scholarly journals Prefabricated vertical drains (PVDs) in soft Bangkok clay: a case study of the new Bangkok International Airport project

2002 ◽  
Vol 39 (2) ◽  
pp. 304-315 ◽  
Author(s):  
Dennes T Bergado ◽  
A S Balasubramaniam ◽  
R Jonathan Fannin ◽  
Robert D Holtz
Keyword(s):  
Soft Clay ◽  
Field Measurements ◽  
Full Scale ◽  
Maximum Height ◽  
Vertical Movements ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
International Airport ◽  
Prefabricated Vertical Drain ◽  
Test Embankment

This paper presents the performance of a full-scale test embankment constructed on soft Bangkok clay with prefabricated vertical drains (PVDs) at the site of the new Bangkok International Airport in Thailand. The embankment was square in plan with a maximum height of 4.2 m, 3H:1V side slopes, and base dimensions of 40 m by 40 m. The piezometric level with depth is characterized by negative drawdown starting at around 8-10 m depth caused by excessive withdrawal of groundwater. Instrumentation was provided to monitor both horizontal and vertical movements of the test embankment. The measured increases in undrained shear strengths with depth are in agreement with the values calculated from the SHANSEP technique. The secondary compression ratio, Cα, was 0.018, or within the normal values for marine clays. The coefficient of horizontal consolidation measured in the field, Ch(field), was higher for soil at 4 and 10 m depths than for the weakest soil at 6 m depth. The back-calculated Ch(field) values range from 3 to 8 m2/year, and the ratio of Ch(field) to Ch(lab) ranges from 4 to 5, where Ch(lab) is the coefficient of horizontal consolidation measured in the laboratory. The degree of consolidation estimated from the pore-pressure dissipation measurements agreed with those obtained from settlement measurements. The water-content reductions from field measurements were also in good agreement with the values computed from the consolidation settlements. The full-scale study confirmed that the magnitudes of consolidation settlements increased with the corresponding decrease of PVD spacing at a particular time period. Lastly, the results of the full-scale study have proven the effectiveness of PVDs for the improvement of soft Bangkok clay.Key words: soft clay, consolidation, prefabricated vertical drain, preloading, test embankment.

Numerical modeling of vertical drains with smear and well resistance installed in soft clay

2000 ◽  
Vol 37 (1) ◽  
pp. 132-145 ◽  
Author(s):  
B Indraratna ◽  
I W Redana
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Clay ◽  
Field Measurements ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Modified Cam Clay ◽  
Lateral Displacements ◽  
Strain Model ◽  
Cam Clay

This study describes the behavior of embankments stabilized with prefabricated vertical drains installed in soft clay foundations, based on several fully instrumented case histories selected from Thailand and Malaysia. A multidrain analysis is conducted based on an equivalent, plane strain model developed by the authors. The deformation of soft clay beneath an embankment (i.e., along and away from the centerline) is predicted and compared with the available field measurements. The effects of both smear and well resistance are incorporated in the analytical formulation, which is used in conjunction with the modified Cam-clay theory. It is demonstrated that the installation of vertical drains significantly increases the rate of settlement, improves the dissipation of pore-water pressure, and decreases the lateral deformation of the soft clay foundation. To obtain better predictions, especially of pore pressures and lateral displacements, the equivalent discharge capacity of the drains needs to be modeled appropriately. The inclusion of the effects of smear and well resistance in the analysis of vertical drains improves the accuracy of predictions significantly, in comparison with the field measurements.Key words: clay, consolidation, embankment, finite element method, settlement, smear zone, vertical drain.

scholarly journals Ground settlement prediction of embankment treated with prefabricated vertical drains in soft soil

2018 ◽  
Vol 195 ◽  
pp. 03014
Author(s):  
Siswoko Adi Saputro ◽  
Agus Setyo Muntohar ◽  
Hung Jiun Liao
Keyword(s):  
Numerical Study ◽  
Soft Soil ◽  
Soil Permeability ◽  
K Value ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Prefabricated Vertical Drain ◽  
Actual Settlement ◽  
Final Settlement ◽  
Best Fit

Excessive settlement due to consolidation can cause damage to the structure’s rest on soft soil. The settlement takes place in relatively longer. The preloading and prefabricated vertical drain (PVD) is often applied to accelerate the primary settlement. The issue in this research is the estimation of the settlement. The Asaoka method and the finite element method using PLAXIS-2D are used to estimate the final settlement of a PVD treated embankment. For the former, a complete record of the settlement was required; for the latter, some ground parameters are needed for the PLAXIS-2D analysis, such as the permeability of the soil. Because the installation process of PVD tends to influence the permeability of the in-situ soil around the PVD, the soil permeability after the installation of PVD needs to be adjusted. The numerical results were compared with actual settlement data to find out the best-fit input parameters (i.e. soil permeability) of the actual data. It was found that the best-fit soil permeability (k) used in the numerical study was about one-half of the k value determined from the laboratory test. The Root Mean Square Deviation shows that the settlement predicted by the numerical analysis has approximately 30% of the actual settlement.

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.

scholarly journals Uncertainty Analysis in Prediction of Settlements for Spatial Prefabricated Vertical Drains Improved Soft Soil Sites

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 42
Author(s):  
Jemal Jibril Muhammed ◽  
Priyantha W. Jayawickrama ◽  
Stephen Ekwaro-Osire
Keyword(s):  
Granular Layer ◽  
Soft Soil ◽  
Contributing Factors ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Class A ◽  
Numerical Predictions ◽  
Soil Deposits ◽  
Class C ◽  
Test Embankment

This paper presents the quantification of uncertainties in the prediction of settlements of embankments built on prefabricated vertical drains (PVDs) improved soft soil deposits based on data collected from two well-documented projects, located in Karakore, Ethiopia, and Ballina, Australia. For this purpose, settlement prediction biases and settlement distributions were statistically computed based on analyses conducted on two Class A and Class C numerical predictions made using PLAXIS 2D finite element modelling. From the results of prediction bias, Class C predictions agreed well with the field measured settlements at both sites. In Class C predictions, the computed settlements were biased to the measured values. For Class A predictions, the calculated settlement values were in the range of mean and mean minus 3SD (standard deviations) for Karakore clay, and they were within mean and mean minus 2SD limit for the Ballina soil. The contributing factors to the settlement uncertainties of the Karakore site may include variability within the soil profile of the alluvial deposit, particularly the presence of interbedded granular layer within the soft layers, and the high embankment fills, and the limited number of samples available for laboratory testing. At the Ballina test embankment site, the uncertainties may have been associated with the presence of transitional layers at the bottom of estuarine clay and sensitivity of soft soil to sample disturbances and limitations in representing all the site conditions.

scholarly journals EVALUASI KINERJA VERTICAL DRAIN PADA PROYEK JALAN TOL DI SUMATERA DITINJAU DARI ASPEK KONSOLIDASI

2021 ◽  
Vol 4 (2) ◽  
pp. 417
Author(s):  
Erika Oktavia ◽  
Andryan Suhendra
Keyword(s):  
Pore Water ◽  
Theoretical Calculations ◽  
Soft Soil ◽  
Stable Condition ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Model Soil ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain ◽  
The Difference

Over time, there has been more development, this has made less land for development. However, development still has to go on. One of the infrastructure that is currently needed is toll roads to increase the efficiency of movement from one place to another. One of the serious problems at this time is that many soils have small bearing capacity and large settlement, for example, such as soft soil. In order for this model soil to have a stable condition, the solution is loaded so that the pore water from the soil can be pressed out. However, it takes a long time to achieve the desired settlement, here the prefabricated vertical drain method is used to accelerate the settlement. Prefabricated vertical drain here makes the distance between the pore water that was previously thick as soft soil, to half the distance between prefabricated vertical drains. The analysis calculation in this thesis uses the one dimensional consolidation method, the finite element method, and the asaoka method as the calculation of the actual results from field data. The results of this study found that the difference in the degree of consolidation between the theoretical calculations and the Asaoka method was 3.4303%.

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