Pile Structure Research Articles

Low-Contact Impedance Textile Electrode for Real-Time Detection of ECG Signals.

The quality of the electrocardiography (ECG) signals depends on the effectiveness of the electrode-skin connection. However, current electrocardiogram electrodes (ECGE) often face challenges such as high contact impedance and unstable conductive networks, which hinder accurate measurement during movement and long-term wearability. Herein, in this work, a bionic 3D pile textile as an ECGE with high electrical conductivity and flexibility is prepared by a facile, continuous, and high-efficiency electrostatic self-assembly process. Integrating pile textiles with conductive materials creates a full textile electrode for bioelectrical signal detection that can retain both the inherent characteristics of textiles and high conductivity. Moreover, the dense piles on the textile surface make full contact with the skin, mitigating motion artifacts caused by the sliding between the textile and the skin. The continuous conductive network formed by the interconnected piles allows the pile textile ECGE (PT-ECGE) to function effectively under both static and dynamic conditions. Leveraging the unique pile structure, the PT-ECGE achieves superior flexibility, improved conductivity, low contact impedance, and high adaptivity, washability, and durability. The textile electrode, as a promising candidate for wearable devices, offers enormous application possibilities for the unconscious and comfortable detection of physiological signals.

Settlement of a Pile Foundation Considering Linear and Rheological Properties of Soils

Despite numerous studies of single piles and practical experience with their application, methods for calculating settlements of pile foundations remain limited. The existing objective need for specialized methods of pile foundation settlement calculation that take into account the rheological properties of the base soils is becoming more and more important, especially in the construction of unique objects in complex ground conditions. When predicting the stress–strain state of the pile–raft-surrounding soil mass system, it is allowed to consider not the entire pile foundation as a whole, but only a part of it—the computational cell. In the present work, we have solved the problems of determining the strains of the computational cell consisting of the pile, the raft and the surrounding soil according to the column pile scheme and hanging pile scheme, on the basis of the Kelvin–Voigt rheological model, which is a model of a viscoelastic body consisting of parallel connected elements: Hooke’s elastic spring and Newtonian fluid. According to our results, we obtained graphs of the dependence of strains of the computational cell on time at different pile spacing and different values of coefficients of viscosity of the surrounding soil, and a formula for calculating the reduced modulus of deformation of the pile. The results of the present study can significantly improve the accuracy of calculations during construction on clayey soils with pronounced rheological properties and, as a result, increase the reliability of pile structures in general.

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.

Characterization of pore model and percolation simulation of bulk grain pile porous media

AbstractTo ensure the quality of grain storage, researchers have developed a variety of models for the morphological structure of bulk grain piles. However, traditional characterization methods suffer from issues such as inaccurate models, limited size ranges, and low precision. In this study, x‐ray computed tomography was employed for the first time to capture real three‐dimensional (3D) images, revealing the surface porosity distribution ranging from 30% to 38% along the slice direction and a fractal dimension primarily distributed between 1.45 and 1.47. Moreover, the box counting method was used to determine the representative elementary volume (REV) comprising 600 × 600 × 600 pixels, effectively characterizing pore structure using porosity as an index. Connectivity analysis of the REV was conducted by integrating the refined central axis method and the 3D watershed algorithm. Equivalent diameters of connected pores were mainly distributed between 0.5 and 3.5 mm, with an average pore diameter of 2.22 ± 0.02 mm, an average coordination number of 7.04 ± 0.07, and an average tortuosity of 1.58 ± 0.01. Based on the characteristic parameters of connected pores, an equivalent pore network model (EPNM) was reconstructed for numerical simulation of single‐phase percolation of bulk grain pile. In addition, the constructed experimental platform demonstrates that the constructed EPNM closely corresponds to the real pore structure of the seed body, accurately reflecting pore–throat size, connectivity, and morphological characteristics within the grain pile. Furthermore, this research model can be applied to the study of gas flow, heat transfer, and mass transfer within porous media.

Structural stability of China’s asteroid mission target 2016 HO3 and its possible structure

ABSTRACT Asteroid 2016 HO$_3$, a small asteroid (<60 m) in super fast rotation state ($\sim$28 min), and is the target of China’s Tianwen-2 asteroid sample-return mission. In this work, we investigate its structural stability using an advanced soft-sphere-discrete-element-model code, dembody, which is integrated with bonded-aggregate models to simulate highly irregular boulders. The asteroid body is numerically constructed by tens of thousands particles, and then is slowly spun up until structural failure. Rubble piles with different frictions, cohesions, morphologies, grain size distributions, and structures are investigated. We find a 2016 HO$_3$ shaped granular asteroid would undergo tensile failure at higher strengths as opposed to shear failure in lower strengths, regardless of its shape and constituent grain size ratio. In the tensile failure regime, the critical tensile strength is proportional to the square of the spin rate, but surprisingly, is independent of the internal friction angle. Such relations indicate that the Maximum Tensile Stress criterion emerges as superior paradigm for investigating the failure behaviour of fast-rotating asteroids. We predict that the high-spin rate of asteroid 2016 HO$_3$ requires a surface strength over $\sim$3 Pa and a bulk tensile strength over $\sim$10–30 Pa. Through comparing these strength conditions with the latest data from asteroid missions, we suggest a higher likelihood of a monolithic structure over a typical rubble pile structure. However, the possibility of the latter cannot be completely ruled out. In addition, the asteroid’s surface could retain a loose regolith layer globally or only near its poles, which could be the target for sampling of Tianwen-2 mission.

Elucidating bacterial coaggregation through a physicochemical and imaging surface characterization

Bacterial coaggregation is a highly specific type of cell-cell interaction, well-documented among oral bacteria, and involves specific characteristics of the cell surface of the coaggregating strains. However, the understanding of the mechanisms promoting coaggregation in aquatic systems remains limited. This gap is critical to address, given the broad implications of coaggregation for multispecies biofilm formation, water quality, the performance of engineered systems, and diverse biotechnological applications. Therefore, this study aims to comprehensively characterize the cell surface of the coaggregating strain Delftia acidovorans 005P, isolated from drinking water, alongside a non-coaggregating strain, D. acidovorans 009P. By analyzing two strains of the same species, we aim to identify the factors contributing to the coaggregation ability of strain 005P. To achieve this, we employed a combination of physicochemical characterization, Fourier-transform infrared spectroscopy (FTIR), and advancing imaging techniques [transmission electron microscopy and cryo-electron tomography (cryo-ET)]. The coaggregating strain (005P) exhibited higher surface hydrophobicity, negative surface charge, and cell surface and co-adhesion energies than the non-coaggregating strain (009P). The chemical characterization of bacterial surfaces through FTIR revealed subtle differences, particularly in spectral regions linked to carbohydrates and phosphodiesters/amide III of proteins (860–930 cm−1 and 1212–1240 cm−1, respectively). Cryo-ET highlighted significant differences in pili structures between the strains, such as variations in length, frequency, and arrangement. The pili in the 005P strain, identified as pili-like adhesins, serve as key mediators of coaggregation. By integrating physicochemical analyses and high-resolution imaging techniques, this study conclusively links the coaggregation ability of D. acidovorans 005P to its unique pili characteristics, emphasizing their crucial role in microbial coaggregation in aquatic environments.

Cryo-EM structure of the R388 plasmid conjugative pilus reveals a helical polymer characterized by an unusual pilin/phospholipid binary complex

Bacterial conjugation is a process by which DNA is transferred unidirectionally from a donor cell to a recipient cell. It is the main means by which antibiotic resistance genes spread among bacterial populations. It is crucially dependent upon the elaboration of an extracellular appendage, termed "pilus," by a large double-membrane-spanning secretion system termed conjugative "type IV secretion system." Here we present the structure of the conjugative pilus encoded by the R388 plasmid. We demonstrate that, as opposed to all conjugative pili produced so far for cryoelectron microscopy (cryo-EM) structure determination, the conjugative pilus encoded by the R388 plasmid is greatly stimulated by the presence of recipient cells. Comparison of its cryo-EM structure with existing conjugative pilus structures highlights a number of important differences between the R388 pilus structure and that of its homologs, the most prominent being the highly distinctive conformation of its bound lipid.

Nonlinear Soil–Pile–Structure Interaction Behaviour of Marine Jetty Structures

Nonlinear soil–pile–structure interaction (SPSI) phenomena are known to play a vital role in the response of bottom-fixed marine structures. For such structures, these phenomena are commonly considered by the imposition of p-y, τ-z, and q-z springs, representing the lateral and axial shaft and axial base soil resistances, respectively. The importance of each resistance mechanism depends on the type of foundation system, with only very limited studies investigating their roles in the response of piled marine structures, such as jetties. Within this context, this study presents numerical three-dimensional pushover analysis results for two marine jetties, a smaller model with four piles and a larger model supported by twenty-four piles. SPSI effects are considered through p-y, τ-z, and q-z springs, the behaviours of which are determined by following commonly employed procedures. The structures’ responses are investigated under the influence of various assumptions regarding the behaviours of springs, as well as steel plasticity. The current investigation underscores the substantial influence of the axial soil–pile interaction on the response of the jetty, particularly in terms of its failure mode. Moreover, it demonstrates the importance of incorporating p-y springs, even though the choice between their linear or nonlinear constitutive behaviour is found to be less critical. Finally, the study concludes that the behaviours of the springs significantly affect the system’s ductility and the degree of steel yielding in the piles, while also highlighting the unconservative influence of neglecting SPSI phenomena.

Numerical analysis on seismic response and failure mechanism of articulated pile–structure system in a liquefiable site from shaking-table experiments

Numerical analysis on seismic response and failure mechanism of articulated pile–structure system in a liquefiable site from shaking-table experiments

The crystal structure of the N-terminal domain of the backbone pilin LrpA reveals a new closure-and-twist motion for assembling dynamic pili in Ligilactobacillus ruminis.

Sortase-dependent pili are long surface appendages that mediate attachment, colonization and biofilm formation in certain genera and species of Gram-positive bacteria. Ligilactobacillus ruminis is an autochthonous gut commensal that relies on sortase-dependent LrpCBA pili for host adherence and persistence. X-ray crystal structure snapshots of the backbone pilin LrpA were captured in two atypical bent conformations leading to a zigzag morphology in the LrpCBA pilus structure. Small-angle X-ray scattering and structural analysis revealed that LrpA also adopts the typical linear conformation, resulting in an elongated pilus morphology. Various conformational analyses and biophysical experiments helped to demonstrate that a hinge region located at the end of the flexible N-terminal domain of LrpA facilitates a new closure-and-twist motion for assembling dynamic pili during the assembly process and host attachment. Further, the incongruent combination of flexible domain-driven conformational dynamics and rigid isopeptide bond-driven stability observed in the LrpCBA pilus might also extend to the sortase-dependent pili of other bacteria colonizing a host.

CryoEM reveals the structure of an archaeal pilus involved in twitching motility

Amongst the major types of archaeal filaments, several have been shown to closely resemble bacterial homologues of the Type IV pili (T4P). Within Sulfolobales, member species encode for three types of T4P, namely the archaellum, the UV-inducible pilus system (Ups) and the archaeal adhesive pilus (Aap). Whereas the archaellum functions primarily in swimming motility, and the Ups in UV-induced cell aggregation and DNA-exchange, the Aap plays an important role in adhesion and twitching motility. Here, we present a cryoEM structure of the Aap of the archaeal model organism Sulfolobus acidocaldarius. We identify the component subunit as AapB and find that while its structure follows the canonical T4P blueprint, it adopts three distinct conformations within the pilus. The tri-conformer Aap structure that we describe challenges our current understanding of pilus structure and sheds new light on the principles of twitching motility.

Two distinct archaeal type IV pili structures formed by proteins with identical sequence

Type IV pili (T4P) represent one of the most common varieties of surface appendages in archaea. These filaments, assembled from small pilin proteins, can be many microns long and serve diverse functions, including adhesion, biofilm formation, motility, and intercellular communication. Here, we determine atomic structures of two distinct adhesive T4P from Saccharolobus islandicus via cryo-electron microscopy (cryo-EM). Unexpectedly, both pili were assembled from the same pilin polypeptide but under different growth conditions. One filament, denoted mono-pilus, conforms to canonical archaeal T4P structures where all subunits are equivalent, whereas in the other filament, the tri-pilus, the same polypeptide exists in three different conformations. The three conformations in the tri-pilus are very different from the single conformation found in the mono-pilus, and involve different orientations of the outer immunoglobulin-like domains, mediated by a very flexible linker. Remarkably, the outer domains rotate nearly 180° between the mono- and tri-pilus conformations. Both forms of pili require the same ATPase and TadC-like membrane pore for assembly, indicating that the same secretion system can produce structurally very different filaments. Our results show that the structures of archaeal T4P appear to be less constrained and rigid than those of the homologous archaeal flagellar filaments that serve as helical propellers.

Numerical Validation of Fully Coupled Nonlinear Seismic Soil–Pile–Structure Interaction

While many researchers have broadly studied soil–structure interaction (SSI) problems to comprehend SSI effects on the overall system’s behavior, some critical numerical modeling issues have not been sufficiently investigated to achieve the most accurate results. Furthermore, most scholars have not provided detailed explanations of the validation process for their proposed numerical models. Modeling pile foundations in a three-dimensional (3D) continuum system in a fully coupled manner is often challenging for engineers who do not specialize in structural and geotechnical earthquake engineering, as it can be very time-consuming and complicated. Therefore, this work aims to validate a finite element model of seismic soil–pile–structure interaction (SPSI) problems in a continuum soil body by comparing the results of numerical models with those of a centrifuge test and computed numerical simulations available in the literature. In this regard, several newly developed elements in OpenSees (Version 3.6.0) are tested. The results of this work demonstrate a closer alignment with prior experimental research findings. It is believed that providing detailed numerical modeling and validation processes will assist researchers in better understanding crucial issues in modeling soil–pile–structure interaction problems.

METHOD FOR CALCULATING THE BEARING CAPACITY OF A SCREW PILE WITH A SPIRAL BLADE BY THE SOIL

Purpose. The purpose of the scientific article is to study and substantiate the principle methodology for calculating the bearing capacity of a screw pile with a spiral blade on the basis of field tests of a prototype pile using existing methods of theoretical calculation of similar piles. Determination of the bearing capacity of a pile with a spiral blade by the soil according to the first limit state. Also, the goal is to determine certain regularities in the modeling of pile structure. Methodology. A metal elements pile is used as a test sample. Determination of the theoretical bearing capacity of the pile in the vertical direction is conducted using formulas and calculation data from Appendix H.5 (DBN B.2.1-10-2009, 2011). The basic solution is that the load-bearing capacity of the pile is achieved due to the adhesion of each individual blade to the soil, which in total reflects the final value of the load-bearing capacity of the pile. Findings. Six experimental piles were installed and tested with static axial compressive and pullout loads. The estimated compressive, pullout and horizontal loads allowed for test piles, turned in to the design mark and tested without soaking subsoils, were determined. In this work, on the basis of experiments, the possibility of using the calculation data existing in the regulatory documentation as a justified theoretical calculation of pile-based foundations in the design of buildings and structures in general with the use of piles with a spiral blade is proven. Originality. A refined mathematical dependence for determining the bearing capacity of a screw pile with a spiral blade by the soil is proposed and the possibility of its use is confirmed experimentally. Practical value. The proposed method makes it possible to substantiate and use screw piles with a spiral blade for pile foundations.

Analysis on the mechanics and deformation of side pile structure in metro station with the PBA method

There are few researches on the interaction mechanism between the buckling load of the side pile top and the soil pressure behind pile (SPP) and the side pile structure. While the side pile structure is the key component of the lining structure of the metro with pile-beam-arch (PBA) method, which plays a very important role in the mechanical stability and deformation control of the lining system of station. Therefore, relying on the metro project about Guangzhou Metro Line 11, this paper investigates the influence law of mechanical characteristics and deformation of the side pile structure of the station with PBA method, taking into account the factors such as different buckling loads (including horizontal load of arch (HLA) and vertical load of arch (VLA)) and SPP, and puts forward corresponding construction suggestions. It is found that the lateral displacement and deformation of side pile structure are controlled by the HLA, and the optimal HLA is 1200kN. The influence of HLA on the bending moments about side pile are greater than that of the axial force. The VLA has more significant effect on vertical settlement of side pile, but little effect on lateral deformation about pile body. The SPP has significant impact on the stability of side pile structure, so it is recommended to take appropriate lining measures to ensure the stability of side pile structure when the SPP is too large.

Experiment investigation on the local scour around circular and square piles in open wharf

Open wharves often rely on pile structures for stability, but these can cause local scouring, risking structural integrity and safety. Understanding scour mechanisms induced by propeller jet flow is crucial for effective scour protection, yet research on square piles and double piles is limited. This study presents a series of flume tests to investigate the local scour mechanisms around square piles and circular piles under propeller jet flow. The experiments consist of seven different configurations, including single square piles, double square piles, single circular piles, double circular piles, and a control case without any piles. The main focus of this research is to understand the development and variations of scour depth and scour pit dimensions induced by propeller jet flow. Additionally, the scour mechanisms of square piles are compared with those of circular piles, and the influence of double piles and pile spacing is examined. It can be found that substituting circular piles with square piles in practical engineering will generally lead to an increase in the overall scouring range of the foundation. The horizontal scouring range of double piles is significantly influenced by the pile spacing, resulting in a larger range with increased spacing. However, the variation in pile spacing has minimal impact on the vertical scouring range of the double piles. The shape of piles significantly impacts scour depth in both single and double-pile setups, with square piles resulting in deeper scour. Furthermore, increased pile numbers and narrower spacing contribute to higher scour depths. The results of this study enhance understanding of scour characteristics and offer valuable insights for designing and maintaining pile-supported open wharves, ensuring the safety and durability of waterfront structures through effective scour protection measures.

Vibration reduction effect of retaining pile structure under the action of damping hole—A case study

In the context of mitigating the impact of blasting-induced seismic waves on excavation processes and reducing the vibrational load on retaining pile structures, this study examines the influence of predetermined damping hole parameters on the damping effect. It also evaluates the protective efficacy of damping holes on retaining pile structures. Leveraging the foundation pit project at the Julong Avenue Station of Wuhan Metro Line 7 as a reference, on-site blasting construction was monitored to obtain vibration velocities at the top of the retaining pile structure. A numerical calculation model for blasting in the foundation pit was established using LS-DYNA software, and its reliability was verified through the integration of on-site monitoring data at the top of the retaining pile. Multiple damping hole excavation schemes were devised, and their effects on the damping effectiveness were analyzed with respect to various parameters. Safety criteria for the stability of the retaining pile structure were proposed based on the ultimate tensile stress criterion, ultimate shear stress criterion, and Mohr’s criterion. Under the optimized scheme, the dynamic response characteristics of the retaining pile structure were analyzed, and the practical application effects on-site were observed. The research findings indicate that the depth, spacing, and number of damping holes have a significant impact on the damping effect. The safety criterion for the vibrational velocity of the retaining pile structure during blasting is determined to be 26.10 cm/s. Under the optimized scheme, the vibrational velocities at various monitoring points on the retaining pile structure all fall within the safe range, with a maximum reduction rate of 30.9%.

Asymmetric deterioration of reinforced concrete marine piles subjected to nonuniformly localized corrosion: Experimental study

Reinforced concrete (RC) marine piles usually suffer from local stiffness deterioration caused by chloride attack in splash and tidal zones. Moreover, pre-existing concrete cracks and defects at the steel–concrete interface usually lead to nonuniformly localized corrosion, which has seldomly been discussed. In this study, the effects of nonuniformly localized corrosion on the lateral behaviours of piles were experimentally studied. The localized electrochemical chloride erosion (LECE) technique was employed, and the corrosion level was represented by the number of corroded steel bars and the length of the corroded sections. Results show that the nonuniform localized corrosion caused asymmetric force–displacement hysteresis curves and changed the failure mode of pile structure under cyclic loading. The highly contrast mechanical responses suggest the importance of the loading directions in assessing the mechanical behaviours of corroded piles. Skeleton curves, stiffness degradation and energy dissipation capacity were further analysed to investigate the bearing capacity of corroded piles. These findings can benefit the comprehensive understandings and assessment of the asymmetric stiffness deterioration of corroded marine RC piles.

Investigation of a Cathodic Protection Configuration for the Steel Casing Pipes in Reinforced Concrete Bridge in the Niger Delta

This paper details the Design of a Cathodic Protection System on the steel casing pipes of the 60m reinforced concrete bridge project in the Niger Delta, Nigeria. Galvanic anode cathodic protection system was provided for the submerged steel support piles on the newly reinforced concrete bridge to ensure adequate corrosion protection of the structures. A total of fifty-six (56) Aluminum Anodes (32 kg) were used. Two of the Aluminum anodes were installed on each of the twenty-eight (28) steel casing piles. The anode installation was achieved by means of clamping at the predetermined water depth of 37.2 m with purpose made carbon steel clamps. The bonding of the anode to the pile structure to make electrical contact was achieved through welding of the pre-installed anode steel core extension bar against the steel pile at the water splash zone area of the river. A pre- and post-installation test and survey activities were conducted on each of the steel piles to ascertain the integrity of the installation and degree of corrosion protection of the steel casing piles. The field test and measurement results indicated mean values of open circuit potential of 0.600 Volts and polarized corrosion potential of 0.850 Volts. The recorded corrosion potential for the installed cathodic protection system confirmed adequate corrosion protection for ten (10) years from anode life for the steel casing supports of the 60 m reinforced concrete bridge.

Cryo-EM structures of type IV pili complexed with nanobodies reveal immune escape mechanisms

Type IV pili (T4P) are prevalent, polymeric surface structures in pathogenic bacteria, making them ideal targets for effective vaccines. However, bacteria have evolved efficient strategies to evade type IV pili-directed antibody responses. Neisseria meningitidis are prototypical type IV pili-expressing Gram-negative bacteria responsible for life threatening sepsis and meningitis. This species has evolved several genetic strategies to modify the surface of its type IV pili, changing pilin subunit amino acid sequence, nature of glycosylation and phosphoforms, but how these modifications affect antibody binding at the structural level is still unknown. Here, to explore this question, we determine cryo-electron microscopy (cryo-EM) structures of pili of different sequence types with sufficiently high resolution to visualize posttranslational modifications. We then generate nanobodies directed against type IV pili which alter pilus function in vitro and in vivo. Cryo-EM in combination with molecular dynamics simulation of the nanobody-pilus complexes reveals how the different types of pili surface modifications alter nanobody binding. Our findings shed light on the impressive complementarity between the different strategies used by bacteria to avoid antibody binding. Importantly, we also show that structural information can be used to make informed modifications in nanobodies as countermeasures to these immune evasion mechanisms.