scholarly journals Applying the Equivalent Plane Strain solution to design the soft soil improvement by vertical drains

2020 ◽  
Vol 61 (3) ◽  
pp. 28-37
Author(s):  
Nu Thi Nguyen ◽  
Keyword(s):  
Plane Strain ◽  
Permeability Coefficient ◽  
Soft Soil ◽  
Soil Improvement ◽  
Field Monitoring ◽  
Soft Ground ◽  
Vertical Drains ◽  
Equivalent Permeability ◽  
Ground Treatment ◽  
Treatment Design

The soft soil improvement by vertical drains (PVD, sand drains) are widely used in Vietnam. One of the methods is used for designing soft soil improvement by vertical drains is the Equivalent Plane Strain solution. To use this solution, the permeability coefficient of soil is converted into the equivalent permeability under plane strain. The paper presents the application of this solution to design soft soil improvement by sand drains at Km 3+130 Vi Thanh - Can Tho. It indicated that the settlement results of the soft ground treatment design based on Equivalent Plane Strain solution are similar to those from the Axisymmetric Condition analysis and field monitoring.

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 Assessment the Engineering Characteristics of the Smear Zone around PVDs Using Laboratory Tests

2019 ◽  
Vol 25 (11) ◽  
pp. 67-81
Author(s):  
Ahmed Shakir Kamil ◽  
Ala Nassir Aljorany
Keyword(s):  
Permeability Coefficient ◽  
Laboratory Testing ◽  
Soft Soil ◽  
Geotechnical Properties ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Coefficient Of Permeability ◽  
Shear Strains ◽  
Horizontal Permeability ◽  
Intact Soil

Smear zone is usually formed around the prefabricated vertical drains (PVD’s) due to mandrel driving. The geotechnical properties of the soil in this zone exhibit significant changes that affect the performance of the PVD’s. The most relevant property in this respect is the coefficient of permeability. So far, no serious attention is paid to investigate the effects of shearing under large shear strains on the geotechnical properties of the soft soil in Fao region. In this study, an extensive laboratory testing program was conducted to assess the characteristics of the smear zone with an emphasis on the permeability coefficient of Fao soft soil. The results show that the permeability of the smear zone is about 70% of the horizontal permeability of the intact soil. An attempt was made to estimate the extension of the shearing zone in the direct shear test. The analysis results indicate that thickness of the shearing zone is about (2.4) cm.  

Modelling the effect of vertical drains in two-dimensional finite element analyses of embankments on soft ground

1995 ◽  
Vol 32 (5) ◽  
pp. 795-807 ◽  
Author(s):  
C.C. Hird ◽  
I.C. Pyrah ◽  
D. Russell ◽  
F. Cinicioglu
Keyword(s):  
Finite Element ◽  
Plane Strain ◽  
Unit Cell ◽  
Lateral Strain ◽  
Soft Ground ◽  
Two Dimensional ◽  
Finite Element Analyses ◽  
Case Histories ◽  
Vertical Drains ◽  
Dimensional Finite Element

A recently developed method for modelling the effect of vertical drains in plane strain finite element analyses of consolidation beneath embankments on soft ground is applied to three case histories. Analyses are reported for the consolidation of the soil served by a single drain (a unit cell) under conditions of no lateral strain. In all three cases a good match was obtained between the average degrees of consolidation in an axisymmetric unit cell and the equivalent plane strain unit cell. This suggests that the method could be used to facilitate full two-dimensional analyses of many embankments. The results of the analyses are also compared with the available field data. Key words : vertical drains, consolidation, finite elements, embankments.

scholarly journals Deformation behaviour of granular column reinforced by geosynthetic encasement

2021 ◽  
Vol 4 (2) ◽  
pp. first
Author(s):  
Lê Quân ◽  
Võ Đại Nhật ◽  
Nguyễn Việt Kỳ ◽  
Phạm Tiến Bách
Keyword(s):  
Bearing Capacity ◽  
Soft Soil ◽  
Thermal Power ◽  
Soil Improvement ◽  
Soft Ground ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Geological Conditions ◽  
Consolidation Settlement ◽  
Granular Column

In Vietnam, the overpopulation and strong economic development require the synchronous development of infrastructure such as roads, urban areas, industrial parks, export processing zones, etc. With such requirements, the development of land fund for infrastructure construction is an indispensable need. Meanwhile, the appropriate land fund is very limited. Therefore, the land fund must be developed for areas with little value for agriculture, such as swamps, estuaries, and coastal areas, etc. These areas often have weak geological conditions; hence, to meet the requirements of infrastructure construction on the soft ground, it is necessary to carry out soil improvement to ensure load bearing capacity, total settlement, and consolidation settlement but still ensuring economic effectiveness. Beside several conventional methods widely used for soft soil improvement in order to increase bearing capacity and accelerate consolidation settlement of the ground, geosynthetic reinforced granular column is one of the new methods that has been applied to improving soft ground in designing practice in the recent years due to the many advantages of this method compared with other methods. In this paper, based on the unit cell model, the authors research on deformation behavior of granular column reinforced by geosynthetic encasement through the analytical analysis by varying external loadings corresponding to column diameter, stiffness of geosynthetic encasement. The settlements of a single geosynthetic encased granular column and load bearing capacity of the composite foundation are calculated on geological conditions of Ash Pond Area of Song Hau 1 Thermal Power Plant located in Hau Giang Province. The relationship between settlement and load bearing capacity with external loadings for different column diameters and geosynthetic stiffnesses are shown schematically. Other considerations related to factor of safety are also presented. The future researches are also proposed.

scholarly journals The potential of using fine rock for replacing soft soil in construction of a breakwater at Chan May port

2020 ◽  
Vol 61 (4) ◽  
pp. 75-85
Author(s):  
Nu Thi Nguyen ◽  
Son Truong Bui ◽  
Dung Tien Le ◽  
Keyword(s):  
Sea Level ◽  
Soft Soil ◽  
Soil Layer ◽  
Soft Ground ◽  
Ground Treatment

Breakwater is an important construction in Chan May port. The construction of breakwaters faces many difficulties due to the soft soil layer with a thickness of more than ten meters and located under the sea level. Breakwater is unstable as well as high of settlement. Therefore, the soft soil under the breakwater was replaced by fine rock. The results show that it is feasible to replace soft soil by fine rock when constructing breakwater in the sea. This is the basis for the design of soft ground treatment for breakwaters in Vietnam.

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.

Solutions of Technical Problems in Ultra-Soft Soil Improving Projects

2013 ◽  
Vol 275-277 ◽  
pp. 1398-1402
Author(s):  
Yong Hua Cao ◽  
Chang Quan Yin
Keyword(s):  
Building Materials ◽  
Soft Soil ◽  
Soil Improvement ◽  
New Method ◽  
Vacuum Preloading ◽  
Typical Application ◽  
Prefabricated Vertical Drains ◽  
Technical Problems ◽  
Vertical Drains ◽  
Preloading Method

Ultra-soft soil improvement projects are new trend in present China because of the limitation of construction period. Technical problems occur when traditional vacuum preloading method is applied for ultra-soft soil. This paper firstly gave an analysis of the main technical problems which include construction channel problems for building materials and workers, portion division problems of project area, installation problems of prefabricated vertical drains and formation problems of horizontal drainage cushion. Then solutions for these problems were presented. Based on the solutions and traditional vacuum preloading method, a new method for ultra-soft soil improving was put forward. A typical application of this new method was give at the end of this paper.

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