Displacement Piles Research Articles

Investigation of the large-diameter monopiles response under flow-controlled loading

The mechanical behavior of monopile support systems for offshore wind turbines under current-induced loads was investigated through numerical simulations. Using the Large Eddy turbulence model, the fluid-structure coupling was analyzed in both unidirectional and bidirectional directions. In the unidirectional coupling, the pressure and velocity profiles of the fluid around the pile were determined. While in the bidirectional coupling, the force distribution, pile displacement, and moment distribution were obtained, along with the current-induced load transmitted from the pile to the soil. The coupling analysis revealed that the fluid flow around the pile exhibited cyclic loading behavior due to the interaction between the fluid and the pile, effectively resulting in an oscillating pile within a steady flow. Additionally, the pile’s stress distribution remained within the tensile yield limit of the steel, indicating a stable state in the fluid-pile model within the given flow conditions. Furthermore, the soil reaction forces obtained from the fluid-pile-soil coupling model validated the accuracy of the current-induced load calculations. This study introduces a novel approach that considers the fluid-pile-soil coupling, offering valuable insights for pile foundation design. The findings of this research have significant engineering implications and practical value, providing a robust foundation for future offshore wind turbine installations.

Thermo-Mechanical Coupling Load Transfer Method of Energy Pile Based on Hyperbolic Tangent Model

By employing the hyperbolic tangent model of load transfer (LT), this paper establishes the thermo-mechanical (TM) coupling load transfer analysis approach for an energy pile (EP). By incorporating the control condition of the unbalance force at the null point, the method for determining the null point considering the temperature effect is enhanced. The viability of the presented method is validated through the measured outcomes from model experiments of energy piles. A parametric investigation is conducted to explore the impact of the soil shear strength parameters, upper load, temperature variation, head stiffness, and radial expansion on the axial force, strain, and displacement of the energy pile under thermo-mechanical coupling. The results suggest that the locations of the null point and the maximum axial force are dependent on the constraint boundary conditions of the pile side and the two ends. When the stiffness of the pile top increases, axial stress and displacement increase, while strain decreases. An increase in the drained friction angle leads to an increase in axial stress under thermal-load coupling, but strain and displacement decline. The radial expansion has a negligible influence on the thermo-mechanical interaction between the pile and the soil.

Stability and failure probability analysis of super-large irregularly shaped deep excavation in coastal area considering spatial variability in soil properties

ABSTRACT The objective of this paper is to investigate the effects of spatial variability in coastal silty soil properties on the stability and failure probability of deep excavation. A super-large irregularly shaped deep excavation in the coastal area in Wenzhou, China, is considered. A numerical model is established based on the random field theory, finite difference method and Monte-Carlo simulation method. Focusing on the friction angle and cohesion, the effects of horizontal and vertical correlation distances and variation coefficients on excavation stability are systematically studied. Meanwhile, the reliability evaluation approach is also applied to systematically examine the impact of the correlation distance on the surface settlement and horizontal displacement of pile. The results show that the greater correlation distance leads to a larger dispersion degree of the ground settlement curve and the displacement curve of the diaphragm wall around. The influence of the horizontal correlation distance on land settlement is more significant. The horizontal and vertical displacements of the pile top are less affected by the correlation distance. Compared with the deterministic analysis, the random analysis results considering the soil spatial variability produce larger displacement.

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.

Performance Analysis of Pile Group Installation in Saturated Clay

In offshore pile engineering, the installation of jacked piles generates compaction effects within soil, thus further affecting previously installed adjacent piles. This study proposes a three-dimensional numerical model for pile group installation, soil consolidation, and loading analysis. Subsequently, the effect of pile spacing and pile length-to-diameter ratio on the deformation, internal forces, and vertical bearing capacity of adjacent piles are investigated. The results indicate that with an increase in pile center distance, the peak lateral displacement of the adjacent piles decreases, whereas the peak vertical displacement increases. As the pile length-to-diameter ratio increases, the peak vertical and lateral displacements of the adjacent piles are enhanced. In addition, the peak axial force of the adjacent piles initially decreases and then increases with the penetration depth of the subsequent pile, whereas the peak bending moment initially increases and then decreases. The vertical bearing capacity of the subsequent pile is significantly superior to that of the adjacent piles. Therefore, the effects of pile installation on adjacent piles should be included in pile engineering. The impact of the subsequent pile installation on the bearing capacity of adjacent piles can be significantly reduced by increasing the pile center distance and pile length-to-diameter ratio. The findings provide useful guidance for pile group engineering.

The load-transfer method as a tool for determining the load-displacement curve of piles

The paper presents two applications (software packages) in which the load-transfer method is used for axially loaded Kelly drilled bored piles and displacement ductile iron piles. In the first, the ultimate friction is related to the effective stress via the so-called β method. The β method is refined into three stages to cover the variety of soils typical of Central Europe. For the driven piles, a different approach is presented in which the ultimate shaft friction is related to the reference hammering time. The recorded hammering time profile is fed directly into the software based on the load-transfer method. Analyses of five loading tests are presented proving that the load transfer method in combination with the β method or the recorded hammering time profile is able to compute the load-displacement curve of both replacement and displacement piles with a reasonable accuracy in various geological conditions.

Seismic performance of precast UHPC pipe pile with two pile-cap beam connection types: An experimental and numerical study

To develop an effective pile foundation scheme for earthquake-prone regions, this study introduces a novel pile structure that integrates ultra-high-performance concrete (UHPC) with traditional prestressed high-strength concrete (PHC) pipe piles. The research focuses on assessing the impact of various connection forms between the pile and cap beam on the seismic performance of bridge substructures. Two 1/3-scale specimens were meticulously designed and tested: one featuring a cast-in-place (CIP) connection and the other incorporating precast assembly (PA) connection between the pipe pile and cap beam. Cyclic loading tests were conducted to evaluate the failure mode, lateral capacity, ductility, energy dissipation ability, residual displacement, rebar strain, curvature distribution and rotation of UHPC pipe piles with the two connection forms. The results indicate that the specimen with a CIP connection exhibits a higher horizontal load capacity and stronger energy dissipation ability, while the specimen with the PA connection displays superior self-centering ability, increased ductility, and causes less damage to the cap beam. Finally, finite element models were developed to analyze the effects of design parameters on the seismic performance of the pile connected by the two methods. This research may provide valuable design guidance for incorporating UHPC in pile foundations. To facilitate its practical implementation in engineering projects, further theoretical and experimental research is recommended in this paper.

A Transparent Soil Experiment to Investigate the Influence of Arrangement and Connecting Beams on the Pile-Soil Interaction of Micropile Groups.

The use of a micropile group is an effective method for small and medium-sized slope management. However, there is limited research on the pile-soil interaction mechanism of micropile groups. Based on transparent soil and PIV technology, a test platform for the lateral load testing of slopes was constructed, and eight groups of transparent soil slope model experiments were performed. The changes in soil pressure and pile top displacement at the top of the piles during lateral loading were obtained. We scanned and photographed the slope, and obtained the deformation characteristics of the soil interior based on particle image velocimetry. A three-dimensional reconstruction program was developed to generate the displacement isosurface behind the pile. The impacts of various arrangement patterns and connecting beams on the deformation attributes and pile-soil interaction mechanism were explored, and the pile-soil interaction model of group piles was summarized. The results show that the front piles in a staggered arrangement bore more lateral thrust, and the distribution of soil pressure on each row of piles was more uniform. The connecting beams enhanced the overall stiffness of the pile group, reduced pile displacement, facilitated coordinated deformation of the pile group, and enhanced the anti-sliding effect of the pile-soil composite structure.

Investigating the influence of an approach bridge on a pile-supported wharf at a liquefiable site under horizontal and vertical seismic excitations

The approach bridge of the pile-supported wharf is an important structure that connects the pile foundation platform and the land, and it has a significant impact on the safety of the high-pile wharf. However, the influence of an approach bridge on the seismic dynamic response of a pile-supported wharf has often been neglected in previous studies. Besides, the excess pore water pressure (Δu) generated under combined vertical and horizontal seismic components is typically greater than that induced by unidirectional excitations, which may further impact the dynamic response of pile-supported wharf. Firstly, this study developed a numerical method for simulating the approach bridge of a pile-supported wharf. Secondly, the three-dimensional finite element model of a pile-supported wharf with an approach bridge is established to investigate the dynamic response during horizontal and vertical seismic components. Additionally, the effects of seismic frequency and relative density of liquefied layer on the dynamic response of pile-supported wharf were also studied. By comparing with the experimental results, the numerical model effectively simulated the overall response of the pile-supported wharf and the liquefaction behavior of the surrounding soil. During high-frequency earthquakes, the influence of the approach bridge on the dynamic response of the pile-supported wharf is minimal, whereas it has a more significant impact during low-frequency earthquakes. Furthermore, vertical seismic components significantly amplify the effect of approach bridge on the lateral displacement and internal forces of piles. The effect of the approach bridge on the lateral displacement and internal force of the pile decreases with the increase of the relative density of the liquefaction layer.

Base Resistance of Screw Displacement Piles in Sand

Base Resistance of Screw Displacement Piles in Sand

Cyclic loading experiments and numerical analysis of laterally loaded piles constructed in marine soil

This study aims to thoroughly analyze the lateral loads that impact tubular steel piles, which are extensively employed in the construction of coastal structures. The ASTM D 3966 standard was followed for conducting field tests on test piles installed at the Mersin International Port. The “time-displacement” and “load-displacement” curves were obtained from the cyclic loading test of the laterally loaded piles at the construction site. The finite elements models of the tests conducted on the construction site with the same parameters was built to perform numerical analysis. At the end of the analysis, it was determined that the numerical model's results were highly consistent with those obtained from the field test. After verifying the field experiments with numerical models, a parametric study was conducted. Parametric studies were conducted to compare the lateral displacements of tubular steel piles with variations in pile diameter, wall thickness, and load application height effect. The relationship between pile head displacements and these parameters appears to be almost linear. It is noteworthy that a change of approximately 10 percent in these parameters shows a correlation with changes of up to 3 percent in deformations.

Research on Numerical Pile Testing Methods and Parameter Selection for Large-Diameter Steel Pipe Piles at Sea

Numerical test research and inverse analysis research on large-diameter steel pipe piles are particularly important for optimizing design parameters. Based on the field pile test results completed at an offshore wind farm in Jiangsu Province (including compression static load test, pull-out test, and horizontal load test), the actual geological conditions and loading process of the site were simulated, and numerical pile tests were systematically conducted. Sensitivity analysis of some key parameters was carried out, parameter value methods were proposed, and on this basis, the deformation failure modes of the foundation under different loading conditions, the mechanism and distribution law of pile side friction resistance under compression and pull-out conditions, and the relationship between foundation resistance and pile displacement under horizontal loading conditions (p-y curve) were studied.

Effects of Soil Liquefaction to Foundation Bearing Capacity Based on Empirical and Numerical Simulation

Abstract Soil liquefaction is one of the collateral hazards of earthquakes which can cause a soil layer to lose its bearing capacity, which can affect the stability of structures. Failure of a building structure can cost many lives, especially in strategic buildings. This research discusses bored pile foundations from the planned construction of elevated road in the Purwomartani area which located in moderate liquefaction vulnerability zone. The objective of this study is to estimate the influence of soil liquefaction on pile foundation capacity in elevated road construction plan in Purwomartani. This research uses empirical approach of Reese and O’Neil 1989 to calculate the axial bearing capacity of the pile under static and liquefaction conditions, and numerical simulation with the help of RSPile software to model the soil-pile interaction and the pile displacement under lateral loading. The data used in this research includes liquefaction potential data, foundation profile, soil investigation, standard penetration test, and laboratory tests. The analysis results showed that liquefaction caused a reduction in the foundation bearing capacity where axial bearing capacity reduce about 39,92 – 21,28% and lateral bearing capacity reduce by 5,31%.

Prediction of adjacent single pile deformation induced by tunnel excavation based on the Pasternak model

The construction of metro tunnels in soft ground would cause significant settlement of the ground surface and deformation of buildings and their foundations in the vicinity of the tunnels. The deformation laws of the pile of the neighbouring structures induced by the tunnel construction have not yet been fully identified. This paper analyzed the impact mechanism of tunnel construction on piles based on the Pasternak model, deduced the calculation methods of additional horizontal displacement and additional internal force of piles, and introduced three solution methods. The computational method results have been validated through numerical simulations using coupling of discrete element method and finite difference method and compared to select laboratory data. The results show that the model accuracy is better when the tunnel axis burial depth is less than the pile bottom burial depth. The analysis shows that the tunnel burial depth significantly influences the displacement distribution of the adjacent single pile, while the impact on the peak displacement is insignificant. The thickness of the elastic layer (C) is inversely related to the maximum horizontal displacement and internal force, but it does not impact the distribution patterns of the displacement and internal force. For thickness of the elastic layer (C), the bending moment’s point is constant at 2 m above and below the tunnel axis, whereas the shear force’s point remains constant at the buried tunnel axis’s depth and 4 m above the tunnel axis.

Impact Analysis of Stiffness Degradation of Laterally Loaded Reinforced Concrete Piles on Horizontal Displacement of Piles

Impact Analysis of Stiffness Degradation of Laterally Loaded Reinforced Concrete Piles on Horizontal Displacement of Piles

Parametric analysis of a strain state of a soil base strengthened with vertical elements

Purpose is to identify vertical displacements of the “soil basem strengthened with piles or micropiles based upon drilling-mixing technology” system relying upon parametric analysis of strain state of the mentioned system, and arrangement of the strengthening elements. Methods. Mathematical modeling took place for twelve finite-element models using the computing complex SCAD intended to analyze strength of structures by means of finite-element method. Numerical analysis was carried out with variation of elastic-strain modulus of vertical reinforcing elements and change in distance between them (3d and 6d of micropiles). Findings. Results of parametric analysis have been obtained for a model without a micropile (non reinforced soil base); a model with a single micropile; a model with two micropiles where distance between them is 1.5 m, i.e. 3d of micropiles; and a model with two micropiles where distance between them is 3.0 m, i.e. 6d of micropiles. The performed comparative analysis has made it possible to obtain the results proving the hypothesis by the authors as for the specific nature of vertical displacement formation of the “soil base strengthened with piles or micropiles based upon drill-mixing technology” system. Originality. It has been identified for the first time that basing upon the standardized document for the auger or displacement piles, it is impossible to decrease efficiently vertical displacements while approaching micropiles since distance between the micropiles is 3d for elements, developed on the basis of the drilling-mixing, is minimal. Practical implications. The obtained results of a strain state may become the keystone for the development of the genera-lized strain theory of the composite “soil base strengthened with piles or micropiles based upon drilling-mixing technology” system as a medium differing in minor changes of strain characteristics.

Displacement and Internal Force Response of Mechanically Connected Precast Piles Subjected to Horizontal Load Based on the m-Method

Mechanically connected precast piles are a type of precast piles that utilise snap-type mechanical connectors to restrain the pile ends of two identical or different precast piles at the top and bottom so as to quickly realise the purpose of the connection. However, the gap problem in the connectors of mechanically connected piles can lead to uneven and uniform deformation of the piles under horizontal loading, resulting in additional displacements and rotation angles of the piles at the connection. Solving the problem of calculating the internal force response of discontinuous deformed piles is a prerequisite for promoting and applying mechanically connected precast piles. Firstly, the theoretical derivation of mechanically connected piles with fixed constraints at the pile bottom is carried out. Secondly, the pile response equations of mechanically connected piles are established, and the theoretical solutions of pile displacement and internal force response of mechanically connected piles under horizontal loading are derived. Thirdly, the pile-soil model of the test pile is established using ABAQUS software (ABAQUS 2016) in combination with the design data of the test pile. The numerical simulation displacements and angles of rotation are compared with the test results. Finally, the theoretical and numerical simulation displacements and internal forces of the ordinary pile and the mechanically connected pile are compared. The relative errors of the displacements and angles of rotation of the established pile-soil model are less than 10%, indicating that the established model has good accuracy. The relative errors of the theoretical and numerical simulation displacements and internal forces of the mechanically connected pile are less than 10%, proving the correctness of the theoretical calculation by the m-method. This study can provide effective theoretical support and methodological guidance for the displacement and internal force response of discontinuous piles.

Stability Investigation of Fully Recycled Support System of Steel-Pipe-Anchored Sheet Pile in Soft Soil Excavation

As a temporary project, the supporting system of excavation often encounters issues such as the waste of support components, environmental pollution, and high carbon emissions. This article presents a foundation pit support technology that utilizes steel tube anchorage sheet piles, which can be assembled and fully recycled. The composition of the support system is also introduced. Furthermore, a large-scale model test of steel-pipe-anchored sheet piles was designed and implemented. The displacement of each component of system and stability during excavation were investigated using 3D finite element modeling and analysis. The study results indicate that the deformation and failure mode of the model foundation under the steel-pipe-anchored sheet pile support system are closely related to the distance between the pipe pile and the sheet pile. When the distance is 10 cm, both the pipe pile and the sheet pile tilt simultaneously. When the distance is approximately 30–50 cm, the sliding surface becomes exposed from the position of the pipe pile. At distances up to 100 cm, the sliding surface is exposed between the pipe pile and the sheet pile. The anchoring effect of pipe piles and tie rods can effectively reduce the horizontal displacement of the sheet pile itself. The horizontal displacement at the top of both the pipe pile and sheet pile remains consistent throughout the excavation period of this model foundation. During excavation, measured earth pressure on the sheet pile is less with theoretical active earth pressure. After excavation, the maximum horizontal displacement of the top of the pipe pile exhibits a hyperbolic relationship with excavation depth.

Pile–Soil Interaction during Static Load Test

Abstract This study highlights the possibility of determining the shear stress distribution along the skin of a pile, which represents skin resistance. Geotechnical engineering is plagued by the challenge of designing appropriate piles as a sufficient foundation construction while being economically justified solution. Static load testing facilitates verification if the pile satisfies these requirements. In most cases, the pile skin resistance is undervalued. This study first introduces the general approach based on static load test results using an appropriate mathematical approach in the presence of linear, vertical shear stress distribution boundary conditions as well as phenomena such as pile shortening and Kirchhoff's principle. Moreover, a scientific approach for pile compression and shear stress distribution is presented. Further, the study expands upon previous work by applying mathematical calculus to displacement piles. The promising results indicate that further work on greater number of piles may lead to a better understanding of pile–soil interaction and a more accurate design process.

Analytical solution for axially loaded floating pipe piles in homogeneous elastic soil layer

An analytical solution for the analysis of open-ended floating pipe piles in a homogeneous elastic soil layer is developed in this paper, based on the Tajimi-type elastic continuum model. Solving the governing equations of the outer and inner soil results in closed-form expressions for the external and internal frictional resistances developing at the soil-pile interfaces. The one-dimensional rod theory is adopted to model the pipe pile and its underlying soil hollow column. The external and internal frictional resistances are substituted into the governing equations of the pile and soil column to derive closed-form solutions for the vertical displacement and head stiffness of the pipe pile. The accuracy of the proposed model is verified by comparisons against existing numerical studies. Finally, parametric analyses are presented to discuss the sensitivity of the behavior of axially loaded floating pipe piles to the main problem parameters.