Row Of Piles Research Articles

Kinematic response of pile groups and piled rafts to a distant stationary or moving harmonic load via the FEM

Using the finite-element method (FEM), this study presents results on piled foundations excited by a stationary or moving harmonic vertical point load acting on the soil surface at a given distance. For the stationary loading case, typical configurations of pile groups and corresponding piled rafts are examined in the frequency domain. The contribution of the raft alone in the overall response is also explored. The soil is modelled as a linear-elastic continuum with hysteretic damping. A wide range of frequencies from 8 to 64 Hz is considered. Of interest is the resulting vertical oscillation mode. The influence of the number of pile rows in the direction of wave propagation on the resulting vibration reduction is assessed by monitoring a reference pile at the furthest back pile row and an observation point at the free-field behind. The associated wave-passage effect is quantified through appropriate transfer functions for the piles. Subsequently, the case of a harmonic load travelling with a constant speed parallel to the pile group is investigated. Most importantly, it is revealed that a good approximation for this case is a stationary load located on the moving load path at the shortest distance from the pile group. This has important implications in the vibration protection practice, as detailed modelling of moving loads is then not required. The methodology presented can be extended to arbitrary foundation geometries and layered soil profiles.

Comparison Between the Periodic Trench and the Periodic Row of Piles on Isolating Earthquake Vibration

Comparison Between the Periodic Trench and the Periodic Row of Piles on Isolating Earthquake Vibration

Seismic Fragility Analysis of Steel Pipe Pile Wharves with Random Pitting Corrosion

This paper investigates the seismic damage behavior of steel pipe pile wharves after pitting corrosion. The seismic intensity is treated as random, and a probabilistic strength model for randomly pitting corroded steel is utilized to assess the seismic response of a typical steel pipe pile wharf. By analyzing the internal force response of each pile and the deformation response of the deck and soil slope, the process of seismic failure in steel pipe pile wharves with different pitting corrosion ratios is investigated. The results demonstrate that pitting corrosion amplifies the internal force within the steel pipe piles, leading to more severe seismic damage. Additionally, probabilistic seismic demand functions are established for the most vulnerable row of piles affected by random pitting corrosion, and the seismic fragility of the pipe pile wharves considering different pitting corrosion ratios is evaluated. These findings provide valuable insights for the design and strengthening of steel pipe pile wharves.

The P2.5D finite element method for periodic structures in half-space soil with application to periodic pile rows

In this study, by using periodic pile rows (PPRs) as an example, a new finite element method, namely, the periodic 2.5D finite element method (P2.5D FEM) is developed for the periodic structure embedded in soil. Similar to the 2.5D FEM, the major advantage of the proposed P2.5D FEM is its ability to reduce the 3-D dynamic problem associated with the periodic soil-structure system to a series of 2-D problems. The considered PPR-soil system, referred to as the periodic pile-soil system (PPSS) subsequently is supposed to be subjected to a harmonic point load. To develop the P2.5D FEM for the PPSS, the harmonic point load is decomposed into its wavenumber domain components first. The response of the PPSS to each wavenumber domain load component is then resolved into a series of pseudo plane waves propagating along the z-direction. The quantities for the pseudo plane wave are discretized by the FEM along the cross-section of the PPSS, and the FEM equations for the pseudo plane waves are then established. The eigenequation for the pseudo plane waves can be developed with the aforementioned FEM equations. Summation of the eigenvectors of the eigenequation for the PPSS yields the displacement for the PPSS due to the wavenumber domain load component. Synthesizing the displacements due to all the wavenumber domain load components via the inverse Fourier transform with respect to the wavenumber yields the overall displacement of the PPSS produced by the point load. To show the capability of the proposed P2.5D FEM for the PPSS, some numerical results about the wave barrier effect of PPRs are presented. The developed P2.5D FEM in this study is applicable to the dynamic analysis of various periodic structures embedded in the half-space soil under different types of dynamic loads.

Maximizing the decay of anti-plane shear waves in periodic pile barriers by topology optimization and its application in barrier design considering a moving load

Mitigating ambient vibrations using periodic pile barriers has gained significant attention in the past decade. The width of the bandgap and the attenuation coefficient are two important factors that determine the vibration reduction capabilities of periodic pile barriers. In certain situations, significant vertical anti-plane vibrations may occur, such as those generated by subways. Therefore, the focus of this article is to optimize the attenuation coefficients of anti-plane shear waves in periodic pile barriers. Firstly, a single-objective topology optimization framework is developed based on the Genetic Algorithm (GA) to maximize the attenuation coefficient of anti-plane shear waves in periodic pile barriers at a target frequency. The optimization considers the effects of the target frequency, elastic modulus of soil, and wave vector direction. A comparison between the optimized and traditional pile barriers is performed to demonstrate the superiority of the optimized design. Secondly, a multi-objective optimization framework is developed based on the non-dominated sorting GA II (NSGA-II) to investigate the relationship between the attenuation coefficient and the filling fraction, as well as the relationship between the attenuation coefficient and the bandgap width. The results indicate that a higher filling fraction results in a larger attenuation coefficient, while there is a tradeoff between the filling ratio and the bandgap width. Thirdly, an optimization framework is established considering the effect of a moving load, and the coverage rate of the target frequency range is defined to design periodic pile barriers. Finally, numerical simulations are conducted to validate the effectiveness of periodic pile barriers in mitigating vibrations when a finite number of pile rows is used.

Numerical Simulation and Analysis of Double Row Pile Anchor Composite Support Structure based on FLAC3D

Numerical Simulation and Analysis of Double Row Pile Anchor Composite Support Structure based on FLAC3D

Long-term settlement of metro viaduct piers: A case study in Shanghai soft soil

This study aims to investigate the long-term settlement behavior of metro viaduct piers in soft soil in Shanghai. Field monitoring was conducted for eight years, from the official opening until 2021. The results indicate that the settlement rate of the majority of piers was higher in the initial years and gradually reduced since 2017. Up to 2021, the maximum cumulative settlement St was 15.9 mm, which accounted for 0.8 times the limit of St (Ut). Seven settlement troughs were observed during the monitoring period. Muddy soil and nearby rivers significantly influenced the long-term pier settlements. St decreased proportionally with the thickness of the muddy soil. Piers located near the river experienced higher settlements than those located farther away, with a maximum settlement difference of 0.28–0.42 Ut. The influence of the river on St extended up to a range of 3–4 times the width of the river (Wr). Additionally, there were noticeable differences in settlement between piers constructed with tubular piles and those constructed with bored piles, particularly during the first two years after completion. Under similar conditions, the St of piers with tubular piles were 0.28 Ut (5.5 mm) larger than those of piers with bored piles on average. In addition, the slope k between the excavation-induced pier settlement and the ratio of the excavation depth to the distance was closely related to the type of retaining structure. The ratio of k values for the pit wall soil reinforcement, row piles and diaphragm wall was approximately 4:2:1. To prevent excessive pier settlement under similar geological conditions, it is recommended to employ a more rigid retaining structure and avoid using a soil-reinforced enclosure for pit walls.

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.

Force Calculation of Mechanical Model of Pile-anchored Support Structure Based on Elastic Foundation Beam Method

With the widespread use of deep foundation pit engineering in engineering construction, the force calculation problem about deep foundation pit support engineering has become a common problem in today’s engineering construction process. In this paper, based on the elastic foundation beam method, a simplified mechanical model of pile-anchored structure is proposed, and a systematic and practical calculation method is proposed for the force and deformation calculation of deep foundation pit support structure. The method simplifies the support structure as a vertically placed elastic foundation beam, the support, anchor and geotechnical body are replaced by a spring system, the spring stiffness of geotechnical soil can be calculated by the deformation modulus of geotechnical soil, and a systematic calculation method is proposed for the dynamic characteristics of the construction and structure of the foundation pit project; Based on the monitoring data of a deep foundation pit project, the calculation method of the simplified mechanical model proposed in this paper is verified, and the theoretical calculation value is compared with the field monitoring results; Single factor analysis is carried out on the detailed parameters of pile-anchor supporting structure to study the influence of cable prestress, cable dip Angle, pile diameter, pile length and other related parameters on the deformation and stress characteristics of supporting structure. Then the orthogonal combination of all factors is carried out to propose the optimization design. The results show that the maximum settlement deformation of the calculated value is 23.437 mm, and the maximum settlement deformation of the monitored value is 26.517 mm, and the difference between them is small. The maximum bending moment is 1210 kN⋅m after 150 kN and 250 kN horizontal prestressing is added to the second- and third-layer anchors respectively. After optimization, the maximum bending moment of pile row is 336.87 kN⋅m, and the maximum horizontal displacement of pile body is 16.505 mm, which is reduced by 11.97% compared with the original design.

Analysis of Influence Factors of Anti-Slide Pile with Prestressed Anchor Cable Based on Bearing and Deformation Characteristics of Pile Body

In order to deeply study the mechanism of prestressed anchor anti-slide pile, an indoor model experimental device was developed, and a finite difference and particle flow numerical analysis model of slope anchor cable anti-slide pile was established based on the reinforcement project of prestressed anchor cable anti-slide pile in a mountain road slope. Based on the analysis of the force and displacement characteristics of the anti-slide pile, the influence of the prestress of the anchor cable, the inclination angle of the anchor cable, the width and column spacing of the anti-slide pile and the inclination angle of the landslide, the height and nature of the filling soil on the force and deformation characteristics of the pile are discussed, and some design parameters are optimized. Results show that the larger the prestress of the anchor cable, the smaller the displacement of the pile body, but the excessive stress is not conducive to the safety of the pile body. The optimal tension should be 50–70% of the designed tension of the anchor cable. With the increase in the inclination angle of the anchor cable, the displacement of the pile decreases first and then increases, and there is an optimal inclination angle of the anchor cable. In the double row piles, with the increase in pile spacing, the front row piles gradually change from supporting the soil between the double row piles to supporting the sliding body with the back row piles, and the double row piles are plum-shaped. When the pile spacing is 2.5 times the pile diameter, the force of the front and rear piles is the most reasonable. In the process of soil arching evolution, the influence of cohesion on the soil arching effect is greater than that of the internal friction angle.

Spatial Effect Analysis of a Long Strip Pit Partition Wall and Its Influence on Adjacent Pile Foundations

The spatial effect at the end of the foundation pit partition wall is significant, and the displacement of the retaining wall and soil caused by its demolition leads to an additional displacement and bending moment of the adjacent pile foundations, which in turn deteriorates the work behavior of the pile foundation. Taking the project of an open tunnel under a viaduct located in Hangzhou as an example, site monitoring was performed to determine the effect of the demolition of the partition wall on the displacement of the surrounding retaining wall and the soil in the adjacent area and the monitoring data were compared to the finite element analysis results to check the rationality of the finite element model. This model was used to study the influence of the distance from the pile foundation to the partition wall as well as the stiffness of the retaining wall on the displacement and bending moment of the pile foundation during excavation. These results indicate that because of the support effect of the foundation pit partition wall on the retaining wall, the spatial effect at the end of the partition wall is large, and the displacement and bending moments of the pile foundation in the vicinity of the partition wall are lower than those in the far distance. Demolition of the partition wall will increase the displacement and bending moment of adjacent pile foundations, and this effect decreases with increasing distance. The range of influence of the spatial effect at the end of the partition wall is approximately 1.1 times the depth of the foundation pit. When the pile foundation is in the immediate vicinity of the partition wall, the response of the front-row and rear-row piles to the demolition of the partition wall is significantly different. The front row piles are more affected, while the rear row piles are less affected. As the distance increases, the difference in response gradually decreases and tends to be consistent. As the stiffness of the retaining wall increases, the effect of the demolition of the partition wall on the pile foundation decreases. It is recommended that the stiffness of the supporting system near the partition wall be reduced appropriately, and the partition wall should be set at the foundation pit section near the pile foundation, but the response of the foundation pit and the adjacent pile foundation should be paid close attention to when the partition wall is demolished.

Study of Rheological-Mechanical Properties and Vibration Mechanics Bandgap of Row Pile Foundation

To analyze the rheological and mechanical properties as well as the vibration-mechanical forbidden zone effect of row pile foundations, this paper employs time-dependent modulus to examine the rheological mechanics of soil. Drawing from viscoelastic theory, we derive the expression of deformation modulus in the frequency domain to analyze the frequency dependence of the shear modulus of rheological soils. We construct a continuous medium dynamics model of the pile-soil periodic structure, taking into account soil rheology, and derive the dispersion equation of shear waves in the periodic structure using the multiple scattering method. The band gap characteristics and parameters that influence the law of shear waves in rheological soil-row pile foundations are studied through the analysis of arithmetic cases. The results show that under the loading condition, the zero-frequency shear modulus of soil is larger than the initial modulus value, and the real part of the shear modulus decreases monotonically with the increase of frequency and finally converges to the initial modulus value; under the unloading condition, the zero-frequency shear modulus of soil is smaller than the initial modulus value, and the real part of the shear modulus increases monotonically with the increase of frequency and finally converges to the initial modulus value; the larger the relaxation time of soil, the faster the convergence rate; the imaginary part of the shear modulus of soil The imaginary part of the soil shear modulus is positive under loading condition and negative under unloading condition, the value of the imaginary part increases and then decreases with increasing frequency and finally converges to 0. The imaginary part reaches the peak at the critical frequency, the larger the relaxation time the smaller the critical frequency, and the peak of the imaginary part is independent of the relaxation time. This study analyzed the dispersion curve of shear waves in a pile-soil periodic structure and found that increasing low-frequency shear wave velocity in rheological soil pile foundation shifts the band gap position to a higher frequency band, resulting in a smaller band gap width than in linear elastic soil. The relaxation time of soil affects the frequency position and width of the band gap, with larger relaxation times resulting in higher frequency positions and smaller widths. Additionally, soil rheology widens the forbidden vibration band gap of the pile periodic structure when the filling rate of the pile foundation is larger.

An automated health monitoring system for uncoordinated deformation between the metro station side wall and row piles

An automated health monitoring system for uncoordinated deformation between the metro station side wall and row piles

Engineering Characteristics and Application Analysis of Red Sandstone in the Lanzhou Metro

The water-rich red sandstone strata at the Lanzhou Metro site area have special engineering properties and vary greatly in their speed of disintegration when exposed to water. There is an urgent need for a comprehensive and systematic study of the engineering properties of red sandstone and their classification. From the disintegration speed of red sandstone encountered during the excavation of Lanzhou metro lines 1 and 2, the relationship between physical parameters such as particle size, composition, dry density, and permeability coefficient as well as mechanical parameters such as shear wave speed, dynamic penetration test (DPT), natural uniaxial compressive strength, and disintegration speed of red sandstone was analyzed through indoor and outdoor tests and geological exploration data statistics, and classification guidelines for red sandstone are given. The results show a significant correlation between dry density, permeability coefficient, natural uniaxial compressive strength, and disintegration speed. The red sandstone can be classified as I, II, and III according to the disintegration speed, dry density, permeability coefficient, and natural uniaxial compressive strength. The design of the foundations is differentiated according to the classification, and different support systems are used for the deep foundation pits of the metro stations. The category I red sandstone pit is supported by diaphragm walls with internal bracing, the category II pit by bite piles with internal bracing, and the category III pit by row piles with internal bracing. The study results can provide technical support and experience reference for the investigation, design, and construction of metro projects in similar red sandstone distribution areas.

Numerical analysis for isolation of vibrations by pile rows in transversely isotropic saturated media due to moving loads

An analytical layer-element–boundary-element coupling approach is presented to explore the isolation effect of pile rows in stratified transverse isotropic saturated media for moving-load induced vibration. The analytical layer-element basic solution for the soils is derived. The soil flexibility matrices are obtained using boundary integral equations for pile-soil. Then, the pile is modeled as a Bernoulli–Euler beam utilizing the finite difference approach. The dynamic equations for the piles are achieved by considering the pile-soil displacement coordination condition. Finally, to obtain the amplitude reduction ratio, the displacement of an observation point is calculated with and without pile isolation, respectively. The results are in good consistency with the existing solutions. The impacts of the soils’ transverse isotropy, the pile’s size and physical properties on the isolation effect are evaluated using numerical examples. It is observed that when the pile length exceeds a certain value, the increment in the pile length shows no obvious improvement in the vibration isolation effect. A stiffer pile has a greater impact on vibration reduction. The material anisotropy is also an important parameter for the pile isolation problem.

Formation and Failure Characteristics of a Landslide Induced by Excavation in Western Henan, China

Engineering construction in mountainous areas is a key factor inducing slope failure, which poses severe threats to life and property safety during construction and operation. Thus, clear understanding of slope structure and potential failure mechanisms is of great importance for slope reinforcement. The Shangge landslide, located in a mountainous area of Western Henan, China, was triggered by excavation along a toll station. The slope was still unstable after a row of anti-sliding piles were constructed. To clarify the deformation characteristics and failure mechanism of this landslide and provide reinforcement guidance for slopes with similar geological conditions, a combined method of field investigation, displacement monitoring, and numerical simulation was employed. The results indicate that the natural slope comprises a dual structure of soil and rock, and that the soil, with poor permeability and high water moisture, was prone to form a potential sliding surface. Secondly, slope excavation was the direct triggering factor. Lastly, but most importantly, the preliminary investigation work failed to accurately expose the potential position of the sliding surface, and the existing anti-slide piles failed to cross the potential sliding surface, which made them unable to effectively improve slope stability. The numerical simulation verified that the recommended piles installed on the platform of level 2 could significantly improve slope stability. Therefore, when carrying out engineering slope design in similar geological environments, the slope structure and material composition should be fully identified, and the influence of groundwater on the slope stability state should be emphasized. These results can provide a reference for similar slope reinforcement designs.

Assessment of Small Diameter Steel Pile as a Stabilizing Element for Transmission Tower Slope Stability

Background: Stabilization of unstable slopes with relatively large reinforced concrete piles has been widely adopted over the past several decades. Small diameter steel piles have several advantages as a slope reinforcement technique for an unstable transmission tower slope where space and access restrictions that typically occur render alternate approaches unfeasible. Methods: In this study, a numerical performance assessment of small diameter steel pile as a stabilizing element for transmission tower slope stability was carried out using an uncoupled analysis, in which the pile response and slope stability are considered separately. Numerical evaluations are presented and the influencing parameters that could affect the behavior of reinforcing piles to increase transmission tower slope stability are investigated. Results: The numerical analysis results indicate that the soil properties, slope geometry, pile location, pile diameter, pile length and number of pile rows have a combined effect on the performance of small diameter steel piles to stabilize transmission tower slopes. Conclusion: The numerical assessment can satisfactorily capture some fundamental response of transmission tower slope reinforced with multi-row small diameter steel piles.

Vibration isolation of row of piles due to moving harmonic loads embedded in the layered isotropic saturated medium

AbstractThis paper develops an analytical layer element‐boundary element coupling method to study the vibration isolation effect of pile rows in multi‐layered isotropic saturated soils subjected to a moving harmonic load. The isotropic saturated soil is represented using an analytical layer‐element solution as a kernel function, and the pile‐soil boundary integral equation is applied to obtain the soil flexibility matrices. The finite difference method is used for the piles modeled as a Bernoulli–Euler beam. The dynamic response equations of the pile rows under a harmonic moving load are achieved by considering pile‐soil displacement coordination condition. Then, the displacements of the observation point with and without the pile effect are calculated, respectively. Several numerical examples are presented to examine the influences of the soils’ stratification characteristics, the pile length, pile spacing, pile‐soil Young's modulus ratio, and the load moving speed on the isolation effect of the pile rows.

Limit Analysis for 3D Stability of Unsaturated Inhomogeneous Slopes Reinforced with Piles

Achieving slope stabilization by placing anti-slide piles has become an effective slope-reinforcement technique in geotechnical engineering. Based on the limit analysis method, this study investigated the 3D stability of unsaturated inhomogeneous piled slopes, incorporating three failure patterns: toe-failure, face-failure, and base-failure. The suction and effective unit weight profile under different effective saturation were considered and the soil cohesion was assumed as varied linearly with depth. A theoretical analysis of the lateral force acting on a row of rigid anti-slide piles with the same spacing in a row through plastically deforming soils is described while considering the soil suction and inhomogeneity. In addition, a new formula was developed to calculate the lateral forces provided by a row of piles. The genetic algorithm (GA) was used to obtain the minimum value of the factor of safety FS and the corresponding critical slip surface. The results of the study were compared with those of the existing literature to verify the feasibility of the proposed approach. In addition, the influences of key parameters on FS of 3D piled slopes were investigated by parametric analysis. The numerical results indicate that piled slope stability will be underestimated when the 3D effects and suction are not considered, and soil inhomogeneity has a negative impact on piled slope stability. It was also found that the probability for the occurrence of face-failure increases with increasing inhomogeneity and decreasing suction-induced effect, and the occurrence of face-failure significantly reduces the pile reinforcement effect. In addition, when the anti-piles are located at the slope toe, the base-failure mechanism yields the critical values of FS in most cases. This study can provide several reasonable suggestions for engineering applications and a theoretical basis for further studies on the stability of slopes reinforced with piles.

Field test study on soil squeezing effect of H-type prestressed concrete revetment pile

The pretensioned H-type prestressed concrete revetment pile is a new product specially developed for the protection of coastal dykes in rivers and lakes. Its cross section is H-shaped, and the H-type revetment pile is also a soil squeezing pile. The excess pore pressure and soil displacement caused by the soil squeezing effect of H-shaped piles are deeply analyzed. The influence range of excess pore water pressure is 14~15d, and the excess pore water pressure completely dissipates after 6d. The farther the vertical distance from the pile tip is, the less obvious the horizontal displacement is. In a row of piles. In the process, it will cause repeated uplift and settlement; However, after the erection, the law of vertical deformation is reflected in the near settlement and the far uplift.