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.

Long-term performance of a wide embankment on soft clay improved with prefabricated vertical drains

2008 ◽  
Vol 45 (8) ◽  
pp. 1073-1091 ◽  
Author(s):  
S. R. Lo ◽  
J. Mak ◽  
C. T. Gnanendran ◽  
R. Zhang ◽  
G. Manivannan
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Clay ◽  
Foundation Soil ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Long Term Performance ◽  
Term Performance

This paper presents the long-term performance of a wide geogrid-reinforced road embankment constructed on soft clay improved with prefabricated vertical drains (PVDs) at a freeway extension site 150 km north of Sydney in Australia. The foundation soil and the embankment were instrumented and monitored for about 400 days for excess pore-water pressure, earth pressure, and reinforcement tension, and for 9 years for displacement profiles. The embankment was constructed in stages and surcharged in an attempt to reduce post-construction settlement. As the embankment width was wide relative to the thickness of the soft clay, the settlement near the centre was modelled by a unit cell analysis. The equivalent horizontal permeability was determined by back analysis of the central zone using the first 12 months of settlement data. All other soil parameters were determined from the laboratory and field testing. The predicted pore-water pressure response over the first 400 days showed reasonable agreement with measured values. The same analysis was then continued to predict settlement over a period of 9 years. The predicted settlement was, however, smaller than the measured value at the centre region of the embankment.

Finite-element analysis of deep excavation in layered sandy and clayey soil deposits

1994 ◽  
Vol 31 (2) ◽  
pp. 204-214 ◽  
Author(s):  
Chang-Yu Ou ◽  
Ching-Her Lai
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Deep Excavation ◽  
Element Analysis ◽  
Modified Cam Clay ◽  
Soil Deposits ◽  
Cam Clay

This paper presents an application of finite-element analysis to deep excavation in layered sandy and clayey soil deposits using a combination of the hyperbolic and the Modified Cam-clay models. In the analysis, the drained behavior of cohesionless soil and the undrained behavior of cohesive soil were simulated using the hyperbolic and Modified Cam-clay models, respectively. A rational procedure for determining soil parameters for each of the models was established. A simulation of the dewatering process during excavation was proposed. The analytical procedure was confirmed through an analysis of three actual excavation cases. Finally, analyses considering pore-water pressure dissipation during the actual elapsed time for each construction phase were carried out. The results indicate that the calculated displacement of a retaining wall during excavation is smaller than that given by undrained analysis. It was thought that some degree of pore-water pressure dissipation actually occurs during the intermediate excavation stages. This results in a decrease in the final deformation of the wall and ground.-surface settlement than would be predicted by undrained analysis. Key words : finite-element analysis, deep excavation, hyperbolic model, Cam-clay model.

scholarly journals Deformation and Stability of Soft Foundation Improved by Prefabricated Vertical Drains Adjacent to River Bank

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Changqing Qi ◽  
Liuyang Li ◽  
Jiabing Qi
Keyword(s):  
Pore Water Pressure ◽  
Lateral Displacement ◽  
Water Pressure ◽  
Measurement Data ◽  
Shallow Foundation ◽  
Left Shoulder ◽  
Prefabricated Vertical Drains ◽  
River Bank ◽  
Vertical Drains ◽  
The Right

This paper presents a finite element analysis on a soft embankment foundation improved by prefabricated vertical drains. A plane strain analysis was performed using equivalent permeability. The predictions of settlement, pore water pressure, and lateral displacement were compared with the available field measurement data, and a general fair agreement was observed. Numerical results indicate that the settlement below the left part of the embankment is obviously larger than that of the right part. The maximum settlement occurs below the left shoulder of the embankment and reaches 1.26 m. The entire shallow foundation shows a movement trend to the left toe. The designed left embankment shoulder was suggested to be 0.16 m higher than the right side. Monitoring and simulation results demonstrate that the foundation is stable during the construction. The factor of safety at the end of the final loading stage is about 1.81. The performance of the embankment is consistent with the design prescriptions, confirming the effectiveness of the soil improved technique included in this project.

scholarly journals Numerical modelling of the hydrogeological and geomechanical behaviour of a large slope movement: the Triesenberg landslide (Liechtenstein)

2007 ◽  
Vol 44 (7) ◽  
pp. 840-857 ◽  
Author(s):  
B François ◽  
L Tacher ◽  
Ch. Bonnard ◽  
L Laloui ◽  
V Triguero
Keyword(s):  
Finite Element ◽  
Numerical Modelling ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Temporal Distribution ◽  
Field Measurements ◽  
Slope Movement ◽  
Three Dimensions ◽  
Hydrogeological Model ◽  
Modified Cam Clay

Using advanced hydrogeological and geomechanical finite element modelling, it has been possible to model the mechanical behaviour of a large slope movement, the Triesenberg landslide. This slope is located along the Rhine valley in the Principality of Liechtenstein and covers an area of around 5 km2, which includes two villages. Pore-water pressure fields calculated by the hydrogeological model were used as input for the geomechanical model. The results obtained through numerical simulation agree fairly well with field measurements of peak velocity, spatial and temporal distribution of velocity, and total displacements. Such results were obtained using a modified Cam-Clay elastoplastic constitutive model for which the required material parameters were obtained through careful geotechnical tests. These finite element models were carried out in two and three dimensions to gradually improve the understanding of the physical phenomena governing the hydrogeological conditions and the movements of the slope.Key words: landslides, slope movement, hydromechanical coupling, elastoplasticity, numerical modelling.

Finite difference analysis of prefabricated vertical drains assisted with surcharge preloading of Hiep Phuoc soft clay in Vietnam

2022 ◽  
pp. 1-40
Author(s):  
Cong-Oanh Nguyen ◽  
Thi Van-Tram Dao ◽  
Thi-Thanh Tran
Keyword(s):  
Finite Difference ◽  
Pore Water Pressure ◽  
Container Terminal ◽  
Water Pressure ◽  
Soft Clay ◽  
Soft Ground ◽  
Prefabricated Vertical Drains ◽  
Difference Analysis ◽  
Finite Difference Analysis ◽  
Constant Rate

A series of finite difference analysis of the soft ground treatment with PVDs application has been performed with the application of the newly developed consolidation model. The model utilizes the concept of multi-compression indices and coefficients of consolidation to investigate the behaviors of the soft ground deposit on pore water pressure dissipation, surface and sub-layered ground settlement and to validate the newly developed CONSOPRO finite-difference procedure. Furthermore, the pre-consolidation pressures of the soft ground deposit are characterized with the combination of the piezocone penetration profiling and constant rate of strain consolidation tests under 0.02 %/min. on undisturbed samples which were retrieved at the investigated site, Saigon Premier Container Terminal (SPCT) in the South of Vietnam. On the comparison of the back-calculation results to the field observing data, the correlation between the coefficients of consolidation determined by constant-rate-of-strain (CRS) consolidation tests and those from piezocone dissipation tests, which were carried out after the soil improvement, is developed.

Improving consolidation of dredged slurry by vacuum preloading using prefabricated vertical drains (PVDs) with varying filter pore sizes

2020 ◽  
Vol 57 (2) ◽  
pp. 294-303 ◽  
Author(s):  
Jun Wang ◽  
Yongli Yang ◽  
Hongtao Fu ◽  
Yuanqiang Cai ◽  
Xiuqing Hu ◽  
...  
Keyword(s):  
Pore Size ◽  
Fine Particles ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Pore Sizes ◽  
Filter Surface ◽  
The Difference

Prefabricated vertical drains (PVDs) have been used extensively to accelerate the consolidation rate of dredged slurry. While some fine particles from dredged slurry can easily squeeze through the filter into the drainage channel, many cannot. As such, these soil particles deposit on the filter surface causing partial clogging of the drainage path. Although the pore size of filter is recognized as an important factor that influences PVD clogging, the standards for determining the pore size of the filter are lacking. To this end, the traditional gradient ratio tests with four different filter pore sizes were conducted, and the results show that the permeability of the filter at a given head increases with the increase in the pore size of the filter. To remove the effect of the difference between static hydraulic gradient and vacuum pressure, the vacuum preloading tests with varying pore sizes of filters were further conducted. Through these vacuum preloading tests, the degree of vacuum, settlement, pore-water pressure, water content, vane shear strength, and other parameters of PVDs with various filter pore sizes were obtained, and the optimal pore size of filter was determined.

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.

Finite element analysis of an embankment on a soft estuarine deposit using an elastic–viscoplastic soil model

2009 ◽  
Vol 46 (3) ◽  
pp. 357-368 ◽  
Author(s):  
Curtis Kelln ◽  
Jitendra Sharma ◽  
David Hughes ◽  
James Graham
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Element Analysis ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Deformation Response ◽  
Soil Model ◽  
Excess Pore

A new elastic–viscoplastic (EVP) soil model has been used to simulate the measured deformation response of a soft estuarine soil loaded by a stage-constructed embankment. The simulation incorporates prefabricated vertical drains installed in the foundation soils and reinforcement installed at the base of the embankment. The numerical simulations closely matched the temporal changes in surface settlement beneath the centerline and shoulder of the embankment. More importantly, the elastic–viscoplastic model simulated the pattern and magnitudes of the lateral deformations beneath the toe of the embankment — a notoriously difficult aspect of modelling the deformation response of soft soils. Simulation of the excess pore-water pressure proved more difficult because of the heterogeneous nature of the estuarine deposit. Excess pore-water pressures were, however, mapped reasonably well at three of the six monitoring locations. The simulations were achieved using a small set of material constants that can easily be obtained from standard laboratory tests. This study validates the use of the EVP model for problems involving soft soil deposits beneath loading from a geotechnical structure.

scholarly journals Analysis of settlement prediction due to preloading and vertical drain applications on runway construction

2020 ◽  
Vol 156 ◽  
pp. 02002
Author(s):  
Adriyati Meilani ◽  
Rifa’i Ahmad ◽  
Faris Fikri
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soil Layer ◽  
Soil Mass ◽  
Research Area ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Consolidation Settlement ◽  
Primary Consolidation

Consolidation settlement is a general geotechnical problem particularly found in the area where is composed of soft soil. It is caused by the discharge of pore water pressure induced by the increase of stress in the soil mass. Construction of runway above soft soil requires analysis for stability related to the reduction of consolidation settlement and the recovery. This study aims to analyze the settlement comprehensively using empirical methods of Prefabricated Vertical Drains (PVD) and preloading installation. Preloading is a technique by which consolidation of soil can be achieved to a substantial amount before the imposition of actual construction load. According to soil investigation, the characteristic of the soil layer is clay soil, which has the potential to consolidation settlement. The result of the settlement analysis of the taxiway in the research area is from 33 cm to 214 cm. It takes ten years for primary consolidation to reach a 90% degree of consolidation. However, in the Hansbo method of Prefabricated Vertical Drains (PVD) and preloading are applied, with triangular configurations in depth of 11 meters and duration for variation embankment spacing of 1 m is 79 days, 1.5 m is 202 days and 2 m is 390 days. The conclusion of efficient distance of PVD installation and preloading is spacing of 1 m with 79 days for primary consolidation.

scholarly journals Comparative Analysis of Settlement and Pore Water Pressure of Road Embankment on Yan soft soil Treated with PVDs

2019 ◽  
Vol 5 (7) ◽  
pp. 1609-1618
Author(s):  
Rufaizal Che Mamat ◽  
Anuar Kasa ◽  
Siti Fatin Mohd Razali
Keyword(s):  
Numerical Simulation ◽  
Comparative Analysis ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Coefficient Of Determination ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Significant Difference

The application of prefabricated vertical drains (PVDs) in the road embankment construction has been successfully performed in many projects throughout the country. The simulation of finite element method (FEM) can assist engineers in modelling very complex structures and foundations. This paper presents a plane–strain numerical analysis that was performed to verify the effectiveness of the model embankment stabilised with PVD using Plaxis 2D version 8. This study employed the smear effect of permeability ratio (kr) of 3 in the PVD modelling. The data of settlement and pore water pressure in the left and right sides of road embankment were monitored for 177 days, then the data were collected and compared by a numerical simulation. The coefficient of determination (R2) was used to assess the performance of the comparative analysis. The results of numerical simulation on settlement and pore water pressure obtained a coefficient of determination of greater than 0.9 which has reached a good agreement with those of the field measurement. On other the hand, there was no significant difference in the performance between both sides of the embankment. The smear effect parameter (kr = 3) is recommended for PVD designs and can provide accurate FEM prediction.

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