Modeling of Ground Improvement by Prefabricated Vertical Drains in Highly Variable Soils

2012 ◽  
Author(s):  
Mohamed A. Shahin ◽  
Md Wasiul Bari
Keyword(s):  
Ground Improvement ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains

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.

Application of Depth-Measurable Prefabricated Vertical Drains for Soft Ground Improvement

2013 ◽  
Vol 405-408 ◽  
pp. 466-469
Author(s):  
Yong Hua Cao ◽  
Jian Yu
Keyword(s):  
Ground Improvement ◽  
Measuring Method ◽  
Soft Ground ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Impulse Method ◽  
Installation Depth ◽  
Soft Ground Improvement

A kind of depth-measurable prefabricated vertical drains (PVD) was applied for soft ground improvement in Tianjin, China. Test was conducted to check the effectiveness of impulse method for detection of installation depth of PVD. The PVD were set into two groups in length: 20 m and 8 m. The installation depth of PVD was checked in 24 hours since they were installed. The tests result revealed that the measuring precision of impulse method is fairly good but it can be effect by the installation depth. The measuring precision can be controlled in 2% for most PVD when the installation depth was about 20 m. There is a fall down of precision when the installation depth was about 8 m. There is no need for additional construction measures when the PVD for impulse method are installed. All of the PVD installed can be checked for installation depth easily, so the apparatus and measuring method are good in operability and stability.

scholarly journals A Case Study of Combined Drainage Consolidation-Preloading Methods for a Highway Subgrade on Peat Soils

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yue Gui ◽  
Shengjun Liu ◽  
Xiaqiang Qin ◽  
Jianfei Wang
Keyword(s):  
Ground Improvement ◽  
Sri Lankan ◽  
Peat Soils ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Consolidation Coefficient ◽  
Gravel Pile ◽  
Insight Into

A highway project of up to 100 km/h is currently being constructed between Colombo and Katunayake International Airport across a Sri Lankan muskeg area. At this site, peat deposit was initially 0.8∼15.3 m thick and was underlain by sand, clay, or gneiss. The ground improvement methods adopted in the project were combined drainage consolidation-preloading methods, pipe pile foundation, and geogrids. This paper provides a detailed insight into the implementation of combined drainage consolidation-preloading methods used in the project, including sand pile, gravel pile, and plastic drainage plate as the prefabricated vertical drains. Periodical field-level observations were taken during the ten years, including the construction and postconstruction periods. The results show that peat soils’ consolidation coefficient has been increased several times to tens of times due to ground improvement. After removing the temporary surcharge, the highway embankments did not heave and was followed by long-term settlements totaling 1.3∼7.4 cm over the following seven years of observations. Analysis of the settlement records shows that combined drainage consolidation-preloading methods have helped accelerate drainage consolidation and reduce postconstruction settlement.

The Experimental Research of Slurry Improvement with Different Kinds of Vertical Drains under New Vacuum Conditions

2013 ◽  
Vol 405-408 ◽  
pp. 396-401
Author(s):  
Jian Chen ◽  
Qiao Liang Tang ◽  
Shi Jing Liu
Keyword(s):  
Experimental Research ◽  
Ground Improvement ◽  
Soil Improvement ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Drain Spacing ◽  
Soil Zone ◽  
Reclaimed Soil ◽  
Improvement Effect

The results of experimental research are presented and discussed with focus on the ground improvement effect of slurry with different kinds of vertical drains under new vacuum conditions. In these conditions, horizontal sand cushion, which is requested in regular vacuum preloading method, is cancelled. Vertical drains are connected with sealed pipes, so the vacuum head can be transmitted into vertical drains without decreasing. For the experimental research, slurry taken from reclaimed soil zone is placed into six model casing boxes. Different kinds of vertical drains (prefabricated vertical drains (PVDs) and sand drains) are installed into the soil with different spacing (0.4 m and 0.8 m). A vacuum pressure of 80 kPa was applied continuously for 90 days. The effect of filter type of PVD, type of vertical drain and drain spacing under new vacuum preloading condition to slurry soil improvement is examined. Test results show that this new vacuum preloading condition can transmit vacuum head into vertical drains efficiently and the effect of drain filter to slurry improvement is affected by the drain spacing.

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).

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