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Analysis of Bearing Capacity and Settlement of Piled-Raft Foundation on Clayey Soils

Ebrahimi Khaledi, Masoud | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50544 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadi, Mohammad Mahdi
  7. Abstract:
  8. Investigating the behavior of piled-raft foundations is a three-dimensional problem. The shape and location of the piles in the raft as well as the complex interaction of the soil-structure in these foundations should be analyzed in a three-dimensional fashion to indicate the real behavior of this type of foundations. The soil must also be analyzed in a nonlinear state to achieve the correct bearing capacity of these foundations. In this research, a nonlinear 3D analysis was performed using FLAC3D to investigate the behavior of piled-raft foundations, and the effect of various factors such as the length, arrangement and number of the piles, the loading level and the thickness of the raft, on the average and differential settlement, and the load sharing between the piles and the raft (αpr) is also analyzed. It should be noted that the soil is undrained clay and the piles are cast in-place. Also, in order to achieve closer results to actual conditions, the original geometry of the piles and raft have been modeled and the structural elements that already exist in the software (e.g pile and shell) have not been used. By doing this research, it was found that as a result of increasing the length and number of piles in the foundation, the average settlement decreases and the piled-raft coefficient increases. It was also observed that the increase in the length of the piles had a harmful effect on the differential settlement and could increase it; but for each piled-raft foundation there exists a specific Ag/Ar ratio for which the value of differetial settlement equals zero. In general, it can be said that in the case of having a fixed cost (corresponding to nLp), the optimal arrangement for minimizing the average and differential settlements and increasing the bearing capacity in the piled-raft foundations is to use a small number of long piles in the central area of raft (Ag/Ar between 0.2 to 0.6). Also, the thickness of the raft should be such that it does not fit into the category of flexible ones
  9. Keywords:
  10. Piled-Raft Foundations (PRF) ; Bearing Capacity ; Settlement ; Clay Soils ; Soil-Structure Interaction ; Nonlinear Three Dimensional Analysis

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