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.

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.

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 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.

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 New approach of vacuum preloading with booster prefabricated vertical drains (PVDs) to improve deep marine clay strata

2018 ◽  
Vol 55 (10) ◽  
pp. 1359-1371 ◽  
Author(s):  
Yuanqiang Cai ◽  
Zhiwei Xie ◽  
Jun Wang ◽  
Peng Wang ◽  
Xueyu Geng
Keyword(s):  
Lateral Displacement ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Marine Clay ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
New Approach ◽  
Study Results ◽  
Prefabricated Vertical Drain

This paper presented a new approach for ground improvement of deep marine clay in which the conventional booster tube in the current air booster vacuum preloading technology was replaced by a booster prefabricated vertical drain (PVD). In comparison to the ordinary PVD, the booster PVD could provide inflow channels for the compressed air when the booster pump was in operation. To examine the performance of this new air booster vacuum preloading technology, in situ field tests were conducted at Oufei sluice project in Wenzhou, China, where the thickness of the soft soil layers (i.e., marine clay) was more than 20 m. An extensive monitoring system was implemented to measure the vacuum pressure, pore-water pressure, settlement, and lateral displacement at this reclamation site. With the collected field monitoring data, a comprehensive data analysis was carried out to evaluate the extent of ground improvement. The study results depicted that this new air booster vacuum preloading technology was more effective for the ground improvement of the deep marine clay layers, in comparison to the conventional vacuum preloading technology.

scholarly journals Effect of Improvement and Application of Composite Prefabricated Vertical Drain Method in Marine Soft Ground: A Case Study

2019 ◽  
Vol 2019 ◽  
pp. 1-18 ◽  
Author(s):  
Jianqing Jiang ◽  
Reqiang Liu
Keyword(s):  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Field Monitoring ◽  
Hyperbolic Model ◽  
Soft Ground ◽  
Prefabricated Vertical Drains ◽  
Prefabricated Vertical Drain

One of the commonly used techniques to improve marine soft ground is the drainage consolidation method by plastic board drains (PBDs). But some complex marine soft ground will cause construction inconvenience of PBDs in certain areas of these sites, thus affecting the improvement effect. An alternative possible approach to overcoming these deficiencies may be the combination of PBDs and sand wick drains (SWDs) (i.e., composite prefabricated vertical drains (CPVDs)) as vertical drainage channels in the same site. In order to verify the suitability and performance of this method in marine soft ground improvement, a case study was performed based on the field monitoring and construction of the marine soft ground of an intercity express railway project in China. The construction procedure using the CPVD system, the field monitoring instrumentation scheme, and the design of fill surcharge level were described, and the field monitoring data were presented. The settlement characteristics, dissipation features of pore water pressure, and the horizontal movement pattern were assessed. In addition, predictions of ultimate settlement, postconstruction settlement, and consolidation degree were discussed by applying a modified hyperbolic model. The results show that the marine ground improved by the CPVD system is suitable for the construction of intercity express railway and high-speed railway. The improvement construction period of complex marine soft ground will be greatly shortened by the proposed parallel construction programme. This work will provide technical supports and application reference for the improvement of the similar marine soft ground.

scholarly journals A Simplified Method for Analysis of Laterally Loaded Piles considering Cyclic Soil Degradation

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yuzhe Yang ◽  
Xiaodong Gao ◽  
Wenbing Wu ◽  
Kangyu Xing
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Lateral Displacement ◽  
Water Pressure ◽  
Soft Clay ◽  
Degradation Model ◽  
Laterally Loaded Pile ◽  
Simplified Method ◽  
Strain Wedge ◽  
Laterally Loaded

This paper proposes a simplified method to analyze the bearing behavior of pile undergoing cyclic lateral load. Firstly, a modified strain model is proposed by utilizing the Duncan–Chang model to describe the stress-strain behavior of soils in the strain wedge. Then, a cyclic degradation model of soft clay considering the accumulation of plastic strain and pore water pressure is presented based on the cyclic triaxial test. Combining with the modified strain wedge model and degradation model of soil, a simplified method is established for the cyclic laterally loaded pile. The accuracy of the present method is verified by comparing it with existing model tests. The results show that the pile lateral displacement and strain wedge depth increase with the number of cycles and cyclic load amplitude. It is necessary to consider the effect of cumulative pore water pressure during the analysis of cyclic laterally loaded pile embedded in soft clay.

scholarly journals Finite Element Analysis of Vertical and Horizontal Drainage Structures under Vacuum Combined Surcharge Preloading

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Daqing Wang ◽  
Dong Wei ◽  
Guoyi Lin ◽  
Jiannan Zheng ◽  
Zhiting Tang ◽  
...  
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Horizontal Displacement ◽  
Reinforcement Effect ◽  
Vacuum Suction ◽  
Prefabricated Vertical Drains ◽  
Surcharge Preloading ◽  
Prefabricated Vertical Drain

Combined vacuum and surcharge preloading has gradually been widely used because of its advantages of low cost, green environmental protection, and good treatment effect. The conventional prefabricated vertical drain presents obvious defects in vacuum preloading treatment, such as obvious silting, serious bending of the drainage board, large attenuation of vacuum degree of drainage board along the depth, long construction period, and so on, which affect the final reinforcement effect. In this paper, the MIDAS finite element simulation of combined vacuum and surcharge preloading of prefabricated vertical drains (PVDs) and prefabricated horizontal drains (PHDs) is established through the comparative experiment of the engineering field. The comparative experimental study is carried out from the aspects of the vertical settlement, horizontal displacement, and pore water pressure. The results show that under combined vacuum and surcharge preloading, the consolidation effect of soft soil with PHDs is better than that with PVDs. When PHDs are used, the vertical settlement increases by 7.2% compared with PVDs; the horizontal displacement is larger; and the pore water pressure dissipates faster. This is because when the PHDs are adopted, the consolidation direction of the soil is consistent with the direction of the vacuum suction, which is mainly caused by vertical settlement. With the consolidation, the spacing between PHDs is gradually shortened, and the drainage distance is reduced, which can effectively reduce the consolidation time and improve the reinforcement effect of the soil. In addition, the PHDs can move downward uniformly with the soil during the consolidation process and have almost no bending deformation, which makes the vacuum transfer more uniform and effective.

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