İnşaat mühendisliği uygulamalarında temel zemini özellikleri, tasarım ve imalat aşamalarında önemli bir role sahiptir. Bununla birlikte inşası planlanan yapıların heyelan riski bulunan alanlara, dolgu sahalarına ve kayma direnci düşük zeminlere yapılması gerekebilmektedir. Günümüzde bu problemin önüne geçebilmek adına birçok zemin iyileştirme yöntemi geliştirilmiştir. Zemin iyileştirme yöntemleri artan maliyetler nedeniyle kimi zaman üst yapı projesinden bile daha maliyetli olabilmektedir. Artan nüfus ve hızla yayılan kentselleşme yapılara yönelik talepleri arttırmakta beraberinde çevre kirliliğine neden olmakta ve atıklar oluşturmaktadır. Ülkemizde de imalatı yapılan ürünlerden hatırı sayılır oranda atıklar çıkmaktadır. Atık malzemelerin çevremize ve dolaylı olarak da insanlığa zararlı yanları vardır. Günümüzde atık vb. gibi katkı malzemeleri ile zemin iyileştirilmesi popüler olan yöntemlerden biridir. Bu çalışmada, Cam Elyaf Takviyeli Polyester (CTP) boru kesme atıklarının zemin iyileştirme yöntemlerinden biri olan derin karıştırma yöntemi (DSM) ile kullanılarak ince daneli zeminin taşıma gücüne olan etkisi araştırılmıştır. Yapılan deneysel çalışmalar laboratuvar ve saha olmak üzere iki grupta gerçekleştirilmiştir. Laboratuvar deneylerinde Sakarya ili Adapazarı ilçesinden 3 ila 4 metre derinliğinden alınan doğal siltli zeminin CTP ile karıştırılmasıyla elde edilen numuneler kullanılmıştır. Saha deneyleri kapsamında da Yalova ilinde bulunan bir şantiyede derin karıştırma metodu ile doğal zeminde çimento ağırlığının % 0, 3, 6, 9 oranında CTP boru kesme atığı ilave edilerek DSM kolonları oluşturulmuştur. Laboratuvar ve saha çalışması dayanım deney sonuçlarının bir uyum içinde olduğu gözlemlenmiştir. Laboratuvar deneylerinde siltli zemin birimine ağırlığınca %3 oranında CTP boru kesme atığı ilavesi yapılan numunenin maksimum kuru birim hacim ağırlığı verdiği tespit edilmiştir. Saha deneylerinde ise çimento ağırlığınca %3 oranında CTP boru kesme atığı kil zemine ilave edildiğinde maksimum dayanım elde edilmiştir. Deneyler sonucunda, CTP atığının ince daneli zeminlerin dayanımına olumlu katkı yaptığı, derin karıştırma yönteminde kullanılması durumunda ise imalatı yapılan zemin karışımında homojenlik sağladığı, harcın yoğunluğunu düşürerek uygulamada delgi ve geri çekim aşamasında kolaylık sağladığı gözlemlenmiştir. Ayrıca uzaklaştırma ve depolama maliyeti olan bir atığın zeminlerde iyileştirme malzemesi olarak kullanılması ile tekrar kazanımı ve atık bertarafı konusunda fayda sağlanacağı anlaşılmıştır. Sonuç olarak CTP boru kesme atıklarının zemin iyileştirmesi yönteminde alternatif bir katkı olarak kullanılabileceği kanaatine varılmıştır.
Basic soil properties in civil engineering applications have an important role in the design and manufacturing stages. However, the structures planned for construction may need to be built on creek beds, areas with landslide risk, embankments and soils with low bearing capacity. Today, many methods have been derived for soil improvement to ensure the highest achievable strength and least compressibility in soils. While the method to be applied on soils is expected to improve the mentioned geotechnical properties of the soil, it must also have the capacity to satisfy economically. Increasing population also causes waste accumulation and environmental pollution. Recycling and disposal of wastes without causing environmental pollution is an important issue that shall not be underestimated in today's world. That's why it is regulated within the scope of Environmental Legislation. Besides, the reduction of natural materials used in the construction has increased the importance of waste recycling, and the recycled wastes provide significant raw material and energy savings. The recycling of waste materials for soil improvement is almost the first to appear with fly ash. Studies with fly ash show that this material both has a positive effect on soil strength and helps to improve some geotechnical problems of soils. However, this material, which is a calcium-based stabilizer such as lime, can also allow the formation of detrimental substances as a result of chemical reactions which may be caused by the chemical and mineralogical structure of the soil. For this reason, it is becoming more and more important to try different wastes in order to utilize them into the different soils. A large amount of waste is generated as a result of cutting the Glass Fiber Reinforced Polyester (GRP) pipes by grinding in the production of sleeves for bringing the pipes to appropriate sizes and joining them together. Accumulating enormous amount of waste generated during pipe manufacturing has recently become a very important problem. The need to dispose of these high amounts of waste raises the questions of what kind of advantages it can bring if it is used on construction materials such as soils. This material, which has been almost never tried to improve the geotechnical properties of fine-grained soils, will be an important step in the literature as both an economical and a new soil improvement method if it can be used to provide improvement in sites with problematic and collapsible soils. Bagriaçik et al. studied on the utilizing GRP pipe waste in the form of powder into the soils to question its effectiveness on bearing capacity of only sandy soils. On this context, after mixing pipe powder with sand at different rates, shear strength parameters were determined by direct shear tests. It was concluded from the tests, for this kind of soil the shear strength can be enhanced up to almost 31 % of its initial strength. The use of this waste, which was mostly used as an additive in concrete and improves its properties in a positive way, needs to be investigated and tested further in the soils. Deep Soil Mixing (DSM) is one of the soil improvement methods in which soil improvement with different materials is allowed to be applied in the field environment. The method enables to the additives which mixed with the soil and provides the formation of continuous column with the soil. It was first applied in the USA in 1954 with a single drill bit. In Europe, it was first used to create lime columns on soft clay soils in Sweden in 1967, and then this method became widespread and continued to be used. In the 1990s, applications similar to today's construction method started to be applied. When the DSM method is analyzed compared to other soil improvement methods, it has advantages in terms of economic, environmental, geotechnical, logistics and applicability. In general, the DSM method is used more in clayey soils than in coarse-grained soils and stands out as it is practical and economical. It has been determined by past studies that many engineering parameters such as the shear strength of the soils, compressibility properties, consolidation parameters, elasticity modulus are improved in the columns formed by this method. In this environmentally friendly method, columns consisting of materials such as lime, cement, fly ash, fibers can be formed. Columns formed by the DSM method are applied as one of the soil improvement methods for purposes such as reducing the liquefaction potential, creating a support system in deep excavations, increasing the foundation bearing capacity by increasing the soil strength parameters and controlling the settlements. However, ensuring the homogeneity and sufficient rigidity of the columns formed is one of the primary objectives and this situation can be affected by many parameters such as contribution rate, retraction and rotational speed. Therefore, it is an important point to be able to adjust the consistency of the soil in order to ensure sufficient progress on the soils where the mixing will be applied. In this study, the effect of Glass Fiber Reinforced Polyester (GRP) pipe cutting waste on the shear strength of fine-grained soils was investigated by using the deep soil mixing (DSM) method, which is one of the soil improvement methods. The experimental studies were carried out in two groups, laboratory and field. In laboratory experiments, samples obtained by mixing natural silty soil taken from Adapazarı district of Sakarya province from a depth of 3 to 4 meters with GRP were used. Within the scope of field experiments, DSM columns were formed by adding GRP pipe cutting waste at the rates of 0, 3, 6, 9% of cement weight on natural soil by deep mixing method. It has been observed that the laboratory and field strength test results are in harmony. In laboratory experiments it has been detected that maximum value of dry unit weight of silty soil was obtained by 3% GRP addition. On the other hand, in field the maximum strength was gained by adding 3 percentages of GRP by cement weight to the clayey soil. It has been observed that the GRP waste additive to the fine-grained soil contributes positively to the strength, provides homogeneity in the soil mixture produced by using the deep mixture method, and reduces the density of the mortar and provides convenience in the drilling and withdrawal stages in the application. In addition, it has been understood that a waste that has a cost of removal and storage will benefit from its recovery and disposal. As a result, it has been concluded that GRP pipe cutting wastes can be used as an alternative contribution to the soil improvement method.
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