An experimental study of the interaction of vertically loaded pile groups in sand

2005 ◽  
Vol 42 (5) ◽  
pp. 1485-1493 ◽  
Author(s):  
Su-Hyung Lee ◽  
Choong-Ki Chung
Keyword(s):  
Model Test ◽  
Load Transfer ◽  
Interaction Model ◽  
Pile Group ◽  
Pile Groups ◽  
Free Standing ◽  
Pile Installation ◽  
Current Design ◽  
Load Tests ◽  
Design Factors

The interactions among closely located piles and a cap in a pile group are complex. The current design practice for vertically loaded pile groups roughly estimates their overall behavior and generally yields conservative estimations of the group capacity. For a proper pile group design, factors such as the interaction among piles, the interaction between cap and piles, and the influence of pile installation method all need to be considered. This paper presents the results of the model test, which can be used to better understand the interactions of vertically loaded pile groups in granular soil. Load tests were carried out on the following: an isolated single pile, single-loaded center piles in groups, a footing without any piling, free standing pile groups, and piled footings. The influences of pile driving and the interactions among bearing components on load–settlement and load transfer characteristics of piles and on the bearing behavior of a cap in a group are investigated separately by comparing their respective test results. The favorable interaction effects that increase pile capacities are identified.Key words: pile group, pile installation, interaction, model test, free standing, piled footing.

scholarly journals Large-scale model tests of a single pile and two-pile groups for an offshore platform in sand

2021 ◽  
Author(s):  
Aligi Foglia ◽  
Khalid Abdel-Rahman ◽  
Elmar Wisotzki ◽  
Tulio Quiroz ◽  
Martin Achmus
Keyword(s):  
Large Scale ◽  
Load Transfer ◽  
Pile Group ◽  
Scale Model ◽  
Single Pile ◽  
Pile Groups ◽  
Group Efficiency ◽  
Large Scale Model ◽  
Load Tests ◽  
The Given

Estimating pile group efficiency for open-ended steel piles in small group arrangements is a challenging task for designers. This paper reports on the large-scale experimental campaign performed for the BorWin gamma offshore converter platform, which involved single piles and two-pile group systems on a scale of 1:10. The experimental works included installation, dynamic end-of-driving tests, dynamic restrike tests, and static load tests of a single pile and a pair of two-pile groups in densely compacted, artificially prepared homogeneous sand. The CPT profiles and the blow counts confirmed that the foundation systems are comparable to each other. The experimental results of the single pile system were compared with conventional design methods. Such comparison indicated that CPT-based methods and load-transfer methods are applicable at the considered model scale. The bearing capacity prediction obtained via the CAPWAP method is conservative with respect to the static capacity. A consistent setup effect can be detected by analyzing the complete dynamic loading session. The pile group efficiency for the given foundation system was found to be less than 1.0 at both very small and very large soil strains, while it equaled 1.0 at failure.

Load tests on full-scale bored pile groups

2012 ◽  
Vol 49 (11) ◽  
pp. 1293-1308 ◽  
Author(s):  
Guoliang Dai ◽  
Rodrigo Salgado ◽  
Weiming Gong ◽  
Yanbei Zhang
Keyword(s):  
Load Transfer ◽  
Pile Group ◽  
Interaction Coefficient ◽  
Full Scale ◽  
Pile Groups ◽  
Interaction Coefficients ◽  
Bored Pile ◽  
Load Response ◽  
Load Tests ◽  
Single Piles

The interactions between closely spaced piles in a pile group are complex. Very limited experimental data are available on the loading of full-scale bored pile groups. This paper reports the results of axial static load tests of both full-scale instrumented pile groups and single piles. The load tests aimed to ascertain the influence of number, length, and spacing of the piles on pile group load response. Experiments varied in the number of piles in the group, pile spacing, type of pile groups, and pile length. All piles had a diameter of 400 mm. Two-, four-, and nine-pile groups with pile lengths of 20 and 24 m were tested. As the isolated piles and some piles in the pile groups were instrumented, the load transfer and load–settlement curves of both piles in isolation and individual instrumented piles in the groups were obtained. The interaction coefficient for each pile in the group was back-calculated from the measured data. The interaction coefficients are shown to be dependent on pile proximity, as usually assumed in elastic analyses, but also on settlement and on the size of the group.

Dynamic analysis of laterally loaded pile groups in sand and clay

2002 ◽  
Vol 39 (6) ◽  
pp. 1358-1383 ◽  
Author(s):  
Yasser E Mostafa ◽  
M Hesham El Naggar
Keyword(s):  
Dynamic Loading ◽  
Dynamic Load ◽  
Load Transfer ◽  
Pile Group ◽  
Nonlinear Behaviour ◽  
Single Pile ◽  
Offshore Platforms ◽  
Group Effect ◽  
Pile Groups ◽  
Pile Head

Pile foundations supporting bridge piers, offshore platforms, and marine structures are required to resist not only static loading but also lateral dynamic loading. The static p–y curves are widely used to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. However, the concept of the p-multiplier has not yet been considered for the dynamic loading case, and hence it is undertaken in the current study. An analysis of the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static p–y curve approach and the plane strain assumptions to represent the soil reactions within the framework of a Winkler model. The model accounts for the nonlinear behaviour of the soil, the energy dissipation through the soil, and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An intensive parametric study was performed employing the proposed analysis, and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. "Dynamic" p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, soil type, peak amplitude of loading, and the angle between the line connecting any two piles and the direction of loading. The study indicated the effect of pile material and geometry, pile installation method, and pile head conditions on the p-multipliers. The calculated p-multipliers compared well with p-multipliers back-calculated from full scale field tests.Key words: lateral, transient loading, nonlinear, pile–soil–pile interaction, p–y curves, Statnamic.

scholarly journals 3D Numerical Modeling of Pile Group Responses to Excavation-Induced Stress Release in Silty Clay

2018 ◽  
Vol 8 (1) ◽  
pp. 2577-2584
Author(s):  
M. A. Soomro ◽  
A. S. Brohi ◽  
M. A. Soomro ◽  
D. K. Bangwar ◽  
S. A. Bhatti
Keyword(s):  
Load Transfer ◽  
Pile Group ◽  
Small Strain ◽  
Transportation Systems ◽  
Silty Clay ◽  
Pile Groups ◽  
Stress Release ◽  
3D Numerical Modeling ◽  
Hypoplastic Model ◽  
Induced Stress

Development of underground transportation systems consists of tunnels, basement construction excavations and cut and cover tunnels which may encounter existing pile groups during their construction. Since many previous studies mainly focus on the effects of excavations on single piles, settlement and load transfer mechanism of a pile group subjected to excavation-induced stress release are not well investigated and understood. To address these two issues, three-dimensional coupled-consolidation numerical analysis is conducted by using a hypoplastic model which takes small-strain stiffness into account. A non-linear pile group settlement was induced. This may be attributed to reduction of shaft resistance due to excavation induced stress release, the pile had to settle substantially to further mobilise end-bearing. Compared to the Sp of the pile group, induced settlement of the single pile is larger with similar settlement characteristics. Due to the additional settlement of the pile group, factor of safety for the pile group can be regarded as decreasing from 3.0 to 1.4, based on a displacement-based failure load criterion. Owing to non-uniform stress release, pile group tilted towards the excavation with value of 0.14%. Due to excavation-induced stress release and dragload, head load of rear piles was reduced and transferred to rear piles. This load transfer can increase the axial force in front piles by 94%.

The bearing capacity of rigid piles and pile groups under inclined loads in clay

1981 ◽  
Vol 18 (2) ◽  
pp. 297-300 ◽  
Author(s):  
G. G. Meyerhof
Keyword(s):  
Bearing Capacity ◽  
Ultimate Bearing Capacity ◽  
Test Results ◽  
Pile Groups ◽  
Free Standing ◽  
Previous Theory ◽  
Inclined Loads ◽  
Load Tests ◽  
Batter Piles ◽  
Piled Foundations

The ultimate bearing capacity of rigid vertical and batter piles and pile groups in clay has been determined under various inclinations of the load, varying from the vertical to horizontal directions. The results of load tests on single model piles of different lengths and inclinations and on free-standing groups and piled foundations are compared with theoretical estimates. The influence of load inclination on the bearing capacity can be represented by simple interaction relationships between the axial and normal components of the ultimate load. The effect of eccentricity of the load on the ultimate bearing capacity of pile groups is discussed on the basis of previous theory and model test results.

scholarly journals Proposal for considering the group effect in the prediction of settlements in pile groups through load transfer methods

2021 ◽  
Vol 44 (2) ◽  
pp. 1-8
Author(s):  
Francisco Vladson Cardins Gomes Filho ◽  
Alfran Sampaio Moura
Keyword(s):  
Load Transfer ◽  
Load Capacity ◽  
Experimental Results ◽  
Interactive Effects ◽  
Group Effect ◽  
Pile Groups ◽  
Limit States ◽  
Load Tests ◽  
Settlement Ratio

When designing a foundation project, it is necessary to ensure that all the elements meet both ultimate and serviceability limit states, which call for predictions of settlement and load capacity. The load transfer methods are a widely used alternative to estimate the load-settlement ratio of piles in the design of foundation projects. However, traditional load transfer methods do not consider the interactive effects between the elements in pile groups. This study proposes changes to the load transfer curves developed by Bohn et al. (2016), aiming to incorporate the group effect in the analysis of load-settlement relationships in pile groups. Comparisons between the predicted settlements obtained using the proposed method and the results of load tests performed by Dai et al. (2012) in Jiangsu, China, showed that the modifications proposed in this study agreed well with the experimental results for most of the analyzed groups.

Small scale model test on lateral behaviors of pile group in loose silica sand

2021 ◽  
Vol 18 (1) ◽  
pp. 41-54
Author(s):  
Amir Vakili ◽  
Seyed Mohammad Ali Zomorodian ◽  
Arash Totonchi
Keyword(s):  
Model Test ◽  
Pile Group ◽  
Lateral Load ◽  
Reduction Factor ◽  
Silica Sand ◽  
Scale Model ◽  
Small Scale ◽  
Pile Groups ◽  
Pile Spacing ◽  
Group Reduction

The accurate predictions of load- deflection response of the pile group are necessary for a safe and economical design. The behavior of piles under the lateral load embedded in soil, is typically analyzed using the Winkler nonlinear springs method. In this method, the soil-pile interaction is modeled by nonlinear p-y curves in a way that the single pile p-y curve is modified using a p-multiplier (Pm) for each row of piles in the group. The average Pm is called the group reduction factor. The Pm factor depends upon the configuration of pile group and the pile spacing (S). The present study was conducted to investigate the effects of various parameters, such as the pile spacing in the group, different layouts and the lateral load angle (Ѳ) change as a new parameter on the Pm factor and group efficiency based on the 1-g model test. The Pm factor is well comparable with the results of the full-scale test on pile group. However, based on the results, the calculated values of the Pm factor for 3×3 pile groups under 2.5-diameter spacing was estimated about 0.38 and under 3.5-diameter spacing was estimated about 0.52, so the calculated values at S/D=3, obtained from interpolation the values of group reduction factor at S/D=2.5 and S/D=3.5, are close to the AASHTO recommendation.

scholarly journals FLOATING RAFT-PILE FOUNDATIONS ANALYSIS USING NUMERICAL SIMULATION

2011 ◽  
Vol 7 (2) ◽  
pp. 40
Author(s):  
Helmy Darjanto
Keyword(s):  
Numerical Simulation ◽  
Pile Foundation ◽  
Load Transfer ◽  
Numerical Models ◽  
Pile Group ◽  
Vertical Displacement ◽  
Constitutive Law ◽  
Pile Foundations ◽  
Pile Groups ◽  
Foundation Soil

The numerical simulation of raft-pile foundations subjected to vertical load is presented in this paper. For comparison study, numerical models of single raft and pile groups are completed. The numerical models are adopting the elastic constitutive law for the materials. The stresses and vertical displacement of the models are observed. The behaviour of the raft-pile foundation compared to the pile-group is then investigated. The results using the same external load show that the raft-pile foundation has smallest displacement compared to the others. In terms of stresses, the raft shows contribution of the load transfer to the underneath soil as well as the piles. Moreover, the behaviour of the raft-pile system appears to be a combination of the pile-group and the single raft. In order to estimate the bearing capacity of the raft-pile system, it is suggested that the contribution of the raft should be included in addition of the piles’. Keywords: raft-pile foundation, soil-structure interaction, floating foundation

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.

scholarly journals Experimental testing of a full-scale of group efficiency in multiple soil layers

2019 ◽  
Vol 13 (3) ◽  
pp. 135-142
Author(s):  
Le Thiet Trung ◽  
Duong Diep Thuy ◽  
Pham Viet Anh
Keyword(s):  
Load Transfer ◽  
Experimental Testing ◽  
Pile Group ◽  
Load Testing ◽  
Group Effect ◽  
Pile Groups ◽  
In Situ Tests ◽  
Group Efficiency ◽  
Pile Group Effect

Results of in-situ tests showed that the performance of single isolated piles and individual piles within a group is largely different. When piles are arranged in a group, the interaction between piles and the foundation depends on the pile arrangement and the pile group effect. To date, studies on the pile group effect in Vietnam have been limited to reduced-scale laboratory testing or static load testing where piles are installed into homogeneous sandy or clayey foundation. This paper presents in situ tests which were performed on both single piles and pile groups, loaded to failure, with the aim of studying the pile group effect of piles embedded in multi-layered foundation. Strain gauges were installed along the shaft of 10 m long steel pipe piles, with a diameter of 143 mm. The influence of loose sand layers on the group effect in case of friction piles was evaluated. The experimental results indicated that the influence of sand layers was evident, and the group factor was calculated to be 1.237. Keywords: group efficiency; pile groups; axial capacity; load transfer.

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