Cylindrical Pile Research Articles

Optimising the embodied carbon of laterally loaded piles using a genetic algorithm and finite element simulation

With the need to cut embodied carbon from the construction industry, there has been a growing interest in optimising the design of different structural elements. This paper, for the first time, minimises the embodied carbon of laterally-loaded piles using a hybrid genetic algorithm. The research is split into four stages. Firstly, the optimisation algorithm is set and run to produce the optimal piles of lateral capacity 0.5 MN at a 25 mm lateral displacement limit, the embodied carbon of solid cylindrical and hollow cylindrical optimised pile designs is compared showing a significant reduction in the embodied carbon when the hollow geometry is used. Then an analysis is presented to test the effect of different displacement limits on the resulting embodied carbon, showing that the lateral displacement limit has a significant effect on the overall embodied carbon of the pile designs, highlighting a scope for reducing the embodied carbon if more pile displacement is permissible. A finite element model is built using ABAQUS simulation package to investigate the soil-pile interaction and compare the two optimal pile designs. Finally, the lateral load capacity of four different pile geometries is calculated to demonstrate the effect of pile geometry on its lateral load capacity, hollow cylindrical piles, showed to have the highest lateral load capacity compared to the other pile types. We conclude that the opportunity for significant carbon savings exists in laterally loaded piles through both optimisation and careful consideration of performance criteria.

Experimental investigation on the mechanism of local scour around a cylindrical coastal pile foundation considering sloping bed conditions

Sea-crossing bridges are often subjected to local scour, significantly impacting the bearing capacity of the foundation system and potentially leading to bridge failures. This study presents experimental investigations of local scour around a cylindrical pile under different sediment slope conditions in unidirectional currents. Unlike previous studies that focused on horizontal sediment beds, this research explores the influence of inclined sediment beds, which reflect coastal and offshore topographies, which have some angles of inclination. Utilizing flume tests, the research investigates the evolution of scour depth, scour range, and the morphology of the sediment bed across various angles of inclination. The study also evaluates the effectiveness of a scour countermeasure involving rip-rap material around the pile on sloping beds. Specifically, a steeper inclination angle induces a faster flow velocity, resulting in increased scour depth at the upstream side of the pile and a reduced scour range at the downstream side due to backfilling. The countermeasure scenario reveals a significant reduction in both scour depth and range. This research provides analysis of the effects of inclined sediment beds, which reflect coastal topographies than horizontal ones, thereby providing insights for the design and protection of bridge foundations in diverse coastal conditions.

Seismic response assessment of tapered piles in sandy soils: A numerical investigation

For the same volume, tapered (non-prismatic) piles have premium advantages over conventional (prismatic) cylindrical piles with respect to the axial and lateral load resistance and, thereby, are considered an economical alternative to prismatic piles. While previous investigations have studied the behavior of tapered piles subjected to different dynamic loading conditions, their seismic response has not yet received a comprehensive examination. This study aims to investigate the seismic response of tapered piles in sandy soils using non-linear three-dimensional (3D) finite element analyses. A total of 3084 cases were studied using MIDAS software to consider a wide range of parameters, including variations in soil density (Dr), taper angle (θ°), slenderness ratio (L/DAvg), and different earthquake recorded data. A parametric analysis was also undertaken to investigate the behavior of the pile lateral displacement, pile bending moment, and frictional resistance. The findings of the study reveal that tapering enhances the lateral stiffness of the pile, resulting in reduced lateral deflections and decreased sensitivity to changes in L/DAvg and ground motion intensity. Furthermore, under higher ground motion intensity, improved pile stiffness through tapering contribute to an increase in bending moments experienced by the pile. Another significant observation is the substantial improvement in frictional resistance due to soil densification. This emphasizes the critical importance of considering the soil behavior and its density in the design of pile foundations, particularly when aiming to withstand seismic loads effectively. These insights offer valuable guidance for designing pile foundations that can reliably endure the dynamic forces present during seismic events.

Establishing patterns of change in the coefficients of reflection, transmission, and dissipation of wave energy depending on parameters of a permeable vertical wall

The object of research is permeable vertical walls (breakwaters) with different degrees of permeability. This paper reports the results of experimental research into the interaction of gravity waves with models of permeable vertical walls (breakwaters), which were formed from cylindrical piles of circular cross-section. With the help of visual and instrumental studies, the features of interaction of surface gravity waves with permeable vertical walls of different permeability have been identified. The degree of wave transformation by these walls was also determined in the form of reflection, transmission, and dissipation coefficients of wave energy. It was established that with a decrease in the permeability of the vertical wall and an increase in the steepness of the initial wave and a decrease in its period, the height of the reflected wave increased. The pattern of the transmitted wave height had the opposite trend. It was determined that the wave reflection coefficient increased with a decrease in the permeability of the vertical wall and the steepness of the initial wave. The wave transmission coefficient had the opposite trend, namely, it increased with increasing wall permeability and with decreasing steepness of the initial wave. The gravity wave energy dissipation coefficient decreased with increasing vertical wall permeability, but for waves with a significant steepness hi/λ>0.038, a decrease in the wave energy dissipation coefficient was observed for walls with low permeability and the appearance of extreme values of this coefficient. Thus, features in the interaction of surface gravity waves with permeable vertical walls (breakwaters) of different permeability have been researched and the degree of wave transformation by these walls has been determined, which could make it possible to effectively design and operate permeable vertical walls as coastal protection structures

Embodied carbon optimisation of concrete pile foundations and comparison of the performance of different pile geometries

Concrete production and construction are responsible for a considerable share of the total carbon emissions annually. With the emerging need to cut carbon emissions from the construction sector, there has been a big interest in optimising the embodied carbon of superstructures. However, limited attention is given to optimising the embodied carbon of foundations as most designers are more interested in addressing the optimal foundations cost instead. For the first time in the open literature, this paper presents a generic genetic-algorithm-based tool to optimise the design of reinforced concrete piles. The algorithm is capable of allocating the optimal design parameters and geometry for reinforced concrete piles at any given soil conditions and required pile capacities. The algorithm is used to compare the environmental impact of different concrete pile types; solid cylindrical piles, hollow cylindrical piles, solid tapered piles and hollow tapered piles at different load capacities, the optimisation results are then compared to common industrial pile designs to quantify the possible carbon and material savings. Results show that a significant cut of more than 70% of the embodied carbon values can be achieved if the optimal pile type is used compared to common industrial design. Moreover, a finite element model built and validated over ABAQUS is used to compare the geotechnical performance of the different pile geometries. Finite element analysis results show a negligible difference between the stiffness of the different pile types when tested in the same soil conditions highlighting an outstanding optimisation efficiency of the proposed optimisation tool.

Time Domain Nonlinear Dynamic Analysis of Vertically Loaded Tapered Pile in Layered Soils

A simplified model is proposed for predicting the nonlinear dynamic response of vertically loaded tapered piles in the time domain, in which the tapered pile is divided into several frustum segments and the four-spring is used for the simulation of the soil–pile interaction. The differential equations for the tapered pile are given and solved by the finite difference method. The vertical dynamic response of a typical tapered pile is investigated, and the consistency of the computational results compared with the finite element results convincingly verifies the reliability of the proposed simplified model. Then, recommended segment numbers, considering the computational efficiency and accuracy requirements for the dynamic analysis of tapered piles, are given. And parametric studies are also carried out to investigate the effect of soil and pile parameters on the nonlinear dynamic response of the tapered pile. The results show that soil nonlinearity significantly affects the vertical dynamic characteristics of the tapered pile. And the tapered pile shows better dynamic characteristics than the cylindrical pile with the same volume and pile length. In addition, the properties of the soil along the upper part of the tapered pile have a more considerable effect on the dynamic response of the tapered pile. These results help to further improve the theory of nonlinear dynamic response analysis of tapered piles and promote its widespread application in engineering practice.

Lateral Dynamic Response of Helical Pile in Viscoelastic Foundation Considering Shear Deformation

Helical piles are a new type of pile that has good application prospects, and researchers have carried out an in-depth investigation into their vertical uplift and compressive bearing capacity. However, there is relatively little research on the dynamic bearing characteristics of helical piles. Therefore, the lateral vibration of a helical pile embedded in the viscoelastic foundation is systematically studied in this article. Utilizing the equivalent stiffness method to transform a helical pile into a cylindrical pile of special diameter, the lateral vibration model of the helical pile considering shear deformation is established based on the Winkler foundation model and the Timoshenko beam theory. The analytical solutions for the lateral dynamic displacement, bending moment, and shear force of the helical pile are strictly derived, and the rationality of the present solutions is also verified by comparing them with existing solutions. Based on the present solutions, a parametric study is carried out to investigate the influence of the pile and soil properties on the lateral dynamic response of the helical pile. It is found that the load excitation frequency and pile–soil stiffness ratio have a significant influence on the lateral dynamic displacement, bending moment, and shear force of the helical pile with space and time response.

Lateral dynamic responses of coastal group piles considering pile‒water‒soil interactions

In this paper, an analytical framework is developed to investigate the dynamic impedance of pile groups comprising an arbitrary number of cylindrical piles connected with a rigid cap. The solution considers the combination of the secondary ground wave effects transferred by the pile‒soil vibration and the hydrodynamic pressure from the pile‒water interaction. A displacement attenuation function is introduced to define the pile‒to‒pile interaction factor, which describes the relationship between the active and passive piles based on the soil reaction development. The pile is modeled as a Euler‒Bernoulli (EB) beam, and the hydrodynamic pressure is calculated using radiation wave theory. Biot's dynamic poroelastic theory describes the saturated soil around the piles. The rationality and correctness of the proposed theoretical model are verified by degenerating the solution to the existing research results. An extensive parametric analysis is conducted to investigate the effect of various factors on the lateral dynamic impedance of the group pile. Moreover, some interesting findings and meaningful conclusions are obtained.

Laboratory Modelling and Analysis of Displacement Pile in Different Geometries on Alluvial Soils

Alluvial soils are weak soils require precautions, which have disadvantageous engineering characteristics such as low shear strength and bearing capacity, high void ratio and settlement potential. Different foundation systems are preferred for structures built on these soils to transfer the load effects safely. Pile foundations as a deep foundation is classified depending on various parameters such as; material property, application method, load-bearing method. In this study, cylindrical and square concrete piles with different cross-sections and lateral areas placed in the alluvial soil. The natural alluvial soil taken from İzmir province, Balatcik location was placed in displacement-controlled pile model unit with a unit weight of ≈ 17 kN/m3. The manufactured concrete piles were driven into soil with Standard Proctor hammer. Tensile effects were applied at different time intervals to examine long-term and short-term behavior. As result of experiments, load-displacement (p-y) and displacement-time (y-t) graphs were drawn. When the displacement piles were examined under long-term tension, it was seen that the cylindrical piles displaced most. Square piles with same cross-sectional area with cylindrical piles made less displacement. All studies were modeled 1:1 as numerical and compared with experimental results. Studies showed that the experimental and numerical results for pile behavior were compatible.

Pile length estimation based on guided wave theory and dispersion analysis for reuse of foundations

The construction of new structures on existing pile foundations can significantly reduce the overall project costs. The reuse of foundations requires information on the embedded depth of existing piles, which is not always known. In this paper, a novel technique based on the periodic analysis of the phase difference and the 3-dimensional guided wave theory was developed to effectively estimate the embedded depth of unknown foundations. In this method, the guided wave model of a cylindrical pile is built by the spectral element method to determine the dispersion relation. A modified Ridders’ algorithm is proposed for root-searching. According to the phase difference of the responses collected by at least two sensors located on top or the lateral side of the pile, and the dispersion relation obtained by the spectral element method, the dispersion analysis diagram can be obtained to show the relationship between the phase difference and the wavenumber. Through the periodic properties of the dispersion analysis diagram, the pile length can be estimated. Furthermore, the periodic analysis of the phase difference for the signals collected on top of the pile is conducted in this paper using the 3-dimensional guided wave model-based dispersion relation. By comparing with synthetic and experimental data, it was shown that the proposed method can achieve an accuracy of greater than 95% in estimating the pile length of unknown foundations.

Sacrificial piles as a countermeasure against local scour around underwater pipelines

Local scour around pipelines crossing rivers or in marine environments is a significant concern. It can lead to failure of the pipelines resulting in environmental side effects and economic losses. This study developed an experimental method to reduce local scour around pipelines with a steady flow of clear water by installing cylindrical and cubical sacrificial piles. Three sizes of sacrificial piles were examined in a linear arrangement. Sacrificial piles were installed on the upstream side of the pipeline at three distances. Maximum scour depth reduction rates below the pipeline were computed. The results showed that sacrificial piles could protect a pipeline from local scour. A portion of scoured sediment around the sacrificial piles was deposited beneath the pipeline. This sediment accumulation reduced the scour depth beneath the pipeline. Analysis of the experimental results demonstrated that the size of piles (d), the spacing between piles, and the distance between the pipe and piles (Xp) were the variables that reduced the maximum scour beneath the pipeline with a diameter of D. For the piles with d = 0.40D and 0.64D, Xp = 40D was the optimal distance to install a group of piles, and cubical piles could mitigate scour more effectively than cylindrical piles under similar conditions. For the piles with d = D, the greatest reduction in scour depth was achieved at Xp = 50D with any desired spacings between piles, and cylindrical piles in this dimension could protect the pipeline against scour more effectively than cubical piles.

Mathematical simulation of backwater and velocity distribution around tandem cylindrical piles

Nowadays, with the extensive development and utilization of coastal engineering, the research on the flow field around pile groups is becoming more important. In this paper, the flow velocity and water level distribution around tandem cylindrical and rectangular piles are calculated and studied by the numerical simulation method based on delft3D. The results show that the water level of the piles in the front row of the tandem pile group increases greatly, and the influence of the rear row of the piles is small due to the shielding effect.

Guided wave and genetic algorithm-based inversion for characterization of pile foundations

The characterization of geometric and mechanical properties is of great importance for the reuse of unknown foundations. In this paper, we propose a pile characterization method to non-invasively estimate the length and mechanical properties of a pile simultaneously and automatically. The forward model is established based on the guided wave theory for a cylindrical pile and a genetic algorithm-based method is proposed for the inversion process. The guided wave model is built using the spectral element method, which can generate the dispersion relation for the given physical properties. The resonance data (including the resonance frequency and the resonance number) and pile length can be related to the phase velocity, which can be derived by assuming either the displacement control or stress control boundary conditions. The loss function in the inversion method is defined by linking the dispersion relation of the forward model and the resonance analysis for those two boundary conditions. The proposed method is validated against the experimental data. By using the proposed method, pile characterization can be achieved automatically. The average accuracy of the proposed method for characterizing the pile properties (such as pile length, shear wave velocity, and longitudinal wave velocity) and the pile length is within 5% error for each variable.

Forces of fully nonlinear interfacial periodic waves on a cylindrical pile in a two-layer fluid with free-surface boundary conditions

In the frame of fully nonlinear potential flow theory, series solutions of interfacial periodic gravity waves in a two-layer fluid with free surface are obtained by the homotopy analysis method (HAM), and the related wave forces on a vertical cylinder are analyzed. The solution procedure of the HAM for the interfacial wave model with rigid upper surface is further developed to consider the free surface boundary. And forces of nonlinear interfacial periodic waves are estimated by both the classical and modified Morison equations. It is found that the estimated wave forces by the classical Morison equation are more conservative than those by the modified Morison’s formula, and the relative error between the total inertial forces calculated by these two kinds of Morison’s formulae remains over 25% for most cases unless the upper and lower layer depths are both large enough. It demonstrates that the convective acceleration neglected in the classical Morison equation is rather important for inertial force exerted by not only internal solitary waves but also interfacial periodic waves. All of these should further deepen our understanding of internal periodic wave forces on a vertical marine riser.

Centrifuge Model Tests Investigating Initiation and Propagation of Pile Tip Damage during Driving

A number of incidents of pile tip damage and extrusion buckling have been reported within the offshore industry, generally arising during driving of relatively thin-walled tubular pile foundations through hard layers or potentially heterogeneous sediments. The issue has become of particular concern with modern trends toward larger diameter piles, with higher ratios of diameter to wall thickness, for monopile or jacket foundations of offshore wind turbines. The paucity of good-quality data available in the public domain about this kind of failure has impaired the development of simple design guidelines for industry to address the issue. The paper presents results from a series of centrifuge model tests where pile tip damage and extrusion buckling were observed during driving of either (1) undamaged cylindrical piles into a sand bed containing a layer of different sizes of boulders, or (2) predented piles into medium dense homogeneous sand. Following a previously reported pilot study, a new and higher energy model pile-driving hammer was designed to permit driving through the hard layers and allow pile embedment by up to five diameters. Two test beds were prepared, one of which contained boulder layers of different sizes either near the surface or at a depth of about one pile diameter, into which piles of two different diameter to wall thickness ratios were driven. The test series led to observations of pile tip damage that ranged from abrupt tip crumpling to gradual extrusion buckling. For 2 of the 22 piles installed, dent growth during installation was detected by optical fiber sensors attached to the piles. For the uninstrumented piles, damage was deduced from the trends in blow counts during installation, with later confirmation from detailed visual inspections and laser scanning, and also from careful layer by layer excavation of each sample. The high-quality database generated from the model tests forms a valuable resource for further study and validation of advanced numerical models to simulate pile tip damage and for calibration of simple guidelines for practical design.

A Simple Approach for the Dynamic Analysis of a Circular Tapered Pile under Axial Harmonic Vibration

The tapered pile offers sustainable use of construction materials due to its higher axial and lateral capacity and better performance owing to its geometry. This paper develops a semi-analytical solution of the vertical dynamic impedance of the tapered pile based on the dynamic Winkler theory and transfer matrix method. The accuracy and reliability of the proposed approach are verified by comparing the impedance functions of cylindrical and tapered piles obtained from the analytical solution and finite element analysis. A parametric study is performed to investigate the influence of the taper angle on the vertical dynamic impedance and resonant frequency. The results reveal that the taper angle has a significant influence on the vertical dynamic impedance, while it does not affect the oscillation period of the dynamic impedance and the resonant frequency. Besides, the vibration performance of the tapered pile is better than that of a cylindrical pile with the same volume. For a fixed-volume tapered pile, varying the pile length while keeping the pile tip diameter constant yields a better dynamic impedance than varying the pile tip diameter while keeping the pile length constant. Finally, the vertical displacement amplitude of the tapered pile decreases as the taper angle increases, especially for high-frequency excitation.

Evaluation of waste in seismic metamaterial applications

Within the scope of this study, a simulation study was carried out in order to prove the usability of waste in seismic metamaterial studies. In the study, a square array field application was preferred, and a 3-layer cylindrical pile design was used. In addition, direct contact of waste with soil and direct air is prevented. Within the scope of the study, polypropylene, which is frequently contained in medical products, concrete as a containment layer, and lime materials to prevent leakage of hazardous waste were used as materials. In addition, a design has been made within the soil structure as the ground structure. As a result of the study, it was determined that transmission losses occur in low frequency regions such as 3-10 Hz values due to obtaining partial band gaps. In addition, when looking at the propagation of the vibration waves in the field plane depending on the time, it is seen that the waves are significantly reduced, and the results are promising.

Uplift Load Carrying Capacity of Cylindrical and Belled Pile in Cohesive soil Bed

Foundation of some structures like transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures etc. are subjected to uplift loads. Literature reflects that scholars have conducted pull out field prototype and model test and failure pattern of soil is studied for belled piles in loess soil and cohesionless soil. In this research work, the authors have carried out 36 tests on single pile and pile groups and uplift load carrying capacity is obtained by experimental investigation of single pile, triangular pattern (2x1) and square pattern (2x2) using the model piles of cylindrical and belled shaped in cohesive soil of soft consistency. The piles are having 20 mm shaft diameter and varying L/d ratio of 6, 8,10,15,18 and 20 for both cylindrical pile and belled pile. Belled portion is cast in belled pile with an angle of 70° with horizontal and having base diameter of 60 mm and height 55 mm. Spacing between two piles in various pile group was kept three times the piles shaft diameter (3d) in all experiments. Based on the experimental results as the L/d ratio increases uplift load carrying capacity increases. Uplift load carrying capacity of single pile, triangular pile group and square pile group of belled pile is 410%, 280% and 240% more than cylindrical piles. Uplift load carrying capacity of triangular pile group and square pile group increases by 182% and 273% for cylindrical pile and 104% and 141% for belled pile in comparison with single pile. Failure pattern of soil is obtained from experiments performed on belled pile and by using this failure pattern, theoretical uplift load carrying of belled pile is obtained.Uplift load carrying capacity.

Calculation method and model tests of pile frost jacking for railway overhead contact systems in permafrost regions

One of the major challenges encountered in electrification reconstruction project of Golmud-Lhasa section of Qinghai-Tibet railway of China is ensuring the frost jacking stability of the pile foundation of overhead contact system mast (OCSM). To evaluate the resisting frost jacking performance of OCSM pile in permafrost regions, a theoretical model of OCSM pile in permafrost soils under the effect of frost heave was constructed based on superposition principle and deformation coordination relationship between the pile and soil. The model was solved by using the finite difference method combined with MATLAB. Then, large scale model tests were performed to investigate the thermodynamic behaviors of OCSM piles with different sections (equal section circular pile, straight cone cylindrical pile and curved cone cylindrical pile) in the permafrost soils under freeze-thaw actions, after which the theoretical model were validated. It was found that distribution curves of pile axial force obtained by the calculation method is basically consistent with model test results in the overall trend, implying that the calculation model is reasonable and feasible. During soil freezing, the pile is under tension as a whole, and the axial force is greatest near the depth of frost penetration. The maximum value of tangential frost-heave stress occurs near the ground surface. The total tangential frost heaving force of the curved cone cylindrical pile is the smallest, and the effect of resisting frost jacking is the best. These research results can provide a reference for resisting frost jacking design of OCSM pile in permafrost regions.

Bending and Free Vibration Analysis of Functionally Graded Sandwich Pile on Elastic Foundation Using Rayleigh-Ritz Method

The present study aims to carry out a parametric investigation on a pile made of different materials, and subjected to static and dynamic loading resulting from the weight of the structure and the shear force acting on the head of the pile. It is worth specifying that the pile is anchored in the ground on a Winkler-Pasternak elastic foundation that is made up of five different layers. In this study, the equilibrium equations were treated using the high-order theory with a new shear deformation shape function of a cylindrical pile made of an isotropic material and a sandwich functionally graded material.The results obtained with a numerical study based on the minimization of energies by the Rayleigh-Ritz method was carried out in order to highlight the influence of the geometric ratio, the volume fraction of the functionally graded material, and the type of loading on the vibration frequencies and the admissible stresses in order to determine the most appropriate material for the pile so that extreme stresses can be absorbed. The precision and the applicability of the method with new solution of the transverse shear deformation are demonstrated through this study with modeling of the layered property of the soil, were then compared with those reported in previous work available in the literature. It turned out that these results are in good agreement with each other, for the different materials of pile and for all boundary conditions considered. The results of pile with sandwich functionally graded material, it is revealed that the role of this material has an influence on the type of loading, especially, in the case statique of a pile subjected to a compound bending weight and the shear effect, in case dynamique the pile with vibration flexible or rigid .