Pullout Capacity Analysis of Horizontal Plate Anchors with Tensile Strength Cutoff
Publication: International Journal of Geomechanics
Volume 24, Issue 7
Abstract
The conventional Mohr–Coulomb (M-C) failure criterion is commonly used in existing studies to determine the ultimate pullout capacity of plate anchors buried in cohesive-frictional soils. However, this criterion overestimates the tensile strength of these soils by assuming a linear failure envelope (in both compression and tensile regimes) within the normal-shear stress space. In this study, the ultimate pullout capacity of horizontally buried plate anchors in cohesive-frictional soils was determined, accounting for the effect of tensile strength cutoff. The study proposed a series of semianalytical solutions utilizing the kinematic horizontal slice approach and investigated the ultimate pullout capacity of four different anchor shapes, including circular, square, rectangular, and strip anchors. The impact of nonassociated flow rule on the results was also examined. It has been observed that the results obtained using the M-C failure criterion with a tension cutoff are significantly lower than those obtained using the conventional M-C failure criterion. The difference between both results increases as soil cohesive strength increases and anchor burial depth decreases. These findings clearly demonstrate that eliminating tensile strength from the strength envelope leads to a more conservative estimate of plate anchor pullout capacity. The study emphasizes changes in anchor failure surfaces for various parameter combinations and provides results that are consistent with specific solutions reported in the literature.
Practical Applications
The study investigates using plate anchors to enhance the stability of both onshore and offshore structures, including transmission towers, guyed masts, chimneys, and mooring platforms. These structures often encounter significant vertical pullout forces. The research establishes a theoretical framework for calculating the ultimate vertical pullout capacity of plate anchors with various shapes (strip, rectangular, and circular) when buried in cohesive-frictional soils. A crucial aspect of this analysis involves incorporating the specified/limited value of tensile strength in cohesive-frictional soils when assessing the ultimate pullout capacity of plate anchors. This consideration is vital for ensuring a safe and conservative design, especially for structures subject to uplift forces. The findings provide valuable insights for engineers and practitioners, offering a reliable method to optimize the usage of plate anchors in the design of pullout-resistant structures.
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Data Availability Statement
All data, models, and codes generated or used during the study appear in the published article.
Notation
The following symbols are used in this paper:
- B
- width of the strip/rectangular plate anchor;
- bi
- width of the ith slice;
- c
- cohesion;
- cm
- modified cohesion to consider the effect of ψ;
- D
- diameter of circular plate anchor;
- rate of energy dissipation per unit area along failure surface;
- f3t
- theoretical tensile strength under triaxial stress condition;
- fc
- uniaxial compressive strength;
- Fp
- pullout capacity factor;
- Fq
- pullout capacity factor for surcharge pressure component;
- ft
- uniaxial tensile strength;
- theoretical uniaxial tensile strength from the M-C failure criterion;
- pullout capacity factor for unit weight component;
- H
- burial depth of anchors;
- hi
- height of the ith slice;
- L
- length of the plate anchor;
- li
- length of the ith slice;
- lmi
- average length of the ith slice;
- n
- number of slices;
- pu
- pullout capacity of the plate anchor;
- q
- surcharge pressure along the ground surface;
- T
- stress vector;
- T
- external surface loads;
- TV
- rate of total work done by the external surface loads;
- V
- velocity of the failure soil mass;
- V
- velocity field of the sliding mass;
- [V]
- velocity vector;
- W
- weight of the sliding mass;
- WV
- rate of total work done by the soil weight;
- (x, y, z)
- Cartesian coordinates;
- δi
- instantaneous friction angle of the ith slice;
- ϕm
- modified angle of internal friction to consider the effect of ψ;
- Γ
- failure surface;
- Ω
- region of failure soil mass;
- γ
- unit weight of the soil mass;
- δ
- instantaneous friction angle;
- ξ
- tensile strength cutoff factor;
- σ
- normal stress at failure;
- τ
- shear strength;
- ψ
- dilatancy angle; and
- ϕ
- angle of internal friction of soil mass.
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Published In
International Journal of Geomechanics
Volume 24 • Issue 7 • July 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Oct 18, 2023
Accepted: Jan 30, 2024
Published online: May 8, 2024
Published in print: Jul 1, 2024
Discussion open until: Oct 8, 2024
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