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 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%.

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 ANALISIS PENGGUNAAN PREFABRICATED VERTICAL DRAINS (PVD) PADA TANAH LEMPUNG LUNAK YANG TERDAPAT LAPISAN LENSA

2020 ◽  
Vol 3 (1) ◽  
pp. 119
Author(s):  
Andreyan Prasetio ◽  
Aniek Prihatiningsih
Keyword(s):  
Soft Soil ◽  
Soil Improvement ◽  
Cohesive Soils ◽  
Consolidation Process ◽  
Prefabricated Vertical Drains ◽  
Soil Layers ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Installation Depth ◽  
Consolidation Time

Problem that often occurs in soft cohesive soils is settlement caused by consolidation process. If  construction activities doing when the soils has not been consolidated, settlement can occur. To accelerate  the consolidation process, soil improvement are usually do, one method of soil improvement to accelarate the consolidation process is vertical drain using prefabricated vertical drains (PVD). The soft soil layers in the field are not always continuous, sometimes found soft soil layers that have a lens layer. In this study, will discuss about the settlement and consolidation time of soft  soil layers that have a lens layer which has been improved by PVD with 1 meter distance. Infrastructure that stand on a location that is installed by PVD is taxiway and loading by Airbus A380 aircraft of 18,22ton/m2. Analysis using the 1 dimensional consolidation theory of Terzaghi. For PVD installation to a depth of 50 meters, preloading settlement of 234,80 cm with a consolidation time of  2260 days for the square pattern PVD and 1918 days for triangle pattern PVD. Post loading settlement for PVD installation depth of 50 meters by 2,50 cm. AbstrakMasalah yang sering terjadi pada tanah kohesif dan lunak adalah penurunan yang disebabkan proses konsolidasi. Penurunan dapat menyebabkan keretakan pada struktur konstruksi yang berada di atasnya. Jika suatu kegiatan konstruksi dilakukan saat tanah belum terkonsolidasi, maka konstruksi tersebut dapat mengalami penurunan.. Untuk mempercepat proses konsolidasi biasanya dilakukan perbaikan tanah, salah satu metode perbaikan tanah untuk mempercepat proses konsolidasi yaitu vertical drain dengan menggunakan prefabricated vertical drains (PVD). Lapisan tanah lunak yang terdapat di lapangan tidak selalu kontinu, terkadang ditemukan lapisan tanah lunak yang terdapat lapisan lensa. Pada penelitian ini, penulis akan membahas mengenai waktu konsolidasi yang dibutuhkan oleh lapisan tanah kohesif dan lunak yang terdapat lapisan lensa yang telah diperbaiki dengan menggunakan PVD berjarak 1 meter. Infrastruktur yang berdiri di atas lokasi yang dipasang PVD berupa taxiway dengan beban berupa pesawat Airbus A380 sebesar 18,22 ton/m2. Analisis dilakukan menggunakan teori konsolidasi 1 dimensi Terzaghi. Untuk pemasangan PVD hingga kedalaman 50 meter diperoleh penurunan pra pembebanan sebesar 234,80 cm dengan waktu konsolidasi selama 2260 hari untuk pemasangan PVD pola persegi dan selama 1918 hari untuk pola segitiga . Penurunan pasca pembebanan untuk pemasangan PVD hingga kedalaman 50 meter sebesar 2,5 cm.

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 Modelling of a vacuum consolidation project in Vietnam

2020 ◽  
Vol 9 (1) ◽  
pp. 78-101
Author(s):  
Nguyen Trong Nghia
Keyword(s):  
Analytical Solution ◽  
Numerical Modelling ◽  
Plane Strain ◽  
Ground Improvement ◽  
Soft Soil ◽  
Design Tool ◽  
In Situ Monitoring ◽  
Improvement Project ◽  
Prefabricated Vertical Drains ◽  
Prefabricated Vertical Drain

Ground improvement technique by prefabricated vertical drain (PVD) in combination with vacuum preloading is widely used to facilitate consolidation process and reduce residual settlement. However, this technique seem hardly be estimated by both analytical method and numerical method because it has complex boundary conditions (such as vacuum pressure changing with time). Moreover, lateral displacements caused by this technique are also significant problem. Numerical modelling may be an effective design tool to estimate behavior of soft soil treated by this method, however it needs to have a proper calibration of input parameters. This paper introduces a matching scheme for selection of soil/drain properties in analytical solution and numerical modelling (axisymmetric and plane strain conditions) of a ground improvement project by using Prefabricated Vertical Drains (PVD) in combination with vacuum and surcharge preloading. In-situ monitoring data from a case history of a road construction project in Vietnam was adopted in the back-analysis. Analytical solution and axisymmetric analysis can approximate well the field data meanwhile the horizontal permeability need to be adjusted in plane strain scenario to achieve good agreement. In addition, the influence zone of the ground treatment was examined. The residual settlement was investigated to justify the long-term settlement in compliance with the design code. Moreover, the degree of consolidation of non-PVD sub-layers was also studied by means of two different approaches.

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.

scholarly journals Influence of vertical drains on improving dredged mud by vacuum consolidation method

2018 ◽  
Vol 12 (5) ◽  
pp. 63-72
Author(s):  
Phan Huy Dong
Keyword(s):  
Soft Soil ◽  
Drainage System ◽  
Soil Improvement ◽  
Vacuum Consolidation ◽  
Vertical Drains ◽  
Fine Grained ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain ◽  
Reclamation Area ◽  
Preloading Method

Vacuum consolidation preloading method (VCM) has been widely adopted as an effective solution for soft soil improvement over the world. Recently, VCM has been successfully applied for improving the geotechnical properties of dredged mud, which is normally dumped at reclamation area by hydraulic pumping. However, it has been also reported that application of VCM for treatment of the dredged mud has been failed in some particular cases. The failures are mainly caused by clogging problem in vertical drains due to fine-grained soils that reduces the drainage efficiency of drainage system. To address this issue, a series of model tests have been conducted to investigate the performances of vertical drains among prefabricated vertical drain, sand drain and filter pipe. As the goal, the performances of types of the vertical drain solutions are analyzed based on the monitoring data of settlement, influencing zone surrounding the vertical drains. The test results reveal that sand drain shows the best performance among the others. In addition, the clogging problem is clearly shown in case of PVD. Keywords: dredging slurry; vacuum consolidation method; model test; PVD; filter pipe; sand drain.

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