Browsing by Author "Pulat, HF"

Now showing 1 - 8 of 8
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    Mechanism and modelling of shallow soil slope stability during high intensity and short duration rainfall
    Egeli, I; Pulat, HF
    Shallow landslides in nearly saturated uncohesive to slightly cohesive soils are triggered by high intensity, short duration rainfall which infiltrates into soil and changes intergranular friction and effective stresses. For this, the especially developed Soil-Water Interaction Modelling System (SWIMS) was used with CL-ML type soils. For simplicity, rainfall intensity and duration were kept constant. Results showed that (1) All 35 degrees slopes were failed by translational failure. For the other (15 degrees, 25 degrees) slopes, no failures were observed; (2) For all slopes, FOS increased with increasing compaction degree and decreased with increasing slope angle; (3) Other parameters, such as soil density, porosity, saturation degree, water contents, and water permeability may also affect shear strength/slope stability, especially for low degrees of saturation (S < 95%), compared to high degrees of saturation (S =, > 95%). (4) A correlation of SWIMS tests observed that average wetting band depths (h(obser)), with the calculated wetting band depths from the Lump Equation (h(LE)), were poor, as h(obser) values were much higher than hLE values. Differences increased for very low degrees of saturation (S), compared to S > 95%. This meant that the Lump equation underestimated wetting band depths. Further, if the Lump equation is still considered valid, this would imply either water-permeability increases, porosity decreases or both occur towards full saturation; a process where the last possibility is the most probable occurrence. (C) 2012 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.
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    The effect of soil mineralogy and pore fluid chemistry on the suction and swelling behavior of soils
    Pulat, HF; Yukselen-Aksoy, Y; Egeli, I
    Soil suction is one of the most important parameters for describing the moisture condition and engineering behavior of unsaturated soils. Therefore, changes in suction behavior of soils in the presence of saline waters are important for engineered barriers. The aim of this study was to determine the change in suction and swelling behavior of soils, which were exposed to salt solutions (NaCl, CaCl2, natural seawater) with respect to distilled water. The three soil samples were gathered with different mineralogy and plasticity characteristics and tested for determining matric and total suction values and for obtaining free swelling characteristics in the presence of salt solutions. The bentonitic soil sample had the highest total suction value in the presence of seawater. Kaolinitic and zeolitic soil samples had the highest total suction values in the presence of NaCl solution. The highest modified free swell index value of the samples was obtained in the presence of NaCl solution for all the soil samples. No relationship was found between the total suction, matric suction and the modified free swell index value of the tested soils.
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    Developing cation exchange capacity and soil index properties relationships using a neuro-fuzzy approach
    Pulat, HF; Tayfur, G; Yukselen-Aksoy, Y
    Artificial intelligence methods are employed to predict cation exchange capacity (CEC) from five different soil index properties, namely specific surface area (SSA), liquid limit, plasticity index, activity (ACT), and clay fraction (CF). Artificial neural networks (ANNs) analyses were first employed to determine the most related index parameters with cation exchange capacity. For this purpose, 40 datasets were employed to train the network and 10 datasets were used to test it. The ANN analyses were conducted with 15 different input vector combinations using same datasets. As a result of this investigation, the ANN analyses revealed that SSA and ACT are the most effective parameters on the CEC. Next, based upon these most effective input parameters, the fuzzy logic (FL) model was developed for the CEC. In the developed FL model, triangular membership functions were employed for both the input (SSA and ACT) variables and the output variable (CEC). A total of nine Mamdani fuzzy rules were deduced from the datasets, used for the training of the ANN model. Minimization (min) inferencing, maximum (max) composition, and centroid defuzzification methods are employed for the constructed FL model. The developed FL model was then tested against the remaining datasets, which were also used for testing the ANN model. The prediction results are satisfactory with a determination coefficient, R (2) = 0.94 and mean absolute error, (MAE) = 7.1.
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    Influence of Seawater on the Suction and Swelling Behavior of Clayey Soils
    Pulat, HF; Yukselen-Aksoy, Y
    The present study examines the suction characteristics and swelling behavior of clayey soils when exposed to natural seawater with respect to distilled water. The effects of saline waters on the engineering behavior of soils need to be determined since the salinity of the pore fluid of soils near coastal areas increases continuously. Six clayey soil samples with different mineralogy and characteristics were gathered and tested to determine the suction and swelling characteristics in the presence of natural seawater and distilled water. The results show that the total suction values of the samples are higher in the presence of seawater than in distilled water. The samples with high swelling potential have lower matric suction values than nonswelling soils. Moreover, in contrast to swelling-type soils, the matric suction values of the nonswelling soils remain similar in the presence both distilled water and seawater. The modified free swell index (MFSI) of the samples is well correlated with the liquid limit (LL), plasticity index (PI), and cation exchange capacity (CEC) in distilled water. However, coefficients of determination decreased in the presence of seawater. Also, there is no significant correlation existing between total and matric suction values and the MFSI values of the samples.
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    Investigation of the biopolymer additives effect on permeability and shear strength of clayey and sandy soils
    Pulat, HF; Taytak, B; Yukselen-Aksoy, Y
    Many methods are used to improve the engineering properties of the soils. While the some of the developed methods cannot produce an effective solution, some of them are not economical for practical solution. In this study, permeability and shear strength behaviors of natural kaolin, bentonite and sand mixtures have been investigated in the presence of three different biopolymers (xanthan gum, chitosan and chitin) and different concentrations (0.25-0.50-0.75 and 1%). The results have shown that, the xanthan gum and chitosan addition decreased the permeability coefficient almost 30 hold. While the biopolymer effect on shear strength behavior is investigated, 1% xanthan gum and chitosan concentration addition provided 15-10% increase in angle of internal friction. The obtained test results have shown that, biopolymers can be used in dams and landfills at impermeable clay liner applications.
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    Composition and degradation effects on the compaction characteristics of municipal solid wastes
    Pulat, HF; Yukselen-Aksoy, Y
    In order to protect environment and human health, MSW must be stored regularly and confidently. For safe and economic MSW storage, significant processes are initialized (dumping, spread out, burying and compacting). Compaction is the one of the most important stages of the storage process. Well compacted MSW renders less volume than the same weighted uncompacted MSW. Furthermore, well compaction provides safer storage area. In this study, the effect of composition, degradation, and energy on the compaction behavior of artificially prepared and natural fresh and aged MSW samples were determined. The standard and modified proctor tests were performed on the fresh and aged samples. Artificial samples were prepared in different compositions to examine the effect of composition. In addition to the synthetic MSW samples, natural MSW samples were provided from municipal landfill area of Manisa city.
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    Suction characteristics of compacted zeolite-bentonite and sand-bentonite mixtures
    Durukan, S; Pulat, HF; Yukselen-Aksoy, Y
    Soil suction is one of the most important parameters describing soil moisture conditions for unsaturated soils used in landfill liners. However, few studies have been conducted on the suction characteristics of compacted zeolite-bentonite mixtures (ZBMs) and sand-bentonite mixtures (SBMs), which are proposed for use as liner materials. Nevertheless, zeolite is known for its microporous skeleton containing cages and tunnels and it has a great physical affiliation to water uptake. Zeolite and bentonite, in a mixture, are thought to be in competition for water uptake and this may alter the distribution of water content for each soil in the mixture. The present study investigated the suction properties of compacted ZBMs and SBMs for varying mixing ratios and compaction water contents. The soil suction measurement technique chosen was the filter-paper method. The suction characteristics of powdered, granular, and block zeolites, as well as 0, 10, and 20% bentonite in ZBMs and SBMs were measured and compared with each other. Contaminated compacted ZBMs are compared with those of uncontaminated compacted ones at the optimum water content for the 10% and 20% mixtures. The results show that suction capacity of zeolite increases with grain size. As bentonite content increases, both matric and total suction increase for both mixtures. ZBMs have higher matric suction values than SBMs, but not total suction values. Contaminated total suction values are found to be higher than those of uncontaminated samples due to an increase in dissolved ion concentration.
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    Compaction behavior of synthetic and natural MSW samples in different compositions
    Pulat, HF; Yukselen-Aksoy, Y
    Compaction is the one of the most important stages of the storage process in landfills. Well-compacted municipal solid waste (MSW) occupies less volume than an uncompacted MSW sample of the same weight and provides a safer storage area. The composition of MSW changes in between countries and even cities. For that reason, for effective compaction, the composition effect should be investigated. In this study, effects of composition, degradation and energy on the compaction behavior of artificially-prepared and natural fresh and aged MSW samples were determined. Artificial samples were prepared in representative different compositions Europe (E-1), Turkey (T-1) and the USA (U-1) to examine the effect of the composition. In addition to the synthetic MSW samples, natural MSW samples were obtained from the municipal landfill area of Manisa, Turkey. The standard Proctor test results have shown that the highest maximum dry unit weight was observed with the U-1 composition, which has the lowest organic content and the highest metal content. The degradation effect was investigated on the natural samples. The degraded MSW sample (3-4 years) has significantly higher maximum dry unit weight than the fresh natural MSW sample because of its low organic content. According to the results of this study, with respect to the composition effect, the percentage of organic waste is the most important factor on the compaction behavior of MSWs. As paper, organic and plastic contents increase in the MSW composition the (dry-max) value decreases and w(opt) increases. The ash content does it reversely, as such that any increase in (dry-max) decreases the w(opt) value of the MSW.