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The undrained bearing capacity of shallow circular piles in non-homogeneous and anisotropic clay is investigated by the lower bound (LB) finite element limit analysis (FELA) under two-dimensional (2D) axisymmetric condition using second-order cone programming, and the new solution of the problem is presented. Modified from the isotropic von Mises yield criterion, a cross-anisotropic undrained strength criterion of clays under the axisymmetric state of stress requiring three input shear strengths in triaxial compression, direct simple shear, and triaxial extension is employed in the 2D axisymmetric LB FELA. Parametric studies on the effects of pile embedment ratio, dimensionless strength gradient, anisotropic strength ratio, and pile roughness are investigated extensively, while the predicted failure mechanisms associated with these parameters are discussed and compared. Numerical results of undrained end bearing capacity of shallow circular piles are summarized in the form of design tables that are useful for design practice and represent a new contribution to the field of pile capacity considering the combined effects of undrained strength non-homogeneity and anisotropy. 相似文献
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Ukritchon Boonchai Ouch Rithy Pipatpongsa Thirapong Khosravi Mohammad Hossein 《Acta Geotechnica》2019,14(6):2103-2122
In this paper, the stability and failure mechanism of soil blocks that were reinforced by brittle shear pins and rested on a low-interface friction plane were studied by means of physical and numerical models. The humid silica sand no. 6 was employed to build the physical models of soil blocks, while the Teflon sheet was employed as the low-interface friction plane. To study the effect of stabilizing piles on slopes, the soil blocks were reinforced by brittle shear pins using pencil leads with 2 mm in diameter. Three-dimensional finite element analyses were employed to analyze the stability of this problem. The effects of numbers and patterns of shear pins on the stability and failure mechanisms of physical and numerical models were compared and discussed.
相似文献3.
Lower bound limit analysis of an anisotropic undrained strength criterion using second‐order cone programming 
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下载免费PDF全文 In this paper, the formulation of the lower bound limit analysis of an anisotropic undrained strength criterion using second‐order cone programming is described. The finite element concept was used to discretize the soil mass into 3‐noded triangular elements. The stress field was modeled using a linear interpolation within the elements while stress discontinuities were permitted to occur at the shared edges of adjacent elements. An elliptical yield criterion was adopted to model the anisotropic undrained strength of the clay. A statically admissible stress field was defined by enforcing the equilibrium equations within all triangular elements and along all shared edges of adjacent elements, stress boundary conditions, and no stress violation of the anisotropic strength envelope cast in the form of a conic quadratic constraint. The lower bound solution of the proposed formulation was solved by second‐order cone programming. The proposed formulation of the anisotropic undrained strength criterion was validated through comparison of the model's predictions with the known exact solutions of strip footings, and was applied to solve undrained stability of a shallow unlined square tunnel. Computational performance between the proposed approach of second‐order cone programming and linear programming was examined and discussed. 相似文献
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Bearing capacity of shallow foundations in clay with linear increase in strength and adhesion factor
Boonchai Ukritchon Sothoan Yoang Suraparb Keawsawasvong 《Marine Georesources & Geotechnology》2018,36(4):438-451
In this paper, the computational lower bound (LB) limit analysis using finite element with second-order cone programming was used to investigate the LB solutions of the undrained bearing capacity of continuous footing with a linear increase in the strength profile and an adhesion factor at the soil–footing interface. A full range of parametric studies of the dimensionless strength gradients and adhesion factors at the soil–footing interface were performed in the LB calculations. The results were verified by comparison with the available solution from the method of characteristics (slip-line analysis) for perfectly smooth and rough footings. The LB analyses were able to complete a prior solution of undrained bearing capacity with a linear increase in the strength profile by incorporating the influence of adhesion factor at the soil–footing interface. Based on the nonlinear regression to the computed LB solutions, an approximate expression of the LB solution regression was proposed, which is applicable to an accurate prediction of a safe load for offshore shallow foundations in clay with an arbitrary linear increase in strength and adhesion factor at soil–foundation interface in practice. 相似文献
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A paper recently published by Camargo et al. (Acta Geotech 11(6):1369–1383, 2016) (hereafter identified as “the authors”) presented the numerical limit analysis method (NLA) to compute the safety factor and collapse mechanism of three-dimensional (3D) slopes. For NLA, the authors employed the discrete three-dimensional lower bound formulation with pore water pressure consideration and Drucker–Prager yield criterion, and cast a slope problem as a second-order conic programming problem. The developed program was implemented in MATLAB and validated through three examples of slope problems, and was applied to solve a large-scale 3D slope problem of a failure case study. The discussion of this article focuses on the formulation of the developed 3D NLA and static admissibility of stress field solutions obtained from NLA. 相似文献
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