Bearing capacity factor <i>N</i><sub>c</sub> under ϕ=0 condition for piles in clays

Khatri, Vishwas N.; Kumar, Jyant

doi:10.1002/nag.763

Cited by 44 publications

(23 citation statements)

References 18 publications

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“…Note that the present N γ solutions are found to be slightly lower (better) than the upper bound solution given by Lyamin et al (2007) based on the threedimensional finite element limit analysis. In Table 1, the obtained magnitudes of N c for ϕ ¼ 0 ○ but with different values of m, were also compared with (i) the solutions of Khatri and Kumar (2008), (ii) the solutions of Houlsby and Martin (2003) based on the method of the stress characteristics, and (iii) the upper bound solution of Kusakabe et al (1986) based on rigid blocks mechanism. The present upper bound values of N c are found to be slightly lower than the upper bound solution given by Kusakabe et al (1986).…”

Section: Results and Comparisonmentioning

confidence: 99%

Bearing capacity of circular foundations reinforced with geogrid sheets

Chakraborty

Kumar

2014

Soils and Foundations

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The ultimate bearing capacity of a circular footing, placed over a soil mass which is reinforced with horizontal layers of circular reinforcement sheets, has been determined by using the upper bound theorem of the limit analysis in conjunction with finite elements and linear optimization. For performing the analysis, three different soil media have been separately considered, namely, (i) fully granular, (ii) cohesive frictional, and (iii) fully cohesive with an additional provision to account for an increase of cohesion with depth. The reinforcement sheets are assumed to be structurally strong to resist axial tension but without having any resistance to bending; such an approximation usually holds good for geogrid sheets. The shear failure between the reinforcement sheet and adjoining soil mass has been considered. The increase in the magnitudes of the bearing capacity factors (N c and N γ ) with an inclusion of the reinforcement has been computed in terms of the efficiency factors η c and η γ . The results have been obtained (i) for different values of ϕ in case of fully granular (c ¼ 0) and c Àϕ soils, and (ii) for different rates (m) at which the cohesion increases with depth for a purely cohesive soil (ϕ ¼ 0 ○ ). The critical positions and corresponding optimum diameter of the reinforcement sheets, for achieving the maximum bearing capacity, have also been established. The increase in the bearing capacity with an employment of the reinforcement increases continuously with an increase in ϕ. The improvement in the bearing capacity becomes quite extensive for two layers of the reinforcements as compared to the single layer of the reinforcement. The results obtained from the study are found to compare well with the available theoretical and experimental data reported in literature.

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Section: Results and Comparisonmentioning

confidence: 99%

Bearing capacity of circular foundations reinforced with geogrid sheets

Chakraborty

Kumar

2014

Soils and Foundations

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“…The standard constraints of the LB requirements are summarized below here. Readers are referred to Tang et al and Khatri and Kumar for the details of coefficients associated with vectors and matrices of the standard constraints.…”

Section: D Axisymmetric Lb Felamentioning

confidence: 99%

“…It can be observed that the nonlinear term of r in Equation makes it not possible for the stress state to satisfy the equilibrium equations in every material point within triangular elements by enforcing these at their corner nodes. To derive the equilibrium constraints of triangular elements, this paper adopts the concept of enforcing the equilibrium equations at the centroid of the element as proposed by Khatri and Kumar and Tang et al Thus, the first set of the equilibrium constraint on the unknown nodal stress can be obtained by substituting Equation into Equation and imposing at the centroid of each element as

([], A_{italiceq}) ({}, σ) = ({}, B_{italiceq})

…”

Section: D Axisymmetric Lb Felamentioning

confidence: 99%

“…The development of LB FELA under axisymmetric condition was initially introduced by Pastor and Turgeman using LP with 3 p inequality constraints imposed at each node of triangular elements, where p is the number of sides of the polygon for the linearized Mohr‐Coulomb yield surface. Later, Khatri and Kumar and Kumar and Khatri proposed a modified axisymmetric LB FELA that required only p +3 inequality linear constraints per node rather than 3 p , which significantly decreased a computational time. Kumar and Chakraborty proposed the axisymmetric LB FELA using LP approach with the linearization usage of the truncated icosahedron for the Drucker‐Prager yield criterion.…”

Section: Introductionmentioning

confidence: 99%

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Undrained lower bound solutions for end bearing capacity of shallow circular piles in non‐homogeneous and anisotropic clays

Ukritchon

Keawsawasvong

2019

Num Anal Meth Geomechanics

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SUMMARY 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.

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“…Also, by using the method of characteristics, Siva Reddy et al (1991) have obtained the solutions for both strip and circular smooth footings for the cases of footing placed at very shallow depths from ground surface. More recently, by using the lower bound limit analysis in conjunction with finite elements, the bearing capacity factor N c for several rates of increase of cohesion with depth has been estimated by Khatri and Kumar (2009) for axially loaded piles. In the existing investigations, for layered soils, the effect of an increase of soil cohesion with depth has not been addressed in detail.…”

Section: Introductionmentioning

confidence: 99%

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

et al. 2012

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Natural soils are often deposited in layers. The estimation of the bearing capacity of the soil, using conventional bearing capacity theory based on the properties of the top layer, introduces significant inaccuracies if the thickness of the top layer is comparable to the width of the rigid footing placed on the soil surface. Saturated normally consolidated and lightly overconsolidated clays indicate that under undrained condition the cohesion of soil mass increases almost linearly with depth. A few theoretical studies have been proposed in the literature to incorporate the variation of cohesion with depth in the computation of the ultimate bearing capacity of strip and circular footings. In this paper, after reviewing previous works, numerical computations using the FLAC code (Fast Lagrangian Analyses of Continua) are reported to evaluate the two layered clays effect on the bearing capacity beneath rigid strip footing subject to axial static load. The results of the bearing capacity relating to the relative thickness of the top layer, the strength ratio of the soil two-layered clays and the rates of the increase of soil cohesion with depth are presented in Tables and graphs. The obtained results are compared with previous published results available in the literature.

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Bearing capacity factor N_c under ϕ=0 condition for piles in clays

Cited by 44 publications

References 18 publications

Bearing capacity of circular foundations reinforced with geogrid sheets

Bearing capacity of circular foundations reinforced with geogrid sheets

Undrained lower bound solutions for end bearing capacity of shallow circular piles in non‐homogeneous and anisotropic clays

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

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Bearing capacity factor Nc under ϕ=0 condition for piles in clays

Cited by 44 publications

References 18 publications

Bearing capacity of circular foundations reinforced with geogrid sheets

Bearing capacity of circular foundations reinforced with geogrid sheets

Undrained lower bound solutions for end bearing capacity of shallow circular piles in non‐homogeneous and anisotropic clays

Bearing Capacity of Shallow Foundation on Two Clay Layers by Numerical Approach

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Bearing capacity factor N_c under ϕ=0 condition for piles in clays