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.

scholarly journals Comparison of Coupled and Uncoupled Consolidation Equations Using Finite Element Method in Plane-Strain Condition

2016 ◽  
Vol 2 (8) ◽  
pp. 375-388 ◽  
Author(s):  
Mohamadtaqi Baqersad ◽  
Abbas Eslami Haghighat ◽  
Mohammadali Rowshanzamir ◽  
Hamid Mortazavi Bak
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Pore Pressure ◽  
Effective Stress ◽  
Excess Pore Pressure ◽  
Soil Deformation ◽  
Soil Consolidation ◽  
Time Step ◽  
Excess Pore ◽  
Element Method

In the current paper, the consolidation settlement of a strip footing over a finite layer of saturated soil has been studied using the finite element method. In Biot’s coupled consolidation equations, the soil deformation and excess pore pressure are determined simultaneously in every time step which refers to the hydro-mechanical coupling. By considering a constant total stress throughout the time and by assuming that volume strain is a function of isotropic effective stress, uncoupled consolidation equations can be obtained using coupled consolidation equations. In these uncoupled equations, excess pore pressure and deformation are determined separately. In this approach, the excess pore pressure can be identified in the first stage. Using the calculated excess pore pressure, the soil deformation is determined through effective stress-strain analyses. A computer code was developed based on coupled and uncoupled equations that are capable of performing consolidation analyses. To verify the accuracy of these analyses, the obtained results have been compared with the precise solution of Terzaghi’s one-dimensional consolidation theory. The capability of these two approaches in estimation of pore water pressure and settlement and to show Mandel-Crayer’s effect in soil consolidation is discussed. Then, the necessity of utilizing coupled analyses for evaluating soil consolidation analysis was investigated by comparing the coupled and uncoupled analyses results.

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

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.

Excess Pore Pressure Dissipation Characteristics of Different Soil by CPTU on Pearl River Delta

2011 ◽  
Vol 71-78 ◽  
pp. 4606-4609
Author(s):  
Yan Chun Tang ◽  
Gao Tou Meng
Keyword(s):  
Pore Pressure ◽  
Pearl River Delta ◽  
Clay Soil ◽  
Soil Layer ◽  
River Delta ◽  
Excess Pore Pressure ◽  
Pearl River ◽  
Silty Clay ◽  
Sand Soil ◽  
Excess Pore

Through a lot of CPTU excess pore pressure dissipation tests on Pearl River Delta in China, excess pore pressure dissipation characteristics of different soil layer on Guangzhou-Zhuhai section of Beijing-Zhuhai Expressway and Taishan section of Guangdong West Coast Expressway has been analyzed. The dissipation time of 50% dissipation degree t50 of excess pore pressure dissipation curve by CPTU can be used as the auxiliary method to determine the type of soil, and through CPTU excess pore pressure dissipation tests, the t50 value of sand soil, silt, silty clay, clay soil and silt soil has been obtained; through comparison with the t50 value of different soil, the difference of sand soil, silt and clay soil can be roughly distinguished; the obvious boundary value between the t50 value of clay soil, silty clay and silt soil is not existed, so the t50 value can not be direct to determine the type of these clay type of soil. The achieved results can provide a research foundation for CPTU application research on Pearl River Delta in China.

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.

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.

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.

Study on Variation Rule of Pore Pressure on CPTU Model Test

2010 ◽  
Vol 160-162 ◽  
pp. 544-549
Author(s):  
Yan Chun Tang ◽  
Gao Tou Meng
Keyword(s):  
Pore Pressure ◽  
Clay Soil ◽  
Excess Pore Pressure ◽  
Horizontal Distance ◽  
Penetration Test ◽  
Piezocone Penetration Test ◽  
Saturated Clay ◽  
Short Time ◽  
Variation Rule ◽  
Excess Pore

Through a series of Piezocone Penetration Test (CPTU) model tests with saturated clay soil, excess pore pressure produced by CPTU penetrating and dissipating has been measured by CPTU probe and pore pressure mini-transducers, the variation rules of excess pore pressure has been analyzed, the results show that at the same transducers layer, the value of initial excess pore pressure at the probe is biggest, and with the horizontal distance from probe increasing, the value of initial excess pore pressure measured by transducers around the probe has been decreased quickly; at the same dissipating process, the value of initial excess pore pressure measured by transducers locating in the same horizontal plane with probe is bigger than the value by transducers of the other layer; difference between the variation rule of excess pore pressure dissipation measured by CPTU probe and pore pressure mini-transducers is that after the value of excess pore pressure is maximum, with the dissipating time increasing, the value of excess pore pressure measured by probe decreased rapidly, but at first the value of excess pore pressure measured by transducers decreased slowly and then after a short time decreased rapidly; the time of 90% of the maximum of excess pore pressure dissipating measured by CPTU probe is longer than the time of 90% of the maximum of excess pore pressure dissipating measured by transducers; at the same transducers layer, with horizontal distance from the probe increasing, the time of 90% of the maximum of excess pore pressure dissipating decreased. The achieved result can provide a foundation for further study for CPTU mechanism.

Sign in / Sign up

Export Citation Format

Share Document