Combined effects of reinforcement and prefabricated vertical drains on embankment performance

2001 ◽  
Vol 38 (6) ◽  
pp. 1266-1282 ◽  
Author(s):  
Allen Lunzhu Li ◽  
R Kerry Rowe
Keyword(s):  
Shear Strength ◽  
Design Procedure ◽  
Strength Gain ◽  
Foundation Soil ◽  
Simple Method ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Prefabricated Vertical Drain ◽  
Degree Of Consolidation ◽  
Embankment Stability

The behaviour of geosynthetic-reinforced embankments constructed over soft cohesive soils installed with prefabricated vertical drains (PVDs) is investigated by numerically examining an embankment constructed over different foundation soils. The partial consolidation during embankment construction, the consequent shear strength gain of the foundation soil, and the effect of the use of reinforcement on the mobilization of shear strength are examined. It is shown that the combined use of reinforcement and PVDs can significantly increase embankment stability and potentially allow the rapid construction of higher embankments than could be achieved with either method of soil improvement alone. Construction rate and spacing of PVDs can significantly affect the degree of consolidation at the end of construction and the stability of the embankment. For the situation examined, the effect of well resistance of typical vertical drains is insignificant. A relatively simple method for calculating the degree of consolidation and the strength gain of the foundation soil during construction is evaluated based on finite element results and is shown to be reasonably conservative. A design procedure is proposed to combine the design of reinforcement and PVDs.Key words: soft clay, prefabricated vertical drain, reinforcement, embankment stability, consolidation, strength gain.

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.

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%.

Consolidation in Soft Soil – Case Study on Prefabricated Vertical Drains (PVDs)

2021 ◽  
Vol 15 (1) ◽  
pp. 310-319
Author(s):  
Nadarasa Kuganeswaran ◽  
Afikah Rahim ◽  
Nazri Ali
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
3D Analysis ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain ◽  
Improvement Method ◽  
Plaxis 3D

Background: Constructing on soft ground is one of the challenges of geotechnical engineering. The unpredictable behaviour and characteristics of soft soil can cause much damage resulting in high maintenance costs in the post-construction phase. Objective: The purpose of this study is to analyse the consolidation process and ground improvement method using surcharge and a prefabricated vertical drain by measuring the accuracy of the prediction settlement value with the actual site settlement results. Methods: An effective ground improvement method is the application of a surcharge and prefabricated vertical drains (PVDs). Various methods can be used to predict the settlement effectively, one such method being PLAXIS 3D simulation. A case study on ground improvement works was selected for this research, where PVDs were constructed and implemented at the site. A few undisturbed samples were collected from the site to generate the parameters based on the lab test conducted in the simulation process. This parameter was carefully studied and representing the principal input for the 3D model, which is generated and represents the actual ground improvement method for the selected case study. The analysis was performed using a borehole and soft soil model to generate the diagram. The prediction settlement value was generated from the PLAXIS 3D analysis as the baseline comparing to the actual results. The factors that influence the settlement value, such as the length and spacing of the prefabricated vertical drain, construction method, and soil characteristics, are also discussed. Results: A predicted settlement of 2553 mm was generated by the simulation, while the actual settlement outcome at the site was 2096 mm, a difference of 457 mm, and a prediction accuracy of 82.1%. Conclusion: The study found that the combination of surcharge and prefabricated vertical drain in the ground improvement worked well. Also, discussed were the factors that influenced the accuracy of the prediction and the site results.

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

2009 ◽  
Vol 46 (3) ◽  
pp. 270-280 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna
Keyword(s):  
Shear Strength ◽  
Design Procedure ◽  
Undrained Shear Strength ◽  
Soil Consolidation ◽  
Linear Variation ◽  
Vertical Drains ◽  
Multi Stage ◽  
Surcharge Preloading ◽  
Zone Ii ◽  
Undrained Shear

A system of vertical drains with surcharge preloading is an effective method for promoting radial drainage and accelerated soil consolidation. This study presents a procedure for the design of vertical drains that significantly extends the previous technique proposed by the authors to include: (i) a linear reduction of lateral permeability in the smear zone, (ii) the effect of overlapping smear zones in a closely spaced drain network, and (iii) the gain in undrained shear strength due to consolidation. Design examples are provided for both single stage and multi-stage embankment construction demonstrating the convenient use of the proposed solutions in practical situations.

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.

scholarly journals Consolidation Effect of Prefabricated Vertical Drains with Different Lengths for Soft Subsoil under Vacuum Preloading

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Chenhui Lou ◽  
Junfeng Ni ◽  
Jingchun Chai ◽  
Hongtao Fu ◽  
Xiuqing Hu ◽  
...  
Keyword(s):  
Laboratory Model ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Shallow Layer ◽  
Pore Water Pressures ◽  
Practical Engineering ◽  
Different Depths ◽  
Degree Of Consolidation ◽  
Consolidation Effect

The application of vacuum preloading to prefabricated vertical drains (PVDs) with different lengths is widely used in practical engineering to investigate their consolidation at the same depths of even and multilayer subsoils from the seabed. In a laboratory, model experiment was conducted using even subsoil and embedded PVDs with lengths of 0.6 and 1.2 m. The obtained results showed that in the even subsoil, the 1.2 m PVDs maintained a higher vacuum pressure in the shallow layer and demonstrated better consolidation behavior as compared to those of the 0.6 m PVDs. In the upper subsoil layer, the average vane shear strengths of these two systems increased to 18.2 and 22.6 kPa, respectively. The degree of consolidation of the upper subsoil layers in the two model experiments calculated from the pore water pressures under boundary drainage conditions were 51% and 68%, respectively. For practical verification purposes, similar experiments were conducted for multilayer subsoil by inserting PVDs with lengths of 6 and 15 m into different test sites. As a result, the vane shear strengths of the upper 6 m subsoil layers increased to 26.3 and 33 kPa, while the degree of consolidation were 72.1% and 80.9%, respectively, although some irregularities were observed at different depths.

Design charts for vertical drains considering construction time

2001 ◽  
Vol 38 (5) ◽  
pp. 1142-1148 ◽  
Author(s):  
Guofu Zhu ◽  
Jian-Hua Yin
Keyword(s):  
Design Procedure ◽  
Technical Note ◽  
Engineering Properties ◽  
Construction Time ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Design Charts ◽  
Degree Of Consolidation ◽  
Free Strain ◽  
Consolidation Time

This technical note presents design charts for use in determining the required drain spacing explicitly using free strain assumption. The influence of time-dependent loading is incorporated in the design charts. The design procedure is also described. When the radius of vertical drain, required degree of consolidation, time available, and pertinent geotechnical engineering properties of a soil are given, the charts can be used to design a vertical drain system without unnecessary trial and error processes.Key words: consolidation, vertical drain, design charts, time dependence, drainage.

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.

Influence of electro-osmosis activation time on vacuum electro-osmosis consolidation of a dredged slurry

2018 ◽  
Vol 55 (1) ◽  
pp. 147-153 ◽  
Author(s):  
Jun Wang ◽  
Hongtao Fu ◽  
Feiyu Liu ◽  
Yuanqiang Cai ◽  
Jie Zhou
Keyword(s):  
Shear Strength ◽  
Ground Improvement ◽  
Strength Distribution ◽  
Soil Consolidation ◽  
Activation Time ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Electro Osmosis ◽  
Study Laboratory

Combining vacuum preloading with electro-osmosis of a dredged slurry is a significantly effective technology for ground improvement. Despite extensive research, the mechanism of vacuum preloading combined with electro-osmosis is still not properly understood, especially regarding the optimum electro-osmosis activation time. In this study, laboratory tests were performed to confirm the influence of electro-osmosis activation time on vacuum electro-osmosis consolidation of a dredged slurry. A total voltage of 12 V was used in five tests with different electro-osmosis activation times. During the combined process of vacuum preloading and electro-osmosis, the vacuum pressure, electric current, and volume of extracted water were monitored. The water content and shear strength were measured after the tests. The results indicated that electro-osmosis was activated when the degree of consolidation for the soil reached 60%. Thus, this approach can significantly promote the effectiveness of soil consolidation. The shear strength distribution along the depth was much more uniform in all tests with electro-osmosis. The shear strength decreased linearly with increasing distance from the anode rows, but sharp increases occurred near the cathode row (or prefabricated vertical drains).

Sign in / Sign up

Export Citation Format

Share Document