Shear Stress Redistribution as a Mechanism to Mitigate the Risk of Liquefaction

Green, Russell A.; Olgun, C. Güney; Wissmann, Kord J.

doi:10.1061/40975(318)115

Cited by 27 publications

(13 citation statements)

References 2 publications

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“…The concept of shear strain compatibility, as originally proposed by Baez (1995), assumes that the granular columns only deform in pure shear and, being stiffer than surrounding soil, attract a greater share of the earthquake-induced shear stresses than the surrounding soil. However, recent studies suggest that granular columns may deform in both flexure and shear such that they are far less effective in reducing shear stresses in surrounding soils than predicted by shear strain compatibility (Goughnour and Pestana 1998;Green et al 2008;Olgun and Martin 2008;Rayamajhi et al 2014). Rayamahji et al (2014) used linear-elastic three-dimensional (3D) finite-element analyses to develop a simplified relationship for estimating the shear stress reduction in soil treated with granular columns.…”

Section: Introductionmentioning

confidence: 99%

Dense Granular Columns in Liquefiable Ground. I: Shear Reinforcement and Cyclic Stress Ratio Reduction

Rayamajhi

Ashford

Boulanger

et al. 2016

J. Geotech. Geoenviron. Eng.

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The installation of dense granular columns by various construction techniques can be used to mitigate liquefaction through a combination of densification, increase of lateral stresses, reinforcement, and drainage. The contributing mechanism of shear reinforcement is isolated and explored using nonlinear three-dimensional (3D) finite-element (FE) analysis. FE models representing both dry and saturated conditions were developed to evaluate cases with and without generation and dissipation of excess pore-water pressures. The shear stress and strain distributions between the granular columns and surrounding soil, and the level of shear stress reduction, were investigated for a practical range of treatment geometries, relative stiffness ratios, vertical stresses, and relative densities of the surrounding soil. A set of 10 acceleration time histories were used as input motions. The FE results show that granular columns undergo a shear strain deformation pattern that is noncompatible with the surrounding soil. As such, the achieved reduction in cyclic stress ratios imposed on the treated soil is far less than that predicted by the conventional shear strain compatibility design approach. Reductions in cyclic stress ratios are insensitive to the applied surface pressure, granular column length/diameter ratio (L/D), and relative density of the surrounding soil for the range of area replacement ratio and column-soil shear modulus ratio examined. A modified design equation to estimate the reduction in cyclic stress ratio provided by dense granular columns is shown to provide good agreement with the FE simulation results.

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Section: Introductionmentioning

confidence: 99%

Dense Granular Columns in Liquefiable Ground. I: Shear Reinforcement and Cyclic Stress Ratio Reduction

Rayamajhi

Ashford

Boulanger

et al. 2016

J. Geotech. Geoenviron. Eng.

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“…Regarding shear stress distribution mechanisms, some researchers hypothesized that stone columns work as a pure shear beam (Baez 1995), while others argue that stone columns behave in both flexure and shear and may not be effective to reduce shear stress in the surrounding soil (Green et al 2008;Goughnour and Pestana 1998;Olgun and Martin 2008). No clear understanding has been developed regarding the reinforcing mechanism of stone columns.…”

Section: Discussionmentioning

confidence: 99%

Reducing Seismic Risk to Highway Mobility: Assessment and Design Examples for Pile Foundations Affected by Lateral Spreading

Ashford¹,

Scott²,

Rayamajhi³

2013

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“…The deformations in the discrete column are extracted for the element located near the edge of the discrete column (point 5) as shown in Figure 1d. Green et al (2008) and Olgun and Martin (2008) found that cumulative shear and flexure deformation varies linearly with time when subjected to ground motion and the percentage contribution of shear and flexure deformations remains relatively constant. Based on their finding, we can even estimate the relative contributions of shear and flexure deformations from the pseudo-static analysis.…”

Section: Deformation Behaviormentioning

confidence: 99%

“…To investigate the deformation behavior of discrete reinforcing columns, the shear deformation (γ) and flexure deformation (θ) in the column was extracted using the expressions available in literature (Oesterle et al 1979, Shiu et al 1981, Green et al 2008, Olgun and Martin 2008. The deformations in the discrete column are extracted for the element located near the edge of the discrete column (point 5) as shown in Figure 1d.…”

Section: Deformation Behaviormentioning

confidence: 99%

“…Later, other researchers (Green et al, 2008;Olgun and Martin, 2008) observed that the combination of shear and flexure in the stone columns reduced their effectiveness (i.e., shear strains were not compatible between the stone columns and surrounding soil). Thus, the level of shear stress reduction in the surrounding soil due to installation of stone columns (or any other discrete column) is not clear yet.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Discrete Columns on Shear Stress Distribution in Liquefiable Soil

Rayamajhi¹,

Nguyen²,

Ashford³

et al. 2012

GeoCongress 2012

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Stone and soil-cement columns are often used to improve the liquefaction resistance of loose sandy ground potentially subjected to strong shaking. The shear stress reduction in the loose ground resulting from the reinforcing effect of these stiffer discrete columns is often considered as a contributing mechanism for liquefaction mitigation. Current design practice commonly assumes that discrete columns and soil deform equally in pure shear (i.e. shear strain compatible deformation). In addition, since the discrete column is stiffer than the soil, it is assumed to attract higher shear stress, thereby reducing the shear stress in the surrounding soil. In this paper, the shear stress distribution mechanism of discrete columns and the shear stress reduction in liquefiable soils are investigated using 3-D finite element analysis. From the analysis, it is found that discrete columns behave in both shear and flexure, such that the shear strain compatibility assumption can be significantly unconservative. The investigation indicates that the shear reinforcement of stiffer discrete columns is less effective than commonly used in current design practice. A revised design equation is proposed to conservatively estimate the shear stress reduction ratio.

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Shear Stress Redistribution as a Mechanism to Mitigate the Risk of Liquefaction

Cited by 27 publications

References 2 publications

Dense Granular Columns in Liquefiable Ground. I: Shear Reinforcement and Cyclic Stress Ratio Reduction

Dense Granular Columns in Liquefiable Ground. I: Shear Reinforcement and Cyclic Stress Ratio Reduction

Reducing Seismic Risk to Highway Mobility: Assessment and Design Examples for Pile Foundations Affected by Lateral Spreading

Effect of Discrete Columns on Shear Stress Distribution in Liquefiable Soil

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