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    Geotechnical properties of tire-cohesive clayey soil mixtures as a fill material
    (ELSEVIER SCIENCE BV, 2006) Cetin, Hasan; Fener, Mustafa; Gunaydin, Osman
    Geotechnical properties of pure fine and coarse grained tire-chips and their mixtures (10, 20, 30, 40 and 50%) with a cohesive clayey soil were investigated through a series of soil mechanical tests in order to investigate possibilities of their usage as a lightweight fill material. Grain size and Atterberg limits analysis, permeability, direct shear and compaction tests were performed on the clayey soil, tire chips (both fine and coarse) alone and their mixtures. The results indicate that the use of used tire-chips mixed with clayey soils as a fill material is possible. The mixtures up to 20% coarse grained tire-chips and 30% fine grained tire-chips can be used above ground water tables where low weight, low permeability and high strength are needed in fills such as highway embankments, bridge abutments and backfills behind retaining structures especially when they are to be built on weak foundation soils with low bearing capacity and high settlement problems. They should not be used where drainage is needed to prevent the development of pore pressures during loading of fills under saturated conditions. In these cases, they may, however, be used by mixing with high permeability material such as sand and gravel. (c) 2006 Elsevier B.V. All rights reserved.
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    Soil structure changes during compaction of a cohesive soil
    (ELSEVIER SCIENCE BV, 2007) Cetin, Hasan; Fener, Mustafa; Soeylemez, Mehmet; Guenaydin, Osman
    Orientations of particles, pores and other constituents during compaction of an artificially made clayey soil were studied in order to investigate how soil structure, and in turn, engineering parameters such as dry unit weight, porosity, void ratio and compaction characteristics, change during compaction of a cohesive soil at different moisture contents on both the dry and wet sides of the optimum moisture content. The results show that the orientation pattern at the very dry stage of the compaction curve is nearly random. The overall degree of preferred orientation increases as the moisture content increases until the optimum moisture content is reached. Edge-edge contacts between the particles and/or domains at the very dry stage of the compaction curve first become mainly edge-face and then become face-face contacts near the optimum moisture content. Around the optimum moisture content, the overall degree of preferred orientation becomes the highest. From this point on, however, the overall degree of preferred orientation starts to decrease again indicating that further moisture content increase does not cause additional overall preferred orientation. The structure beyond the optimum moisture content is mainly characterised by long strings of differently oriented packets in the form of curved trajectories and mainly face-to-face contacts between the particles and/or domains in the packets. Though there is a high degree of preferred fabric orientation in each individual packet, the overall degree of preferred orientation decreases because the packets are themselves oriented in different directions. The results agree with previous studies showing that the soil fabric dry of optimum is randomly oriented but becomes increasingly oriented towards the optimum. However, as the moisture content increases on the wet side of optimum, the overall degree of preferred orientation decreases as opposed to the generally accepted view. (C) 2007 Elsevier B.V. All rights reserved.