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The undrained lateral capacity of a group of two side-by-side piles has been studied in uniform clay, but the effect of spatial variability in clay strength on lateral pile capacity remains unclear. This paper describes probabilistic ultimate lateral capacity for two circular piles in spatially variable undrained clay. An adaptive finite element limit analysis based on random field generation combined with Monte Carlo simulations is applied. The lateral capacity statistics of two-pile groups with different combinations of pile spacings and pile roughness are presented. It is found that the consideration of the random nature of clay strength leads to a significant decrease in the lateral pile capacity, especially at a pile spacing approximately equal to the pile diameter. The factor of safety required to attain a target probability of failure is provided as a function of pile spacing. The obtained results give guidance for the reliability-based design of laterally-loaded two-pile groups in spatially varied clay and can also be applicable for understanding the lateral translation of two interfering cables and pipelines deeply buried in random clay. [ABSTRACT FROM AUTHOR]

The use of alternative reinforcement material to enhance the performance of the pile capacity has gained increasing interest in recent years. This study seeks to probe the improvement of the ultimate pile capacity, reduction the deformation, and the financial results of using alternative reinforcement material such as glass fiber-reinforced polymers (GFRP), geosynthetics geogrids, as well as a combination of geosynthetics geogrids and a central steel bar. Axial load investigations were conducted on circular piles with 150 mm diameter and 1050 mm height. The experimental results revealed an improvement in the axial capacity of up to 25.4% and an enhancement in performance represented in ductility. Furthermore, financial and weight comparisons showed a decrease in the cost by up to 15%. Moreover, a nonlinear finite element (FE) study with Abaqus software was employed to standardize the numerical outcomes with the laboratory findings. The FE analysis was also verified with the previous studies. The 3D nonlinear finite element numerical model performed showed convergence with and without representing the surrounding soil of the pile; thus, confirming the adequacy of the experimental setup adopted. Finally, a suggested theoretical equation is developed to evaluate the change in pile axial load capacity based on the use of different reinforcement materials. The application of the proposed theoretical equation provides further insight into the governing equation involving different reinforcing materials. [ABSTRACT FROM AUTHOR]

This paper proposes a practical approach for data-efficient metamodeling and real-time modeling of laterally loaded monopiles using physics-informed multifidelity data fusion. The proposed approach fuses information from one-dimensional (1D) beam-column model analysis, three-dimensional (3D) finite element analysis, and field measurements (in order of increasing fidelity) for enhanced accuracy. It uses an interpretable scale factor–based data fusion architecture within a deep learning framework and incorporates physics-based constraints for robust predictions with limited data. The proposed approach is demonstrated for modeling monopile lateral load–displacement behavior using data from a real-world case study. Results show that the approach provides significantly more accurate predictions compared to a single-fidelity metamodel and a widely used multifidelity data fusion model. The model's interpretability and data efficiency make it suitable for practical applications. [ABSTRACT FROM AUTHOR]

Major structures like offshore platforms, wind turbines, transport infrastructure, tall buildings, etc., resting on soft compressible clays, are often supported by pile foundations. Apart from usual vertical loading (dead load, live load, etc.), these piles are subjected to significant cyclic loads arising from actions of waves, ship impacts, winds or moving vehicles. Under such circumstances, the lateral mode of cyclic loading is predominant and affects the overall foundation stability. Such repetitive loading leads to stress reversal in adjacent soft clay initiating progressive degradation in soil strength and stiffness, deteriorating the pile capacity with unacceptable displacements. Although several past studies investigated the response of single pile under lateral cyclic loading, a detailed investigation on pile group in clay subjected to cyclic lateral loading, which is of immense practical interest to field engineers, is yet to be carried out. In this paper, in-depth study has been carried out by developing a three-dimensional dynamic finite element model. Comparison of the computed results with available test data validates the numerical model. Extensive parametric studies with field data indicate that both the axial and lateral pile capacities and displacements have been significantly influenced by the cyclic loading parameters. Relevant design curves are also constructed. [ABSTRACT FROM AUTHOR]

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With developments in maritime trade, the need to increase port capacities has emerged. It is important that the reconstruction of such port structures be carried out without disrupting the activities of the existing port and without damaging the old structures. However, the reconstruction and strengthening of these structures require significant engineering work. Especially in the design of such structures, geotechnical and structural engineering theories and practices need to be considered together. The most important challenge in this type of engineering design is to ensure harmony in geotechnical and structural analyses. In this study, the strengthening of a port structure in Guinea is taken as a case study. First, the existing quay wall was evaluated, and then the geotechnical and structural design of the new structure to be built for capacity increase was discussed. A geotechnical design was made with the Plaxis 2D program, and the structural design was made with the Sap2000 program. The soil behavior was analyzed nonlinearly with the Plaxis program and was modeled with the same accuracy as the Sap2000 program. In addition, pile capacities were confirmed by loading tests performed on the piles. The results show that complex hybrid solutions consisting of reinforced and unreinforced piles can be modeled with the finite element method. As seen from this case study, the capacities of existing port structures can be safely increased, provided that necessary geotechnical precautions are taken. [ABSTRACT FROM AUTHOR]

This paper analyzes a piled-raft foundation on non-homogeneous soils with variable layer depth percentages. The present work aims to perform a three-dimensional finite element analysis of a piled-raft foundation subjected to vertical load using the PLAXIS 3D software. Parametric analysis was carried out to determine the effect of soil type and initial layer thickness. The parametric study showed that increasing the relative density from 30 % to 80 % of the upper sand layer and the thickness of the first layer has led to an increase in the ultimate load and a decrease in the settlement of piled raft foundations for the cases of sand over weak soil. In clay over weak soil, the ultimate load of the piled raft foundation was increased, and the settlement decreased by increasing the clay cohesion of the upper layer from 20 kPa to 70 kPa. It was observed that the load shared by the raft was very effective when using dense sand in the upper layer. In the case of dense sand over stiff clay, the percent of load carried by the raft is (30-40) %. Although, for the case of stiff clay over soft clay, the load percentage was almost constant (16-20) %. While for other issues, the sharing load of raft foundation was close and had the same behavior, the load carried by raft is between (8-12) %.

The response of laterally loaded piles installed near the crest of clay slopes is analysed. Three-dimensional finite element analyses are presented for piles at various distances from a slope crest and for different pile shape. The results of these analyses are used to study the variation of the pile displacement, the bending moment of the pile and the soil resistance in relation to pile to slope distance and pile shape. The obtained results show that the proximity of slope significantly affects the lateral load capacity of the piles but not significantly when the piles are placed at 7D (where D is pile diameter) or greater from the slope crest. Furthermore, the lateral soil resistance on the ground surface for circular piles is larger than that for rectangular piles at the same lateral load in level ground. The decrease rate of lateral soil resistance on the ground surface for circular piles gets faster as the slope ratio and load level increase. [ABSTRACT FROM AUTHOR]

Featured Application: The presented techniques can be applied to access a splice depth and a total length of driven precast piles. The difficulties with the application of low strain integrity testing for evaluating the length of driven precast piles of two sections justify the need for new data acquisition and analysis techniques. The standard time domain analysis of the recorded signals may not allow for distinguishing the desired responses from a pile toe and a splice. In this paper, we propose the use of a set of hammers of different weights and tip materials that will provide various sensitivities of the test to a pile splice. To further analyze the collected data, we study the distributions of phase angles obtained using complex continuous wavelet transform. The characteristic phase shifts that distribute from higher to lower frequencies can be interpreted as responses from a pile toe and a splice. To verify the proposed approaches, a series of numerical simulations were performed using the finite element method for the driven pile models with the different properties of a splice zone. Numerical simulation results show that the pile splices are clearly identified when using the shorter input pulses which can be generated by light hammers with a hard head material. The total length of a simulated pile with a 1 mm air gap between sections was undetectable by standard data analysis approaches and was evaluated when analyzing the wavelet phase angle distributions. Numerically validated data acquisition and analysis techniques were applied to field data analysis and allowed us to confidently identify the length of two-section piles grouped with a pile cap. [ABSTRACT FROM AUTHOR]

This paper presents an analytical solution for evaluating kinematic response in piles subjected to shear waves. The proposed model treats the pile as a Timoshenko beam supported by a two parameter Winkler foundation, capturing both transverse and rotational ground reactions. Validation against both analytical and numerical solutions from the literature, particularly 3D finite element models, shows very good agreement. The proposed model generalizes different solutions currently applied in practice, covering various pile slenderness ratios and ground conditions. This approach addresses limitations in existing Euler-Bernoulli beam resting on Winkler or Vlasov-Pasternak foundation models, by incorporating shear distortions in the structure and ground friction at the interface. Shear stresses induced by the rotational springs are found to significantly influence the kinematic factors, as well as bending and, particularly, shear forces. Finally, simplified expressions for kinematic interaction factors and forces are provided for expedited analyses of practical engineering problems. • An improved model based on Timoshenko beam on two parameter foundation is proposed. • Model includes transverse and rotation springs, and shear distortion in the beam. • Relevant differences with Euler-Bernoulli beam on Winkler foundation are found. • Simplified solutions for long piles are proposed. • The model overcomes limitations of existent analytical solutions in literature. [ABSTRACT FROM AUTHOR]

This paper presents the dynamic response of soil-piles-mattress-slab and soil-piles-slab systems under seismic loading. In this context, a three-dimensional numerical model using finite elements is proposed; the piles of two systems are embedded in a soft soil. The reinforced soil is surmounted by a load-transfer mattress setup at the rigid piles head level. The piles are embedded in the soft soil and are perfectly connected to a 0.6 m thick slab. The soil-piles-mattress-slab and soil-piles-slab systems are subjected to a horizontal seismic loading. The soil and the mattress are modeled by volume elements, the rigid piles and piles are modeled by beam elements and the slab is by structural elements. The formulation is based on the direct method and the calculations are done considering elastic and elasto-plastic behaviors for the soil mass. The obtained results are compared in terms of horizontal displacements and internal stresses according to the piles length. The obtained results show the effectiveness of the soil-piles-mattress-slab system, the load transfer mattress constituted an energy dissipation zone for the two behaviors. The embedding at the head of the piles induces very high shear forces and bending moments at the level of the pile-structure connection. These efforts could damage the structure. The soil-piles-mattress-slab system eliminates these major efforts at the head of the rigid piles by separating the structure with a mattress. The non-linearity of the ground must be taken into account for further study. [ABSTRACT FROM AUTHOR]

Several methods are available to design piles subjected to horizontal loadings. A simplified, one-dimensional finite element model that is applicable for various types of lateral loadings such as harmonic or impact loading as well as applicable for soil with different types of inhomogeneity that can be used in preliminary design was needed. The model is based on the beam on a dynamic Winkler foundation model with the simplicity that the connected springs and dashpots at the side and at the base of the pile are frequency independent for a wide range of loading frequencies. The model is validated in two ways. First, the model results are compared with the results of a three-dimensional finite element solution. Second, the model results are compared to a case where the soil stiffness and damping are frequency dependent. For validation, the response of piles to harmonic and impact loading as well as piles in inhomogeneous soils is presented. The determination of the active length of the piles was also determined. The simplified model response is shown to be quite satisfactory. Thus, this simplified model will be of value to design engineers in their preliminary analysis. [ABSTRACT FROM AUTHOR]

Numerical investigations on the shielding efficiency of single piles and pile groups in the wave field of a stationary or moving harmonic load This article presents results from finite‐element analyses on the kinematic interaction of single piles and pile groups. The focus lies on the assessment of the resulting transfer functions due to an excitation with a stationary or moving harmonic vertical point load. A moving constant load is also considered. The soil is modelled as a linear viscoelastic continuum, and further distinguished between a half‐space and a stratum on rigid base. The finite‐element model has been optimised with respect to its size and the fineness of the discretization. The achieved accuracy is assessed on the basis of comparisons with exact solutions for the near‐ and the far‐field. A frequency range between 20 and 40 Hz is examined. The results on the vertical response show that the vibrations of the pile head are considerably smaller than those of the free‐field and that this reduction is more pronounced at higher frequencies. The connection of the piles through a rigid massless cap leads to an additional reduction of the vibration level in the pile group. In the case of a moving load, the shielding efficiency, as indicated by the emanating shadow zones, becomes stronger as the load passes by at minimum distance. [ABSTRACT FROM AUTHOR]

• V-H-M failure envelopes and failure mechanisms of tripod pile foundations are identified considering a bunch of practical factors. • The direction of loading plane affects both the size and the location of the failure envelope in loading space for the tripod pile configuration. • An empirical design approach is proposed to predict the failure envelopes of tripod pile foundations in the 3D V-H-M space which will be helpful for engineering practice. The problem considered in this computational study is for the bearing capacity determination of three-dimensional (3D) rigid tripod-pile groups subjected to combined vertical (V), horizontal (H), and bending moment (M) loads. Using the adaptive 3D finite element limit analysis (FELA) coupled with lower bound, upper bound and mixed Gauss element formulations, numerical results are compared with those of the previous study under a single-component loading (V , or H, or M). The failure envelope in the 3D V – H – M loading space is then constructed, and several failure mechanisms presented to complement the discussions on the complex 3D responses. This is followed by a parametric study for the various factors such as the pile length, pile spacing, pile-soil adhesion factors as well as the loading direction angle. Finally, a closed-form design expression of failure envelopes considering the abovementioned influential parameters and the combined load are derived. Noting that the current industry-based design procedures for tripod-pile groups are rarely found, the outcome of the present study can be used with great confidence in design practice. [ABSTRACT FROM AUTHOR]

A new model for laterally loaded piles is proposed, consisting of a linear part and a non-linear iterative part. The linear part is based on the Green's function method, which strictly satisfies the displacement and stress continuity conditions at the pile-soil interface and leads to a rigorous solution. The non-linear iterative part assumes that the shear modulus of the soil around the pile decreases with the average strain of the soil layer. Only two soil parameters need to be calibrated, including the initial shear modulus of the soil and the reference shear strain at half the initial modulus. Compared to the finite element model, the advantage of this model is that it converges quickly while maintaining accuracy, which greatly improves computational efficiency. The advantage of this model over the p-y curve model is that it does not have the difficulty of selecting p-y spring parameters, especially for monopiles. The accuracy of this model is verified by comparison with three-dimensional finite element models and nine existing studies, including numerical models, field tests and centrifuge tests. These cases cover various piles with diameters of D∼0.273–10 m and aspect ratios of L/D∼3–40, installed in sand or clay by driving, jacking or vibration. • A new model for laterally loaded piles is proposed. • Only two soil parameters need to be calibrated in the model. • The model is suitable for piles of any aspect ratio in both clay and sandy soils. • The accuracy of the model is similar to that of the FEM model. • The computation time is comparable to the p-y curve model. [ABSTRACT FROM AUTHOR]

During a high-magnitude earthquake, drag loads can be induced by liquefaction of soils, defined as the additional vertical load caused by the settlement after soil liquefaction around the pile due to yielding and volume decreasing in soft soils layers, causing a downdrag displacement. In several projects, the magnitude of these loads and settlements caused by downdrag in piles is not well defined. In this research, we advance towards estimating this drag loads and their impact on projects. For this purpose, a case study considering the 2010 Maule earthquake was analyzed, comparing methodologies of shaft loads against numerical modelling results using nonlinear finite element method, in order to estimate the range of settlement, shear stress at the soil-structure interface, the axial loading in the pile and the volumetric strain, among others. It can be demonstrated that the studied piles show downdrag with its consequently drag loads, which is shown as the effective mobilization in the surrounding soil of the southeast and northeast piles, with a strain of 0.2% and 0.1% respectively. These strains imply an additional shear stress in the soilstructure interface, with axial loadings of 45 and 36 ton respectively. [ABSTRACT FROM AUTHOR]

Modes of vibration play a dominant role in the design of WTG (Wind Turbine Generator) support structures. It is necessary to choose the overall system frequency such that the modes of vibration do not coincide with the rotor frequencies as well as the wave frequencies. WTG supported on multiple foundations (such as jackets or seabed frames) may exhibit rocking modes of vibration if the vertical stiffness of the foundation is not large enough which in turn may have serious implications on the fatigue performance of the overall structure. From the O&M (Operation and Maintenance) point of view, it is necessary to design the overall system to have sway-bending as the dominant mode of vibration. This paper develops a formulation for obtaining foundation (for both piles and shallow suction caissons) sizes and spacing such that rocking vibrations are prevented and sway-bending vibrations are achieved. Expressions for the minimum vertical stiffness of foundations are proposed for different configurations: square base, symmetrical (equilateral) triangle, or asymmetrical (isosceles) triangle. Verification of the method is carried out through finite element analysis and a step-by-step solved example is taken to show the application of the formulation. It is hoped that the formulation will assist designers to optimize the foundation arrangement and provide preliminary sizing for tender design. • Establishing criteria for different modes of vibrations for jackets supporting wind turbines. • Formulations for the minimum vertical stiffness of foundation to avoid rocking. • Example showing the applicability of the formulation. • Effects of foundation configuration (symmetric or symmetric) and spacing on modes of vibration. [ABSTRACT FROM AUTHOR]

Tunnel construction below or adjacent to piles will affect the performance and eventually the stability of piles due to ground deformation resulting in the movement of piles and changes in the axial force distribution along the piles. A three dimensional finite element analysis using PLAXIS 3D (2013) was performed to study the behaviour of a single pile and 3 x 3 piles group during the advancement of shield tunnelling in ground. The 10-node tetrahedral elements were used to model both the soil and the tunnel lining. The Hardening Soil (HS) model was used to simulate the soil structure interaction at the tunnel-soil interface. An isotropic elastic model was used for the pile, piles cap, tunnel lining and tunnel boring machine shield (TBM). Several parametric studies were attempted including the longitudinal, lateral, and vertical tunnel location relative to pile embedded in different types of soil (clay or sand). The results showed that the pile head settlement increases during the tunnelling advancement in larger values than that for ground surface settlement. A zone of influence was determined in the range of twice the tunnel diameter in the longitudinal direction (forward and backward of the pile), and transverse direction (left and right of the tunnel centreline). If the tunnel boring is kept off this zone then there is no fear of pile collapse. [ABSTRACT FROM AUTHOR]

This research aims at examining the stability condition of the slope on which Qinglong- Xingyi Expressway Contract Section T1(K11+790∼K11+875) is built as well as put forward a suitable stabilization method. A 2D simulation model of the slope was developed for analysis using the Finite Element Software ANSYS. The main slip section (K11+850) was considered for developing the 2D model of the slope for simulation. The simulation results revealed a deep-seated failure surface in slip zone. The safety factor of the slope after the landslide was found to be 1.085, just around equilibrium. This meant that the slope was highly susceptible to failure in case of any trigger mechanisms hence reinforcement was inevitable in order to keep any eventuality at bay. Piles embedded in the bedrock were the best reinforcement method to contain the deep-seated failure surface developing in the sliding layer. Assurance of slope stability after reinforcement with piles is evident in the disappearance of the failure surface in the plastic strain plot, significant reduction in displacement, plastic strain and stress values. The findings of this research serve to strengthen numerical analysis by strength reduction as a tool for decision making in taking care of slope stability issues. [ABSTRACT FROM AUTHOR]

Summary: An approximate static solution is derived for the elastic settlement and load‐transfer mechanism in axially loaded end‐bearing piles in inhomogeneous soil obeying a power law variation in shear modulus with depth. The proposed generalised formulation can handle different types of soil inhomogeneity by employing pertinent eigenexpansions of the dependent variables over the vertical coordinate, in the form of static soil "modes", analogous to those used in structural dynamics. Contrary to available models for homogeneous soil, the associated Fourier coefficients are coupled, obtained as solutions to a set of simultaneous algebraic equations of equal rank to the number of modes considered. Closed‐form solutions are derived for the (1) pile head stiffness; (2) pile settlement, axial stress, and side friction profiles leading to actual, depth‐dependent Winkler moduli, (3) displacement and stress fields in the soil; and (4) average, depth‐independent Winkler moduli to match pile head settlement. The predictive power of the model is verified via comparisons against finite element analyses. The applicability to inhomogeneous soil of an existing regression formula for the average Winkler modulus is explored. [ABSTRACT FROM AUTHOR]

Using the finite-element method (FEM), this study presents results on piled foundations excited by a stationary or moving harmonic vertical point load acting on the soil surface at a given distance. For the stationary loading case, typical configurations of pile groups and corresponding piled rafts are examined in the frequency domain. The contribution of the raft alone in the overall response is also explored. The soil is modelled as a linear-elastic continuum with hysteretic damping. A wide range of frequencies from 8 to 64 Hz is considered. Of interest is the resulting vertical oscillation mode. The influence of the number of pile rows in the direction of wave propagation on the resulting vibration reduction is assessed by monitoring a reference pile at the furthest back pile row and an observation point at the free-field behind. The associated wave-passage effect is quantified through appropriate transfer functions for the piles. Subsequently, the case of a harmonic load travelling with a constant speed parallel to the pile group is investigated. Most importantly, it is revealed that a good approximation for this case is a stationary load located on the moving load path at the shortest distance from the pile group. This has important implications in the vibration protection practice, as detailed modelling of moving loads is then not required. The methodology presented can be extended to arbitrary foundation geometries and layered soil profiles. • FE-modelling aspects are highlighted for wave propagation at high frequencies. • Piled foundations are examined over a wide frequency range from 8 to 64 Hz. • Piled rafts with perfect contact between raft and soil are also considered. • The effect of adding pile rows or columns on the vibration reduction is explored. • A stationary harmonic point load is a good approximation for a moving point load. [ABSTRACT FROM AUTHOR]

Abstract In this note we investigate how the assumption of small deformations affects the estimation of the ultimate resistance to lateral pile movements in clay. For that we perform coupled hydro-mechanical finite element analyses, using the Modified Cam Clay model to describe soil behaviour. Validation of the numerical methodology via small-strain analyses is followed by an investigation on how the ultimate resistance diverges from exact plasticity solutions when large displacements are considered. Results suggest that the failure mechanism depends on the pile displacement required to mobilise the ultimate resistance, and that small-strain plasticity solutions provide upper bounds of the ultimate resistance. [ABSTRACT FROM AUTHOR]

In the past, there were many research studies carried out on the response of single piles and pile groups under compression loads, but it was comparatively lesser for piles and pile groups under uplift loads. Uplift loads on piles usually occur in pile foundations supporting wind farm structures, tall chimneys, transmission towers and jetty structures. During recent decades, research studies on piles under uplift loads have progressed, and were mainly focused on the capacity, failure modes and load displacement performance of single piles, but no research has been done on the influence zone of a pile and its effects within a group. This paper presents the initial findings of research to investigate the stress distribution and influence zone of a single pile under uplift loads using a hybrid approach combining analytical theory and 2D Finite Element (FE) analysis. Finally, the effect of the estimated influence zone was successfully verified in 3D FE analysis which confirmed that group efficiency reduced when an adjacent pile was within the estimated influence zone and thus piles behave as a group. [ABSTRACT FROM AUTHOR]

In recent years kinematic interaction of piled foundations under seismic loading has been extensively researched from both an experimental and a numerical viewpoint. With regard to numerical aspects, most literature studies implement simplified constitutive models to describe soil and pile behaviour despite current availability of sophisticated constitutive models for both materials. The use of advanced constitutive models is limited in practice due to the difficulty in calibrating several constitutive parameters and the high computation demand which is generally required, particularly if a 3D continuum approach is selected for the analysis. To overcome some of the difficulties above and achieve a better understanding on kinematic response of piles under strong earthquakes, the capability of an advanced but still user-friendly kinematic hardening constitutive soil model has been investigated. The model derives from the classical Von Mises failure criterion with the addition of isotropic and kinematic hardening components to better represent soil response under cyclic loading. Dynamic 3D finite element (f.e.) analyses were performed in the time domain through a simple scheme of a single pile embedded in a soil deposit made of two cohesive layers. The parametric study elucidates the role of soil nonlinearity (stiffness degradation, hysteresis, soil plasticization) on pile kinematic bending response in respect of the adopted input signal, mobilized transient and permanent shear strain developed in the soil layers. For some accelerometric inputs the diffuse plasticization of the soil around the pile leads to compute high kinematic bending moments especially in soil deposits with the upper layer made of low-plasticity index soft clay. Finally, pile nonlinearity has also been considered by implementing bending moment-pile curvature relationships typical of reinforced-concrete piles. [ABSTRACT FROM AUTHOR]

A three-dimensional finite element approach was used to assess the lateral pile and pile group response subjected to pure lateral load. The study evaluated three pile group configurations (i.e. 2 × 1, 2 × 2 and 3 × 2 pile groups) with four values of pile spacing (i.e. 2D, 4D, 6D and 8D, where D is the pile diameter). The results of the influence of load intensities, group configuration, pile spacing are discussed in terms of response of load vs. lateral displacement, load vs. soil resistance and corresponding p-y curves. The improved plots can be used for laterally loaded pile design and also to produce the group action design p-multiplier curves and equations. As a result, design curves were developed and applied in the actual case studies and similar expected cases for assessment of pile group behavior using improved p-multiplier. A design equation was derived from predicted design curves to be used in the evaluation of the lateral pile group action. The equation was used with the previous results to predict the expected design curve take in the account different source of p-multiplier. It was found that the group interaction effect led to reduced lateral resistance for the pile in the group relative to that for the single pile. In addition, the present study was compatible with the results of previous results for the first and second trailing row and was less compatible with the result from the previous works in the case of piles in leading row. [ABSTRACT FROM AUTHOR]

Abstract A three-dimensional finite element technique was used to analyse single pile lateral response subjected to pure lateral load. The main objective of this study is to assess the influence of the pile slenderness ratio on the lateral behaviour of single pile. The lateral single pile response in this assessment considered both lateral pile displacement and lateral soil resistance. As a result, modified p-y curves for lateral single pile response were improved when taking into account the influence lateral load magnitudes, pile cross sectional shape and flexural rigidity of the pile. The finite element method includes linear elastic, Mohr-Coulomb and 16-nodes interface models to represent the pile behaviour, soil performance and interface element, respectively. It can be concluded that the lateral pile deformation and lateral soil resistance because of the lateral load are always influenced by lateral load intensity and soil type as well as a pile slenderness ratio (L/D). The pile under an intermediate and large amount of loading (in case of cohesionless soil) has more resistance (low lateral displacement) than the pile embedded on the cohesion soil. In addition, it can be observed that the square-shaped pile is able to resist the load by about 30% more than the circular pile. On the other hand, pile in cohesionless soil was less affected by the change in EI compared with that in cohesive soil. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to develop a simplified method for computing the load carried by piles, and settlement of piled raft based on the characteristics of an un-piled raft, pile group, and soil. These are important criteria for preliminary piled raft design. Based on the results obtained from finite element analysis, simplified formulas and curves are generated for different conditions of sand and different pile spacing. These formulae and curves contain the stiffness ratio and efficiency factor of the un-piled raft and pile groups. The results of the proposed method were validated using the Poulos-Davis-Randolph method. [ABSTRACT FROM AUTHOR]

An extensive suite of three-dimensional finite-element simulations was carried out to examine the response of pile-raft-soil systems under seismic excitation representative of far-field events. The numerical procedure was first validated by a series of seismic centrifuge tests performed mainly on 4 × 3 pile-raft systems embedded in soft clays and was subsequently extended to study the influence of various factors on the computed raft acceleration and maximum bending moment near the pile head. The factors considered were pile length, pile flexural stiffness, peak base acceleration, superstructural mass, soil stiffness, soil frictional angle, pile density, and soil-layer thickness. With the help of dimensional analysis, the results of the parametric studies were processed and interpreted using regression analysis to derive correlations for predicting the maximum pile-group bending moment and peak raft acceleration. Such correlations are highly useful in the practical seismic design of pile-raft systems embedded in soft soils, because they provide quick first-order predictions for making initial engineering judgments prior to performing more-detailed and rigorous numerical simulations. [ABSTRACT FROM AUTHOR]

Pile-soil interaction has been a subject of interest to many earlier researchers. However, not much work has been done on the effects of structural response of single piles subjected to different combination of axial and lateral loads and hence the respective pile-soil interaction. The main objectives of this paper are to assess the influence of axial load intensities on the lateral single isolated pile response in various pile slenderness ratios. Three-dimensional finite element approach was used to simulate the whole geotechnical system. The finite element included linear elastic model to represent the pile, Mohr-Coulomb to model surrounded soil and 16-nodes interface element to simulate the pile-soil interface. It was found that the lateral deflection is increased with increased the axial load in case of cohesionless soils. While, in case of cohesive soil, reduction in lateral pile displacement is occurred when low axial load is applied (i.e. V less than 4H) and increased when axial load level (i.e. V more than 6H) has been increased. [ABSTRACT FROM AUTHOR]

The axial capacity of novel spun-cast ductile iron (SCDI) tapered pile fitted with a lower helical plate is investigated. Seven instrumented piles, five SCDI tapered and two steel straight shafts, were installed in sand soil using mechanical torque. The piles were tested under axial compressive loading and their ultimate capacities were determined. To assess the cyclic loading effect on the piles performance, two load sequences were adopted: four piles were subjected to monotonic loading, and three were subjected to initial cyclic loading followed by monotonic loading. The installation torque was monitored and the resulting capacity-to-torque ratio was compared to the literature reported values. Tapered helical piles displayed a stiffer response and yielded higher capacities compared to the straight ones. Strain gauges were used to evaluate the piles load transfer mechanism, and demonstrated increased shaft resistance due to the pile taper. The taper helped compact the sand within the zone adjacent to the pile, originally disturbed by the helix penetration, hence increased the soil strength and stiffness. These effects were prominent for larger ratio of shaft/helix diameter. Finally, 3D finite element analyses were conducted to evaluate the axial performance of the system and demonstrated its enhanced frictional resistance. The experimental and numerical results confirmed the superior performance of the proposed system in sands. [ABSTRACT FROM AUTHOR]

A key challenge for estimating seismic response of piles and soils in liquefied and laterally spreading ground is the efficient prediction of local loosening phenomenon (shear localization) at the interlayer between the liquefied loose sand and the overburden crust. To this end, a simplified finite-element (FE) model was developed. In the soil model, a soft interlayer element with a thickness and corresponding low reference shear modulus was developed to represent the shear localization phenomenon. The proposed FE models were then used to simulate centrifuge tests of a single pile, a two-pile group, and a six-pile group in sloping liquefiable profiles that lead to lateral spreading. Predicted results of the shear-localization-induced soil lateral spreading displacement, as well as the structural response, agree reasonably well with the test records, indicating that the proposed FEmodel is capable of approximating the seismic responses of soil and piles in liquefied and laterally spreading ground. In addition, a parametric analysis was performed to build a relationship between the thickness and the low reference shear modulus of the soft interlayer element. [ABSTRACT FROM AUTHOR]

To achieve the satisfactory performance of a machine foundation, the dynamic amplitude should be limited to a few micrometres. In using piles for the foundation, the interaction of the pile with the surrounding soils under vibratory loading will modify the pile stiffness and will generate damping. The results of a three-dimensional, finite element model of a soil–pile system with viscous boundaries were used to determine the dynamic stiffness and damping generated by soil–pile interactions for a single vertical pile subjected to a vertical harmonic loading at the pile head. The pile was embedded in a linearly elastic, homogeneous soil layer with material damping of the hysteretic type. A parametric study was undertaken to investigate the influence of the major factors of the soil–pile system that affect the vertical vibration characteristics of the pile response. These were found to include the dimensionless frequency,ao, soil properties, pile properties, and length and axial load on the pile head. Equations were developed to determine the range of such influence. Two general equations that include all of these parameters and can be used to approximate the stiffness and damping of the pile were developed so that a finite element analysis does not have to be made in every case. [ABSTRACT FROM PUBLISHER]

Effective and convenient prediction of the peak displacement of piles under collision conditions facilitates the design framework preparation and pile damage evaluation. Hence, an energy-based method was proposed to predict the peak displacement of the widely used steel casing composite (SCC) piles under impact loading. The pile deformation energy was first calculated based on its deformation characteristics and the relationship between the sectional bending moment and curvature. The pile deformation energy and pile–soil energy distribution ratio were then employed to determine the relationship between the total absorbed impact energy and pile head displacement, which was represented by curves. The peak pile displacement under lateral impact loading was finally obtained by interpolating the absorbed impact energy curves. By conducting sectional analysis of the pile considering the strain rate effects and using a structural pushover procedure, the peak pile head displacements for various collision cases were predicted with reasonable accuracy. The effectiveness and reliability of the proposed method were verified by comparing its results with those of previous reduced-scale impact tests and validated full-scale finite element models. • An energy-based method was proposed to predict the peak displacement of the SCC pile under lateral collision. • The proposed method required only impact energy input, sectional analysis, and pushover procedure. • The deformation and energy distribution characteristics of piles under static and impact loading were similar. • The SCC piles had two deformation forms: a single plastic hinge and a double plastic hinge. • Pile deformation energy was derived from its deformed shapes and the sectional bending moment–curvature relationship. [ABSTRACT FROM AUTHOR]

This paper presents a simplified modeling for seismic responses of rectangular foundation on piles subjected to horizontal earthquakes. The motions of foundation can be derived simply assuming that the foundation is vibrating in one direction. Time-dependent foundation responses under the earthquake with a bevel angle to the foundation were able to decompose and compute in both longitudinal and transverse directions. Using the explicit finite difference scheme, discrete wave equation analysis was suggested presuming that the lateral boundaries of foundation are free of tractions. The pile-soil-pile and soil elements underneath the rectangular foundation were modeled by springs. Seismic motions of the equivalent piers representing for the pile-soil-pile elements were analyzed using one-dimensional analysis of the single piles. Seismic forces transmitting through these elements to the foundation were able to obtain. The superstructure influences can be monitored assuming that the ratio of superstructure displacement and foundation displacement is constant. The proposed solutions were found compatible to three dimensional finite element ones. Factors to influence the seismic responses of foundation are discussed. The proposed analysis is concluded to provide efficient solutions to the preliminary design of piled raft foundation. [ABSTRACT FROM AUTHOR]

Piles have been used to transfer superstructure (bridges, buildings, etc.) loads to deeper competent bearing strata to minimize settlements. Accurate predictions of design settlements of vertically loaded piles under working load are a critical issue in the design of pile foundations. Numerous comprehensive trials, built on a regression-based predictive formula that produces the axial settlement using elastic shortening as the input variable, were performed in this study, and a simple relationship was established between the elastic shortening of piles and the measured design settlements of 93 full-scale pile load tests installed in variable bearing materials. The calculated axial settlements of piles from the proposed method in this study were compared to the measured axial settlements of the piles. Accuracy and validity of the proposed method were verified through conventional statistical analysis in terms of mean of bias (λm) and coefficient of variation (μ). The proposed method yielded values of λm =1.06 and μ =0.15. [ABSTRACT FROM AUTHOR]

Yatay yüklü kazıkların deformasyon davranışını etkileyen en önemli etkenler zemin koşulları, yükleme durumu ve sınır koşullarıdır. Sonlu elemanlar yöntemleri bu etkilerin hepsinin göz önüne aldığı için çok önemli analiz araçlarıdır. Kazıkların yük-deformasyon davranışının doğruya en yakın modeli üç boyutlu tasarımlarla sağlanabilir. Bu çalışmada sözü geçen etkileri ve üç boyutlu davranışı dikkate alan analizler yapılmıştır. Nümerik analizlerde farklı çaplardaki dairesel şekilli betonarme kazık ve farklı elastik özelliklere sahip zeminler için deformasyon davranışı elde edilmiştir. Zemin özelliklerinin gerilme-deformasyon davranışı üzerindeki etkisi üzerinde durulmuştur.

In this technical note, the results of a set of simplified numerical analyses are presented. The analyses were undertaken in order to examine the validity of a descriptive framework that was previously proposed to illustrate the behaviour of thermally activated piles and to highlight the potential limitations of some analytical methods that are being applied to their study and design. Working on the premise that some soils, specifically moderately to highly over-consolidated clays, may experience thermally induced volume changes larger than concrete elements inserted into the ground, the results of the study highlight that analyses that do not account for the initial temperature field and boundary conditions, and the response of the ground to temperature changes, may yield erroneous conclusions with respect to the performance of operational thermally activated piles used to support temperature-controlled structures. [ABSTRACT FROM AUTHOR]

The performance of four sections of a full-scale embankment constructed on soft soil is examined using a fully coupled and fully three-dimensional finite element analysis. The four sections had similar embankment loadings but different improvement options (one unimproved, one with pile-support only, one with a single layer geotextile-reinforced platform and pile-support, and one with two layers of geogrid-reinforced platform and pile-support). Like the field data, the numerical results show that the inclusion of piles decreases the settlement at the subsoil surface to 52% of that for the unimproved section, and the addition of a single layer of geotextile reinforcement ( J = 800 kN/m) further reduced settlement to only 31% of that of the unimproved section. The effects of geosynthetic reinforcement and multiple layers of reinforcement on the performance of the pile-supported embankment are discussed. The relative load transfer is calculated using eight existing methods and they are compared with the field measurements and numerical results. [ABSTRACT FROM AUTHOR]

A quasi-3D method for the analysis of single piles and pile groups is presented. The method includes an equivalent linear constitutive model for nonlinear analysis, an 8-node pile element that simulates the effects of pile volume and energy transmitting boundaries which are especially important for the analysis of high frequency loading of machine foundations. The quasi-3D formulation and equivalent linear model result in orders of magnitude decreases in computational time. The accuracy and reliability of the approximate approach was validated by comparing results with 3D analytical results from MIT and by data from field tests on single piles and pile groups from Taiwan. The computed results compared very favorably with the analytical and field test data. [ABSTRACT FROM AUTHOR]

This paper presents the results from a series of three-dimensional finite element analyses, which examine the benefits of adopting square pile-tower structures instead of circular monopiles. The advantages of square monopiles are brought out in this paper through a parametric study with a Tresca soil model, where the shear strength and modulus of elasticity varied with depth and the pile-tower structures were modelled as an elastoplastic material. The effects of pile diameter, pile thickness, eccentricity, and pile length for free-head pile-towers embedded in lightly overconsolidated and heavily overconsolidated clays were investigated. From the results of the numerical models, it is clear that the ultimate lateral capacity and stiffness of square pile-tower structures are substantially higher than of circular structures embedded in clay layers. Moreover, the amount of rotation and displacement of square structures are not significantly affected compared to circular monopiles. [ABSTRACT FROM AUTHOR]

A tall public building in Naples (Italy) has recently undergone a seismic vulnerability assessment, following the new Italian code requirements. The building is about 100 m high and is founded on a piled raft floating in a thick layer of soft pyroclastic and alluvial soils. On the basis of a conventional subsoil classification, the inertial seismic actions on the building would lead to expensive measures for seismic retrofitting. By contrast, if site effects and soil-structure interaction are adequately addressed the picture is completely different. First, free-field seismic response analyses highlighted the beneficial effects of a peat layer, acting as a natural damper on the propagation of shear waves. Finite-element analyses of pile-soil kinematic interaction were then carried out to define the foundation input motion, which was found not to be significantly affected. The effects of inertial interaction were evaluated accounting for soil-foundation compliance; they resulted in an increase of the structural period of vibration, while the overall damping did not change compared to that of the fixed-base structure. The increased structural period led to further reduction of spectral acceleration. The results could lead to significant impacts on the seismic assessment of slender buildings founded on piles embedded in deformable soils. [ABSTRACT FROM AUTHOR]

In order to mobilize shallow soil to participate in the interaction of piled raft foundation sufficiently, the concept of piled raft has been modified to new type of foundation named composite piled raft. In the system of composite piled raft, the short piles made of flexible materials were used to strengthen the shallow soft soil, while the long piles made of relatively rigid materials were used to reduce the settlements and the cushion beneath the raft was used to redistribute and adjust the stress ratio of piles to subsoil. Finite element method was applied to study the behaviour of this new type of foundation subjected to seismic forces. This paper focuses on behaviour of various components of foundation system such as long pile, short piles and subsoil under seismic force in subsoil related to Surat city geological condition. A comparative study is done to understand the effect of cushion on axial stresses, shear stresses and shear forces along piles. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear stability analysis of piles under bilateral contact constraints imposed by a geological medium (soil or rock). To solve this contact problem, the paper proposes a general numerical methodology, based on the finite element method (FEM). In this context, a geometrically nonlinear beam-column element is used to model the pile while the geological medium can be idealized as discrete (spring) or continuum (Winkler and Pasternak) foundation elements. Foundation elements are supposed to react under tension and compression, so during the deformation process the structural elements are subjected to bilateral contact constraints. The errors along the equilibrium paths are minimized and the convoluted nonlinear equilibrium paths are made traceable through the use of an updated Lagrangian formulation and a Newton-Raphson scheme working with the generalized displacement technique. The study offers stability analyses of three problems involving piles under bilateral contact constraints. The analyses show that in the evaluation of critical loads a great influence is wielded by the instability modes. Also, the structural system stiffness can be highly influenced by the representative model of the soil. [ABSTRACT FROM AUTHOR]

The effects of tunnel construction on existing single piles have been extensively investigated, but the influence of twin tunnel advancement on an existing pile group is seldom reported in the literature. In this study, a series of three-dimensional (3D) centrifuge model tests and numerical simulations using an advanced hypoplastic soil model were carried out to investigate the response of an existing 2 × 2 pile group to piggyback (i.e. vertically aligned) twin tunnelling at various depths. Soil parameters for 3D numerical back-analyses were obtained from stress-path triaxial tests. In each twin tunnelling simulation in a centrifuge, the first tunnel was advanced three-dimensionally by controlling volume loss in-flight near the mid-depth of the pile shaft, before the second tunnel was constructed either next to the toe of the pile group (test ST), below but to one side of the pile group (test SB) or directly beneath the pile toe (test SU). The piggyback twin tunnelling in test ST resulted in the largest transverse tilting (of 0·2%) but the smallest settlement of the pile group under a working load. This is because the second tunnelling caused significant non-uniform change in vertical effective stress underneath the four piles in the group. On the contrary, the tunnelling directly beneath the pile group (i.e. test SU) caused the smallest tilting but the largest settlement of the pile group (4·6% of pile diameter) and substantial mobilisation of shaft resistance. This is attributable to the most significant and uniform loss of toe resistance of each pile in the group resulting from stress relief from the second tunnelling. Two distinct load transfer mechanisms can be identified in the pile group, namely downward load transfer in test ST and upward load transfer in tests SB and SU. [ABSTRACT FROM AUTHOR]

This paper presents the effect of surcharge support pressure on pile load-settlement response during static load testing. A three-dimensional nonlinear finite-element model is developed to investigate the loading sequences of an axial compressive static load test, using surcharge loads as the reaction system. Results of a static load test at a construction site for which the geotechnical data are available were used for verification of the numerical model. The results show that the surcharge pressure on supports has little impact on the ultimate capacity of the pile, as the shaft skin friction is slightly influenced by the surcharge and the effect on the tip resistance is negligibly small. The initial stiffness of the pile, however, might be considerably affected by the surcharge pressure distributed around the pile shaft. The influence on stiffness increases with increase in the pile diameter. The effect of surcharge pressure is more pronounced for piles embedded in frictional soils compared with cohesive soils. Comparing the results with those available in the literature for pile testing using the reaction pile system shows that the pile stiffness is 15 to 25% less affected in the surcharge reaction system. [ABSTRACT FROM AUTHOR]