scholarly journals Numerical Analysis of Staged Construction of an Embankment on Soft Soil

2021 ◽  
Author(s):  
Ayesha Binta Ali ◽  
Mehedi Ahmed Ansary
Keyword(s):  
Finite Element ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Soft Soil ◽  
Excess Pore Pressure ◽  
Element Analysis ◽  
Staged Construction ◽  
Modeling Software ◽  
Degree Of Consolidation ◽  
Excess Pore

Abstract The objective of this study was to predict the excess pore pressure and settlement of an embankment over soft ground, treated with vertical drain, through numerical analysis of staged construction. To carry out finite element analysis, numerical modeling software PLAXIS 3D was used. The practical demonstration was demonstrated by validating two case studies; the first one was a trial embankment at the Krishnapatnam Ultra Mega Power Project in Nellore, Andhra Pradesh, India and the second one was the Second Bangkok International Airport or Suvarnabhumi Airport, about 30 km from the city of Bangkok, Thailand. After the successful validation of the program, detailed finite element modelling of an embankment resting on soft soil was conducted. Moreover, the degree of consolidation and factor of safety were also determined. There was rapid dissipation of excess pore pressure and maximum settlement at the mid-height of the embankment. In contrast, the dissipation of excess pore pressure was very slow just below the embankment and it increased with the increment of the depth of the clay layer. Moreover, with the rise of the distance from the centre of the embankment, the dissipation of the excess pore pressure also raised and took less time, the settlement also increased.

Numerical Analysis for Excess Pore Pressure Dissipation Process for Pressed Pile Installation

2013 ◽  
Vol 405-408 ◽  
pp. 133-137
Author(s):  
Tai Quan Zhou ◽  
Feng Tan ◽  
Cheng Li
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Excess Pore Pressure ◽  
Soil Behavior ◽  
Element Analysis ◽  
Dissipation Process ◽  
Pile Installation ◽  
Finite Element Software ◽  
Modified Cam Clay ◽  
Excess Pore

The finite element analysis is performed on the excess pore pressure dissipation for pressed pile installation using the ABAQUS finite element software. The modified Cam-Clay model is used to model the soil behavior. The finite slide contact model is used to model the pressed pile installation process. Based on the geology stratum of soils and drainage conditions, the excess pore pressure dissipation process is analyzed using the proposed method. The initial excess pore pressure distribution along the pile depth and the pile radius direction is obtained. The excess pore pressure dissipation after 98 days is analyzed.

Effective-Stress Finite Element Analysis of Spudcan Penetration

2012 ◽  
Author(s):  
Jiang Tao Yi ◽  
Fook Hou Lee ◽  
Siang Huat Goh ◽  
Yu Ping Li ◽  
Xi Ying Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Analysis ◽  
Pore Pressure ◽  
Effective Stress ◽  
Excess Pore Pressure ◽  
Element Analysis ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore

The numerical modeling of spudcan penetration involves technical challenges posed by large soil deformation coupled with significant material non-linearity. The Lagrangian approach commonly used for solid stress analysis often does not work well with large deformations, resulting in premature termination of the analysis. Recently, the Arbitrary Langrangian Eulerian (ALE) and the Eulerian methods have been used in spudcan analysis to overcome problems caused by the soil flow and large deformation. However, most of the reported studies are based on total stress analysis and therefore shed no light on the excess pore pressures generated during spudcan installation. As a result, much remains unknown about the long-term behaviour of spudcans in the ground, which is affected by the dissipation of excess pore pressures. This paper reports an effective-stress finite element analysis of spudcan installation in an over-consolidated (OC) soft clay. The Eulerian analysis was conducted using ABAQUS/ Explicit, with the effective stress constitutive models coded via the material subroutine VUMAT. The results demonstrated the feasibility of conducting effective-stress finite element analysis for undrained spudcan penetration in OC clays. The paper discusses the flow mechanism, stable cavity depths and bearing capacity factors when spudcan installation occurs in various OC soils. It was found that the pore pressure build-up concentrates in a bulb-shaped zone surrounding the spudcan. The size of the pore pressure bulb increases with increasing penetration. The maximum excess pore pressure, which is generated near the spudcan tip, is predominantly controlled by the undrained shear strength at the tip level.

Eulerian finite element analysis of excess pore pressure generated by spudcan installation into soft clay

2012 ◽  
Vol 42 ◽  
pp. 157-170 ◽  
Author(s):  
Jiang Tao Yi ◽  
Fook Hou Lee ◽  
Siang Huat Goh ◽  
Xi Ying Zhang ◽  
Jer-Fang Wu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Pore Pressure ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Element Analysis ◽  
Excess Pore

Behaviour of geosynthetic reinforced column supported embankments

2018 ◽  
Vol 16 (1) ◽  
pp. 44-62 ◽  
Author(s):  
Namal Yapage ◽  
Samanthika Liyanapathirana
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Dissipation Rate ◽  
Load Transfer ◽  
Soft Soil ◽  
Excess Pore Pressure ◽  
Content Type ◽  
Load Transfer Mechanism ◽  
Excess Pore

Purpose This paper aims to investigate the behaviour of geosynthetic reinforced deep cement mixed (DCM) column-supported embankments constructed over soft soils. Design/methodology/approach Coupled consolidation analyses based on the finite element method are carried out assuming that the soil and DCM columns are fully saturated porous mediums. In the first part of the paper, a case study of an embankment constructed over a very soft soil deposit in Finland is presented. Two- and three-dimensional finite element models for the case study are developed including isolated and attached DCM columns beneath the embankment to capture the arching mechanism between DCM columns. The model simulations were carried out considering the actual staged construction procedure adopted in the field. Finite element predictions show good agreement with field data and confirm that the load transfer is mainly between attached columns beneath the embankment. Next, the significance of geosynthetic reinforcement on the load transfer mechanism is investigated. Finally, the influence of permeability of columns and soft soil on the performance of geosynthetic reinforcement column-supported embankments is studied. Findings Results demonstrate that the excess pore pressure dissipation rate is fast in DCM column-improved ground compared to the same case without any columns, although the same permeability is assigned to both DCM columns and surrounding soft soil. When DCM column permeability exceeds soil permeability, excess pore pressure dissipation rate shows a remarkable increase compared to that observed when the DCM column permeability is less than or equal to the permeability of surrounding soft soil. [ ] Originality/value This paper investigates the contribution of permeability and geosynthetic layer on the vertical load transfer mechanism of the embankment and modelling issues related to application of the embankment load and the properties of the cement-improved columns.

Vibro-Stone Column Reinforcement Mechanism and Numerical Analysis

2012 ◽  
Vol 446-449 ◽  
pp. 1940-1943
Author(s):  
Yang Liu ◽  
Hong Xiang Yan
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Pore Pressure ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Excess Pore Pressure ◽  
Stone Column ◽  
Reinforcement Mechanism ◽  
Consolidation Theory ◽  
Excess Pore

Numerical simulation of vibro-stone column is taken to simulate the installation of vibro-stone column. A relationship based on test is adopted to calculate the excess pore pressure induced by vibratory energy during the installation of vibro-stone column. A numerical procedure is developed based on the formula and Terzaghi-Renduric consolidation theory. Finally numerical results of composite stone column are compared single stone column.

The Effects of Geosynthetic-Reinforcement on Consolidation Behavior of Soft Clay Embankment under Step Construction

2018 ◽  
Vol 783 ◽  
pp. 46-50
Author(s):  
Yu Cong Gao ◽  
Rong Chen ◽  
Dong Xue Hao ◽  
Myoung Soo Won
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pore Pressure ◽  
Clay Soil ◽  
Clayey Soil ◽  
Soft Clay ◽  
Excess Pore Pressure ◽  
Calculation Results ◽  
Consolidation Behavior ◽  
Excess Pore

Geosynthetics–reinforced structures are widely used in embankments and walls. This paper presents the simulation of the embankment under load in order to compare the behavior of clay embankment with and without wrapping-facing-geosynthetics-reinforcement using finite element method (FEM) and to analyse the variation of behavior included of displacement and excess pore pressure under the different over-consolidation ratios (OCR). The calculation results show that embankment with higher OCR showing lower displacement compare to embankment with lower OCR. However, OCR isn’t very sensitive to the dissipation of excess pore pressure. Geosynthetics-reinforcements could reduce the displacement of embankment and accelerate dissipation of excess pore pressure after construction and surcharge. Gravel, geosynthetics-reinforcement and clay soil are properly combined, clayey soil is expected to be useful as embankment material.

Liquefaction potential of silts from CPTu

2007 ◽  
Vol 44 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Dawn A Shuttle ◽  
John Cunning
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Earthquake Engineering ◽  
Critical State ◽  
Pressure Ratio ◽  
Excess Pore Pressure ◽  
Liquefaction Potential ◽  
Triaxial Cell ◽  
Excess Pore

Silt tailings (slimes) are difficult materials to test in that, like sands, it is extremely difficult to obtain undisturbed samples and subsequently re-establish them in a triaxial cell for element testing in a laboratory in anything approaching their in situ condition. Evaluation of silt tailing behaviour has to depend on in situ tests, and the piezocone (CPTu) in particular. However, CPTs in silt generate substantial excess pore pressure and there is no established methodology to evaluate the measured responses in terms of soil properties, as drained sand-based CPT interpretation is inapplicable. A case history of particularly loose silt tailings is reported in which the National Center for Earthquake Engineering Research (NCEER) liquefaction assessment method would lead to uncertainty in the liquefaction potential. However, the extremely high CPTu excess pore pressure ratio, Bq, and low dimensionless CPT resistance, Qp, at this site indicates liquefaction is likely occurring during pushing of the CPT. Detailed finite element simulations of the CPT using a critical state model provided an effective stress framework to evaluate the in situ state parameter of the silt from the measured CPT data. This framework shows that the group of dimensionless CPT variables Q(1 – Bq) + 1 is fundamental for the evaluation of undrained response during CPT sounding. And, despite the high silt content, the interpretation indicates that the tailings are indeed liquefiable.Key words: liquefaction, CPT, silt, finite element, critical state.

Effect of Geotextile and Prefabricated Vertical Drains Used in Soft Soil Foundation

2011 ◽  
Vol 197-198 ◽  
pp. 981-986
Author(s):  
Jie Qun Liu ◽  
Jin Long Liu
Keyword(s):  
Pore Pressure ◽  
Lateral Displacement ◽  
Soft Soil ◽  
Excess Pore Pressure ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Lateral Displacements ◽  
Soil Foundation ◽  
Soft Soil Foundation ◽  
Excess Pore

Based on the generalized formulation of two dimensional Biot′s theory of consolidation, the effect of geotextile and prefabricated vertical drains (PVDs) using in soft soil foundation was studied with nonlinear finite element method. The dissipation of excess pore pressure, vertical settlement and lateral displacement of foundation were contrasted between foundations with and without PVDs. It is found that the vertical settlements become lager, the lateral displacements become less and the bulges at the toe of embankment become less at the same time of consolidation when PVDs are used. And the stability of embankment improved for the bearing capacity of soil enhanced with excess pore pressure dissipated fast. Meanwhile, the axial force of geotextile become less when PVDs are used. Those changes showed that the design of foundation can be optimized by shortening the time of consolidation when PVDs are used.

Finite Element Analysis for Subgrade Consolidation Settlement in Soft Soil

2013 ◽  
Vol 448-453 ◽  
pp. 1256-1259
Author(s):  
Feng Tan ◽  
Tai Quan Zhou
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Soil Depth ◽  
Water Pressure ◽  
Soft Soil ◽  
Excess Pore Pressure ◽  
Excess Pore Water Pressure ◽  
Consolidation Settlement ◽  
Excess Pore

The two-dimensional finite element model for subgrade consolidation settlement analysis within soft soil pile is developed using ABAQUS. The numerical simulation on a highway subgrade deformation is performed to study the variation of consolidation settlement and the excess pore water pressure distribution in the central location and the part under centerline of the embankment. The results show that settlement develops gradually with the increasing period of soil consolidation. The excess pore water pressure of deep subgrade soils under embankment centerline rise due to the increased load. After each soil layer was filled, the excess pore water pressure increased in the first and was stable later along with the increase of soil depth. After the embankment soil was filled completely, excess pore pressure dissipated with time developing until the completion of consolidation.

Consolidation of a soil layer subsequent to cessation of deposition

2005 ◽  
Vol 42 (2) ◽  
pp. 678-682
Author(s):  
Guofu Zhu ◽  
Jian-Hua Yin
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Average Degree ◽  
Excess Pore Pressure ◽  
Triangular Distribution ◽  
Pressure Distributions ◽  
Pore Pressures ◽  
Degree Of Consolidation ◽  
Excess Pore Pressures ◽  
Excess Pore

It is necessary in certain cases to estimate the progress of consolidation in a soil layer that has ceased increasing in thickness over time. In this paper, the existing excess pore pressures for two time–thickness relations are used as the "initial" pore pressures for analysing the consolidation of soil subsequent to the cessation of deposition. Average degrees of consolidation of the soil layer are presented for one-way drainage and two-way drainage boundary conditions. The average degrees of consolidation are compared with those for uniform and triangular initial excess pore pressure distributions. It is found that the average degree of consolidation for one-way drainage boundaries can be estimated using the value for the triangular distribution. The average degree of consolidation for two-way drainage boundaries is bound by the averages for both the uniform and the triangular initial excess pore pressure distributions.Key words: consolidation, deposition, drainage, settlement, soil.

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