Analytical and Numerical Modeling of Soft Soil Stabilized by Prefabricated Vertical Drains Incorporating Vacuum Preloading

Indraratna, Buddhima; Sathananthan, Iyathurai; Rujikiatkamjorn, Cholachat; Balasubramaniam, A. S.

doi:10.1061/(asce)1532-3641(2005)5:2(114)

Cited by 155 publications

(105 citation statements)

References 15 publications

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“…Various conversion procedures have been proposed earlier (e.g. Shinsha et al 1982;Hird et al 1992;Bergado and Long 1994;Chai et al 2001;Indraratna et al 2005). Cheung et al (1991) employed the conversion procedure which assumes that the settlement response at 50% degree of consolidation is the same for both 2D and axisymmetric (3D) conditions (Shinsha 1991).…”

Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

“…However, significant differences of the excess pore pressure predictions were found between these two schemes. In this study, the conversion method proposed by Indraratna et al (2005) is adopted for the 2D plane strain analysis. In this approach, not only the entire degree of consolidation response for the equivalent 2D approach is the same as that of the 3D analysis, but also the smear zone was explicitly modelled.…”

Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

“…Details of the permeability conversion for equivalent plane strain condition have been further refined to consider the vacuum consolidation by Indraratna et al (2005). A summary of the conversion from the axisymmetric to the equivalent plane strain model is presented below, for the benefit of the readers.…”

Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

“…Elsewhere, towards the embankment toe, the single drain analysis becomes inaccurate due to the non-uniform surcharge load distribution, large strain cobditions, increased lateral yield, effects of changing embankment geometry and heave at the embankment toe (Indraratna et al, 1997). Hird et al (1992), Chai et al (1995) and Indraratna et al (2005) introduced an equivalent 2D plane strain approach to predict the soft clay behaviour improved by vertical drain system (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, a numerical analysis based on an equivalent plane strain finite element model proposed by Indraratna et al (2005) is compared with a 3D finite element model for evaluating the performance of an embankment constructed on the reclaimed land at Tianjin port, China. At this site, a combined vacuum and surcharge load was employed to achieve the desired degree of consolidation.…”

Section: Introductionmentioning

confidence: 99%

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2D and 3D Numerical Modeling of Combined Surcharge and Vacuum Preloading with Vertical Drains

2008

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Abstract:This paper presents a three-dimensional (3D) and two-dimensional (2D) numerical analysis of a case study of a combined vacuum and surcharge preloading project for a storage yard at Tianjin Port, China. At this site, a vacuum pressure of 80 kPa and a fill surcharge of 50 kPa was applied on top of the 20m thick soft soil layer through prefabricated vertical drains (PVD) to achieve the desired settlements and to avoid embankment instability. In 3D analysis, the actual shape of PVDs and their installation pattern with the in-situ soil parameters were simulated. In contrast, the validity of 2D-plane strain analysis using equivalent permeability and transformed unit cell geometry was examined. In both cases, the vacuum pressure along the drain length was assumed to be constant as substantiated by the field observations. The finite element code, ABAQUS, using the modified Cam-clay model was used in the numerical analysis. The predictions of settlement, pore water pressure and lateral displacement were compared with the available field data, and an acceptable agreement was achieved for both 2D and 3D numerical analyses. It is found that both 3D and equivalent 2D analyses give similar consolidation responses at the vertical cross section where the lateral strain along the longitudinal axis is zero. The influence of vacuum may extend more than 10m from the embankment toe, where the lateral movement should be monitored carefully during the consolidation period to avoid any damage to adjacent structures.

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Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

Section: Two-dimensional Plane Strain Finite Element Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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2D and 3D Numerical Modeling of Combined Surcharge and Vacuum Preloading with Vertical Drains

2008

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A new simplified Hypothesis B method for calculating the consolidation settlement of ground improved by vertical drains

Feng

Yin

2017

Num Anal Meth Geomechanics

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Vertical drains are widely used in soft ground improvements to accelerate the consolidation process. This paper develops a new simplified Hypothesis B method for calculating the consolidation settlement of a soil layer improved by vertical drains under the instant and ramp loadings. As a comparison, the traditional Hypothesis A method is also used to calculate the settlement.Then, a fully coupled finite element consolidation analysis is utilized to examine and verify this simplified method and Hypothesis A method. For the instant loading, Carrillo-Barron method and Zhu-Yin method are used to obtain the average degree of consolidation for vertical drain system. Typical parameters, such as over-consolidation ratio (OCR), smear zone, and space ratio of vertical drains, are considered. It is found that the calculation results from the new simplified method in this study agree well with finite element simulations, and relative errors are in the range of 0.1% to 12.3%. Comparatively, there are obvious differences between the calculated results from Hypothesis A method and finite element results. Carrillo-Olson method and Zhu-Yin method are utilized to obtain the average degree of consolidation for the vertical drain system to consider the ramp loading. Equivalent time is determined from half of the construction period to calculate the creep compression under the ramp loading. The accuracy of this simplified Hypothesis B method using both Carrillo-Olson method and Zhu-Yin method is acceptable with the relative errors less than 9.4%.

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Analytical solution to axisymmetric consolidation of unsaturated soil stratum under equal strain condition incorporating smear effects

Ho¹,

Fatahi

2018

Num Anal Meth Geomechanics

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This paper proposes closed-form analytical solutions to the axisymmetric consolidation of an unsaturated soil stratum using the equal strain hypothesis. Following the 1-dimensional (1D) consolidation theory for unsaturated soil mechanics, polar governing equations describing the air and water flows are first presented on the basis of Fick's law and Darcy's law, respectively. The current study takes into account the peripheral smear caused by an installation of vertical drain. Separation of variables and Laplace transformation are mainly adopted in the analytical derivation to obtain final solutions. Then, the hydraulic conductivity ratio, the radius of influence zone and smear parameters influencing time-dependent excess pore pressures, and the average degree of consolidation are graphically interpreted. In this study, a comparison made between the proposed equal strain results and the existing free strain results suggests that both hypotheses would deliver similar predictions. Moreover, it is found that the smear zone resulting from vertical drain installations would hinder the consolidation rate considerably.

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Analytical and Numerical Modeling of Soft Soil Stabilized by Prefabricated Vertical Drains Incorporating Vacuum Preloading

Cited by 155 publications

References 15 publications

2D and 3D Numerical Modeling of Combined Surcharge and Vacuum Preloading with Vertical Drains

2D and 3D Numerical Modeling of Combined Surcharge and Vacuum Preloading with Vertical Drains

A new simplified Hypothesis B method for calculating the consolidation settlement of ground improved by vertical drains

Analytical solution to axisymmetric consolidation of unsaturated soil stratum under equal strain condition incorporating smear effects

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