Effects of Strength Anisotropy and Strain Softening on Soil Bearing Capacity through a Cosserat Nonlocal Finite-Element Method
Publication: International Journal of Geomechanics
Volume 24, Issue 5
Abstract
The strength anisotropy and strain softening of natural soil can significantly impact the bearing capacity of shallow foundations on clay. In this article, we present a nonlocal numerical method to study the coupled rotation of the maximum normal stress axis and strain softening on the bearing capacity of shallow foundations on clay through a Cosserat strain softening constitutive model. The strength anisotropy and strain softening characteristics were numerically implemented into a finite-element (FE) program by dynamically updating the anisotropic cohesion in global Newton–Raphson iterations. Due to its nonlocal feature, the proposed nonlocal numerical method can overcome the mesh dependence in simulating the progressive failure of clay through the classical FE method. We first validated the efficacy of this method against the results of the plane strain test and numerical results in the literature. We then study the bearing capacity of a strip footing over anisotropic and strain-softening clay through the implemented numerical method. The results indicated that the deposition angle has an important effect on the bearing capacity and failure mode. The effects of the degree of anisotropy and strain softening on the ultimate bearing capacity are quantified through the numerical method. It is found that (1) the proposed method can effectively reflect the characteristics of the maximum normal stress axis rotation on the failure surface of the footing; (2) the ultimate bearing capacity of a footing (Pu) on anisotropic clay could increase linearly with an increase in the anisotropy ratio k (i.e., k is the ratio between C1 and C2) and decreases with an increase in the softening modulus; and (3) the strength anisotropy and strain softening are strongly coupling factors impacting the bearing capacity of anisotropic clay.
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Data Availability Statement
Some or all of the data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request, including all result files obtained from numerical simulations and data in Figs. 9–11, 13, 14, 20–22, and 25–28).
Acknowledgments
This research is supported by the National Natural Science Foundation of China (Grant Nos. 51890912, 51979025, and 52011530189).
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International Journal of Geomechanics
Volume 24 • Issue 5 • May 2024
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© 2024 American Society of Civil Engineers.
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Received: Mar 7, 2023
Accepted: Nov 21, 2023
Published online: Mar 8, 2024
Published in print: May 1, 2024
Discussion open until: Aug 8, 2024
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