Waste automobile tires are used as additives or replacements instead of traditional materials in civil engineering works. In geotechnical engineering, tires are shredded to certain sizes and mixed with soil, especially used as backfill material behind retaining walls or fill material for roadway embankments. Compared to soil, rubber has high damping capacity and low shear modulus. Therefore, it requires the determination of the dynamic characteristics of rubber/soil mixtures. In this paper, the cyclic behavior of recycled tire rubber and clean sand was studied, considering the effects of the amount and particle size of the rubber and confining stresses. A total of 40 stress-controlled tests were performed on an integrated resonant column and dynamic torsional shear system. The effects of the relative size and proportion of the rubber on the dynamic characteristics of the mixtures are discussed. The dynamic properties, such as the maximum shear modulus, strain-dependent shear modulus, and damping ratio, are examined. For practical purposes, simple empirical relationships were formulated to estimate the maximum shear modulus and the damping ratio. The change in the shear modulus and damping ratio with respect to shear strain with 5% of rubber within the mixture was found to be close to the behavior of clean sand.

The use of dispersive soils, which are common in many parts of the world, in engineering applications such as water structures, earthen dams and road embankments is possible with their improvement. Recently, the effects of different chemicals on the stabilization of dispersive soils have been investigated. The use of waste materials in stabilization is preferred both because of the more sustainable environment and the economic advantages it provides. The use of silica fume (SF) as a waste material in different engineering applications provides an important advantage in environmentally and economically sustainable ways. Many studies have been carried out regarding silica fume, especially in the construction industry. Although SF is used in many industries, there is no study about its potential impact on the stabilization and dynamic properties of dispersive soils. In this study, first, Atterberg limits and standard Proctor compaction tests were performed on the mixtures prepared by adding different SF percentages (0, 5, 10, 15, 20, 25 and 30%). Afterward, pinhole tests and resonant column tests were performed to determine dispersibility and dynamic properties on the samples prepared by compaction characteristics for each SF percentage reached. In general, it was determined that SF contributed to a change in soil class, and improvement in dispersibility and dynamic properties of the soil sample, depending on SF content; positive effects of SF were observed in terms of shallow soil improvement.

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Öz: Atık lastiklerin, inşaat mühendisliği uygulamalarında kullanımı son 30-40 yıl içinde oldukça yaygınlaşmıştır. Geoteknik mühendisliği uygulamalarında olumlu sonuçlar elde edilmiştir. Yol inşaatlarındaki stabilite ve oturma problemlerine karşı, istinat ve dolgu duvarlarında ise hafif malzeme ihtiyacına karşılık geri dolgu malzemesi olarak kullanılmaktadırlar. Çalışmanın amacı yapay olarak oluşturulan demiryolu altyapısına etki eden tekrarlı yükler altında malzeme davranışının incelenmesidir. Bu çalışmada, demiryolu altyapısı temel malzemesi olarak seçilen temiz standart kum örneği ile atık araç lastiklerinden parçalama ve öğütülme yolu ile elde edilen toz, çubuk ve amorf malzeme kütlece %5/95, %10/90 ve %15/85 oranlarında karıştırılmış ve oluşturulan karışım numuneler üzerinde rezonant kolon (RC) deneyleri yapılmıştır. Elde edilen veriler, 100 kPa efektif basınç altında, %5 oranında toz atık lastik karışımı içeren numunelerin kayma modüllerinin, 100 kPa referans örneğe göre, %0,001 birim kayma deformasyon seviyelerinde %26, %0,01 birim kayma deformasyon seviyelerinde %18 ve %0,1 birim kayma deformasyon seviyelerinde ise %35 civarında daha yüksek olduğunu göstermiştir.