Modelling of prefabricated vertical drains in soft clay and evaluation of their effectiveness in practice

Installing vertical sand drains is a traditional dam foundation consolidation solution that is economical and provides good drainage efficiency. Vertical sand drains can shorten the path of water flow inside the soil and speeds up soil consolidation. This study investigated the effect of sand drains in the foundation of the Sombar Dam in Iran on its mechanical behavior. The Sombar Dam is a project to control flooding and provide agricultural water to Gholaman city in northeastern Iran. The investigation included the mechanical behavior of the dam with vertical sand drains. The studied parameters were drain diameter, depth and spacing in addition to the vertical-to-horizontal permeability ratio (ky/kx) of the foundation soil during the time of construction of the dam using a Mohr-Coulomb (MC) model in the software application GeoStudio. The results revealed that reducing the drain spacing (increasing the number of drains) and increasing the depth and diameter of the drains led to an increase of the settlement rate (up to 90%) and the stability of the dam over a shorter period of time (24 months) compared to no drain condition. With a decrease in the ratio of vertical-to-horizontal permeability (ky/kx = 0.1) for all drain parameters there was a decrease in the value of the dam settlement rate and the safety factor.

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“…Thus, the diameter dw formed in a wall drain with width a and thickness b can be calculated by Eq. (2), as adopted from Indraratna, et al [17].…”

Section: Soil Typementioning

confidence: 99%

Mechanical Behavior of Dam Foundation with Vertical Sand Drain, Case Study: Sombar Dam

Mahmood

Akhtarpour

Alali

2019

J. Eng. Technol. Sci.

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“…Since 1995, the consolidometer has been used by University of Wollongong researchers to study various aspects of vertical drain consolidation (Indraratna & Redana, 1995, 1998a, 1998bIndraratna et al, 2002Indraratna et al, , 2004. cell consists of two stainless steel sections bolted together along the two joining flanges.…”

Section: Laboratory Verificationmentioning

confidence: 99%

Vertical drain consolidation with non-Darcian flow and void-ratio-dependent compressibility and permeability

Walker¹,

Indraratna²,

Rujikiatkamjorn³

2012

Géotechnique

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Vertical drains increase the rate of consolidation in soft soils by facilitating faster dissipation of excess pore water pressure through short, horizontal drainage paths. This paper presents an analytical solution for nonlinear radial consolidation under equal-strain conditions incorporating smear but ignoring well resistance. Three aspects of non-linearity are considered: (a) non-Darcian flow, (b) a log-linear void-ratio-stress relationship; and (b) a log-linear void-ratio-permeability relationship. The analytical solution to non-linear radial consolidation can explicitly capture the behaviour of both overconsolidated and normally consolidated soils. For non-linear material properties, consolidation may be faster or slower when compared with the cases with constant material properties. The difference depends on the compressibility/ permeability ratios (Cc/Ck and Cr/Ck), the preconsolidation pressure and the stress increase. If Cc/Ck < 1 or Cr/Ck < 1 then the coefficient of consolidation increases as excess pore pressures dissipate, and the corresponding rate of consolidation is greater. Vertical drains increase the rate of consolidation in soft soils by facilitating faster dissipation of excess pore water pressure through short, horizontal drainage paths. This paper presents an analytical solution for non-linear radial consolidation under equal-strain conditions incorporating smear but ignoring well resistance. Three aspects of non-linearity are considered: (a) non-Darcian flow, (b) a log-linear void-ratio-stress relationship; and (b) a log-linear void-ratio-permeability relationship. The analytical solution to non-linear radial consolidation can explicitly capture the behaviour of both overconsolidated and normally consolidated soils. For non-linear material properties, consolidation may be faster or slower when compared with the cases with constant material properties. The difference depends on the compressibility/ permeability ratios (C c /C k and C r /C k ), the preconsolidation pressure and the stress increase. If C c /C k < 1 or C r /C k < 1 then the coefficient of consolidation increases as excess pore pressures dissipate, and the corresponding rate of consolidation is greater.

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“…The conversion techniques of axisymmetric solution to an equivalent plane strain model are demonstrated by several researchers (e.g., Hird et al 1992, Indraratna andRedana 1997). This can be done by: (i) geometric matching in which the spacing of the drains is matched while the permeability is reserved the same; (ii) permeability matching in which the permeability coefficients are matched while the drain spacing is reserved the same; and (iii) combination of permeability and geometric matching approach in which the plane strain permeability is computed for convenient drain spacing (Indraratna et al 2003). Out of the above three matching theories, the permeability matching technique is considered for the stochastic analyses carried out in the current study.…”

Section: Overview Of Analytical Solution Of Soil Consolidation By Pvdmentioning

confidence: 99%

Effects of soil spatial variability on axisymmetric versus plane strain analyses of ground improvement by prefabricated vertical drains

Bari

Shahin

Nikraz

2012

International Journal of Geotechnical Engineering

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Modelling of prefabricated vertical drains in soft clay and evaluation of their effectiveness in practice

Cited by 11 publications

References 14 publications

Mechanical Behavior of Dam Foundation with Vertical Sand Drain, Case Study: Sombar Dam

Mechanical Behavior of Dam Foundation with Vertical Sand Drain, Case Study: Sombar Dam

Vertical drain consolidation with non-Darcian flow and void-ratio-dependent compressibility and permeability

Effects of soil spatial variability on axisymmetric versus plane strain analyses of ground improvement by prefabricated vertical drains

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