Experimental study of interaction and coupling effects in pile groups subjected to torsion

2008 ◽  
Vol 45 (7) ◽  
pp. 1006-1017 ◽  
Author(s):  
L. G. Kong ◽  
L. M. Zhang
Keyword(s):  
Coupling Effect ◽  
Pile Group ◽  
Test Results ◽  
Pile Groups ◽  
Coupling Effects ◽  
Lateral Resistance ◽  
Torsional Resistance ◽  
Pile Interaction ◽  
Group Configuration ◽  
Centrifuge Model Tests

Piles in a pile group subjected to torsion simultaneously mobilize lateral and torsional resistances. Hence, complicated pile–soil–pile interaction effects and load deformation coupling effects occur in the pile group. In this study, a series of centrifuge model tests were carried out to investigate these effects in three-diameter spaced 1 × 2, 2 × 2, and 3 × 3 pile groups subjected to torsion in both loose and dense sands. The test results showed that the effect of horizontal movement of a pile on lateral behaviors of its adjacent piles is significant in 3 × 3 pile groups and such effect varies with group configuration and pile position. The p-multiplier concept can be used to quantify the effect and values for the p-multiplier are suggested. The effect of lateral movement of a pile on the torsional resistances of its adjacent piles and the effect of torsional movement of a pile on the lateral resistances of its adjacent piles were found to be minor in these tests. For an individual pile in a pile group subjected to torsion, the mobilized lateral resistance was found to substantially increase the torsional resistance of the pile. Such a coupling effect is quantified by a coupling coefficient, β, which describes the contribution of subgrade reaction to the increase of torsional shear resistance.

scholarly journals An Experimental Study on Pile Spacing Effects under Lateral Loading in Sand

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Mahdy Khari ◽  
Khairul Anuar Kassim ◽  
Azlan Adnan
Keyword(s):  
Pile Group ◽  
Experimental Investigations ◽  
Pile Groups ◽  
Dense Sand ◽  
Spacing Effects ◽  
Pile Diameter ◽  
Lateral Resistance ◽  
Model Pile ◽  
Pile Interaction ◽  
Subgrade Modulus

Grouped and single pile behavior differs owing to the impacts of the pile-to-pile interaction. Ultimate lateral resistance and lateral subgrade modulus within a pile group are known as the key parameters in the soil-pile interaction phenomenon. In this study, a series of experimental investigation was carried out on single and group pile subjected to monotonic lateral loadings. Experimental investigations were conducted on twelve model pile groups of configurations 1 × 2, 1 × 3, 2 × 2, 3 × 3, and 3 × 2 for embedded length-to-diameter ratiol/d= 32 into loose and dense sand, spacing from 3 to 6 pile diameter, in parallel and series arrangement. The tests were performed in dry sand from Johor Bahru, Malaysia. To reconstruct the sand samples, the new designed apparatus, Mobile Pluviator, was adopted. The ultimate lateral load is increased 53% in increasing ofs/dfrom 3 to 6 owing to effects of sand relative density. An increasing of the number of piles in-group decreases the group efficiency owing to the increasing of overlapped stress zones and active wedges. A ratio ofs/dmore than6dis large enough to eliminate the pile-to-pile interaction and the group effects. It may be more in the loose sand.

scholarly journals Numerical modelling of perimeter pile groups in clay

2013 ◽  
Vol 50 (3) ◽  
pp. 250-258 ◽  
Author(s):  
A.V. Rose ◽  
R.N. Taylor ◽  
M.H. El Naggar
Keyword(s):  
Load Distribution ◽  
Load Capacity ◽  
Relative Effectiveness ◽  
Pile Group ◽  
Block Type ◽  
Pile Groups ◽  
Total Load ◽  
Group Behaviour ◽  
Pile Interaction ◽  
Spacing Length

The load distribution among piles in a group varies such that the inner piles often carry a smaller share of the total load compared to the outer piles, which is a result of increased soil–pile interaction. The main objective of this paper is to establish the relative effectiveness of pile groups with no inner piles (perimeter group), when compared to the more common grid configuration. The numerical investigation utilized the finite element programme ABAQUS and considered a range of variables that affect pile group behaviour including number of piles, pile spacing, length/diameter ratio, and soil strength. It was demonstrated that a complete grid group is less efficient than a perimeter group, where efficiency is defined as the load capacity of the whole group expressed as a ratio of the number of piles in the group multiplied by the load capacity of a single isolated pile. Efficiencies close to unity were observed for some perimeter groups. Perimeter groups also showed that a “block” type group failure could occur, where piles were placed at a spacing of less than 2.0 pile diameters,d, centre-to-centre. This often, but not always, led to a reduction in the efficiency of the pile group.

Experimental and Numerical Study of Laterally Loaded Pile Groups with Pile Caps at Variable Elevations

2000 ◽  
Vol 1736 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Michael C. McVay ◽  
Limin Zhang ◽  
Sangjoon Han ◽  
Peter Lai
Keyword(s):  
Numerical Study ◽  
Ground Surface ◽  
Pile Group ◽  
Special Device ◽  
Pile Groups ◽  
Finite Element Program ◽  
Lateral Resistance ◽  
Pile Cap ◽  
Element Program ◽  
Pile Caps

A series of lateral load tests were performed on 3×3 and 4×4 pile groups in loose and medium-dense sands in the centrifuge with their caps located at variable heights to the ground surface. Four cases were considered: Case 1, pile caps located above the ground surface; Case 2, bottom of pile cap in contact with the ground surface; Case 3, top of pile cap at the ground surface elevation; and Case 4, top of pile cap buried one cap thickness below ground surface. All tests with the exception of Case 1 of the 4×4 group had their pile tips located at the same elevation. A special device, which was capable of both driving the piles and raining sand on the group in flight, had to be constructed to perform the tests without stopping the centrifuge (spinning at 45 g). The tests revealed that lowering the pile cap elevation increased the lateral resistance of the pile group anywhere from 50 to 250 percent. The experimental results were subsequently modeled with the bridge foundation-superstructure finite element program FLPIER, which did a good job of predicting all the cases for different load levels without the need for soil–pile cap interaction springs (i.e., p-y springs attached to the cap). The analyses suggest that the increase in lateral resistance with lower cap elevations may be due to the lower center of rotation of the pile group. However, it should be noted that this study was for pile caps embedded in loose sand and not dense sands or at significant depths. The experiments also revealed a slight effect for the case of the pile cap embedded in sand with a footprint wider than the pile row. In that case the size of the passive soil wedge in front of the pile group, and consequently the group’s lateral resistance, increased.

Lateral resistance and deflection of flexible piles

1988 ◽  
Vol 25 (3) ◽  
pp. 511-522 ◽  
Author(s):  
G. G. Meyerhof ◽  
V. V. R. N. Sastry ◽  
A. S. Yalcin
Keyword(s):  
Key Words ◽  
Ultimate Load ◽  
Embedment Depth ◽  
Horizontal Load ◽  
Test Results ◽  
Pile Groups ◽  
Single Model ◽  
Lateral Resistance ◽  
Theoretical Analyses ◽  
Lateral Deflections

The ultimate lateral resistance and the groundline lateral deflections under working loads of freestanding single model piles and small pile groups, of various materials and different embedded lengths, subjected to horizontal load have been investigated. The test results of piles of various stiffnesses in sand and clay are compared with theoretical analyses based on the concept of an effective embedment depth in terms of the behaviour of equivalent rigid piles. Key words: clay, piles, displacements, lateral load, lateral resistance, pile stiffness, sand, ultimate load.

scholarly journals Serviceability analysis of piled foundations supporting tall structures

2021 ◽  
Author(s):  
Maria Iovino ◽  
Raffaele Di Laora ◽  
Luca de Sanctis
Keyword(s):  
Coupling Effect ◽  
Pile Group ◽  
Mathematical Framework ◽  
Moment Capacity ◽  
Tall Structures ◽  
Pile Interaction ◽  
Elevated Water ◽  
The Moment ◽  
Water Tanks ◽  
Piled Foundations

AbstractPile foundations supporting tall structures, such as wind turbines, chimneys, silos, elevated water tanks or bridge piers, are subjected during their life span to remarkably eccentric loads. These may lead to significant rotations which, however, cannot exceed the limiting values corresponding to the safe operation of the structure. A physically motivated mathematical framework aimed at the prediction of the serviceability performance of such kind of structures is herein presented and discussed. Piles are idealized as uniaxial nonlinear elements characterized by two yielding loads, one in compression and one in uplift, while pile-to-pile interaction effects are modeled by means of superposition, through an approximate solution. The axial load–moment capacity of the pile group is preliminary determined from a recent closed form, exact solution based on upper and lower bound theorems, allowing the analysis to be performed under load control. The model is capable of accounting for the dependence of the moment–rotation response from the dead load of the structure and the ‘coupling effect’ between generalized loads and displacements. The prediction performance of the proposed calculation method is validated against both numerical and experimental benchmarks. Finally, a parametric study allowed to assess the importance of pile-to-pile interaction on the foundation response under eccentric loads.

Study on Negative Skin Friction of Pile Groups Considering Coupled Effect of Surface Load and Soil Consolidation

2009 ◽  
Author(s):  
Gang-qiang Kong ◽  
Qing Yang ◽  
Mao-tian Luan
Keyword(s):  
Skin Friction ◽  
Influence Factors ◽  
Pile Group ◽  
Engineering Practice ◽  
Surface Load ◽  
Soil Consolidation ◽  
Test Results ◽  
Pile Groups ◽  
Negative Skin Friction ◽  
Group Effects

The study was performed based on an analysis of model test results of 3×3 pile group and confirmed the reliability and accuracy of determining negative skin friction (NSF) using numerical modeling of fluid-soild interaction. A 3D numerical model with surface load and soil consolidation was established using FLAC3D, which focused on the mechanism of NSF and its influence factors such as friction of pile-soil interface, spacing of pile and time of consolidation. The results obtained under different cases in an engineering practice were finally compared with measured and empirical data, showing that it is necessary to consider surface load and soil consolidation when dealing with NSF. The results also indicated the analysis with surface load and soil consolidation could simulate the developing process of NSF and produce a more accurate outcome — closer to measured data. The NSF increases rapidly at beginning and then slowly down, finally stabilized at a constant as soil consolidation progresses. Due to pile group effects, the piles at the centre had a smaller downdrag and settlement than those at corner or at edges; pile group effects became more obvious when pile spacing decreased.

scholarly journals Comparison of static lateral behavior of three pile group configurations using three-dimensional finite element modeling

2018 ◽  
Vol 55 (1) ◽  
pp. 107-118 ◽  
Author(s):  
Murad Abu-Farsakh ◽  
Ahmad Souri ◽  
George Voyiadjis ◽  
Firouz Rosti
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Three Dimensional ◽  
Pile Group ◽  
Lateral Load ◽  
Material Behavior ◽  
Soil Resistance ◽  
Pile Groups ◽  
Element Modeling ◽  
Lateral Resistance

The lateral resistance of three pile group configurations was investigated using three dimensional (3-D) finite element modeling. The three pile groups considered in the study were a vertical pile group, a battered pile group, and a mix of vertical and battered piles in a group. The study was motivated by the full-scale static load test that was conducted on the M19 pier foundation in the I-10 twin span bridge in Louisiana. The static lateral resistance of the M19 battered pile group was investigated previously using a 3-D finite element simulation and verified with the aid of experimental results. In the present study, the M19 battered pile group model was used as the basis for the vertical and mixed pile groups for developing their 3-D finite element models. The nonlinear material behavior was accounted for using elastoplastic constitutive models such as the concrete damaged plasticity model and the anisotropic modified Cam clay model. The lateral resistance of the pile groups was investigated in terms of load–displacement, axial load, bending moment, pile damage, soil resistance, and p-multipliers. The results show that the battered pile group had the largest lateral resistance, followed by the mixed and vertical pile groups, respectively. The largest lateral load share was carried by the two middle rows in the battered pile group, while it was in the leading row in the vertical and mixed pile groups. The soil resistance profiles show that the vertical pile group mobilized greater soil resistance than the battered and mixed pile groups at the same lateral load. The back-calculated p-multipliers are the highest in the battered pile group case, followed by the mixed and vertical pile groups, respectively.

Influence of Pile Geometry on Responses of End-Bearing Pile Groups Subjected to Vertical Dynamic Loads

2020 ◽  
Vol 20 (04) ◽  
pp. 2050050
Author(s):  
Lubao Luan ◽  
Xin Deng ◽  
Weiting Deng ◽  
Chenglong Wang ◽  
Xuanming Ding
Keyword(s):  
Superposition Principle ◽  
Pile Group ◽  
Dynamic Responses ◽  
Stress Distributions ◽  
Pile Groups ◽  
Pile Head ◽  
Interaction Factor ◽  
Pile Interaction ◽  
Refined Technique ◽  
End Bearing Pile

An analytical solution is presented for evaluating the dynamic responses of pile groups subjected to vertical harmonic loads. The solution allows us to consider the effects of pile geometry on the pile head impedance of the vertically loaded pile groups by the use of a new dynamic interaction factor. To this end, the stress distributions of the soil surrounding the vertically vibrating pile is first determined for calculating the pile–pile interaction factor, instead of the classical interaction factor based on two-pile displacements in past studies. Accordingly, the impedances of the pile group are derived using the proposed pile–pile interaction factor and the superposition principle. Some selected examples are presented to demonstrate the proposed refined technique for evaluating the dynamic characteristics of the pile group.

scholarly journals Pile Group Protection with Riprap Mattress

2012 ◽  
Vol 2012 ◽  
pp. 1-7
Author(s):  
Christian Chreties ◽  
Luis Teixeira ◽  
Gonzalo Simarro
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Pile Group ◽  
Flow Conditions ◽  
Pile Groups ◽  
Alternative Methodology ◽  
Edge Failure ◽  
Group Configuration

New experimental data on plan dimensions for riprap mattresses used in pile group protection against edge failure are analyzed. The influence of flow conditions and the distance between piles in plan dimensions of riprap mattresses are addressed. An alternative methodology for the experimental study of edge failure in pile groups is proposed and verified, significantly reducing the duration of tests (from several days to a few hours) and yielding similar results. For the pile group configuration tested, a design expression for minimum riprap width is obtained. The influence of the distance between the piles on the width of riprap dimensions is shown to be small, and the proposed expression compares well with some of the expressions for single piers found in the literature.

scholarly journals LOAD-SETTLEMENT BEHAVIOUR OF MODEL PILE GROUPS IN SAND UNDER VERTICAL LOAD

2017 ◽  
Vol 23 (8) ◽  
pp. 1148-1163 ◽  
Author(s):  
Mauricio Martines SALES ◽  
Monica PREZZI ◽  
Rodrigo SALGADO ◽  
Yoon Seok CHOI ◽  
Jintae LEE
Keyword(s):  
Pile Group ◽  
Single Pile ◽  
Load Testing ◽  
Driven Piles ◽  
Pile Groups ◽  
Pile Installation ◽  
Model Pile ◽  
Group Configuration ◽  
Settlement Behaviour ◽  
Good Agreement

Model pile load testing is effective to study the load-settlement behaviour of pile foundations given the con­trolled environment in which the testing is done. This paper reports a testing program in a large calibration chamber involving individual piles and pile groups installed in sand samples of three different densities. Tests on both nondis­placement and driven piles are evaluated to assess the influence of the pile installation process on pile load-settlement response. A method is proposed to predict the load-settlement response of a pile group based on the response of a single pile. The method is shown to produce estimates that are in good agreement with measurements. The influence of pile group configuration, pile spacing, soil density and method of pile installation is discussed.

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