Geosynthetic Encased Column: comparison between numerical and experimental results

2021 ◽  
Vol 44 (4) ◽  
pp. 1-12
Author(s):  
Nima Alkhorshid ◽  
Gregório Araújo ◽  
Ennio Palmeira
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Experimental Tests ◽  
High Permeability ◽  
Soft Soils ◽  
Column Comparison ◽  
Surrounding Soil ◽  
Granular Column

The use of granular column is one of the ground improvement methods used for soft soils. This method improves the foundation soils mechanical properties by displacing the soft soil with the compacted granular columns. The columns have high permeability that can accelerate the excess pore water pressure produced in soft soils and increase the undrained shear strength. When it comes to very soft soils, the use of granular columns is not of interest since these soils present no significant confinement to the columns. Here comes the encased columns that receive the confinement from the encasement materials. In this study, the influence of the column installation method on the surrounding soil and the encasement effect on the granular column performance were investigated using numerical analyses and experimental tests. The results show that numerical simulations can reasonably predict the behavior of both the encased column and the surrounding soil.

scholarly journals Perbandingan Pengujian Konsolidasi Menggunakan Alat Rowe Cell dan Oedometer pada Tanah Lanau Lunak

2020 ◽  
Vol 22 (2) ◽  
pp. 149-155
Author(s):  
Iskandar ◽  
Rabiya
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soil Samples ◽  
Soil Parameters ◽  
Soil Consolidation ◽  
Test Results ◽  
Soft Soils ◽  
Better Than ◽  
Rowe Cell

Soil consolidation testing using an oedometer and rowe cell. Oedometers are often used on clay and soft soils. However, in the development of the rowe cell device, the results of lowering soft soil were better than the oedometer. The advantage of this rowe cell is that it can determine the saturation value of the soil samples tested. The rowe cell tester can measure the pore water pressure at the beginning and end of each consolidation stage. This rowe cell can provide suitable settlement for soft soils. This consolidation test to obtain soil parameters such as Cv and Cc by using the rowe cell tool. After that, from the test results, the two tools were compared.

Study on Artificial Island Ground Improvement Method and Effect

2014 ◽  
Vol 1030-1032 ◽  
pp. 1037-1040
Author(s):  
Jin Fang Hou ◽  
Ju Chen ◽  
Jian Yu
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Treatment Method ◽  
Surcharge Preloading ◽  
Porosity Ratio ◽  
Improvement Method ◽  
Consolidation Degree

The artificial island ground on an open sea is covered by thick soft soil. It must be improved before using. In accordance with a designing scheme, the ground treatment method is inserting drain boards on land and jointed dewatering surcharge preloading, the residual settlement is not more than 30cm after improvement and the average consolidation degree is more than 85%. In order to estimate ground improvement effect and construction safety, instruments are buried to monitor the whole ground improving processes. By monitoring settlement and pore water pressure, it is shown that the total ground settlement in construction is 2234mm, its final settlement is 2464mm, and consolidation degree and residual settlement respectively satisfy requirements. In ground improvement, horizontal displacement is small and construction is safe. Meanwhile, the results of soil properties and vane shear strength detection tests show the soft soil ground is greatly reduced in water content and porosity ratio, and improved in strength. It is named that the ground improvement method is reasonable and reaches expected effect.

Consolidation Theory for Composite Ground with Granular Columns Based on Different Calculation Models

2011 ◽  
Vol 261-263 ◽  
pp. 1534-1538
Author(s):  
Yu Guo Zhang ◽  
Ya Dong Bian ◽  
Kang He Xie
Keyword(s):  
Pore Water ◽  
Analytical Solutions ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Vertical Flow ◽  
Excess Pore Water Pressure ◽  
Consolidation Theory ◽  
Composite Ground ◽  
Granular Column ◽  
Excess Pore

The consolidation of the composite ground under non-uniformly distributed initial excess pore water pressure along depth was studied in two models which respectively considering both the radial and vertical flows in granular column and the vertical flow only in granular column, and the corresponding analytical solutions of the two models were presented and compared with each other. It shows that the distribution of initial excess pore water pressure has obvious influence on the consolidation of the composite ground with single drainage boundary, and the rate of consolidation considering the radial-vertical flow in granular column is faster than that considering the vertical flow only in granular column.

scholarly journals Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qizhi Hu ◽  
Qiang Zou ◽  
Zhigang Ding ◽  
Zhaodong Xu
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Confining Pressure ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Excess Pore Water Pressure ◽  
Accurate Expression ◽  
Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

scholarly journals Experiment Study of Lateral Unloading Stress Path and Excess Pore Water Pressure on Creep Behavior of Soft Soil

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Wei Huang ◽  
Kejun Wen ◽  
Dongsheng Li ◽  
Xiaojia Deng ◽  
Lin Li ◽  
...  
Keyword(s):  
Pore Water ◽  
Creep Behavior ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Stress Path ◽  
Deviatoric Stress ◽  
Excess Pore Water Pressure ◽  
Pore Water Pressures ◽  
Excess Pore

The unloading creep behavior of soft soil under lateral unloading stress path and excess pore water pressure is the core problem of time-dependent analysis of surrounding rock deformation under excavation of soft soil. The soft soil in Shenzhen, China, was selected in this study. The triaxial unloading creep tests of soft soil under different initial excess pore water pressures (0, 20, 40, and 60 kPa) were conducted with the K0 consolidation and lateral unloading stress paths. The results show that the unloading creep of soft soil was divided into three stages: attenuation creep, constant velocity creep, and accelerated creep. The duration of creep failure is approximately 5 to 30 mins. The unloading creep behavior of soft soil is significantly affected by the deviatoric stress and time. The nonlinearity of unloading creep of soft soil is gradually enhanced with the increase of the deviatoric stress and time. The initial excess pore water pressure has an obvious weakening effect on the unloading creep of soft soil. Under the same deviatoric stress, the unloading creep of soft soil is more significant with the increase of initial excess pore water pressure. Under undrained conditions, the excess pore water pressure generally decreases during the lateral unloading process and drops sharply at the moment of unloading creep damage. The pore water pressure coefficients during the unloading process were 0.73–1.16, 0.26–1.08, and 0.35–0.96, respectively, corresponding to the initial excess pore water pressures of 20, 40, and 60 kPa.

scholarly journals Influence of Soil Structure on the Mechanical Response of Soft Soil

2018 ◽  
Vol 38 ◽  
pp. 03027
Author(s):  
Bin Bin Xu
Keyword(s):  
Yield Stress ◽  
Pore Water ◽  
Soil Structure ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Before And After ◽  
Strain Relationship ◽  
Consolidation Behavior

Usually the natural sedimentary soils possess structure more or less, which makes their mechanical response much different from the fully remolded soils. In this paper, the influence of soil structure on the mechanical response such as compressibility, shear, permeability is literately reviewed. It is found that the compressibility and consolidation behavior of structured and remolded soils can be divided clearly before or after the structural yield stress. The stress-strain relationship can be divided into two segments before and after the structural yield stress. Before the yield stress, the curve is elevating and after the yield stress the curve is decreasing. The increasing rate of pore water pressure increases after the soil reached yield stress.

scholarly journals Numerical Modelling of Prefabricated Vertical Drain for Soft Clay Using ABAQUS

2015 ◽  
Vol 773-774 ◽  
pp. 1502-1507
Author(s):  
Saiful Azhar Ahmad Tajudin ◽  
Mohd Fairus Yusof ◽  
I. Bakar ◽  
Aminaton Marto ◽  
Muhammad Nizam Zakaria ◽  
...  
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Soft Clay ◽  
Elastic Model ◽  
Clay Layer ◽  
Soil Consolidation ◽  
Consolidation Process ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain

Construction, buildings and infrastructure founded on soft clays are often affected by settlement problem. Therefore, Prefabricated Vertical Drain (PVD) is one of the best solutions to accelerate soil consolidation by shortening the drainage path. In this study, numerical investigation was carried out to pursue a better understanding of the consolidation behavior of soft clay improved with PVD. The consolidation process accelerated by PVD with surcharge of 50 kPa was analysed using the ABAQUS software by adopting an elastic model. The aim of this study is to compare the settlement and the required time to fully consolidate the soft soil at different drain spacings (1.0 m, 1.5 m and 2.0 m) for two different thickness of the clay layer. The results shows that the time required to completely consolidate the soft soil for 12 m and 20 m thickness of clay layer with different spacings are in the range of 3 months to 66 months. The settlement rate and excess pore water pressure dissipation are increased when the spacing of the drain closer.

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 Constitutive Model of Lateral Unloading Creep of Soft Soil under Excess Pore Water Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wei Huang ◽  
Kejun Wen ◽  
Xiaojia Deng ◽  
Junjie Li ◽  
Zhijian Jiang ◽  
...  
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Creep Model ◽  
Creep Tests ◽  
Excess Pore Water Pressure ◽  
Model Research ◽  
Creep Time ◽  
Excess Pore

Presented in this paper is a study on the lateral unloading creep tests under different excess pore water pressures. The marine sedimentary soft soil in Shenzhen, China, was selected in this study. The results show that the excess pore water pressure plays a significant role in enhancing the unloading creep of soft soil. Higher excess pore water pressure brings more obvious creep deformation of soft soil and lower ultimate failure load. Meanwhile, the viscoelastic and the viscoplastic modulus of soft soil were found to exponentially decline with creep time. A modified merchant model and a combined model of the modified merchant model and plastic elements are used to simulate the viscoelastic and the viscoplastic deformation, respectively. Therefore, a lateral unloading creep model of soft soil is developed based on the modified merchant model. The accuracy and applicability of this model were verified through identifying the parameters in the model. Research results are of particular significance to the numerical simulation of underground space excavation in soft soil areas which considers the effects of excess pore water pressure.

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.

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