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Criterion for Failure Modes of Suction Caisson
in Sand under Axial Pullout Load
Jinfu Xiao
jxiao3@ncsu.edu
Department of C...
Failure Modes
In Failure Mode I the soil remains in position during the pullout process of suction caisson, only
the pore water is lifte...
In Failure Mode II the core soil-plug moves upward with caisson during the pullout process of
suction caisson, the soil fl...
In Failure Mode III the core soil-plug inside the caisson moves upward with caisson during the
pullout process, the caisso...
Criterion
Criterion for Failure Modes
The failure modes are complex influenced by multiple factors, such as pullout rate,
hydraulic ...
Terminology in the Criterion
Terminology in the Criterion
For more details please refer to the author’s publications.
Failure Mode I, II & III
Failure Mode I, II & III
Failure Mode II & IIIFailure Mode I
Failure Mode II Failure Mode III
if ...
Case Study
In the case study the criterion proposed by in this paper is verified by the experimental data
from five model tests (test...
Failure modes for the model tests determined by criterion
Failure modes for the model tests determined by criterion
Failure modes for the model tests determined by criterion
Failure modes for the model tests determined by criterion
Failure modes for the model tests determined by criterion
Summary
The criterion for failure modes of suction caisson in
sand under axial pullout load has been verified by the
exper...
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Criterion for failure modes of suction caisson in sand under axial pullout load

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Criterion for failure modes of suction caisson in sand under axial pullout load

  1. 1. Criterion for Failure Modes of Suction Caisson in Sand under Axial Pullout Load Jinfu Xiao jxiao3@ncsu.edu Department of Civil, Construction and Environmental Engineering, North Carolina State University Doctoral Preliminary Oral Presentation
  2. 2. Failure Modes
  3. 3. In Failure Mode I the soil remains in position during the pullout process of suction caisson, only the pore water is lifted to fill the induced space beneath the caisson lid as illustrated in Figure (a). The pullout capacity is composed of the caisson’s weight, internal skirt wall friction, external skirt wall friction, suction beneath the lid and the reverse end bearing resistance of the annular caisson’s tip. The internal and external skirt wall friction takes the main contribution to the pullout capacity, so generally the pullout capacity decreases during the pullout process as illustrated in Figure (b). Failure Mode I
  4. 4. In Failure Mode II the core soil-plug moves upward with caisson during the pullout process of suction caisson, the soil flow around the caisson is generated to fill the induced space at the caisson’s base as illustrated in Figure (a). The total pullout capacity is composed of the total weight of caisson and core soil, the external skirt wall friction due to soil flow and the suction at caisson’s base as illustrated in Figure (b). Failure Mode II
  5. 5. In Failure Mode III the core soil-plug inside the caisson moves upward with caisson during the pullout process, the caisson and core soil-plug act together as a pile, the velocity of soil flow generated around the caisson is smaller than the pullout rate of suction caisson, so the soil flow is not enough to fill the induced space at the caisson’s base and cavity occurs at the caisson’s base due to the soil tension failure, as illustrated in Figure (a). The pullout capacity is composed of the total weight of caisson and core soil, the external skirt wall friction and the suction at caisson’s base as illustrated in Figure (b). Failure Mode III
  6. 6. Criterion
  7. 7. Criterion for Failure Modes The failure modes are complex influenced by multiple factors, such as pullout rate, hydraulic conductivity, length of drainage path, shear strength properties of soil. With other parameters being constant, the pullout rate increases during the transition from Failure Mode I to Failure Mode III.
  8. 8. Terminology in the Criterion
  9. 9. Terminology in the Criterion For more details please refer to the author’s publications.
  10. 10. Failure Mode I, II & III Failure Mode I, II & III Failure Mode II & IIIFailure Mode I Failure Mode II Failure Mode III if Vpullout > Vmax if Vpullout > Vliq if Vpullout < Vmax if Vpullout < Vliq if Vpullout < Umax if Vpullout > Umax Step 1a Step 1b Step 1 Step 2 Procedures of judging failure modes (Note: Vmax > Vliq is always and unconditionally true)
  11. 11. Case Study
  12. 12. In the case study the criterion proposed by in this paper is verified by the experimental data from five model tests (test 9, test 10, test 11, test 16 and test 23) performed by Houlsby et al (2005). In the model tests, the dimension of the caisson model is 280 mm in diameter and 180 mm in skirt length (Kelly et al. 2006). The Redhill sand and HPF5 sand were used as test soil samples.
  13. 13. Failure modes for the model tests determined by criterion
  14. 14. Failure modes for the model tests determined by criterion
  15. 15. Failure modes for the model tests determined by criterion
  16. 16. Failure modes for the model tests determined by criterion
  17. 17. Failure modes for the model tests determined by criterion
  18. 18. Summary The criterion for failure modes of suction caisson in sand under axial pullout load has been verified by the experimental data (Houlsby et al 2005). The failure modes determined by the criterion show good agreement with the pullout capacity curve pattern from experimental data.
  19. 19. Thank You!

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