Browsing by Author "Gezgin, Ahmet Talha."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Dilatancy based calculation of lateral earth thrust and the locked-in stress concept
    (Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Gezgin, Ahmet Talha.; Çinicioğlu, Özer.
    Precise calculation of the loads and stresses that are acting on structures that are interacting with soils is central to the design of geotechnical structures. Accordingly, calculation of vertical soil stresses is a straightforward task whereas computation of lateral stresses is a topic of ongoing research. Conventional design methods for retaining structures consider the ultimate lateral earth pressures, namely active and passive earth pressures. As it is clearly identi ed in geotechnical literature, strength of back lls and the shapes of the failures planes control the magnitudes of active and passive thrust on retaining structures. Accordingly, this study attempts to come up with a precise method for the calculation of active and passive earth thrusts. For this purpose, a new equation (Altunba s 2014) that uses dilatancy angle for the calculation of the geometry of the active failure plane is incorporated into the method of slices for the computation of active earth thrust. Accuracy of the proposed method is checked using the results obtained from small-scale physical retaining wall model tests. The same approach is repeated for passive earth thrust. Differences between the computed and measured results are discussed and the reasons for the differences are discussed theoretically. A new concept called locked-in stresses is developed to consider elastically stored residual normal stresses in soil bodies and their in uences strength.
  • Thumbnail Image
    Item
    Discrete element modelling of soil-pile interaction with emphasis on soil characteristics and pile installation methodology
    (Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2021., 2021.) Gezgin, Ahmet Talha.; Çinicioğlu, Özer.
    Soil-pile interaction is a complex geotechnical problem that requires rigorous multi-scale analyses. However, it is challenging to understand the micro aspects of this problem with either experimental approaches or continuum-based numerical models. On the other hand, the discrete element method (DEM) provides a powerful medium for modelling soils as particulate materials and can be used to examine soil-pile interaction at multi-scale. Accordingly, this dissertation aims to investigate soil-pile interaction with DEM modelling. For this purpose, three different subjects are discussed in this dissertation. Initially, a parametrical study has been conducted to clarify the influence of soil properties on pile penetration resistance. Later on, this study tackles the problem of computational cost; it is well known that one limiting aspect of DEM is its high computational demand. Regardingly, this dissertation also aims to clarify the validity of three techniques that are utilized to reduce computational time. In this respect, the appropriate parameters for DEM models are validated using the experimental results of a previous study. Lastly, this dissertation focuses on soil-pile interaction considering the effects of pile installation. Both jacked and replacement piles are installed into each sample and the response of the granular assembly is assessed in detail. Eventually, the jacked and replacement piles are subjected to vertical loading tests to determine their bearing capacity. The results obtained during pile construction and loading stages suggest that installation technique, in addition to soil density state and particle shape, also has a considerable effect on soil-pile interaction.