Browsing by Author "Söylemez, M"

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    An equation for predicting shear strength envelope with respect to matric suction
    Tekinsoy, MA; Kayadelen, C; Keskin, MS; Söylemez, M
    Determining the shear strength parameters of unsaturated soils generally involves costly, time-consuming and sophisticated testing programme. This paper proposes a new method for prediction of shear strength with respect to matric suction. The variation of shear strength with respect to matric suction is described by using the air-entry value and the internal friction angle of a soil specimen. The validity of the method is tested for a number of suction strength data available in the literature. The shear strengths with respect to matric suction obtained from the proposed method are in nicely good agreement with experimental results. (C) 2004 Elsevier Ltd. All rights reserved.
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    Soil-particle and pore orientations during drained and undrained shear of a cohesive sandy silt-clay soil
    Cetin, H; Söylemez, M
    The orientations of particles, pores, and other constituents of an artificially made cohesive sandy silt-clay soil were studied to investigate how they change during drained and undrained shear. The results show that the orientation pattern before shearing is nearly random, although there may be some degree of preferred orientation caused by the overburden pressure. The degree of preferred orientation increases as the shearing increases until failure in both the drained and undrained tests and increases towards the failure plane. After failure, the degree of preferred orientation does not change considerably near the failure plane but does continue to increase away from it. The number of oriented particles, pores, and other constituents increases, but their averages stay about the same as the shearing continues after failure in the drained tests. The differences between the degrees of preferred orientations 5 and 10 mm away from the failure planes at different shear (horizontal) displacements are much less in the drained tests than in the undrained tests, indicating formation of a wider deformation zone in the drained tests. This is probably because particles in the drained tests have enough time to respond to the applied shear stresses and change their orientation. This may explain why deformations occur in wide zones along tectonically active creeping (aseismic) faults, whose mechanisms are analogous to those of drained shear tests, and in narrow zones along seismic faults, whose mechanisms are analogous to those of undrained shear tests.
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    Soil structure changes during compaction of a cohesive soil
    Cetin, H; Fener, M; Söylemez, M; Günaydin, O
    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.