scholarly journals Analytical and numerical solutions for a single vertical drain including the effects of vacuum preloading

2005 ◽  
Vol 42 (4) ◽  
pp. 994-1014 ◽  
Author(s):  
Buddhima Indraratna ◽  
Cholachat Rujikiatkamjorn ◽  
Iyathurai Sathananthan
Keyword(s):  
Finite Element ◽  
Plane Strain ◽  
Numerical Solutions ◽  
Soft Clay ◽  
Vacuum Pressure ◽  
Excess Pore Pressure ◽  
Soil Consolidation ◽  
Vacuum Preloading ◽  
Element Analysis ◽  
Vertical Drains

A system of vertical drains combined with vacuum preloading is an effective method to accelerate soil consolidation by promoting radial flow. This study presents the analytical modeling of vertical drains incorporating vacuum preloading in both axisymmetric and plane strain conditions. The effectiveness of the applied vacuum pressure along the drain length is considered. The exact solutions applied on the basis of the unit cell theory are supported by finite element analysis using ABAQUS software. Subsequently, the details of an appropriate matching procedure by transforming permeability and vacuum pressure between axisymmetric and equivalent plane strain conditions are described through analytical and numerical schemes. The effects of the magnitude and distribution of vacuum pressure on soft clay consolidation are examined through average excess pore pressure, consolidation settlement, and time analyses. Lastly, the practical implications of this study are discussed.Key words: consolidation, finite element method, soft clay, vacuum preloading, vertical drains.

scholarly journals Numerical modelling of soft soil stabilized by vertical drains, combining surcharge and vacuum preloading for a storage yard

2007 ◽  
Vol 44 (3) ◽  
pp. 326-342 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna ◽  
Jian Chu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Plane Strain ◽  
Water Pressure ◽  
Vacuum Pressure ◽  
Element Analysis ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Modified Cam Clay ◽  
Surcharge Load

This paper presents a finite element analysis of a case study of a combined vacuum and surcharge load through prefabricated vertical drains (PVD) at a storage yard at Port of Tianjin, China. The top 15 m of soil at this site was very soft to soft and needed to be improved using preloading surcharges of more than 140 kPa. To avoid any stability problems associated with a high surcharge embankment, 80 kPa vacuum pressure combined with fill surcharge was applied (40 and 58 kPa for sections I and II, respectively). A plane strain analysis was performed using equivalent permeability and transformed unit-cell geometry. The converted (equivalent) parameters were incorporated in the finite element code ABAQUS, using the modified Cam-Clay theory. The performance of a trial embankment at the site of the storage yard is predicted on the basis of a constant vacuum pressure applied on the soil surface and distributed along the length of the drain. The predictions of settlement, pore-water pressure, and lateral displacement were compared with the available field data, and an acceptable agreement was found based on this numerical approach. The combination of vacuum and surcharge load can effectively shorten the preloading period, reduce the height of the embankment, and counterbalance excessive lateral displacements.Key words: consolidation, finite element analysis, plane strain method, soil improvement, vertical drains.

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

2007 ◽  
Vol 44 (2) ◽  
pp. 188-200 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna
Keyword(s):  
Analytical Modeling ◽  
Excess Pore Pressure ◽  
Soil Consolidation ◽  
Factor Analyses ◽  
Soil Permeability ◽  
Vacuum Preloading ◽  
Vertical Drains ◽  
Design Charts ◽  
Horizontal Drainage ◽  
Degree Of Consolidation

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 the 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.Key words: analytical solution, consolidation, design charts, vertical drains.

scholarly journals Finite Element Analysis of Biot’s Consolidation with a Coupled Nonlinear Flow Model

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Yue-bao Deng ◽  
Gan-bin Liu ◽  
Rong-yue Zheng ◽  
Kang-he Xie
Keyword(s):  
Finite Element ◽  
Flow Model ◽  
Numerical Solutions ◽  
Continuity Condition ◽  
Nonlinear Flow ◽  
Weighted Residual Method ◽  
Element Analysis ◽  
Vertical Drains ◽  
Soil Skeleton ◽  
Force Equilibrium

A nonlinear flow relationship, which assumes that the fluid flow in the soil skeleton obeys the Hansbo non-Darcian flow and that the coefficient of permeability changes with void ratio, was incorporated into Biot’s general consolidation theory for a consolidation simulation of normally consolidated soft ground with or without vertical drains. The governing equations with the coupled nonlinear flow model were presented first for the force equilibrium condition and then for the continuity condition. Based on the weighted residual method, the finite element (FE) formulations were then derived, and an existing FE program was modified accordingly to take the nonlinear flow model into consideration. Comparative analyses using established theoretical solutions and numerical solutions were completed, and the results were satisfactory. On this basis, we investigated the effect of the coupled nonlinear flow on consolidation development.

Plane-strain lateral consolidation with non-Darcian flow

2006 ◽  
Vol 43 (2) ◽  
pp. 119-133 ◽  
Author(s):  
Iyathurai Sathananthan ◽  
Buddhima Indraratna
Keyword(s):  
Plane Strain ◽  
Field Data ◽  
Soft Clay ◽  
Test Area ◽  
Excess Pore Pressure ◽  
Good Match ◽  
Lateral Direction ◽  
Vertical Drains ◽  
Axisymmetric Solutions ◽  
Good Agreement

New plane-strain lateral consolidation equations are formulated that neglect the well resistance of vertical drains but are applicable for both Darcian and non-Darcian flow. The results of consolidation analyses using conventional Darcian (linear) flow and the new solution based on non-Darcian (exponential) flow are compared. A good match has been obtained between equivalent plane-strain and axisymmetric solutions. The advantage of the equivalent plane-strain procedure is that it not only matches the average degree of radial (axisymmetric) consolidation but also yields a more realistic excess pore pressure distribution in the lateral direction than the Darcian flow condition. The relevant parameters are illustrated graphically for convenience. Good agreement was obtained between the prediction of the new equivalent plane-strain solution and field data from a test area in Ska-Edeby, Sweden.Key words: plane strain, consolidation, soft clay, vertical drains.

Effectiveness of partially penetrating vertical drains under a combined surcharge and vacuum preloading

2011 ◽  
Vol 48 (6) ◽  
pp. 970-983 ◽  
Author(s):  
Xueyu Geng ◽  
Buddhima Indraratna ◽  
Cholachat Rujikiatkamjorn
Keyword(s):  
Analytical Solutions ◽  
Soft Clay ◽  
Three Dimensional ◽  
Vacuum Pressure ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Degree Of Consolidation ◽  
Pressure Suction

This paper considers the consolidation of a layer of clay in which partially penetrating prefabricated vertical drains (PVDs) are used in conjunction with a combined surcharge and vacuum preloading. Analytical solutions for partially penetrating PVDs are derived by considering vacuum pressure (suction), time-dependent embankment surcharge, well resistance, and smear zone. Three-dimensional seepage with a virtual vertical drain is assumed to reflect real seepage into the soil beneath the tip of a PVD. Analytical solutions were then used to examine the length of the vertical drain and vacuum pressure on soft clay to determine the consolidation time and degree of consolidation, associated settlement, and distribution of suction along the drain. The proposed solutions are then employed to analyse a case history. Finally, an appropriate PVD length in relation to clay thickness and drain spacing is recommended for various loading patterns.

Eulerian finite element analysis of excess pore pressure generated by spudcan installation into soft clay

2012 ◽  
Vol 42 ◽  
pp. 157-170 ◽  
Author(s):  
Jiang Tao Yi ◽  
Fook Hou Lee ◽  
Siang Huat Goh ◽  
Xi Ying Zhang ◽  
Jer-Fang Wu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pore Pressure ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Element Analysis ◽  
Excess Pore

scholarly journals Numerical Investigation to the Effect of Suction-Induced Seepage on the Settlement in the Underwater Vacuum Preloading with Prefabricated Vertical Drains

2021 ◽  
Vol 9 (8) ◽  
pp. 797
Author(s):  
Shu Lin ◽  
Dengfeng Fu ◽  
Zefeng Zhou ◽  
Yue Yan ◽  
Shuwang Yan
Keyword(s):  
Practical Implication ◽  
Soil Surface ◽  
Small Strain ◽  
Seepage Flow ◽  
Excess Pore Pressure ◽  
Combined Effects ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
The Difference

Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

Characterization of a smear zone around vertical drains by large-scale laboratory tests

2000 ◽  
Vol 37 (6) ◽  
pp. 1265-1271 ◽  
Author(s):  
J S Sharma ◽  
D Xiao
Keyword(s):  
Large Scale ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Laboratory Model ◽  
Clay Layer ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Undisturbed Samples ◽  
Oedometer Tests ◽  
Excess Pore

Installation of prefabricated vertical drains using a mandrel causes disturbance of clay surrounding the drain, resulting in a "smear" zone of reduced permeability. In this paper, an attempt is made to characterize the smear zone using large-scale laboratory model tests. Two tests, simulating the cases of "no smear" and "with smear," were conducted. Excess pore-water pressures were monitored at seven different locations along the radial direction. In addition, undisturbed samples were collected at various locations in the clay layer for conducting oedometer tests. The distribution of excess pore pressure due to drain installation gave a clear indication of the extent of the smear zone. The effect of reconsolidation on the properties of clay was found to be much greater than that of the remoulding of the clay. The extent of the smear zone was also confirmed from the change in permeability of the clay layer in the smear zone obtained from oedometer tests. The radius of the smear zone is about four times that of the mandrel, and the horizontal permeability of the clay layer in the smear zone is approximately 1.3 times smaller than that in the intact zone.Key words: consolidation, permeability, smear zone, soft clay, vertical drains.

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