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A Numerical-Analytical Solution for Determining the In-situ Horizontal Stress according to the CPT Measurements

Golestani Dariani, Ali Akbar | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50639 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ahmadi, Mohammad Mehdi
  7. Abstract:
  8. Separation of the effects of the initial horizontal stress and relative density on the cone tip resistance in the sandy soils has been a complicated issue for many years. On the other hand, there is no reliable method for determining the in-situ horizontal effective stress based on the piezocone measurements in the cohesive soils, and the empirical correlations suggested in the literature produce no more than a rough estimation.Considering the aforesaid issues, an attempt is made in this thesis to provide a new innovative solution for determining the in-situ horizontal (effective) stress in the sandy and clayey soils according to the CPT measurements. In this regard, at first, numerical modeling of cone penetration test is performed, and then, the obtained results are used to achieve a reliable analytical solution for determining the in-situ horizontal (effective) stress in terms of the measurable CPT quantites.Numerical simulation of the CPT procedure in the sandy soils is performed in the drained condition, while the coupled and uncoupled modeling of the piezocone test in the clayey soils are done in the undrained condition. The numerical modeling is, then, verified by the measurements of the calibration chamber tests as well as some of the well-known and published field tests.According to the numerical simulation of CPT, the mechanism of the penetration process is scrutinized. The soil around the cone tip and sleeve, in this regard, is divided into two side-by-side located regions in the radial direction, which are the elastic and plastic regions.
    The analytical solution for the sandy soils leads in two relationships for the sleeve friction and cone tip resistance in terms of the initial conditions, while the proposed solution for the clayey soils results in three main relationships which must be used in a trial and error process to obtain the unkown parameters. Thus, performing a cone penetration test in a soil with a given in-situ vertical stress, the initial horizontal (effective) stress can be determined according to the CPT measurements based on the presented solutions.Finally, the proposed numerical-analytical solutions in this study are compared with the laboratory calibration chamber tests and field test measurements. The comparisons indicate acceptable degree of accuracy for predicting the in-situ horizontal (effective) stress form the CPT quantities in both the sandy and clayey soils.
  9. Keywords:
  10. Cone Penetration Test ; Excess Pore Water Pressure ; Clay Soils ; Granular Soil ; Calibration Test ; Cone Resistance ; In-Situ Horizontal (Effective)Stress ; Numerical-Analytical Solution

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