Electroosmosis-enhanced preloading consolidation via vertical drains

1998 ◽  
Vol 35 (3) ◽  
pp. 491-499 ◽  
Author(s):  
J Q Shang
Keyword(s):  
Electric Field Intensity ◽  
Treatment Time ◽  
Spatial Configuration ◽  
Soil Improvement ◽  
Excess Pore Pressure ◽  
Vertical Drains ◽  
Soft Clays ◽  
Surcharge Preloading ◽  
Surcharge Load ◽  
Degree Of Consolidation

An analytical model of electroosmosis-enhanced preloading consolidation via vertical drains is developed for the design of the combined preloading and electroosmotic consolidation of clay soils. The excess pore pressure and average degree of consolidation are computed and examined for the effects of surcharge load, electric field intensity, treatment time, spatial configuration of electrodes, drainage path, and soil properties. The model is evaluated using the results of a well-known electroosmotic consolidation field test reported in the literature.Key words: consolidation, electroosmosis, surcharge preloading, vertical drains, soil improvement, soft clays.

Vacuum preloading consolidation of reclaimed land: a case study

1998 ◽  
Vol 35 (5) ◽  
pp. 740-749 ◽  
Author(s):  
J Q Shang ◽  
M Tang ◽  
Z Miao
Keyword(s):  
Land Reclamation ◽  
Soil Improvement ◽  
Large Area ◽  
Vacuum Preloading ◽  
Reclaimed Land ◽  
Improvement Project ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Soft Clays

This case study presents the design, operation, and results of a soil improvement project using the vacuum preloading method on 480 000 m2 of reclaimed land in Xingang Port, Tianjing, China. The areas treated with vacuum ranged from 5000 to 30 000 m2. The effects of soil improvement are demonstrated through the average consolidation settlement of 2.0 m and increases in undrained shear strengths by a factor of two to four or more. The study shows that the vacuum method is an effective tool for the consolidation of very soft, highly compressive clayey soils over a large area. The technique is especially feasible in cases where there is a lack of surcharge loading fills, extremely low shear strength, soft ground adjacent to critical slopes, and access to a power supply.Key words: vacuum preloading consolidation, soil improvement, soft clays, land reclamation, prefabricated vertical drains.

Soil improvement for a storage yard using the combined vacuum and fill preloading method

2005 ◽  
Vol 42 (4) ◽  
pp. 1094-1104 ◽  
Author(s):  
S.-W Yan ◽  
J Chu
Keyword(s):  
Ground Improvement ◽  
Soil Improvement ◽  
Undrained Shear Strength ◽  
Foundation Soil ◽  
Surcharge Preloading ◽  
Clay Slurry ◽  
Degree Of Consolidation ◽  
Preloading Method ◽  
Undrained Shear

This paper presents a case study of using the combined vacuum and fill surcharge preloading method to improve the foundation soil for a storage yard at Tianjin Port, China. A vacuum load of 80 kPa was applied for 4-8 weeks before fill surcharge was added in stages. The site to be improved was recently reclaimed using dredged clay slurry. Both the consolidated clay slurry fill and the seabed soils were very soft. After the combined vacuum and fill surcharge preloading, the ground settled more than 1 m. The average degree of consolidation achieved was more than 80%. The undrained shear strength of the soil increased twofold. The water content of the soil also decreased substantially. The soil improvement procedure using the combined vacuum and fill surcharge preloading method and the instrumentation scheme are described, the field monitoring data are presented and analyzed, and methods to estimate the degree of consolidation and several other issues related to the combined preloading method are discussed.Key words: case history, consolidation, ground improvement.

scholarly journals Analytical solutions and design curves for vacuum-assisted consolidation with both vertical and horizontal drainage

2007 ◽  
Vol 44 (2) ◽  
pp. 188-200 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna
Keyword(s):  
Analytical Modeling ◽  
Excess Pore Pressure ◽  
Soil Consolidation ◽  
Factor Analyses ◽  
Soil Permeability ◽  
Vacuum Preloading ◽  
Vertical Drains ◽  
Design Charts ◽  
Horizontal Drainage ◽  
Degree Of Consolidation

A system of vertical drains combined with vacuum preloading is an effective method for promoting radial flow to accelerate soil consolidation. This study presents the analytical modeling of the consolidation of vertical drains incorporating vacuum preloading considering both vertical and horizontal drainage. The effects of a number of dimensionless parameters involving the drain length, soil permeability, and vacuum pressure are examined through average excess pore pressure, degree of consolidation, associated settlement, and time factor analyses. An analysis of selected case histories compliments the use of the proposed solutions. Design charts are also presented for practical use.Key words: analytical solution, consolidation, design charts, vertical drains.

scholarly journals EVALUASI SETTLEMENT MENGGUNAKAN SURCHARGE PRELOADING DENGAN PVD PADA PROYEK DI BANDUNG SELATAN

2020 ◽  
Vol 3 (3) ◽  
pp. 911
Author(s):  
Michael Christopher Yapriadi ◽  
Inda Sumarli ◽  
Ali Iskandar
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Improvement ◽  
Soil Layers ◽  
Excess Pore Water Pressure ◽  
Surcharge Preloading ◽  
Improvement Method ◽  
Degree Of Consolidation ◽  
Excess Pore

The development in Indonesia continues to grow. Hence, the feasible land for construction is drastically decreased. However, some projects must be constructed on that kind of land. One solution to solve this problem is by using a soil improvement. A project in Bandung Selatan chose to apply Surcharge Preloading with PVD soil improvement method. This project used a combination of 9,2 metres surcharge preload and a 28 metres depth PVD, with triangular formation and 1,2 metres spacing. The soil improvement was finished after 548 days. This analysis aims to evaluate the settlement from the soil improvement result, which is 1,297 metres. This analysis uses a finite difference method program. The excess pore water pressure from the analysis result is 0,229 T/m2 on the 548th day. Therefore, these soil layers have possibilities to settle again in future. The 90% degree of consolidation settlement for this soil layers is 2,31 metres, which will be reached on the 813,4th days. It is suspected that there are some mistakes either during the soil improvement designing or the soil improvement process. Pembangunan di Indonesia terus berkembang. Akibatnya jumlah tanah yang baik untuk proyek konstruksi semakin menipis. Kendati demikian, ada kalanya suatu proyek harus dilaksanakan di lokasi tersebut. Salah satu solusi yang dapat ditempuh adalah dengan melakukan perbaikan tanah. Sebuah proyek di Bandung Selatan melakukan perbaikan tanah dengan metode Surcharge Preloading dengan PVD. Proyek ini menggunakan kombinasi antara timbunan setinggi 9,2 meter dan PVD sedalam 28 meter, dengan formasi segitiga yang dipasang dengan jarak antar PVD 1,2 meter. Perbaikan tanah dilakukan selama 548 hari. Analisis ini bertujuan melakukan evaluasi terhadap kurang maksimalnya penurunan di lapangan yang hanya mencapai 1,297 meter. Analisis dilakukan dengan bantuan program beda hingga. Berdasarkan hasil analisis, besarnya excess pore water pressure pada hari ke-548 adalah 0,229 T/m,2, sehingga lapisan tanah tersebut masih memiliki potensi untuk mengalami penurunan. Adapun penurunan konsolidasi 90% yang dapat terjadi sebesar 2,31 meter pada hari ke-813,4. Diduga terdapat kesalahan baik dalam perhitungan perencanaan awal ataupun saat pelaksanaan di lapangan.

Analytical solution for radial consolidation considering soil structure characteristics

2015 ◽  
Vol 52 (7) ◽  
pp. 947-960 ◽  
Author(s):  
Cholachat Rujikiatkamjorn ◽  
Buddhima Indraratna
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Vertical Drains ◽  
South Wales ◽  
Surcharge Load ◽  
Speed Up ◽  
Soil Compressibility ◽  
Conventional Models

A system of surcharge load combined with vertical drains to speed up consolidation of soft soil by reducing the drainage path is one of the most efficient and economical ground improvement techniques. In the field, conventional theories including smear zone have been commonly employed to predict the radial consolidation behaviour induced by vertical drains in soft clay. One of the key parameters in conventional analysis is the use of mean coefficient of volume compressibility and soil permeability, which are often assumed to be constant. The effect of drain installation on the soil compressibility of the in situ clay structure is often ignored. Laboratory testing has shown that the soil compressibility and permeability can vary nonlinearly over a considerable range of applied surcharge pressure, and both these properties can be affected during the drain installation. This study presents a mathematical model of radial consolidation via vertical drains incorporating the variations of soil compressibility and permeability as well as highlighting the effects of drain installation on those parameters. The main differences between the proposed and conventional models are elucidated, in terms of stress history and preloading (surcharge) pressure. The effects of preconsolidation pressure and the magnitude of applied preloading are examined through the dissipation of average excess pore pressure and associated settlement. Supported by experimental observations, the proposed theory is validated with field data of a selected case study in the town of Ballina, New South Wales, Australia.

Probabilistic analysis of consolidation with prefabricated vertical drains for soil improvement

1998 ◽  
Vol 35 (4) ◽  
pp. 666-667 ◽  
Author(s):  
H P Hong ◽  
J Q Shang
Keyword(s):  
Soil Improvement ◽  
Uncertain Parameter ◽  
Uncertain Parameters ◽  
Coefficient Of Consolidation ◽  
Consolidation Process ◽  
Expected Cost ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Drain Spacing ◽  
Degree Of Consolidation

Prefabricated vertical drains are often used to accelerate the consolidation and to gain strength in soft clayey soils. The consolidation process depends on several uncertain parameters including the coefficients of consolidation and coefficients of permeability in vertical and horizontal directions and the discharge capacity of the vertical drains. A sensitivity analysis of the degree of consolidation to these uncertain parameters is presented for clayey deposits. Results of the analysis suggest that the most important uncertain parameter that affects the consolidation process is the horizontal coefficient of consolidation. The implication of this uncertain parameter in the design of prefabricated vertical drains for soil improvement is discussed. Two approaches are proposed for selecting drain spacing employing a design value of the horizontal coefficient of consolidation. One of the approaches is probability based and the other is minimum expected cost based.Key words: consolidation, prefabricated vertical drains, drain spacing, probability, expected cost, optimal design.

scholarly journals Numerical Investigation to the Effect of Suction-Induced Seepage on the Settlement in the Underwater Vacuum Preloading with Prefabricated Vertical Drains

2021 ◽  
Vol 9 (8) ◽  
pp. 797
Author(s):  
Shu Lin ◽  
Dengfeng Fu ◽  
Zefeng Zhou ◽  
Yue Yan ◽  
Shuwang Yan
Keyword(s):  
Practical Implication ◽  
Soil Surface ◽  
Small Strain ◽  
Seepage Flow ◽  
Excess Pore Pressure ◽  
Combined Effects ◽  
Vacuum Preloading ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
The Difference

Vacuum preloading combined with prefabricated vertical drains (PVDs) has the potential to improve the soft sediments under water, however, its development is partly limited by the unclear understanding of the mechanism. This paper aims to extend the comprehension of the influential mechanism of overlapping water in the scenario of underwater vacuum preloading with PVDs. The systematic investigations were conducted by small strain finite element drained analyses, with the separated analysis schemes considering suction-induced consolidation, seepage and their combination. The development of settlement in the improved soil region and the evolution of seepage flow from the overlapping water through the non-improved soil region into improved zone are examined in terms of the build-up of excess pore pressure. Based on the results of numerical analyses, a theoretical approach was set out. It was capable to estimate the time-dependent non-uniform settlement along the improved soil surface in response to the combined effects of suction-induced consolidation and seepage. The difference of underwater and onshore vacuum preloading with PVDs is discussed with some practical implication and suggestion provided.

Characterization of a smear zone around vertical drains by large-scale laboratory tests

2000 ◽  
Vol 37 (6) ◽  
pp. 1265-1271 ◽  
Author(s):  
J S Sharma ◽  
D Xiao
Keyword(s):  
Large Scale ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Laboratory Model ◽  
Clay Layer ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Undisturbed Samples ◽  
Oedometer Tests ◽  
Excess Pore

Installation of prefabricated vertical drains using a mandrel causes disturbance of clay surrounding the drain, resulting in a "smear" zone of reduced permeability. In this paper, an attempt is made to characterize the smear zone using large-scale laboratory model tests. Two tests, simulating the cases of "no smear" and "with smear," were conducted. Excess pore-water pressures were monitored at seven different locations along the radial direction. In addition, undisturbed samples were collected at various locations in the clay layer for conducting oedometer tests. The distribution of excess pore pressure due to drain installation gave a clear indication of the extent of the smear zone. The effect of reconsolidation on the properties of clay was found to be much greater than that of the remoulding of the clay. The extent of the smear zone was also confirmed from the change in permeability of the clay layer in the smear zone obtained from oedometer tests. The radius of the smear zone is about four times that of the mandrel, and the horizontal permeability of the clay layer in the smear zone is approximately 1.3 times smaller than that in the intact zone.Key words: consolidation, permeability, smear zone, soft clay, vertical drains.

scholarly journals An educational software for teaching soil consolidation

2017 ◽  
Author(s):  
Gonzalo García Ros ◽  
Manuel Cánovas Vidal ◽  
Juan Francisco Sánchez Pérez ◽  
Iván Alhama Manteca
Keyword(s):  
Educational Software ◽  
Low Cost ◽  
Surface Settlement ◽  
Excess Pore Pressure ◽  
Soil Consolidation ◽  
Depth Of Penetration ◽  
Consolidation Process ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Graphical Environment

The educational tool SICOMED_3D has been created to simulate problems of soil consolidation by prefabricated vertical drains. Thanks to its nice interface of windows, the introduction of data is very fast and easy for the students, while providing users with simple handling and powerful calculations. Its graphical environment allows to get representations of the excess pore pressure, local settlements and total surface settlement. SICOMED_3D can also generate an animation that recreates the evolution of the surface settlement during the consolidation process. The software presents, like commercial softwares, the most common options (e.g., save and open cases files, save animations and representations, etc.). Although the program is created to be used in several fields, among others as an engineering or research tool, the main use of interest for this work is for educational purposes. Another important application is as low-cost laboratory practices, as students can experiment by modifying the soil properties, including the depth of penetration of the vertical drain, in a quick, simple and intuitive way.

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