Investigating performance of micropiled raft in foundation of power transmission line towers in cohesive soil: experimental and numerical study

2018 ◽  
Vol 55 (3) ◽  
pp. 312-328 ◽  
Author(s):  
Ali-Asghar Zekavati ◽  
Alireza Khodaverdian ◽  
Mohammad-Ali Jafari ◽  
Ahmad Hosseini
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Transmission Line ◽  
Power Transmission ◽  
Cohesive Soil ◽  
Undrained Shear Strength ◽  
Sensitivity Analyses ◽  
Power Transmission Line ◽  
Efficiency Coefficient ◽  
Undrained Shear

This paper captures the behavior of micropiled rafts in power transmission line tower foundations in cohesive soil, concentrating on their uplift performance whether due to the tower position along the line or under wind loading conditions. In this regard, first a number of micropiles were driven into the ground of a project site at the ParehSar power plant, Gilan, Iran. Compression and uplift loading tests were conducted according to relevant standards. On the basis of the field data, a three-dimensional finite element model was developed and subsequently calibrated and verified. The behavior of micropiled rafts subjected to uplift, which is a typical type of loading in foundations of 230 kV four-circuit lattice towers, was then studied by means of this model in terms of a wide-ranging parametric study. In the sensitivity analyses, the impacts of various parameters, such as micropile spacing-to-diameter (s/d) and length-to-diameter (l/d) ratios along with undrained shear strength of the soil, on the uplift capacity of an individual micropile within and out of the group were investigated. Furthermore, interaction factors were computed based on diverse values for undrained shear strength of the soil, s/d ratio, l/d ratio, and grout–soil adhesion. From design and analysis perspectives, the finite element method (FEM) outputs revealed that the efficiency coefficient of micropiled rafts during uplift can be considered equal to one. Moreover, it was found that not only does the behavior of micropiles affect the neighboring micropiles immediately adjacent to the loaded one, but it also influences those in further rows, the result of which would be considering their significance as well.

Finite element modeling of partially embedded pipelines in clay seabed using Coupled Eulerian–Lagrangian method

2015 ◽  
Vol 52 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Sujan Dutta ◽  
Bipul Hawlader ◽  
Ryan Phillips
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Strain Rate ◽  
Deep Water ◽  
Strain Softening ◽  
Mesh Size ◽  
Undrained Shear Strength ◽  
Band Formation ◽  
Offshore Pipelines ◽  
Undrained Shear

Vertical seabed penetration and lateral movement of deep-water offshore pipelines are simulated using the Coupled Eulerian–Lagrangian (CEL) approach in Abaqus finite element (FE) software. Abaqus CEL has been used in some previous studies to simulate large-deformation behavior of offshore pipelines; however, the effects of strain rate and strain-softening on undrained shear strength (su) have not been considered. In this study, the effects of these factors are critically examined. The available built-in models in Abaqus CEL cannot account for these factors directly, especially the strain rate; therefore, the development of user subroutines is required. In the present study, a simple but realistic soil constitutive model (published by Zhou and Randolph in 2007) that considers the effects of strain rate and strain-softening on su is implemented in Abaqus CEL. The effects of FE mesh size and shear band formation on penetration resistance are discussed based on a comprehensive FE simulation. Lateral analyses are performed for “light” and “heavy” pipes in clay seabed having a linearly increasing undrained shear strength profile for smooth and rough pipe–soil interface conditions. The FE results are compared with previous theoretical, numerical, and centrifuge test results. Based on the present FE analyses, it is shown that, similar to the remeshing and interpolation techniques with small strain (RITSS) technique developed at the The University of Western Australia, the Abaqus CEL can successfully simulate the response of partially embedded pipelines in deep-water clay seabed, provided strain rate and softening dependent clay models are implemented. A methodology to implement such a model using Abaqus user subroutine is also presented.

Strain Softening and Rate Effects on Soil Shear Strength in Modeling of Vertical Penetration of Offshore Pipelines

2012 ◽  
Author(s):  
Sujan Dutta ◽  
Bipul Hawlader ◽  
Ryan Phillips
Keyword(s):  
Finite Element ◽  
Shear Strength ◽  
Strain Softening ◽  
Undrained Shear Strength ◽  
Lateral Movement ◽  
Offshore Pipelines ◽  
Finite Element Software ◽  
Deformation Problem ◽  
Rate Effects ◽  
Undrained Shear

Offshore pipelines play a vital role in the transportation of hydrocarbon. In deep seas, pipelines laid on the seabed usually penetrate into the soil a certain amount. These pipelines might experience significant lateral movement during the operational period. The resistance to lateral movement depends on vertical penetration and berm formation around the pipe. Vertical penetration is a large deformation problem. Finite element modeling of vertical penetration of offshore pipeline in soft clay seabed in deep water is presented in this study. The modeling was performed using ABAQUS finite element software. Soil was modeled in an Eulerian framework and the pipe in a Lagrangian framework. Strain softening behavior and strain rate effects on undrained shear strength of clay was incorporated in ABAQUS FE software using user subroutines written in FORTRAN. The variation of undrained shear strength with depth is also considered. The results are compared with centrifuge test results and also with available solutions.

scholarly journals Influence of the rotation of principal stress directions on undrained shear strength

2013 ◽  
Vol 45 (2) ◽  
pp. 183-192 ◽  
Author(s):  
Grzegorz Wrzesiński ◽  
Zbigniew Lechowicz
Keyword(s):  
Shear Strength ◽  
Principal Stress ◽  
Laboratory Tests ◽  
Cohesive Soil ◽  
Undrained Shear Strength ◽  
Hollow Cylinder Apparatus ◽  
Stress Directions ◽  
Anisotropic Consolidation ◽  
Undrained Conditions ◽  
Undrained Shear

Abstract Influence of the rotation of principal stress directions on undrained shear strength. The paper presents the results of research on natural cohesive soil carried out in the Hollow Cylinder Apparatus (HCA). The main goal of this study was to determine the values of undrained shear strength at different angle of the rotation of principal stress directions. The research were carried out with anisotropic consolidation and shearing in undrained conditions (CAU) on cohesive soil with overconsolidation ratio (OCR) equals 4 and plasticity index (Ip) about 77%. The results of laboratory tests allow to assess the influence of the rotation of principal stress directions on undrained shear strength

scholarly journals Five Mass Power Transmission Line of a Ship Computer Modelling

2016 ◽  
Vol 46 (1) ◽  
pp. 3-16
Author(s):  
Alexander Borisoff Kazakoff ◽  
Boycho Ivanov Marinov
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Transmission Line ◽  
Frequency Domain ◽  
Power Transmission ◽  
Model Parameters ◽  
Power Transmission Line ◽  
Mass Model ◽  
Element Analysis

Abstract The work, presented in this paper, appears to be a natural continuation of the work presented and reported before, on the design of power transmission line of a ship, but with different multi-mass model. Some data from the previous investigations are used as a reference data, mainly from the analytical investigations, for the developed in the previ- ous study, frequency and modal analysis of a five mass model of a power transmission line of a ship. In the paper, a profound dynamic analysis of a concrete five mass dynamic model of the power transmission line of a ship is performed using Finite Element Analysis (FEA), based on the previously recommended model, investigated in the previous research and reported before. Thus, the partially validated by frequency analysis five mass model of a power transmission line of a ship is subjected to dynamic analysis. The objective of the work presented in this paper is dynamic modelling of a five mass transmission line of a ship, partial validation of the model and von Mises stress analysis calculation with the help of Finite Element Analysis (FEA) and comparison of the derived results with the analytically calculated values. The partially validated five mass power transmission line of a ship can be used for definition of many dy- namic parameters, particularly amplitude of displacement, velocity and acceleration, respectively in time and frequency domain. The frequency behaviour of the model parameters is investigated in frequency domain and it corresponds to the predicted one.

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