Open-ended pipe piles (OEPPs) are widely used in offshore foundations, yet accurately predicting their driving responses remains challenging due to soil plug complexities. Existing pile driving analysis models inadequately characterize the effects of soil plug, potentially leading to driving problems such as hammer refusal, pile running, and structural damage. This paper proposes an effective soil plug (ESP) model for OEPP driving analysis. The ESP model considers the effective range of soil plug, which exerts internal resistance that increases exponentially with depth while the beyond of effective range contributes only mass inertia. It also accounts for the relative slippage at the pile-soil plug interface. A differential iterative method is developed to solve the ESP model. Subsequently, investigations including the model validation and parameter analysis are conducted. Model validations against existing models and field measurements confirms the reliability of the ESP model. Parameters sensitivity analysis reveals the importance of soil plug length and distribution type of internal resistance on the pile dynamic responses. In addition, if soil plug slippage occurs, the displacement peak of soil plug increases with depth rather than one-dimensional wave attenuation. Furthermore, contrary to previous assumptions of continuous slippage, the soil plug experiences a discontinuous jump-sliding mode under long-duration impact loading. These findings provide theoretical basis for OEPP driving simulation and interpretations of high-strain dynamic test.
Precast driven piles are extensively used for infrastructure on soft soils, but the buildup of excess pore water pressure associated with pile driving is a challenging issue. The process of soil consolidation could take several months. Measures are sought to shorten the drainage path in the ground, and permeable pipe pile is a concept that involves drainage channels at the peak pore pressure locations around the pile circumference. Centrifuge tests were conducted to understand the responses of permeable pipe pile treated ground, experiencing the whole pile driving, soil consolidating, and axially loading process. Results show that the dissipation rate of pore pressures can be improved, especially at a greater depth or at a shorter distance from the pile, since the local hydraulic gradient was higher. Less significant buildup of pore pressures can be anticipated with the use of permeable pipe pile. For this, the bearing capacity of composite foundation with permeable pipe pile can be increased by over 36.9%, compared to the case with normal pipe pile at a specific time period. All these demonstrate the ability of permeable pipe pile in accelerating the consolidation process, mobilizing the bearing capacity of treated ground at an early stage, and minimizing the set-up effect. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).
Vertical-inclined alternating composite steel pipe pile(VIACP) is a new green foundation pit support technology. A numerical experimental study on the mechanical properties of vertical-inclined combination piles with different pile inclination angles and lengths was carried out with a foundation pit in Longli County, Guizhou Province, as the research object. Results demonstrate that the VIACP reduces maximum deformation by 57.8% (20.07 mm) compared to traditional cantilever piles (47.57 mm), aligning closely with field monitoring data (16.94 mm). The parametric study shows that the maximum horizontal displacement of the pile decreases and then increases as the inclination angle (5 degrees-30 degrees) increases, with the minimum displacement (20.07 mm) at 20 degrees, which is the optimum angle. Increasing pile lengths lead to progressively reduced displacements followed by stabilization while alternating long-short pile configurations exhibit synergistic effects. Mechanically, axial forces and lateral friction resistance show negative correlations with inclination angles, while bending moments adopt an S-shaped distribution along pile depth with minimal sensitivity to angle variations. Mechanism analysis highlights that the inclined piles in the structure have a pull-anchor effect, the soil between the piles together has a gravity effect, and the alternating arrangement of piles has a spatial structure effect. The three major effects increase the stiffness and stability of the support structure, which is conducive to the deformation control of the foundation pit. The research results will provide a theoretical basis for the popularization and application of the structure.
Permeable pipe pile, a novel pile foundation integrating drainage and bearing functions, improves the bearing capacity of the pile foundation by accelerating the consolidation of the soil around the pile. In this study, a mathematical model is established to simulate the consolidation of surrounding clayey soils and the pile-soil interaction, where the rheological properties of the soils are described with the fractional derivative-based Merchant model, and the impeded drainage boundary is used to simulate the pile-soil interfacial drainage boundary. Corresponding solutions for pile-soil relative displacement, skin friction, and axial force on the pile shaft are derived by means of semi-analytical methods, and they are validated by comparing with experimental results and numerical simulation results. Based on the proposed semi-analytical model, a series of parametric analyses are conducted to investigate the influences of fractional orders, viscosity coefficients, pile-soil interface parameters, and pile-head loads on the pile-soil interaction characteristics. It is observed that during the transition stage, the axial force increases linearly with depth in the plastic segment, and then increases nonlinearly in the elastic segment until it decreases after reaching the neutral plane. In the elastic segment, the axial force on the pile shaft for a given time increases with the increases in the fractional order or the pile-soil interface parameter, but decreases with the increase of viscosity coefficient.
Wind energy offers significant advantages over fossil fuels, including extensive energy storage and environmental sustainability. Offshore wind turbines serve as the primary technology for harnessing offshore wind power. However, the corrosive effects of the marine environment pose serious threats to their safety and stability. This paper provides a comprehensive overview of corrosion issues affecting steel pipe pile infrastructure, focusing on the following key aspects: (1) Differentiating corrosion mechanisms under various environmental conditions, (2) analyzing the comprehensive corrosion response, particularly the changes in mechanical properties of the pile-soil interface and the bearing capacity of steel pile foundations, (3) summarizing the patterns and trends in corrosion processes to offer theoretical insights for engineering design, and (4) reviewing commonly employed corrosion prevention methods and their respective applicability in relation to specific corrosion mechanisms and responses.
In order to study the squeezing effect of static press large-diameter single pile and piles group in layered soil, field tests of static press large-diameter pipe piles were carried out based on a project under construction, and numerical simulations of the squeezing effect of single piles and piles group were conducted using finite element software. It is shown that during the process of pile penetration, the pore water pressure in the soil surrounding the pile rapidly increases to a higher initial value. Subsequently, the excess pore pressure will rapidly dissipate and gradually stabilize. The simulated and measured values of pile top displacement show a pattern of larger displacement at the pile top when the pile is first penetrated, and smaller displacement at the pile top when the pile is penetrated later. The measured horizontal displacement of the soil layer at each observation point of the group of 7 piles showed a turning point at a depth of about 2.5 m and fluctuated with increasing depth. The measured displacement reached its maximum value between 25 and 30 m and then rapidly decreased. The finite element simulation results of squeezing effect of the group of 20 piles show that the squeezing effect around the pile is very obvious within the depth range of the pile length. The horizontal displacement of the soil below the pile length rapidly decreases, and the maximum horizontal displacement of the soil at different depths around the pile mainly occurs at the surface. In addition, the reasons for the errors between the finite element simulation values and the measured values were analyzed.
This study integrates cross-anisotropic and viscoelastic properties into the solid skeleton of unsaturated soils, conceptualized as a three-phase medium comprising solid, water, and air, in order to explore the torsional response of pipe pile. The stress-strain relationships are characterized using cross-anisotropic and fractional derivative models, resulting in more accurate torsional dynamic equations for the soils surrounding and inside the pipe pile. The torsional governing equations are solved in the frequency domain by applying the separation of variables and leveraging properties of fractional derivatives, while considering boundary continuity conditions and trigonometric orthogonality to derive the pipe pile's torsional complex impedance. The time-domain response to a half-sine excitation load is determined using inverse Fourier transforms and the convolution theorem. After validating the computational model, numerical analyses are conducted to explore the effects of model and geometric parameters on the complex stiffness, twist angle, and torque at the pipe pile head.
Permeable pipe piles accelerate the bearing capacity of the pile foundation by releasing the excess pore water pressure (EPWP) of the soil around the pile through appropriate openings in the pile body. This study couples the Material Point Method (MPM) and the Finite Element Method (FEM) to establish a full-process model of pile driving and consolidation of permeable piles, and proposes a continuous drainage boundary condition that can reflect the plugging effect of permeable holes. The correctness of the model and boundary conditions are verified by comparison with experiments, and then the effects of soil properties, opening characteristics, and boundary permeability on the accelerated consolidation effect of permeable piles are analyzed. The results show that: the permeable pile with a permeable area ratio greater than 50% and a local opening ratio greater than 5% can save more than 60% of the consolidation time compared to conventional piles; the proposed boundary conditions can accurately describe the permeability of the permeable hole under the influence of plugging; in addition, the calculation formulae for the accelerated consolidation effect of permeable piles and the variation of continuous drainage boundary interface parameters with permeable area ratio are given, which can provide references for engineering design.
Large-diameter pipe piles are widely applied in various civil engineering fields due to their outstanding load- bearing capability. The unsaturated characteristics, anisotropy, and heterogeneity of the soil jointly affect the dynamic response of the pipe pile. However, most previous studies were limited to single-phase or two-phase soil. This paper develops an analytical model for the torsional vibration of a pipe pile in transversely isotropic unsaturated soils considering construction disturbance. Based on transversely isotropic unsaturated soil theory, a pipe pile-soil interaction model has been developed, while the effect of construction disturbance is simulated by the radial heterogeneity of the soil. The general solution for the unsaturated soil is obtained using the separation of variables method with the boundary conditions. Then, the solution for the whole pipe pile-soil system is derived by considering the pile-soil interface conditions. The accuracy of the proposed solution is verified through comparisons with previous research results. The results show that unsaturated characteristics, construction disturbance, and transverse isotropy of the soil have significant effects on the impedance of large- diameter pipe piles. Specifically, with a low degree of saturation, there will be significant prediction errors when using previous works based on single-phase or two-phase soil theory to predict the dynamic response of large-diameter pipe piles.
An analytical solution for investigating the torsional dynamic response of a pipe pile in unsaturated poroelastic transversely isotropic soil under time-harmonic load is proposed. By employing the Biot's type three-phase porous media model and the three-dimensional continuum theory, taking into account the transversely isotropic characteristics of the soil skeleton, as well as the viscosity and inertial coupling between different phases, distinct dynamic governing equations are derived for the soils surrounding and inside the pipe pile. By considering the boundary and continuity conditions at the interface between the pipe pile and the soils surrounding and inside the pipe pile in the frequency domain, a mathematical expression is derived to describe the torsional dynamic behavior of the pipe pile. A parametric study aimed to investigate how the anisotropy of the soils surrounding and inside the pipe pile (soil plug) impacts its torsional complex impedance, twist angle, and torque was conducted. The parametric study also considered variations in saturation, pile lengths, porosity, the height of the soil plug and excitation frequencies to explore the effects of these parameters on the torsional behavior of the pipe pile.