Analytical solutions and design curves for vacuum-assisted consolidation with both vertical and horizontal drainage

Abstract

A system of vertical drains combined with vacuum preloading is an effective method for promoting radial flow to accelerate soil consolidation. This study presents the analytical modeling of a consolidation of vertical drains incorporating vacuum preloading considering both vertical and horizontal drainage. The effects of a number of dimensionless parameters involving the drain length, soil permeability and vacuum pressure are examined through average excess pore pressure, degree of consolidation, associated settlement and time factor analyses. An analysis of selected case histories compliments the use of the proposed solutions. Design charts are also presented for practical use.

Ground improvement by vacuum consolidation – a review

“…As they have become cheaper, flexible PVDs have generally replaced sand drains and granular piles (Dam et al, 2006;Indraratna, 2010 Design charts for vertical drains were developed by Rujikiatkamjorn and Indraratna (2007) in order to estimate an appropriate drain spacing, considering a larger range of soil properties and drain installation patterns. In plan, vertical drains are generally arranged in either a square or triangular grid pattern.…”

“…For soft clays, the k h /k s ratio is generally in the range 1-8 (Rujikiatkamjorn and Indraratna, 2007). Saowapakpiboon et al (2011) performed a large-scale oedometer study of soft Bangkok clay improved by surcharge preloading and PVDs, both with and without application of vacuum.…”

“…This is mainly because the time required to compute a full plane-strain simulation is considerably reduced compared with a full 3D simulation (Indraratna and Redana, 2000;Indraratna et al, 2004). Rujikiatkamjorn and Indraratna (2007) proposed a comprehensive solution incorporating vertical and horizontal drainage and that also accounted for smear effects. Walker and Indraratna (2009) produced a more rigorous solution to the consolidation problem which can be applied to multi-layered deposits through the spectral method -a mesh-less approach involving a series of matrix operations.…”

Nonlinear Analysis for a Single Vertical Drain Including the Effects of Preloading Considering the Compressibility and Permeability of the Soil

“…Zhu and Yin (2001) have presented a solution based on the theory of free strain, subjected to ramp loading. For equal strain theory, Indraratna et al (2005a, b) and Rujikiatkamjorn et al (2007Rujikiatkamjorn et al ( , 2009 have made an attempt to analyse the vacuum consolidation behaviour of soil based on the equal strain assumptions. However, all the existing theories still consider the coefficients of permeability and compressibility to be constant during the consolidation process (Basak and Madhav 1978;Cai et al 2007; Davis and Raymond.…”

Design procedure for vertical drains considering a linear variation of lateral permeability within the smear zone

“…Rujikiatkamjorn and Indraratna (2007) proposed a new design method to avoid the cumbersome trial and error approach for determining the drain spacing. However, in this approach, the effects of quasi-linear variation of horizontal permeability in the smear zone and the possibility of overlapping smear zones at close drain spacing were not considered.…”