Pile Head Research Articles

Ultimate Lateral Resistance of Single Piles in Sand

The p-y curve method is currently the most widely utilized analytical approach for horizontally loaded piles. Precisely determining the ultimate soil resistance is essential to enhance the accuracy of the p-y curve. Despite various scholars proposing methods to establish the law governing ultimate soil resistance with soil depth in the sand, significant discrepancies exist among these approaches. This paper posits that the three-dimensional failure mode of the shallow soil in front of the pile manifests as a cone when it reaches the limit state. The expression for the ultimate soil resistance of a single pile in shallow soil is derived through limit equilibrium theory, and subsequently, the modified p-y curve is obtained. The accuracy was validated through a comparison between the corrected p-y curve and results obtained from centrifugation experiments and field studies. In contrast to the API specification method, the refined hyperbolic function p-y curve demonstrates enhanced precision, facilitating precise predictions of pile head displacement and pile bending moments under horizontal loads.

Analytical solution for simplifying the pile-soil interaction to a spring-damping system under horizontal vibration

An analytical solution is developed to investigate the model of simplifying the pile-soil interaction to a spring-damping system when the horizontal earthquake input or the top of the model is subjected to horizontal dynamic load. Based on Euler-Bernoulli theory, the dynamic equilibrium equations of pile in soil and air are established, respectively. Then, utilizing the corresponding boundary conditions, potential function decomposition, and transfer matrix method, the analytical expression of impedance at the pile head whether the horizontal earthquake input or the top of the system is subjected to horizontal dynamic load can be presented. Furthermore, the model of the pile-soil complex interaction can be simplified as a spring-damping system according to the stress equilibrium at the pile bottom in the air. Moreover, the rationality of the present solution (without simplification) is verified by comparison with existing methods, and then the difference between the present solution (without simplification) and the spring-damping system (simplification) is also compared. Finally, the influence of the parameter variation in the pile buried in the soil and soil free-field on the simplified model are discussed. The research results will be instructive for the simplification of numerical model for pile-soil interaction.

To Study the Behaviour of Single Pile Foundation Under Vertical Loading using Geo 5’’

The objective of the project is to analyze a pile foundation and determine it’s load bearing capacity by static method and a software and compare the results. This project includes the analysis of pile formed on black cotton soil at site of the “Galaxy Sky Residency” Miraj.. The calculations were carried out using the commercial software GEO5 from FINE Inc. This software computes the load-displacement curve on the pile head and the distribution of normal and shear forces along the shaft. The shear behavior of the pile-soil interface is de-scribed according to a modified Mohr- Coulomb’s theory. This paper also focuses on the de-termination of parameters of strength (angle friction and cohesion) and settlement (Young modulus) for deep foundation. The use of GEO4 for foundation design is explained in details herein.

Analysis of laterally loaded floating piles using a refined Tajimi model

AbstractThis paper presents a novel mathematical model for the analysis of laterally loaded floating piles embedded in a homogeneous soil layer of finite thickness. The governing equations of the soil surrounding the pile are established by treating soil as a Tajimi‐type continuum, and their solution yields a closed‐form expression that provides the lateral force developing to resist pile deflection. Accordingly, analytical expressions are obtained for the swaying, swaying‐rocking and rocking pile head stiffness, as well as for pile displacement and rotation along its length. The derived expressions are functions of parameters that have direct physical meaning, such as pile and soil elastic stiffness. As such, they pose as an attractive alternative to numerical methods for the low‐cost calibration of Winkler‐based model empirical parameters associated with small pile deflections. The presentation concludes with a parametric study focused on exploring the sensitivity of pile stiffness and deformations to the main problem parameters, and on highlighting differences in the lateral response of floating and end‐bearing piles.

Performance of Pile–Wall System Adjacent to Footings

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall’s performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing.

Experimental investigation of dynamic behaviour of pile-supported bridges in sandy deposits

This paper presents the results of centrifuge tests performed on reinforced concrete (RC) pile–supported simply supported girder bridge models in non-liquefiable (unsaturated) and liquefiable (saturated) slightly inclined sandy soil sites. The main objectives were to investigate the dynamic response characteristics of RC pile–supported simply supported girder bridges in non-liquefiable and liquefiable soils, examine the mechanisms causing beam collapse and damage to pile–pier yielding, and verify the effectiveness of cable restrainers. The centrifuge tests were conducted in non-liquefiable and liquefiable sites, each consisting of a three-span RC pile–supported simply supported girder bridge model and a control model with a superstructure equipped with a cable restrainer. First, the dynamic characteristic parameters of the soil and structural models in both sites were obtained. Subsequently, the conventional test results were interpreted, including the excess pore pressure ratio, acceleration, and displacement. The analysis included examining the moment demand of the pile–pier structure and seismic damage mechanisms. Finally, a correlation analysis was performed to evaluate the inertial and kinematic effects on the moment demand of the pile–pier structure. The results show that the acceleration response after soil liquefaction at the inclined sites is amplified unilaterally in the downslope direction and spikes appear. The liquefiable foundation is displaced to the downslope. However, major earthquake induces foundation displacement, and liquefaction leads to a longer duration and more significant soil displacement. The installation of cable restraints significantly increased the acceleration response of the superstructure. Still, it effectively reduced the relative displacement of the superstructure and prevented the beam from collapsing. Soil liquefaction decreases the bending moment of the pile–pier structure, and the cable restrainer causes the damage mode of the pile–pier structure to shift from the pile head to the pier bottom. In the non-liquefiable scenario, the bending moment demand at the pile head has a more significant influence on the inertial effect. Additionally, using the cable restrainer system can increase the kinematic effect after liquefaction. The test results can be used to validate numerical models and provide a reference for pile foundation design.

Experimental and Computational Analyses of Sustainable Approaches in Railways

Railway transportation is widely recognized as an environment-friendly and sustainable means for conveying freight and passengers over long distances. This article investigates the effectiveness of utilizing scrap tire rubber granules and geosynthetics to enhance track performance in response to the growing demands for railway transport and the consequent escalation of train-induced loading. A multi-faceted methodology, incorporating experimental, numerical, and analytical techniques, is employed to examine the efficacy of these sustainable approaches. Results from three-dimensional (3D) finite element (FE) analyses conducted on slab tracks for high-speed railways reveal that the addition of a resilient layer, comprising scrap tire rubber granules, reduces vertical stress within the track substructure. Laboratory investigations on an innovative composite material consisting of soil, scrap rubber granules, and polyurethane demonstrate its potential to enhance track performance. Findings from two-dimensional (2D) FE analyses conducted on pile-supported railway embankments highlight an enhanced transfer of load to the pile head following the installation of a geogrid layer at the embankment base. Finally, the results from the analytical approach indicate a reduction in track settlement and a decrease in the track geometry degradation rate on reinforcing the ballast layer with 3D cellular geoinclusion. The novelty of this study lies in the comprehensive assessment of the innovative composite material under drained and cyclic loading conditions, the investigation of the influence of train loading on geosynthetic tension and the load transfer mechanism in railway embankments, and the development of an innovative computational methodology capable of assessing the effectiveness of 3D cellular inclusions in improving the ballasted railway track performance. The findings from this article underscore the effectiveness of these sustainable approaches in mitigating the challenges posed by increased loads on railway tracks, providing valuable insights for the ongoing efforts to optimize railway transportation infrastructure.

Effect of Seismic Loading on Porewater Pressure in Clayey Soil under Disconnected Piles-Raft Foundation

The disconnected piled raft foundation (DCPRF) is one of the newly introduced foundations for specialization in geotechnical engineering, which significantly reduces the moment and stress on the pile head. In addition, this type of foundation is an ideal choice in areas with seismic activity due to the presence of cushion material between the raft and the piles. This work aims to present a numerical model in PLAXIS 3D software for connected piled raft and disconnected piled raft foundations under the influence of seismic loads and investigate the effect of pore water pressure on the disconnected foundation compared to the connected foundation. The study will depend on the earthquake that struck Iraq in November 2017 in the Halabja region. Strength was 7.3 on the Richter scale with PGA (0.1g). The results of changing pore water pressure showed the variation of pore water pressure. In the case of a DCPRF, the porewater pressure and excess porewater pressure in the soil are much greater than in the case of a CPRF. The increase in the porewater pressure is due to the weight of the building and the weight of the additional cushion layer on the soil. The mechanism for transferring the load in the case of a DCPRF is carried out by raft, then to the cushion, and then to the soil and piles. The load transferred to the soil in the case of DCPRF is more than that transferred to the soil in the CPRF system.

Investigating the wave attenuation capabilities of rectangular pile head breakwater: A physical modelling approach

The study provides a comprehensive examination of single row Rectangular Pile Head Breakwaters (RPHB), encompassing both non-perforated and perforated variations. In the non-perforated RPHB category, the investigation delves into the effects of pile head height and width, and wave climate. For perforated RPHB structures, the study analyses the influence of percentage of perforations, perforation size, and depth of water. Further, the research includes a comparative assessment between non-perforated and perforated RPHB structures. Additionally, the research conducts a comparative analysis with similar structures. In the case of non-perforated RPHB, the configuration with relative pile head diameter (D/d) of 2.4 and relative pile head height (Y/Hmax) of 1.5 stood out as the most effective model. Similarly, the perforated RPHB demonstrated its maximum wave attenuation potential with percentage of perforations (P) of 24% with relative size of perforations (S/D) of 0.25. This optimal configuration achieved a minimal wave transmission coefficient (Kt) of 0.53, reflection coefficient (Kr) of 0.33, and energy dissipation coefficient (Kd) of 0.79 at a relative water depth (h/H) 0.865. Notably, the introduction of perforations on the RPHB structure led to an improvement in wave attenuation performance by 4–8%, resulting in lower reflection and higher energy dissipation. Comparatively, the RPHB structure outperformed the Enlarged (cylindrical) Pile Head Breakwater (EPHB) and Conical Pile Head Breakwater (CPHB) structures in terms of wave attenuation, exhibiting higher reflection and superior energy dissipation characteristics. The consistent outcome of these investigations reveals that the RPHB exhibits superior hydrodynamic performance characteristics and design suitability, making it a promising choice for breakwater applications.

Non-Destructive Evaluation of Material Stiffness beneath Pile Foundations Tip Using Harmonic Wavelet Transform

Pile foundations are used to support superstructures and play an important role in the safety of these structures. The performance of pile foundations generally depends on the conditions of the pile itself and the material under the pile tip(i.e., bottom), especially for end-bearing piles installed in soft soil volumes. Therefore, to assess the performance of existing pile foundations, it is crucial not only to evaluate the structural integrity of the pile itself, but also to assess the ground conditions, such as subsoil stiffness beneath the pile foundation tip. Accessing the subsoil beneath the pile foundation tip is highly challenging in the field. Hence, there is a need for the development of non-destructive pile evaluation methods that allow the assessment of subsoil stiffness beneath the pile tip without direct access to the subsoil. Various non-destructive methods have been developed for pile performance assessment. However, these conventional non-destructive methods are primarily designed for assessing the structural integrity of the pile itself, and there are no existing non-destructive pile integrity testing methods applicable to evaluate the subsoil stiffness beneath the pile tip. In this study, a non-destructive method is developed to evaluate the subsurface soil stiffness beneath pile tip without direct access. The proposed method involves applying impact loading to the easily accessible pile head and measuring the elastic waves propagated within the pile foundation due to the impact loading. These wave signals are then recorded at the pile head. The measured time–history signals are decomposed using harmonic wavelet transform. This allows the obtainment of well-defined magnitude and phase information over time for various individual frequency components composing the wave. In this study, a method is proposed to assess the stiffness of the subsoil beneath the pile tip by simultaneously utilizing the magnitude and phase information of the measured signals obtained through harmonic wavelet transform. To facilitate this, a step-by-step data analysis procedure for evaluating the subsoil stiffness beneath the pile tip is introduced. To validate the proposed method, numerical simulations were conducted using ABAQUS. The experimental data obtained from the numerical simulations were processed using the proposed method to assess the subsoil stiffness beneath the pile. The determined subsoil stiffness was then compared with the exact soil stiffness used in the numerical simulation to evaluate the validity of the proposed method. Through this analysis, the proposed method demonstrated its effectiveness in assessing the subsoil stiffness beneath piles tip installed in weak soil volume.

Thermomechanical Analysis of Energy Piles Using a Load-transfer Approach Considering Soil Coupling Effects

Energy piles are inevitably subjected to thermomechanical loads due to their dual role of utilizing geothermal energy and supporting structural loads. The load-transfer approach is a suitable predictive method for addressing the analysis and design of energy piles, but it generally does not properly consider the continuity and deformation behavior of the soil mass. This study presents experimental and analytical investigations on the thermomechanical behavior of full-scale energy piles. A new thermomechanical load-transfer approach allowing consideration of the soil coupling effects was proposed by involving the soil deformation and the soil-pile interface behavior. Through comparative analysis with experimental data, the proposed method (with soil coupling effects) demonstrated superior predictive accuracy compared to the existing method (without soil coupling effects). In this field condition, ignoring soil coupling effects could result in an underestimation of nearly 48.8% of pile head settlement. The validated method was further used to analyze the thermally induced cyclic behavior of energy piles under various mechanical load levels. The results indicated that the thermally induced response of energy piles was directly associated with the level of the head load. The energy piles under higher axial loads may show irreversible thermomechanical behavior when subjected to cyclic thermal loading.

Full-scale tests of a long energy pile subjected to separated and coupled thermo-mechanical loads

In this paper, four individual full-scale tests were carried out to study the mechanical response of a cast-in-place energy pile beneath a liquefied natural gas (LNG) tank subjected to separated and coupled thermo-mechanical loads. The results show that the temperature profiles displayed a comparable trend in response to pile heating, cooling and recovery. Specifically, the temperature at the mid-depth of the pile fluctuated rapidly, while the changes at both ends were relatively slower. During the thermal stages, when the pile had the flexibility to expand or contract, the observed strain at the pile head significantly deviated from the free thermal strain. In contrast, the strain at the pile toe was relatively aligned with the free thermal strain. The thermally induced stress obtained at the end of the coupled loading–cooling stage was found to exceed the tensile strength of the C40 reinforced concrete. However, under the actual testing conditions, both the settlement and the bearing capacity of the pile remained well within the required values, ensuring the structure of the LNG tank will not be damaged.

Simplified Design Method of Laterally Loaded Rigid Monopiles in Cohesionless Soil

This paper presents a simplified design method for laterally loaded rigid monopiles in cohesionless soil. The proposed design method is based on a constant depth of the rotation point and a bi-linear distribution of soil lateral reaction along the embedded length of the monopile. Furthermore, a mobilization coefficient of soil resistance is introduced to quantify the magnitude of the soil reaction mobilized under a certain load level applied at the pile head. The mobilization coefficient is found to be directly related to the pile head rotation by back-analyzing test results measured from 13 laterally loaded piles in the published literature. The feasibility and reliability of the proposed design method are evaluated with another 23 laterally loaded piles, which are compiled in a database. The results show that the proposed design method yields relatively satisfactory predictions of the nonlinear load-deformation responses of these piles. Furthermore, comparison of soil lateral reaction profiles between those measured and calculated with the proposed method proves the validity of the assumed soil reaction profiles. As the mobilization coefficient is back-analyzed from piles mostly embedded in uniform ground and the pile bending and translational deformations are neglected in this study, the proposed method is suitable for monopile designs in uniform sites with medium~medium-dense sand, in which the pile bending and translational deformations can be ignored.

Experimental and Numerical Simulation Study of Water Infiltration Impact on Soil-Pile Interaction in Expansive Soil

A laboratory model of a single pile embedded in Nanyang expansive soil and subjected to water infiltration is applied in this study to examine the interaction between the expansive soil and pile foundation upon water infiltration. The soil matric suction decreases as a result of the rising soil-water content. The amount of soil ground heave reaches its peak of 10.7 mm after 200 hours of water infiltration. As matric suction decreases, pile shaft friction also declines, which causes more of the load at the pile head to be carried by the pile base resulting in more pile settlements. A new numerical simulation method is provided to simulate this issue by coupling the subsurface flow, soil deformation, and hygroscopic swelling to investigate the expansive soil-pile response upon water infiltration. From the numerical simulation model, hygroscopic strain arises as a result of elevated moisture levels resulting from the entry of water, and due to ground heave and the mobilization of lateral soil swelling, the shear stress at the interface between the soil and the pile gradually increases over time. It reaches its maximum value of 4420 Pa at upper depths around 200 hours after the infiltration. The comparison between the lab model testing data and the numerical model results demonstrates a good level of concurrence.

Seismic behavior of highway embankment reinforced with remedial countermeasures on saturated loose sandy layer

A hybrid pile system is proposed to suppress excessive settlement and lateral spreading, which are regarded as main causes of highway embankment failure due to earthquakes. This system, combining two groups of vertical and inclined piles arranged on both sides of highway embankment slope, can be applied to existing highway embankments. In this research, a series of 1 g shaking table tests were performed together with modeling the performance of highway embankments incorporating three cases with different reinforcements subjected to two sinusoidal waves. Several aspects of acceleration time history, pile deformation, and embankment settlement under three configurations were revealed and discussed to confirm the effectiveness of the proposed countermeasures. The results indicate that (1) the hybrid pile system can still ensure sufficient functionality to maintain the highway embankment after two consecutive strong earthquakes; (2) this system can also enhance the integrity of loose sandy layer to reduce the settlement and lateral spreading of embankment; (3) the inclined piles effectively reduce pile head deformation by increasing the shear strength of the pile.

Influence of pore water pressure on concrete creep and a creep model considering the effect of cohesion and internal friction angle

AbstractA new nonlinear viscoplastic body considering cohesion and internal friction coefficient versus time is proposed by considering cohesion and internal friction angle. A new creep model for concrete considering cohesion and internal friction angle is obtained by interlocking it with the conventional model. The results show that the creep model can properly reflect the creep development of soft‐cut concrete at the pile head by comparing the creep model with the three‐dimensional creep test data trends under various levels of loading. The model can well describe the whole process of creep deformation and also better compensate for the shortcomings of the traditional creep model that cannot describe the characteristics of accelerated creep deformation.

Vertical seismic response of end-bearing piles in nearly saturated soil

This paper presents a study on the effect of the degree of saturation of the foundation soil on the vertical seismic response of end-bearing piles subjected to P-waves. The research focuses on nearly saturated soil, where the air phase is not continuous and air bubbles are dissolved in the pore water, and thus can be treated as two-phase material. The response of the two-phase soil–pile system is quantified by means of a rigorous coupled hydromechanical model, which is based on Biot’s theory for poroelastic media and treats the air bubbles–pore water mixture as a homogeneous fluid obeying Boyle’s law. Numerical results are used to illustrate the influence of the degree of saturation of the soil layer on the seismic strong motion transferred to the pile head, i.e., the capacity of piles to filter seismic wave energy. This work bridges the gap between single-phase and two-phase saturated soil models, which predict profoundly different pile head displacements at incident wave frequencies of practical interest, and elucidates the mechanisms that lead to these differences.

A CPT-based multi-spring model for lateral monopile analysis under SLS conditions in sand

Monopiles are the most common Offshore Wind Turbine (OWT) foundations due to their simplicity in design, fabrication, and installation. However, large new-generation turbines have led to significant changes in monopile dimensions, necessitating extensive finite element analyses and ground investigations to meet design requirements. While Cone Penetration Test (CPT)-based p-y methods can analyse slender pile lateral behaviour, they often miss additional resistance mechanisms relevant to rigid monopiles. This paper introduces CPT-informed resistance mechanisms for monopiles to incorporate additional lateral resistances beyond p-y modelling capabilities. Distributed moment–rotation (m-θ) springs are defined by repurposing CPT-based axial capacity estimation methods for piles; and pile tip shear and moment springs are informed by approximating a residual bearing stress post-installation using local CPT qc values. The performance of the multi-spring model is appraised against data reported from monotonic pile pushover tests conducted at two sand sites. Results show that the multi-spring model is capable of predicting pile head deflections reasonably well within serviceability deflection limits against the reported test data, but ultimate failure loads cannot be predicted using the proposed model. A clear sensitivity in pile response to local variations in CPT qc is demonstrated.

Pengendalian Durasi Optimal pada Pembangunan Myze Hotel Sumenep Menggunakan CPM dan Metode PERT

The project owner expressed a desire to accelerate the project to avoid delays. According to observations and progress reports, the week 45 progress was 76.071% with a deviation of -7.894%. The delay was caused by the contractor's poor time and cost management which affected the project implementation. Warning letter 1 is given by the owner so that the contractor evaluates and accelerates implementation. Time control is required, as well as time optimization analysis using the PERT method for a more efficient and faster duration. PERT focuses on scheduling with synchronization of project elements, taking into account the uncertainty of the duration of tasks and the overall project. This research aims to identify project duration control by applying PERT and CPM methods, as well as exploring the cost of potential project acceleration through subcontractor integration. Data collection techniques are through project observation and documents such as cost budget plans, S-curves, progress reports, and reference drawings. This data is used to analyze the optimal time through identifying critical activities with CPM and determining the optimal duration using PERT. Alternative project acceleration with the addition of subcontractors. In the research results, the CPM method identifies critical activities such as procurement, piling, connection, and cutting pile heads, from the PERT method the optimal duration is 45 days, with a probability of 59.18%. Alternative acceleration by applying subcontractors occurred cost savings of Rp. 84,855,111.02 or 1.11% of the total normal cost so that the cost of acceleration with subcontractors amounted to Rp. 7,547,781,459.38.

Elastic–Plastic Analysis of Rigid Passive Piles in Two-Layered Soils

The paper analyses the behavior of a rigid passive pile embedded in a soil profile consisting of a stable layer underlying an unstable layer subjected to a uniform soil displacement. Pile-soil interaction is considered by modeling the soil by a series of elastic–plastic springs along the pile shaft. The modulus of horizontal subgrade reaction is assumed to linearly increase with depth in the unstable layer and constant in the stable one. The ultimate soil resistance is assumed increasing with depth in both layers. The results of analysis are presented in dimensionless form in terms of shear force developed at the slip surface as a function of the pile embedment into the stable layer and the distribution of soil characteristics over depth. The method allows capturing pile response not only at the soil ultimate state but also at the intermediate states. Specifically, the governing equations for the elastic, elastic–plastic and plastic cases are discussed and, whenever possible, a set of closed-form expressions is provided to estimate the maximum bending moment along the shaft and the pile head deflection, so that for an assigned value of the required stabilizing force both ultimate and serviceability limit state of the pile can be checked. A numerical example is given to illustrate the application of the proposed procedure.