Settlement analysis of pile groups in layered soils

2006 ◽  
Vol 43 (8) ◽  
pp. 788-801 ◽  
Author(s):  
Roberto Cairo ◽  
Enrico Conte
Keyword(s):  
Dynamic Stiffness ◽  
Pile Group ◽  
Nonlinear Behaviour ◽  
Layered Soils ◽  
Pile Groups ◽  
Linear Elastic ◽  
Vertical Loading ◽  
Stiffness Matrices ◽  
Interaction Factor ◽  
Settlement Analysis

This paper presents a method to perform a nonlinear analysis of pile groups subject to vertical loading. The method makes use of the dynamic stiffness matrices to simulate the response of layered soils. These matrices are incorporated in a calculation procedure that is computationally very efficient because the response of a pile group can be achieved using essentially the solution for a single pile. The method is first used to perform a linear elastic analysis of pile groups and is then extended to include the nonlinearity effects. In this context, the widely accepted approach is adopted in which nonlinearity is considered to be confined in a narrow zone close to each pile, whereas outside this zone the soil is assumed to behave as a linear elastic medium. Moreover, a global interaction factor is introduced to account for the interaction among the piles in the group. The theoretical predictions from the proposed method are compared with experimental measurements from several published full-scale and model tests on pile groups loaded up to failure. The agreement between predicted and observed behaviour is found to be very satisfactory, even approaching the ultimate load, when the results of loading tests on single piles are available and the group efficiency with respect to the failure load is close to unity.Key words: pile groups, settlement analysis, nonlinear behaviour, layered soils.

A simplified nonlinear approach for pile group settlement analysis in multilayered soils

2001 ◽  
Vol 38 (5) ◽  
pp. 1063-1080 ◽  
Author(s):  
K M Lee ◽  
Z R Xiao
Keyword(s):  
Transfer Function ◽  
Analytical Method ◽  
Pile Group ◽  
Shear Stresses ◽  
Nonlinear Behaviour ◽  
Test Results ◽  
Pile Groups ◽  
Nonlinear Load ◽  
Multilayered Soils ◽  
Settlement Analysis

A simplified analytical method is presented for nonlinear analysis of the behaviour of pile groups under vertical loads. A hyperbolic approach is adopted to describe the nonlinear relationship between the shaft shear stresses and the relative shaft displacements along a confined disturbed soil zone around a pile-soil interface. Outside the disturbed zone, the soils are assumed to behave in a linearly elastic state. By adopting the elastic closed-form analytical solution to approximate the displacement fields around a single vertically loaded pile, and the principle of superposition, a new transfer function is presented for analysis of the behaviour of pile groups in multilayered soils. Furthermore, with a simplified assumption of separating the shaft from the base interaction factors for individual piles in a pile group, a highly effective iterative procedure is developed to examine the nonlinear load–displacement behaviour of a pile group up to the failure state. Comparisons of the load–settlement responses for a number of well-instrumented field pile group test results are given to demonstrate the effectiveness and accuracy of the proposed analytical method. The computed nonlinear responses of the pile group compare favourably with measured field test results under both rigid and flexible pile cap conditions.Key words: pile groups, interface, transfer function, settlement analysis, nonlinear behaviour.

Dynamic Response of 3D Surface/Embedded Rigid Foundations of Arbitrary Shapes on Multi-Layered Soils in Time Domain

2019 ◽  
Vol 19 (09) ◽  
pp. 1950106 ◽  
Author(s):  
Zejun Han ◽  
Mi Zhou ◽  
Xiaowen Zhou ◽  
Linqing Yang
Keyword(s):  
Dynamic Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Dynamic Stiffness ◽  
Dynamic Responses ◽  
Rigid Foundation ◽  
Layered Soils ◽  
Stiffness Matrices ◽  
The Time Domain ◽  
Arbitrary Shapes

Significant differences between the predicted and measured dynamic response of 3D rigid foundations on multi-layered soils in the time domain were identified due to the existence of uncertainties, which makes the issue a complicated one. In this study, a numerical method was developed to determine the dynamic responses of 3D rigid surfaces and embedded foundations of arbitrary shapes that are bonded to a multi-layered soil in the time domain. First, the dynamic stiffness matrices of the rigid foundations in the frequency domain are calculated via integral domain transformation. Secondly, a dynamic stiffness equation for rigid foundations in the time domain is established via the mixed variables formulation, which is based on the discrete dynamic stiffness matrices in the frequency domain. The proposed method can be applied to the treatment of systems with multiple degrees of freedom without losing the true information that concerns the coupling characteristics. Numerical examples are presented to demonstrate the accuracy of the proposed method for predicting the horizontal, vertical, rocking, and torsional vibrations. Further, a parametric study was carried out to provide insight into the dynamic behavior of the soil–foundation interaction (SFI) while considering soil nonhomogeneity. The results indicate that the elastic modulus of the soil has a significant impact on the dynamic responses of the rigid foundation. Finally, a numerical example of a rigid foundation resting on a six-layered, semi-infinite soil demonstrates that the proposed method can be used to deal with multi-layered media in the time domain in a relatively easy way.

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.

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.

Stiffness constants and interaction factors for vertical response of pile groups

1990 ◽  
Vol 27 (6) ◽  
pp. 813-822 ◽  
Author(s):  
Bahaa El Sharnouby ◽  
Milos Novak
Keyword(s):  
Group Analysis ◽  
Pile Group ◽  
Soil Parameters ◽  
Pile Groups ◽  
Continuous Transition ◽  
Interaction Factor ◽  
Wide Range ◽  
Interaction Factors ◽  
New Type ◽  
Single Piles

Stiffness constants and flexibility coefficients of single piles and interaction factors are presented to facilitate the analysis of pile groups subjected to static vertical loads. A continuous transition from friction to end-bearing piles is accounted for. A new type of interaction factor, established from subgroups of five piles, is introduced for end-bearing piles. This interaction factor allows for the stiffening effect of the piles occurring between the two reference piles. This feature improves the accuracy of group analysis for end-bearing piles. Numerical results for axially loaded single piles and pile groups are presented for a wide range of pile and soil parameters. The results are applicable toboth rigid and flexible caps. Key words: piles, pile group, settlement, interaction

scholarly journals Pile group settlement analysis on the basis of Static Load Test

2019 ◽  
Vol 97 ◽  
pp. 04031 ◽  
Author(s):  
Nikola Dudek
Keyword(s):  
Pile Group ◽  
Load Test ◽  
Static Load Test ◽  
Pile Groups ◽  
Stiffness Modulus ◽  
Test Load ◽  
Bored Pile ◽  
Driven Pile ◽  
Settlement Analysis ◽  
Element Method

Settlement of large pile groups is most often estimated by the Alternative Foundation Method. However, this method has some limitations related to assumed uniformity of pile loads. A very big problem is also related to estimating the stiffness of subgrade loaded by a group of piles. Similar problems arise when piled foundation is numerically modelled in Finite Element Method or Boundary Element Method programmes. The results obtained are highly dependent on the input data, especially on characteristics describing soil subgrade stiffness and strength and moduli at pile – soil contact. The paper presents an example of using the results of trial static calculations for the pile made using a technology not identical with that ultimately implemented for the project. The subgrade stiffness modulus was determined with Inverse Analysis using bored pile test load. The results attained were used for further calculations (forecast) the settlement of prefabricated driven pile (a single one) and then to estimate of pile group settlement under full load from bridge structure abutment.

Effects of dead loads on the lateral response of battered pile groups

2002 ◽  
Vol 39 (3) ◽  
pp. 561-575 ◽  
Author(s):  
L M Zhang ◽  
M C McVay ◽  
S J Han ◽  
P W Lai ◽  
R Gardner
Keyword(s):  
Pile Group ◽  
Lateral Load ◽  
Load Test ◽  
Vertical Load ◽  
Pile Groups ◽  
Dead Load ◽  
Vertical Loading ◽  
Lateral Resistance ◽  
Tension And Compression ◽  
Load Tests

The effects of vertical load on the lateral resistance of single piles were initially reviewed to facilitate the interpretation of the test results of pile groups. Then, 18 different lateral load tests were carried out in the centrifuge on the 3 × 3 and the 4 × 4 fixed-head battered pile groups to investigate the effects of vertical load on the group lateral resistance. Vertical dead loads ranging from approximately 20 to 80% of the vertical ultimate group capacity Puv were applied. Based on these tests, the effects of vertical dead load on the lateral resistance of the battered pile groups are found to depend on pile arrangement, pile inclination, and soil density. The lateral resistances of the 3 × 3 pile groups do not appear to vary considerably with the vertical dead loads in the range of the vertical loads studied. For the 4 × 4 pile groups however, the lateral resistances at vertical loads of approximately 50 and 80% Puv may be 26-29% and even 40% higher than that at the 20% Puv dead load. It may be inferred that designs based on standard lateral load tests with small vertical dead loads would be on the safe side. Three mechanisms for vertical load effects are discussed in terms of axial tension and compression failures, influence of pile inclination, and initial subgrade reaction caused by vertical loading. Preliminary numerical analyses are also performed to simulate the responses of some of the battered pile groups.Key words: pile group, battered pile, lateral resistance, load test, pile-soil interaction, centrifuge test.

Seismic Response of Pile Groups Improved with Deep Cement mixing Columns in Liquefiable Sand: Shaking Table Tests

2021 ◽  
Author(s):  
Dingwen Zhang ◽  
Anhui Wang ◽  
Xuanming Ding
Keyword(s):  
Seismic Behavior ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Pile Group ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Shaking Table Tests ◽  
Pile Groups ◽  
Acceleration Response ◽  
Table Model

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared to those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

scholarly journals Comparison of Induced Deflection and Forces in Piles Adjacent to Tunnelling and Deep Excavation in 2D and 3D Problems

2018 ◽  
Vol 203 ◽  
pp. 04011
Author(s):  
Ong Yin Hoe ◽  
Hisham Mohamad
Keyword(s):  
Bending Moment ◽  
Pile Group ◽  
3D Models ◽  
Deep Excavation ◽  
Pile Groups ◽  
Out Of Plane ◽  
National University ◽  
Plane Direction ◽  
2D And 3D ◽  
2D Model

There is a trend in Malaysia and Singapore, engineers tend to model the effect of TBM tunneling or deep excavation to the adjacent piles in 2D model. In the 2D model, the pile is modelled using embedded row pile element which is a 1-D element. The user is allowed to input the pile spacing in out-of-plane direction. This gives an impression to engineers the embedded pile row element is able to model the pile which virtually is a 3D problem. It is reported by Sluis (2014) that the application of embedded pile row element is limited to 8D of pile length. It is also reported that the 2D model overestimates the axial load in pile and the shear force and bending moment at pile top and it is not realistic in comparison to 3D model. In this paper, the centrifuge results of single pile and 6-pile group - tunneling problem carried out in NUS (National University of Singapore) are back-analysed with Midas GTS 3D and a 2D program. In a separate case study, pile groups adjacent to a deep excavation is modelled by 3D and 2D program. This paper compares the deflection and forces in piles in 2D and 3D models.

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