroads built over potentially expansive clay soils may suffer damage from swelling. Considerable research has been done in an attempt to characterize swelling properties of expansive soils. Although direct measurement of swelling pressure is relatively straightforward, it has not drawn much interest. The present study attempts to measure swelling pressure directly. We call experimental techniques for swelling pressure other than this direct method the indirect methods. Some indirect methods require more than one soil sample and that all samples be identical. However, natural soils may not always provide identical samples. Therefore, reconstructed identical soil samples produced from natural soils were used in the present study. For comparison, the restricted swell, swell-consolidation, double oedometer, and zero swell tests were employed as indirect methods. While the restricted swell test slightly underestimated swell pressure, swell-consolidation and zero swell...

Liquefaction-related building damage in Adapazari during the Turkey earthquake of August 17, 1999

The goal of this paper is to present especially the source and the type of liquefaction-related failures of those buildings which satisfied the structural codes of buildings and practices but experienced settlement, tilting and overturning in Adapazari during the Turkey earthquake of August 17, 1999. In this context, the Adapazari region is first evaluated in terms of geological setting, tectonics, seismicity and liquefaction susceptibility based on in situ and laboratory test data. In addition, the number of stories, types of buildings and their related failures have been mapped accordingly. Furthermore, laboratory model tests are conducted to enforce and/or confirm the type of buildings failures with particular reference to their geometrical shape and the number of stories assuming that the models representing buildings satisfy the structural codes of buildings and practices.

Engineering geological aspects of replacing a solid waste disposal site with a sanitary landfill

Abstract The current solid waste disposal site in the Mamak district of Ankara is being engulfed by the growing city. All varieties of solid wastes, including medical wastes, are stored at the present site in an irregular manner. Topographical and geological conditions at Mamak waste site are favorable for constructing a sanitary landfill. Located at the edge of a topographical depression, the site is underlain by the natural hydraulic barriers such as clay and metagreywacke. The terrestrial clay has a permeability of 10 −7 to 10 −8 cm/s and low to moderate values of CEC. The proposed sanitary landfill to replace the present solid waste site has a capacity of storing solid waste over 50 years. The details of base liner, final cover, toe embankment, and drainage of leachate and gas are presented in the paper.

Comparison of three artificial neural network approaches for estimating of slake durability index

Slake durability index (Id2) is an important engineering parameter to assess the resistance of clay-bearing and weak rocks to erosion and degradation. Standard test sample preparation for slake durability test is difficult for some rock types and the test is time-consuming. The paper reports an attempt to define Id2 using other parameters that are simpler to obtain. In this study, three different artificial neural network approaches, namely feed-forward back propagation (FFBP), radial basis function based neural network (RBNN), and generalized regression neural networks (GRNN) were used for estimating Id2. The determination coefficient (R2), root mean square error and mean absolute relative error statistics were used as evaluation criteria of the FFBP, RBNN, and GRNN models. The experimental results were compared with these models. The comparison results indicate that the GRNN models are superior to the FFBP and RBNN models in modeling of the slake durability index (Id2).

Determination of Plastic and Liquid Limits Using the Reverse Extrusion Technique

Consistency limits are fundamental properties of fine grained soils. The techniques used today to determine these parameters are operator dependent; their repeatability is low. In order to overcome and/or reduce those factors affecting the results of conventional testing methods, the reverse extrusion technique was evaluated. Thirty-one inorganic soil samples were used in the experiments. In order to produce a reliable basis for the plastic and liquid limits, a relatively broad database was constituted using the conventional consistency limit tests. Extrusion pressures were then obtained and plotted for different water contents for each sample. A linear relationship was observed among the water content and the logarithm of the extrusion pressure. The extrusion pressures corresponding to the average plastic and liquid limits of the conventional method show a normal distribution about certain values. A more reliable, economical, and robust device with greater repeatability is proposed. The presented approach shows promise in providing a better index parameter to characterize fine grained soils.

Assessing the practicality of the centrifuge method for 1-D consolidation

Conventional laboratory consolidation tests usually take weeks to conduct, depending on the field loading conditions. While centrifuge consolidation has been proven to shorten this period significantly, no attempt has been made to introduce this method to the professional community because the centrifuges are very large and are, for the most part, utilized only by scientists. The aim of this investigation is to illustrate the feasibility of using the centrifuge consolidation test as a practical tool to estimate the consolidation behavior of natural soils by employing a miniature centrifuge apparatus. Thirty-two soil samples were subjected to 1-D conventional and centrifuge consolidation tests. An empirical relationship was established between the two different consolidation techniques to predict the consolidation behavior. The consolidation curves of the 32 soil samples computationally-obtained from the centrifuge method were in good agreement with those obtained by the conventional method, hence it is possible to determine the recompression and compression indices with reasonable accuracy. The only practical limitation with the proposed apparatus is the determination of the consolidation coefficient; this part of the research remains in progress.RésuméLes essais conventionnels oedométriques de laboratoire demandent des semaines pour leur réalisation, suivant les conditions de chargement à reproduire. Alors qu’il est prouvé que la consolidation des sols par centrifugation permet de raccourcir le temps d’essai de façon significative, aucune tentative pour introduire cette technique dans le milieu professionnel n’a été faite car les centrifugeuses sont de gros appareils et sont, pour la plupart, utilisées uniquement par les scientifiques. Le but de cette recherche est d’illustrer la faisabilité d’un essai de consolidation, avec une centrifugeuse miniature, pour estimer la compressibilité des sols. Trente-deux sols ont été soumis à l’essai oedométrique conventionnel et au test de consolidation à la centrifugeuse. Des relations empiriques ont été établies entre les résultats de ces deux essais. Les courbes de consolidation des 32 sols, dérivées par calcul de l’essai à la centrifugeuse, étaient en bon accord avec celles obtenues par la méthode conventionnelle, permettant ainsi de déterminer les indices de recompression et de compression avec une précision raisonnable. La seule limitation pratique, avec l’appareil proposé, est la détermination des coefficients de consolidation, cet aspect de la question faisant encore l’objet de recherches.