Soil-pile Interaction Research Articles

Numerical modeling of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations

Fully-coupled nonlinear dynamic analysis is increasingly used for assessing the seismic performance of pile-supported wharf structures subjected to liquefaction-induced lateral ground deformations. Several numerical challenges exist for analysis of this highly nonlinear soil-structure interaction, which require robust, yet practical, solutions that are validated with experimental data. This study presents a numerical model of a pile-supported wharf and evaluates the applicability of a soil constitutive model, and modeling assumptions and methods by using recorded data from a well-instrumented, large-scale centrifuge test. The objectives of this study include: (a) evaluating the performance of a recently developed pressure-dependent multi-yield surface constitutive soil model (PDMY03) to simulate the behavior of a liquefiable sand (b) assessing the effectiveness of a soil–pile interaction modeling approach in capturing the kinematic displacement demands on piles from a laterally spreading ground, and (c) evaluating the effectiveness and limitations of the 2D numerical model in approximating the 3D behavior of a wharf structure supported by multiple rows of piles, including the dynamic response of the centrifuge container. The implications of these assumptions and lessons learned from this study provide guidance for researcher modelers and practitioners for numerical modeling of similar soil–structure systems.

Evaluation of Train Running Safety on Railway Cable-Stayed Bridge During Seismic Excitation

This research aims to evaluate the dynamic interaction between a cable-stayed bridge (CSB) and operating trains during earthquakes. A three-dimensional finite element modeling approach has been used to analyze the H-shaped pylon CSB along with soil–pile interaction. The train model has been developed using a dynamic system having 10 degrees of freedom. The contact forces between the wheels and the track illustrate the dynamic interaction between the bridge and the train. A Matlab program has been built to receive train–bridge interaction responses. The nonlinear dynamic analysis was performed on CSB using the Bhuj earthquake time history. The structure’s response can then be used to assess the safety of running trains during seismic activity. The dynamic response of the train–bridge interaction system, including the derailment and offloading variables related to the train’s running safety, is evaluated using varied spectral acceleration scaling. The results demonstrate that the acceleration response of the train during seismic events is substantially higher than when there are no earthquake inputs. The operating train’s safety is influenced by both the intensity of the earthquake and the train’s running speed. The operating safety of a moving train during a seismic event is guaranteed by the threshold curve. The proposed bridge modeling technique and simulated results prove that the proposed formulation can accurately envisage dynamic train responses with acceptable computational errors.

Numerical analysis of bridge piers under earthquakes considering pile‒soil interactions and water‒pier interactions

Previous investigations have shown that both pile‒soil interactions and water‒pier interactions have a significant effect on the seismic performance of bridge piers. However, there is a lack of systematic research on the influence of pile‒soil and water‒pier interactions simultaneously on the seismic responses of real bridge piers. This study was conducted to narrow this knowledge gap through a series of numerical analysis. A simplified numerical modelling method for the soil-water-structure system was proposed and validated with results of a centrifuge shaking table test, which considered water‒pier interactions by the additional mass method and pile‒soil interactions by a fine finite element model. The verified numerical modelling method was used to analyse a real bridge pier under near-field and far-field earthquakes. The obtained results show that both pile‒soil interaction and water‒pier interaction increase the pier displacements, and internal forces of the pier decrease by pile‒soil interaction and increase by water‒pier interaction. The effect of water‒pier interaction on the seismic responses of the pier is smaller than that of pile‒soil interaction. The water‒pier interaction significantly increases the bending moments of the base pier considering pile‒soil interactions and shear forces of the base pier without considering pile‒soil interactions.

Nonlinear Predictive Framework of the Undrained Clay Slope Effect on the Initial Stiffness of p-y Curves of Laterally Loaded Piles by FEM

The hyperbolic p-y curve method is commonly used to design laterally loaded piles, in which the initial stiffness is one of the two key parameters that need to be determined. In this paper, the effect of an undrained clay slope on the initial stiffness of p-y curves of laterally loaded piles was explored, and nonlinear models of the reduction factor (μ) were proposed. A series of finite-element analyses was performed for different pile–slope geometric relationships according to whether the slope geometry had influence on pile–soil interaction, in which the geometrical parameters were varied. Based on simulation results, a semi-empirical method was mainly used to derive nonlinear formulations for the undrained clay slope effect on the initial stiffness of hyperbolic p-y curves. The wedge failure theory was also used to analyze the effect of the dimensionless slope height on the initial stiffness. Comparing with other researchers’ reduction factor models, the results of the present model are in the reasonable range and can predict more cases. Test cases were used to validate the proposed model, and the results show that theoretical results are in better agreement with test results using the present model.

Soil Resistance during Driving of Offshore Large-Diameter Open-Ended Thin-Wall Pipe Piles Driven into Clay by Impact Hammers

To investigate soil resistance during driving (SRD) of large-diameter open-ended thin-walled piles (LOTPs) installed in clay by impact drivers, a finite element method (FEM) analysis incorporating the dynamic remeshing and interpolation technique with small strain (RITSS) was conducted. This method was verified using a field case, and its SRD was compared with that of the empirical driving formulas. The dynamic penetrations of LOTPs with three pile inner diameters (2, 4, and 6 m), and three ratios of wall thickness to pile inner diameter (1%, 1.5%, and 2%) were then numerically analyzed. The pile load-bearing performance had a significant dimensional effect, which is characterized that an increase in diameter resulting in a decrease in SRD. The LOTP shaft frictional resistances during driving was generally held in the range of around 0.3–0.5 times the undrained shear strength of the soil (Su), and it was about 6 - 8 times for the pile end resistances. The prediction equation was proposed for SRD behavior with depth, which considered the pile diameter. Then, the curves of the equation were compared with the numerical results. This study can serve as a reference for the dynamic penetration analyses of piles, including the SRD and pile-soil interaction.

Prediction and mitigation of train-induced vibrations of over-track buildings on a metro depot: Field measurement and numerical simulation

To predict the vibration transmission of over-track buildings and investigate the effectiveness of countermeasures, a fully coupled three-dimensional vibration prediction model for over-track buildings with consideration of the pile–soil interaction (PSI) was proposed. The accuracy of this prediction model was validated with field data from in-situ vibration monitoring in a metro depot. The consideration of PSI improved prediction accuracy about the vibration of over-track buildings. Then the effectiveness of different mitigation measures (rail damper and ballast mat) was investigated by this prediction model. It was found that the vibration of over-track buildings was dominated by vertical vibration components. Rail dampers significantly reduced the vibration in the high-frequency range above 80 Hz, while the vibration in the low-frequency range below 10 Hz was amplificated. The insertion loss of ballast mats reached 10 dB in the frequency range above 40 Hz except at the resonance frequency of the track, and mitigation effectiveness gradually decreased with increasing story height. This proposed method can predict the vibration level within over-track buildings and is an effective tool to guide the vibration mitigation design of over-track buildings.

Analytical solution of dynamic response of horizontal vibrating pile with different soil viscoelastic half-space types

An analytical solution has been developed to investigate the dynamic responses of floating pile with different soil viscoelastic half-space types. The dynamic response of a pile is governed by 1D vibration theory, in which the pile is assumed to be viscoelastic material with a circular cross-section and can be divided into two pile segments in a soil-air system. Meanwhile, the dynamic solution for soil is achieved by the application of the potential function decomposition and the variable separation method. Moreover, an analytical solution considering the viscoelastic half-space of the soil free-field under horizontal SV wave is established. Furthermore, the dynamic pile-soil interaction is established and solved efficiently through a precise theoretical derivation based on the displacement compatibility and traction equilibrium at the interface between the pile and soil.The present solution is compared with the substructure method and analytical solution with a rigid foundation to verify the rationality of the present analytical solution. Then, the similarities and differences among several foundation types are discussed based on the present analytical solution. The results have a certain guiding significance for engineering structures.

Lateral capacity of a two-pile group foundation model located near slope in sand

The lateral response for a two-pile group foundation under the lateral load in sloping ground is studied by the experiment tests and lateral load-transfer approach. A simplified physical model is presented to evaluate the lateral response of a two-pile group foundation under lateral load in sloping ground by dint of three-dimensional failure wedge and hyperbolic p-y criterion, which considers the soil-pile and pile-pile interaction. Initially, the results of model tests of pile groups subjected to lateral load located near slope in homogeneous sand are analyzed, which considers the slope angle and pile spacing in homogeneous sand. The pile spacing and the slope angle have significant weakening effect on the lateral pile group's capacity, especially the slope angle. Furthermore, to validate the presented method, the finite difference program is adopted to assess the response of a two-pile group in sloping ground under lateral load and the load-displacement curves, the p-y curves and the change of bending moment with pile are discussed. The results indicates that the present method can be used to predict the lateral response of a two-pile group foundation in sloping ground.

A simplified method for progressive failures of piles in soft ground during rapid embankment construction

A simplified method validated by centrifuge tests is developed to estimate both the deformation and stability of soft ground improved by piles during the rapid construction of embankments. Furthermore, this method, which considers pile-soil interaction, is adopted to investigate the failure mechanism and performance of piles. It is determined that piles embedded in a stiff stratum may be subjected to a dual bending failure. The first failure may occur at the soft-stiff interface because of the embedment effect of the stiff stratum, while the second failure may take place at the upper part of the piles due to the inflexion effect of soft ground movements. A progressive bending failure of piles may also occur as the maximum bending moment of each pile varies with the pile location. The progressive failure could propagate from the piles beneath the embankment toe towards the embankment centre. In addition, the location, stiffness, and fixity of piles have a significant influence on the stability of soft ground. The piles beneath the embankment toe are key piles, and increasing the stiffness and enhancing the embedment of these piles could efficiently ensure the stability of soft ground.

Failure-Mechanism and Design Techniques of Offshore Wind Turbine Pile Foundation: Review and Research Directions

Wind energy is one of the most sustainable and renewable resources for power generation. Offshore wind turbines (OWTs) derive significant wind energy compared to onshore installations. One of the greatest challenges encountered by installing the OWTs is the adequate design of their foundation in relatively soft and compressible marine soil. In most cases, the OWTs are supported by a single pile, termed as ‘monopile foundation’. Apart from the usual loads from the superstructure, these piles are subjected to complex loading conditions under static and cyclic modes in the axial, lateral, and torsional directions due to the primary actions of the wave, wind, and current. To incorporate an appropriate design methodology, understanding the failure mechanisms of such piles is of the utmost necessity. This review paper aims to focus on the progressive development in the analysis of failure mechanisms and design practice relevant to the monopile foundations for OWTs by theoretical and experimental studies conducted globally. An extensive literature survey has been carried out to study the gradual progress on offshore pile-soil interaction, failure mechanisms, and design techniques of OWT supporting monopile foundations. Based on the studies, a brief overview of the various aspects of analysis and design has been carried out, and the relevant conclusions are drawn therefrom.

Innovative Timoshenko soil-pile integrated element for lager diameter laterally-loaded piles considering soil-pile interactions

The large diameter piles (LDP) are designed to provide strong bearing capacity, which should be carefully analysed to ensure the superstructures’ reliability. The conventional discrete spring element (DSE) method with the Euler-Bernoulli beam element is inappropriate for LDPs as the pile’s shear deformations may be considerable. Besides, the nonlinear soil-pile interactions (SPI) cannot be conveniently simulated with the DSE method. To accurately and effectively evaluate the lateral performance of LDP under extreme load, this paper develops an innovative soil-pile integrated element based on the Timoshenko beam theory. The Green-Lagrange strain is used to formulate the potential energy function with the SPI considered. The Gauss integration method is adopted to simplify the element formulation and evaluate the SPI within the element end nodes. The secant and tangent matrixes are derived for calculating the element deformations and internal forces. The transformation matrix describing the nodal parameters’ relation between element local and global coordinate is presented for practical numerical analysis. The soil-pile integrated element avoids using discrete soil spring elements, significantly reducing the modelling and computing efforts. The verification examples demonstrate that the proposed soil-pile integrated element has high accuracy and efficiency in geometrically nonlinear analysis.

Bearing Characteristics of Multi-Wing Pile Foundations under Lateral Loads in Dapeng Bay Silty Clay

This study provides a theoretical basis for reinforcement of the soil around multi-wing piles. Limit analysis was used to determine the ultimate lateral capacity (ULC) of three- and four-wing piles in Dapeng Bay silty clay. The effects of the pile–soil interaction coefficient α, wing width Bw, and lateral-load direction β on the ULC of the pile and the shear plastic zone range of the surrounding soil were analyzed. The normalized ULC of the three-wing pile decreased when the wing–diameter ratio increased. When Bw was 0.15 m and α was 0.4, the ULC of the four-wing pile was 19% higher than that of the three-wing pile. As β increased, the normalized ULC of the four-wing pile decreased, whereas that of the three-wing pile went through a minimum at 30°. The size of the soil shear plastic ring did not depend on α for either pile type; it increased around the three-wing (but not the four-wing) pile with changes in β. However, there was also a double plastic ring of broken soil around the four-wing pile. The four-wing pile had a more symmetrical influence on the soil around the pile than the three-wing pile.

Numerical study on bored Pile-Soil interaction by specified constitutive model in coastal engineering (design)

In Geo-engineering design, Geotech-engineers usually adopt ‘Mohr-Coulomb model (M-C)’ to substitute most soil material, this model is considered as linear elastic and perfectly plastic model, despite, in the coastal engineering, the sand-clay mixed with water, cement, fine aggregate or similar materials are the most common interface medium among soil and pile bodies, the frictions from them have strong affection on piles settlements, due to their complex components and mechanics, never can simulate these interface medium by ‘M-C model’ easily, hereby, the novelty of this article is that author adopt ‘Hardening soil constitutive model (HSs)’ as the interface medium and deployed numerical studies on its application in practical case, the studies included simulating the mechanic behaviors among soil and piles(morphology of deformation), design assumptions based on the analysis of geotechnic report and empirical views, besides compared the pile settlement curves by ‘M-C’ and ‘HSs’ models with the static loads test results, and identified the ‘HSs’ model is a suitable constitutive model for sand-clay mixture soil in this Geo project design. In the end, author proposed a few conclusions about the medium birth mechanism, criteria of model selection and advice for similar engineering reference.

Study on Design and Deformation Law of Pile-Anchor Support System in Deep Foundation Pit

In this study, a deep foundation pit project of Nanlishi Road in the Xicheng District of Beijing was taken as the engineering background. Based on the monitoring method of that project and referring to its design scheme principle, this study applied advanced monitoring technology methods such as anchor axial force and deep horizontal displacement monitoring. The mechanism of pile–soil interaction, the stress change and deformation law of the three-pile and two-anchor support systems of deep foundation pits, and the stability of deep foundation pit support in an anhydrous sandy pebble stratum, were studied in depth. Results show: The axial force of the anchor rod had great loss in the early stage of prestressed tension locking; with the deepening of foundation pit excavation, the lateral pressure of stratum increased gradually, and the prestress of the anchor increased until the end of excavation, where it tended to be stable; the maximum horizontal displacement of the pile was smaller than the design value, and the maximum horizontal displacement was not at the top of the pile; the axial force of the prestressed anchor varied with the formation pressure and surrounding load; the tension of the lower anchor had a certain influence on the axial force of the upper anchor. Except for the east side of the foundation pit, the anchors of the first layer were all stabilized at about 140 kN, and the anchors of the second layer were stabilized at about 150 kN. The third row of anchors on the north side was stable at around 170 kN. By analyzing the variation law of stress and deformation of the supporting structure of the foundation pit, the timeliness of the data during the construction process was improved, and a reference is provided for the informatization construction of related working conditions.

Seismic evaluation of frictional FRP piles in saturated sands using shaking table tests

This manuscript presents results of two shaking table tests that were used to characterize seismic performance of Fibre-Reinforced Polymers (FRP) pile groups in saturated sand. A laminar shear box with a dimension of 1.0 m × 1.0 m and a depth of 1.0 m was employed to contain the soil medium and allow the soil to respond in the same fashion as the free field. Two types of composite group piles (2 × 2) made of Carbon FRP (CFRP) and Glass FRP (GFRP) along with a series of Aluminum model piles were manufactured and embedded as frictional piles within the soil. The pile-soil models were subjected to acceleration time histories adopted from the 2010 Val-des-Bois Earthquake in Canada and the 1995 Kobe Earthquake. The foundation motions recorded along the model piles showed significantly higher levels of excitation compared to the accelerations recorded within the soil at the same level. This was attributed to strong interaction between the soil and the foundation, and higher flexural stiffness of the model piles. Pile material was also found to influence the seismic response of pile caps and its superstructure through kinematic soil-pile interaction and possible rocking motion. The aluminum pile cap experienced significantly higher acceleration response compared to the FRP piles. Among the FRP piles, GFRP piles were shown to provide slightly better performance and could be an appropriate alternative piling material for frictional traditional piles especially in liquefiable soils.

Analytical solution for lateral dynamic response of pile foundation embedded in unsaturated soil

The lateral dynamic interaction of the soil and pile has been extensively studied, however, most of the existing studies simplified the soil medium as a one-phase (solid) or two phase (pore fluid, soil skeleton) medium, which is far from the true condition of the soil in nature. Based on the poroelastic continuum mechanics, a coupled dynamic unsaturated soil-pile interaction model is established in this paper. The potential function, operator decomposition method and variable separation method are introduced herein to obtain the lateral force of the unsaturated soil acting on the pile shaft. Afterwards, the analytical solution of the pile dynamic impedance in the frequency domain is derived by employing the soil-pile continuous deformation conditions and the boundary conditions of the pile. The reliability of the obtained solution is verified through the comparisons against classic simplified answers. The main conclusions found in this paper can be drawn as: (a) The increase in the saturation of the soil would decrease the soil strength, resulting in an increase in the displacements and internal force of the pile; (b) Both the increase in soil permeability and the decrease in soil saturation will lead to the decrease in the pore pressure at the side of the pile. And, the smaller the saturation is, the greater the matrix suction would be; (c) The natural frequency of the pile decreases with the increase of the soil saturation.

A fictitious pile method for interaction factor of two laterally loaded piles in multilayered isotropic soils

An efficient fictitious pile method based on elasticity theory is presented for the analysis of interaction factor of two laterally loaded piles embedded in non-homogeneous soils. The problem is decomposed into two systems, namely the two fictitious piles acted upon by (partial) external loading, and an extended multilayered soil continuum acted upon by a system of pile-soil interaction forces at imaginary positions of the piles. The behavior/responses of the multilayered isotropic soils are analyzed through a computationally effective transfer matrix solution procedure. A Fredholm integral equation of the second kind is then deduced for the load-deformation relationship of a two-pile group system, by considering the equilibrium of the pile-soil interaction forces and the displacement compatibility between the fictitious pile and the extended soil. Comparison of the results calculated by the present fictitious pile method for displacement interaction factor between two piles embedded in multilayered isotropic soils has shown good agreement with the previous ones obtained by using the more rigorous finite element approach. The parametric numerical study demonstrates that the soft-over-stiff-over-soft soil layers have a profound effect on the pile-to-pile displacement interaction factor for the case of moment loading, which should be carefully considered in the practical design.

Lateral Dynamic Response of Offshore Pipe Piles Considering Effect of Superstructure

The dynamic characteristics of pipe piles are of considerable importance for the dynamic foundation design of offshore wind turbines. In this study, we develop an analytical model for the lateral vibration of offshore pipe piles with consideration of the inertia effect and axial loading from the superstructure. A coupled dynamic saturated soil–pile interaction model is established based on Biot’s poroelastic theory and Euler–Bernoulli theory. The potential function, operator decomposition method, variable separation method and matrix transfer method are introduced herein to obtain the lateral force of the inner and outer soil acting on the pile shaft. Then, the analytical solution of the pile dynamic impedance in the frequency domain is derived by employing the soil–pile continuous deformation conditions and the boundary conditions of the pile. The rationality and accuracy of the presented solution have were by comparing its results with those predicted by existing solutions. The influence of superstructure, pile geometry and soil plug height on the lateral dynamic impedance and natural frequency of pipe piles was thoroughly investigated based on the theoretical model. The main findings can be summarized as: (1) The dynamic stiffness of piles will be remarkably underestimated if the inertia effect of the superstructure is not accounted for. (2) The vertical load of the superstructure is main factor affecting the natural frequency, whereas the inertia effect of the superstructure will enlarge the resonance amplitude. (3) The overall lateral dynamic impedance and first-order natural frequency of the pile increase significantly with the soil plug height.

On the mechanisms governing the response of pile groups under combined VHM loading

In this paper, an experimental, numerical and analytical study is conducted on a 2 × 1 bored pile group on saturated sand under combined loading. Initially, a single-degree-of-freedom system founded on the pile group is tested at the ETH Zurich drum centrifuge under vertical, lateral and pushover loading, gaining insights and deriving benchmark results for validation of finite-element (FE) models. The latter account for non-linear soil–pile interaction, using hypoplasticity for sand and appropriate modelling of interfaces and pile response. Combining centrifuge and FE modelling, the governing resistance mechanisms are identified and quantified. The transition from model to prototype scale is achieved after careful consideration of scale effects. The concrete damaged plasticity model is employed to model the non-linear response of the reinforced concrete (RC) piles, accounting for axial load dependency of bending moment capacity. The prototype problem is studied parametrically, deriving failure envelopes for different levels of vertical loading. Distinguishable failure modes are identified, and the contribution of different resistance mechanisms is quantified. Finally, analytical failure envelopes are derived based on limit equilibrium, expanding Broms’ theory to pile groups under combined loading. Accounting for the axial load dependency of RC bending moment capacity, the proposed closed-form solutions provide a useful design tool for engineering practice.

Dynamic response of cable-stayed bridge under wind-wave-current action considering pile-soil interaction

Sea-crossing bridges are generally subjected to the combined wind, wave and current action, making it worthwhile investigating the dynamic response of cable-stayed bridges under wind-wave-current action. In this study, the numerical wave flume is utilised to obtain wave-current action, where a measured spectrum is applied to generate random waves. The stochastic wind field is calculated through the spectral representation model. These actions are validated by comparing experimental and theoretical results. A comparative analysis under different loads provides the theoretical basis for load type determination. The influence of pile–soil interaction is also studied with the consolidation, pile–soil solid contact (PSSC), and soil spring model. The results show that the root mean square (RMS) values of girder displacement are greater under regular wave-wind-current action, while the extreme values of the girder internal force present the opposite pattern due to the statistical characteristics of random waves. It indicates that the statistical characteristics of random waves should be considered to secure the girder safety. For the bridge tower, the random wave-wind-current action has a greater effect on the lateral displacement responses. Furthermore, the model considering the pile–soil interaction gets more flexible, absorbing more energy of low-frequency wave-wind-current action.