Organik kimyasal maddelerinin kil zeminlerin permeabilitesi üzerindeki etkisi

The Effect of organic chemicals on the permeability of the clay soils

Tez No: 66567
Yazar: CENK HOŞCAN
Danışmanlar: PROF. DR. AHMET SAĞLAMER
Tez Türü: Yüksek Lisans
Konular: İnşaat Mühendisliği, Civil Engineering
Anahtar Kelimeler: Belirtilmemiş.
Yıl: 1997
Dil: Türkçe
Üniversite: İstanbul Teknik Üniversitesi
Enstitü: Fen Bilimleri Enstitüsü
Ana Bilim Dalı: Geoteknik Ana Bilim Dalı
Bilim Dalı: Belirtilmemiş.
Sayfa Sayısı: 57

Özet

ÖZET Dünyada teknolojinin ilerlemesine paralel olarak gelişen sanayi, atık problemini de beraberinde getirmiştir. Uygun bir şekilde korunamayan veya yok edilemeyen atıkların yarattığı kirlilik kalıcı, sağlığa zararlı, temizlenmesi zor ve pahalı bir sorun olarak karşımıza çıkmaktadır. Bu sorunun bertaraf edilmesi ancak daha kirlenme başlamadan alınacak önlemlerle mümkün olmaktadır. Çevre koruma hareketlerinin gelişerek bir politik baskı unsuru haline gelmesi hükümetleri çeşitli düzenlemeler yapmaya mecbur kılmıştır. Bu düzenlemeler zaman içerisinde yasal nitelik kazanmış, kapsamları başlangıçta sınırlı iken sonraları çevre ve insan sağlığına zararlı tüm atıkların depolanmasına değin genişlemiştir. Atıkların uygun şekilde depolanması ile tüm sorunlar çözülememiştir. İnşaa edilen katı atık depolan yeni sorular doğurmuş, bu sorunları çözmek amacıyla yeni araştırmalar yapılmıştır. Araştırmaların odak noktası, katı atık depolarından dolayı oluşabilecek yeni kirliliklerin giderilmesi olmuştur. Bu çalışmada atık depolarından sızabilecek organik kimyasal maddelerin kil zeminler üzerindeki etkisi araştırılmıştır. Konunun önemini vurgulamak amacıyla tarihçesine değinilmiştir. Katı atık depolarına genel bir bakış atılmış; atık oluşumu, yer seçim kriterleri ve yarattığı kirlilikler irdelenmiştir. Katı atık depolarından sızabilecek maddeler ile ilgili bilgiler verilmiş ve bu maddelerin kil zeminlerin permeabilitesi ne yönde etkilediği araştırılmıştır. Yapılan permeabilite deneyleri ile teorik bilgiler deneysel alanda incelenmiştir. Organik kimyasal maddelerin kil zeminlerin geçirimliliğini önemli ölçüde arttırdığına dikkat çekilmiş, bu etkinin katı atık depolarının tasannu aşamasında göz önüne alınabilmesi için öneriler yapılmıştır vıı

Özet (Çeviri)

THE EFFECT OF ORGANIC CHEMICALS ON THE PERMEABILITY OF THE CLAY SOILS SUMMARY The destruction of solid waste has been one of the essential matters of the human being from the very first beginning of the social life. The random throw away of the waste had created some serious problems during the history. For instance, the most striking example is the“black death”, the plague epidemic, in the Middle Ages; the main reason being the rats and bugs living in the dust heep environments. Especially, in the 14th century, half of the population had died as a result of epidemics. These bad experiences had made human beings realize that the waste, if not stored carefully, might be so hazardous for the humanity in such a way to even destroy it. However, it is not noticed any legislation relating to the precautions against the environmental pollution until 19th century.“River and Harbor Law”passed in 1899 in the USA was the first example of this type of legislation. This was followed up by the policy determination of each country concerning the waste storage, recycling and destruction, after within the framework of the global environment protection policies. Despite the differences among the systems and designs used by each country in their respective solid waste storages, their approaches are similar concerning the impermeable layers in the said areas. All of them have proposed to use a geomembrane in this impermeable layer, called“liner”. Geomembrane first used in the 1950' s as an impermeable material in the pool systems. It was then used and spread in the 1970' s, in the geotechnical engineering. Currently, lots of synthetic materials are utilized in the solid waste storages. Especially, HDPE (high density polyethylene) is widespread in the liner layer. At the same time with the improvement in the design of the solid waste storages, the know-how about the suitable construction areas of such type of facilities developed. The importance of the matter on the human health has given rise to more comprehensive and serious researches on the subject. Various researches on the waste composition, the chemical components of leachate water, the design on new synthetic materials that can be used in the solid waste storages, the solid waste management have been done by numerous specialized scientists. The current knowledge concerning the subject is mainly the consequence of these researches. The most important problem in the solid waste storages is the pollution of groundwater by the leaked water from solid wastes. The reason of this leakage can be discontinuities on the liner layer and slope failure as well as the insufficient impermeability of the floor of the storage. viaThe criteria in either the selection of the solid waste storage place, or its design tend to reduce the risk of leakage. For this reason, it is not favorable to construct such facilities on the earthquake and dike zones, karstic rocky areas and on the areas where the groundwater level is high, where landslides are observed. Because the risk of water resources pollution is high on such areas due to water leakage from the solid waste storages. Despite the fact that the solid waste storages are constructed with the concern on the environment protection, it is indispensable that they cause pollution. For instance, the stink during the waste storage is unavoidable. The participation of the vehicles, carrying waste into traffic increases the current traffic jam, bringing about much more noise. In addition, such areas increase the population of rats and bugs. Finally, and the most importantly the waste storages cause soil pollution in case of leakage. The main focus of this study is the effect of chemical materials leaked from the waste storages on the clay soils. The permeability properties of the clay soils are modified by different organic chemicals; in the researches done, it is observed an increase of 10-1000 times in the permeability coefficient. In order to observe the effect of organic materials on the clay soils, it is essential to analyze the factors affecting the permeability of clay soils. The primary factor affecting the permeability coefficient is the liquid properties. Concepts such as the liquid viscosity and unit weight affect directly the permeability coefficient. Soil properties such as particles dimensions, void ratio, fabric structure, degree of saturation play an important role in their permeability.Another factor affecting the permeability coefficient is the liquid dielectric constant. Many researches agree that the soil hydraulic conductivity increases with the decrease of liquid dielectric constant. The fact that the dielectric constant of water is higher than those of most hydrocarbons strengthens this theory. It is proved by experiments that the permeability coefficient generally increases in the soils affected by hydrocarbons. Some researchers believe that the dielectric constant does not have a key role on the permeability coefficient. They have demonstrated that the modification in the clay permeability is mainly due to the cation transfer capacity which is a chemical property of the soil. At this point, it is important to mention the pH degrees of liquids affecting clay soils as another chemical property. Liquids, as their acidic property increases (i.e. as their pH degree decreases), result into the flocculation of the soil fabric structure. As a consequence of this reaction, the soil permeability coefficient increases. Experiment systems also differ within the framework of the effects of organic liquids on clay soils. Each researcher in the literature used the best experiment system suitable to his aims. Hence, each experiment system has its advantages and disadvantages. Three axial permeameter is widely used by most researchers. An important advantage of the system is that it is entirely closed to the atmosphere, preventing any contact with the experiment liquid. If it is considered that nearly all of the organic materials IXto be dealt with are harmful to health, the importance of this property is obvious. Physical contact with either toxic or cancerogene materials such as aniline, xlene, toluene, ethanol. methanol may cause serious health problems. Another advantage of working with closed systems is to give the possibility to make experiments with volatile materials. Materials such as acetone which is not harmful to health but volatile can not be used in the systems open to the atmosphere. In addition, it is possible to apply pressure to the soil sample during the experiment with the three axial pressure systems. As a result of this, it is possible to simulate the stress condition of the sample on the field. While working with pressure systems, to saturate the soil specimen does not create any problem. Saturation is reached in a short period of time and the saturation degree can be controlled thanks to the back pressure. Decrease in the period necessary to the sample to reach the saturation in other words decrease in the experiment period is another important property. Some researchers also use wall-fixed permeameter which is an experiment system preferred for long-term (i.e. a couple of years) experiments. Wall-fixed permeameters have a more simple mechanism than three axial systems and are much more stable for long-term experiments. Other mechanisms are also used by scientists studying the hydraulic conductivity. Systems such as sedimentation cells, consolidation-cell permeameter are also mentioned in the literature. At the stage of experimental study, it is necessary to decide on the material and tools to be used. The most advantageous experimental system is determined as the three axial permeameter system. But due to technical inadequacies, a single axial pressure permeameter is designed, and acetic acid (CH3COOH) is chosen as the experiment liquid. The reason to chose the acetic acid is that it is not toxic or harmful to health and volatile. hi the Atterberg limits and compaction experiments on Gürpınar clay, the index properties of the sample are determined. The Atterberg limits experiments were repeated with different concentrations of acetic acid. When the experiment results are assessed, it is observed that the acetic acid has increased the liquid limit (wl) and plastic limit (wp) of clay. The increase in the experiments done with pure acetic acid is about 23%. In order to verify the results, experiments are repeated using another clay sample (red colored clay); same results were achieved with the red colored clay sample. In the experiments with the acetic acid of a concentration of 75%, an increase of 21% in the liquid limit of the clay sample is observed. In the experiments with the acetic acid of a concentration of 100% (pure acetic acid), measurement can not be taken. Sample preparation for the permeability experiments on clay soil bring about the question of which situation will be modeled by the permeability experiment. Many researchers work with samples prepared in different ways, within the framework of their respective aims. Hence, there is not a standard in the way of preparing the experiment sample. If we make a generalization, natural soil is presented in thesamples prepared and its permeability under the influence of organic pollutants is examined. Although the general method in the literature is such, another point of view is taken in the experiments forming the subject of this thesis. Samples from the clay soil are compacted in the optimum water content with the standard proctor energy. The liquid used in this compaction process is acid in different concentrations. In the permeability experiments, water is used as the liquid. The reason to prepare samples in such a way is the fact that the clay soils used as liners in the solid waste storages are polluted by the water leaked from wastes. This pollution causes modification in the pollution permeabilities. But the system behavior is irregular flow rates caused by the seasonal rain regimes, instead of a continuous pollution. Clay soils are never subject to the effect of organic pollutants in the continuous and constant concentrations. The most critical situation is the time when polluted soils are subject to high flow rates during the rainy months, because the soil permeability has been changed under the influence of organic liquids and the soil has become more permeable. As it is known, the greatest part of the flow rate acted on the soil during the rainy months is formed by water; the remaining organic liquids are somewhat rare. As we know that many hydrocarbons in lower concentrations do not change the clay soil permeability coefficient or that the modifications are avoidable, we can say that the flow rates formed by rains can be modeled by water as the experiment liquid. Consequently, to make an experiment with polluted soil sample and water is a more realistic method than to give organic material to the sample, in the permeability experiments. This reflects the behavior of clay soil under solid waste storages in a better way. Sample preparation method is as follows: samples in sacks taken from the field are sifted from 16 numbered sieve, under sieve material is in the optimum water content and compacted with standard Procter energy. The liquid used in the preparation of sample is acetic acid in different concentrations. A series of experiments is formed by experiments with acetic acid in concentrations of 0%, 25%, 50%, 75%, 100%. The permeability experiment is started after that the prepared samples are taken to the permeameter. In the permeability experiments, the process taking the most of the time is the saturation of the sample. From 60% to 80% of the total experiment period is spent by waiting for the saturation. As the result of the experiments, as the acetic acid concentration increases the permeability coefficient of the sample increases. The most attractive aspect of the results is the fact that the permeability coefficient is increased 700 times. Although this result is higher than expected, it fits the values mentioned in the literature. In this study, it is focused on the importance of solid waste storing and the history of its design. In these engineering constructions, permeability problems caused by the leakage of chemical materials to clay soils are mentioned and this modification in clay soils permeability coefficient is observed experimentally. The results of the studies can be summarized as follows: 1. Organic chemical materials change the permeability of the clay soils. The effect of some organic liquids are unavoidable. But some chemicals can even increase 1000 times the clay soils permeability. The acetic acid used in this study affects Gürpınar clay in such a way to increase its permeability 700 times. High increase in the XIpermeability proves the importance of the subject. Therefore, clay soils to be used in the solid waste storages are to be chosen by considering these principles. As clay permeability decreases, leakage problems arise. 2. It is not generally possible to predict which organic material is to be leaked from solid waste storages. Thus, it is not always possible to choose clay soils in such a way to bear organics' effect. Many comprehensive researches are done in developed countries. However, in our country it is not done any study on the analysis of the chemicals in solid waste storages yet. Another problem is storing all sorts of solid wastes together which renders difficult to do a study or even an expectation. 3. The change of the permeability coefficient of clay soils by organics' effects is not formalized yet. The reason is that various factors take part in clay-organics reaction. In the literature scientists explain in various ways the modification in the permeability coefficient; but they agree on the modification itself. Researches to be done in the future will give a better understanding of polluted clay soil behavior. 4. The change in permeability of clay soils is not the only change that occurs by the effect of organics. It is not wrong to presume that their engineering properties will also alter since their structure is changed. However, it is not observed any study on this subject in the literature. Therefore, if this subject is examined comprehensively, that will be an innovation for the sake of science. xu

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