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Showing 32 results for Pile

Kimiaei M., Shayanfar M.a., Hesham Ei Naggar M., Agha Kouchak A.a.,
Volume 2, Issue 2 (6-2004)
Abstract

The seismic response of pile-supported offshore structures is strongly affected by the nonlinear behavior of the supporting piles. Nonlinear response of piles is the most important source of potentially nonlinear dynamic response of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accountsfor soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural non linear behaviors of piles.In this paper, an attempt is made to develop an inexpensive and practical procedure compatible with readily available structural analysis software for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. In the proposed model a BNWF (Beam on Nonlinear Winkler Foundation) approach is used consisting of simple nonlinear springs, dash pots and contact elements. Gapping and caving-in conditions at the pile-soil interfaces are also considered using special interface elements. This model was incorporated into a Finite Element program (ANSYS), which was used to compute the response of laterally excited piles. A linear approach was used for seismic free field ground motion analysis. The computed responses compared well with the Centrifuge test results.This paper deals with the effects of free field ground motion analysis on seismic non linear behavior of embedded piles. Different parts of a BNWF (Beam on Nonlinear Winkler Foundation) model, together with quantitative and qualitative findings and conclusions for dynamic nonlinear response of offshore piles, are discussed and addressed in detail. The proposed BNWF model (only using the existing features of the available general finite element software) could easily be implemented in a more comprehensive model of nonlinear seismic response analysis of pile supported offshore platforms.
Shahram Feizee Masouleh, Kazem Fakharian,
Volume 6, Issue 3 (9-2008)
Abstract

A finite-difference based continuum numerical model is developed for the pile-soil dynamic response during pile driving. The model is capable of simulating the wave propagation analysis along the pile shaft and through the soil media. The pile-soil media, loading and boundary conditions are such that axisymmetric assumption seems to be an optimized choice to substantially reduce the analysis time and effort. The hydrostatic effect of water is also considered on the effective stresses throughout the soil media and at the pilesoil interface. The developed model is used for signal matching analysis of a well-documented driven pile. The results showed very good agreement with field measurements. It is found that the effect of radiation damping significantly changes the pile-soil stiffness due to the hammer blow. The pile tip response shows substantial increase in soil stiffness below and around the pile tip due to driving efforts.
S. N. Moghaddas Tafreshi,
Volume 6, Issue 4 (12-2008)
Abstract

This paper presents the numerical analysis of seismic soil-pile-superstructure interaction in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single piles under seismic loads, based on one-dimensional finite element formulation. The parameters of the proposed model are calibrated by fitting the experimental data of largescale seismic soil-pile-structure tests which were conducted on shaking table in UC Berkeley. A comparative evaluation of single piles shows that the results obtained from the proposed procedure are in good agreement with the experimental results.
M.h. Baziar, A. Ghorbani, R. Katzenbach,
Volume 7, Issue 3 (9-2009)
Abstract

The pile-raft foundation is a combination of a raft foundation with piles. Pile-raft foundation has been widely designed, assuming all structure loads to be transferred to piles without considering contribution of the load taken by contact surface between raft and soil. Methods of analysis currently used in practice are based upon relatively conservative assumptions of soil behavior or on the less realistic soil-structure interaction. In this study the bearing -settlement behavior of combined pile-raft foundations on medium dense sand was investigated. 1g physical model test was performed on a circular rigid raft underpinned with four model piles. Numerical simulation was also carried out on the model test, using FLAC-3D, to show compatibility of the numerical analysis with the test. The obtained results showed very good accuracy of the numerical method used in this study as long as the applied load does not exceed the working load, while the performance of numerical model was relatively good for the loads beyond working load.
F. Messaoud, M. S. Nouaouria,
Volume 8, Issue 1 (3-2010)
Abstract

This paper presents a description of the equipment, testing procedure, and methodology to obtain ground

mechanical parameters. The p-y curves for laterally loaded piles are developed. Methods for the development of p-y

curves from pressure meter and dilatometer (DMT) test are described. P-y curves are used in the analysis to represent

lateral soil-pile interaction. The pressure meter offers an almost ideal in-situ modeling tool for determining directly

the p-y curves for the design of deep foundations. As the pressure meter can be driven into the soil, the results can be

used to model a displacement pile. DMT tests were performed for comparisons with PPMT tests. Correlations were

developed between the PPMT and DMT results, indicating a consistency in soil parameters values. Comparisons

between PPMT and DMT p-y curves were developed based on the ultimate soil resistance, the slope of the initial

portion of the curves, and the shape of the curves. The initial slope shows a good agreement between PPMT and DMT

results. The predicted DMT and PPMT ultimate loads are not similar, while the predicted PPMT and DMT deflections

within the elastic range are identical.


A. Eslami, M. Veiskarami, M. M. Eslami,
Volume 10, Issue 2 (6-2012)
Abstract

It has been realized that the raft (mat) foundations are capable of bearing very large loads when they are assisted with a pile
group. The contribution of both raft and piles to carry the surcharge loads is taken into account, considering the stiffness and
strength of involved elements in the system, i.e. piles, raft and surrounding soil. The piles are usually required not to ensure the
overall stability of the foundation but to act as settlement reducers. There is an alternative design in which, the piles are nonconnected
from the raft to reduce the settlement, which are then known to be "settlement reducer non-connected piles" to increase
the system stiffness. In this paper, two and three dimensional finite element analysis of connected and non-connected pile-raft
systems are performed on three case studies including a 12-storey residential building in Iran, a 39-storey twin towers in
Indonesia, and the Messeturm tower, 256m high, in Frankfurt, Germany. The analyses include the investigation of the effect of
different parameters, e.g. piles spacing, embedment length, piling configuration and raft thickness to optimize the design. The role
of each parameter is also investigated. The parametric study results and comparison to a few field measurements indicate that
by concentrating the piles in the central area of the raft foundation the optimum design with the minimum total length of piles is
achieved, which is considered as control parameter for optimum design. This can be considered as a criterion for project cost
efficiency. On the other hand, non-connected piled-raft systems can significantly reduce the settlements and raft internal bending
moments by increasing the subsoil stratum stiffness. Finally, the comparison indicates that simple and faster 2D analysis has
almost similar results to the time consuming and complicated 3D analysis.


A. Arabzadeh, R. Aghayari, Ali A. R. Rahai,
Volume 10, Issue 4 (12-2012)
Abstract

Strut-and-Tie Model (STM) can be used to model the flow of compression within a concrete strut. Concrete struts are formed

in various shapes such as prismatic or bottle-shaped. In order to study the behavior of concrete struts, a series of simple tests

were performed. Eighteen reinforced concrete isolated struts with compressive strength of 65 MPa were tested up failure under

point loading in the plane of specimens. The tested specimens were reinforced by various reinforcement layouts. The behavior

of tested beams was investigated. Observations were made on transverse displacement, primary cracking and ultimate failure

load and distribution of strain on the face of tested panels. Based on these observations, the geometry of the concrete struts was

examined. a new model to analysis of concrete struts was proposed based on modified compression field theory (MCFT). A

database of 44 tested specimens was compiled to evaluate the proposed model. The results indicate that using the ACI and CSA

codes expressions regarding the amount of minimum required reinforcement in a strut produces conservative but erratic results

when compared with the test data. Conversely, the new proposed model presents a more accurate prediction for the strength of

44 tested struts.


Kwang-Suek Oh, Tae-Hyung Kim,
Volume 11, Issue 2 (11-2013)
Abstract

This study was conducted to determine the effect of vibration on the curing and compressive strength of lightweight air-trapped

soil (ATS). ATS is manufactured by mixing cement with water and sand and injecting bubbles into the mixture. It is light as

compared to regular soil, can reduce the weight on the ground, and has high fluidity. If ATS is used at construction sites with

many vibration sources, such as pile driving, blasting, and construction machinery, the effect of vibration needs to be seriously

considered. If a road is expanded using ATS to reduce traffic congestion, the ATS quality may decrease because of vibration

generated by traffic moving on the road. In particular, because ATS contains many air bubbles and needs time for curing, the

effect of vibration can be greater than expected. Therefore, the effect of vibration on ATS was evaluated during the curing process

by conducting unconfined compression tests on samples prepared with different values of variables including vibration velocity,

starting vibration time, and mixing ratio. Vibration velocities of 0.25 and 0.50 cm/s did not greatly affect the strength. However,

vibration velocities of above 2.50 cm/s significantly affected the decrease in strength, and the starting vibration time also had a

clear effect on specimens cured for less than 2 hours.


I. Hosseinzadeh Attar, K. Fakharian,
Volume 11, Issue 2 (11-2013)
Abstract

Pile foundations are frequently used in industrial projects in southwest lowlands of Iran. Although high setup of shaft resistance

is usually reported in the area, no reliable formulation or guidelines are available for considering the increased capacity in design

applications. Therefore, the pile design practices are usually not optimized. The main objective of this paper is presenting a site

specific formulation for setup effects of a utility plant in southwest Iran in which a good database of prestressed concrete driven

piles is available. Fajr-II Petrochemical site in PetZone of Mahshahr accommodating a utility plant is selected as the database of

the current study. The setup factor (A) and the reference time (t0) are evaluated through processing of a relatively large database

of this well-supervised piling project. As the main portion of variations of driven piles capacity with time is related to shaft, only

shaft resistance variations are considered in this research. The shaft capacity variations are derived from signal matching analysis

on PDA tests. Reliability of PDA tests has been confirmed through comparing with the static load test results. Influence of driving

the surrounding piles on setup factor is also investigated. The results show that the average setup factor (A) and the reference time

(t0) of 0.30 and 0.01 day, respectively, are proper values for estimating the long term capacity in this region. Evaluation of the

results indicates that driving 8 piles around the test pile has increased the “A” factor average of 40% resultingin increase of the

shaft capacity about 19% in one month and 22% in one year, in comparison with the tested piles with no surrounding piles driven.


P. Vahabkashi, A. R. Rahai, A. Amirshahkarami,
Volume 12, Issue 1 (3-2014)
Abstract

Piles or drilled shafts used in bridge foundation, waterfronts, and high rise buildings are generally subjected to lateral loads. In order to study the effect of concrete pile geometry on the structural behavior in layered soils, several models with different shapes and dimensions for piles and different properties for two soil layers with variable thickness were selected and analyzed using the finite difference method. The performance of piles situated in layered granular soil with different compaction and thicknesses were studied in two cycles of lateral loading and unloading. The applied finite difference procedure is also validated based on experimental and published results. The pile head displacement of different models due to their overall deformation and rotation were calculated under maximum loading. For a comparison of pile head displacement due to their overall deformation and rotation in different models, the "performance index” is defined as the ratio of “displacement due to deformation” to the “total displacement”.
J. Nazari Afshar, M. Ghazavi,
Volume 12, Issue 1 (1-2014)
Abstract

The Stone-column is a useful method for increasing the bearing capacity and reducing settlement of foundation soil. The prediction of accurate ultimate bearing capacity of stone columns is very important in soil improvement techniques. Bulging failure mechanism usually controls the failure mechanism. In this paper, an imaginary retaining wall is used such that it stretches vertically from the stone column edge. A simple analytical method is introduced for estimation of the ultimate bearing capacity of the stone column using Coulomb lateral earth pressure theory. Presented method needs conventional Mohr-coloumb shear strength parameters of the stone column material and the native soil for estimation the ultimate bearing capacity of stone column. The validity of the developed method has been verified using finite element method and test data. Parametric studies have been carried out and effects of contributing parameters such as stone column diameter, column spacing, and the internal friction angle of the stone column material on the ultimate bearing capacity have been investigated.
M. B. Esfandiari Sowmehsaraei, R. Jamshidi Chenari,
Volume 12, Issue 1 (1-2014)
Abstract

Soil reinforced with fiber shows characteristics of a composite material, in which fiber inclusion has a significant effect on soil permeability. Concerning to the higher void ratio of carpet fibers, at first stages it may be expected that an increase in fiber content of the reinforced soil would result in an increase in permeability of the mixture. However, the present article demonstrates that fiber inclusion will decrease the permeability of sand-fiber composite.A series of constant head permeability tests have been carried out to show the effects and consequently, a new system of phase relationships was introduced to calculate the dry mass for the sand portion of the composite. Monte Carlo simulation technique adopted with finite element theory was employed to back calculate the hydraulic conductivity of individual porous fibers from the laboratory test results. It was observed that the permeability coefficient of the porous fibers are orders of magnitude less than the skeletal sand portion due to the fine sand particle entrapment and also the fiber volume change characteristics.
A. Eslami, I. Tajvidi, M. Karimpour-Fard,
Volume 12, Issue 1 (1-2014)
Abstract

Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.
H. Shahnazari, M. A. Shahin, M. A. Tutunchian,
Volume 12, Issue 1 (1-2014)
Abstract

Due to the heterogeneous nature of granular soils and the involvement of many effective parameters in the geotechnical behavior of soil-foundation systems, the accurate prediction of shallow foundation settlements on cohesionless soils is a complex engineering problem. In this study, three new evolutionary-based techniques, including evolutionary polynomial regression (EPR), classical genetic programming (GP), and gene expression programming (GEP), are utilized to obtain more accurate predictive settlement models. The models are developed using a large databank of standard penetration test (SPT)-based case histories. The values obtained from the new models are compared with those of the most precise models that have been previously proposed by researchers. The results show that the new EPR and GP-based models are able to predict the foundation settlement on cohesionless soils under the described conditions with R2 values higher than 87%. The artificial neural networks (ANNs) and genetic programming (GP)-based models obtained from the literature, have R2 values of about 85% and 83%, respectively which are higher than 80% for the GEP-based model. A subsequent comprehensive parametric study is further carried out to evaluate the sensitivity of the foundation settlement to the effective input parameters. The comparison results prove that the new EPR and GP-based models are the most accurate models. In this study, the feasibility of the EPR, GP and GEP approaches in finding solutions for highly nonlinear problems such as settlement of shallow foundations on granular soils is also clearly illustrated. The developed models are quite simple and straightforward and can be used reliably for routine design practice.
Q. Q. Zhang, Sh. C. Li, F. Y. Liang, M. Yang, Q. Zhang,
Volume 12, Issue 2 (4-2014)
Abstract

A simplified approach for nonlinear analysis of the load-displacement response of a single pile and a pile group is presented using the load-transfer approach. A hyperbolic model is used to capture the relationship between unit skin friction and pile-soil relative displacement developed at the pile-soil interface and the load-displacement relationship developed at the pile end. As to the nonlinear analysis of the single pile response, a highly effective iterative computer program is developed using the proposed hyperbolic model. Furthermore, determinations of the parameters related to the hyperbolic model of an individual pile in a pile group are obtained considering interactions between piles. Based on the determinations of the parameters presented in the hyperbolic model of an individual pile in a pile group and the proposed iterative computer program developed for the analysis of the single pile response, the conventional load-transfer approach can then be extended to the analysis of the load-settlement response of an arbitrary pile in a pile group. Comparisons of the load-settlement response demonstrate that the proposed method is generally in good agreement with the field-observed behavior and the calculated results derived from other approaches.
U. H Issa, A. Ahmed,
Volume 12, Issue 2 (4-2014)
Abstract

Driven Precast Reinforced Concrete Piles (DPRCP) is extensively used as a foundation for bridges constructed over canals in Egypt in order to avoid the diversion of water canals. The objectives of this research include identifying the main activities of DPRCP execution in the bridge-construction industry in Egypt and the risk factors affecting them. In addition, assessment of the effects of these risk factors on the quality of activities of DPRCP. Four activities are identified in order to execute the process of construction of DPRCP. These activities include: preparing and casting piles, positioning piles and steering the driving machine, handling piles, and driving piles. Thirty one risk factors affecting the DPRCP activities execution are identified. A survey was executed in Egypt concerning probabilities of occurrence of these factors and their impacts on the quality of activities of DPRCP. In addition, a new membership function is introduced to represent the quality of activities and used in a fuzzy model for factors assessment. Results showed that the proposed membership function can be used effectively to assess the quality of activities associated with the construction of DPRCP. A list of risk factors is highlighted to show the most critical risk factors that help in preparing the quality management plan for the upcoming similar projects. The gentile distribution of data obtained for the different activities proved that the investigated risk factors for the DPRCP in this study are significant.
Ali Kavand, S.mohsen Haeri, Arian Asefzadeh, Iraj Rahmani, Abbas Ghalandarzadeh, Ali Bakhshi,
Volume 12, Issue 3 (7-2014)
Abstract

In this paper, different aspects of the behavior of 2×2 pile groups under liquefaction-induced lateral spreading in a 3-layer soil profile is investigated using large scale 1-g shake table test. Different parameters of the response of soil and piles including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in the paper. In addition, distribution of lateral forces due to lateral spreading on individual piles of the groups is investigated in detail. The results show that total lateral forces on the piles are influenced by the shadow effect as well as the superstructure mass attached to the pile cap. It was also found that lateral forces exerted on the piles in the lower half of the liquefied layer are significantly larger than those recommended by the design code. Based on the numerical analyses performed, it is shown that the displacement based method is more capable of predicting the pile group behavior in this experiment comparing to the force based method provided that the model parameters are tuned.
M. Zare, A. Eslami,
Volume 12, Issue 4 (12-2014)
Abstract

Physical modeling for study of deep foundations can be performed in simple chambers (1g), calibration chambers (CC),

and centrifuge apparatus (ng). These common apparatus face certain limitations and difficulties. Recently, Frustum Confining

Vessels (FCV) have been evolved for physical modeling of deep foundations and penetrometers. Shaped as the frustum of a

cone, this device applies steady pressure on its bottom and creates a linear stress distribution along its vertical central core.

This paper presents the key findings in FCV, as developed in AUT. The FCV has a height of 1200 mm, with top and bottom

diameters of 300 and 1300 mm, respectively. By applying bottom pressure up to 600 kPa, the in-situ overburden stress

conditions, equivalent up to 40 m soil deposits, become consistent with the embedment depth of commonly used piles.

Observations indicated that a linear trend of stress distribution exists, and this device can create overburden stress in the

desired control volume along the central core. Moreover, a couple of compressive and tensile load tests were performed on

steel model piles driven in sand with a length of 750 mm, and different length to diameter (L/D) ratios between 8-15.

Comparison between measured and predicted ultimate capacity of model piles performed in FCV demonstrate a suitable

conformity for similar confinement conditions in the field. Therefore, the FCV can be considered as an appropriate approach

for the investigation of piling geotechnical behavior, and the examination of construction effects.


O. Farzaneh, F. Askari, J. Fatemi,
Volume 12, Issue 4 (12-2014)
Abstract

AWT IMAGEPresented is a method of two-dimensional analysis of the active earth pressure due to simultaneous effect of both soil weight and surcharge of strip foundation. The study’s aim is to provide a rigorous solution to the problem in the framework of upper-bound theorem of limit analysis method in order to produce some design charts for calculating the lateral active earth pressure of backfill when loaded by a strip foundation. A kinematically admissible collapse mechanism consisting of several rigid blocks with translational movement is considered in which energy dissipation takes place along planar velocity discontinuities. Comparing the lateral earth forces given by the present analysis with those of other researchers, it is shown that the results of present analysis are higher (better) than other researchers’ results. It was found that with the increase in AWT IMAGE, the proportion of the strip load (q) which is transmitted to the wall decreases. Moreover, Increasing the friction between soil and wall ( AWT IMAGE) will result in the increase of effective distance ( AWT IMAGE). Finally, these results are presented in the form of dimensionless design charts relating the mechanical characteristics of the soil, strip load conditions and active earth pressure.


M. Haghbin,
Volume 12, Issue 4 (12-2014)
Abstract

This research examines the behavior of soil-reinforced piles and applied loads based on the analytical method and by using the numerical results of FLAC3D software for comparison with the analytical results. The analysis was based on a method called virtual retaining wall, the following into consideration: an imaginary retaining wall that passes the footing edge the bearing capacity of footing on reinforced soil with piles, which was determined by applying equilibrium between active and passive forces on virtual wall and a pile row that exists beneath the shallow foundation. To calculate the lateral pile resistance here, an analytical equation was then required. The main objective of this paper is to determine the percentage of applied load on pile. Similarly, the effect of adding pile in various positions relative to the present footing (underpinning) was studied in this research. The various parameters of this study included pile length, vertical distance of pile head to shallow footing, pile distance to center of footing and location of the pile. Finally, the findings were compared with the numerical results of FLAC3D and the formerly presented experimental results. Results show that the analytical method, while being close to other methods is more conservative.



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