Vertical Piles Research Articles

Study on the Structural Behaviour of Berthing Structure due to Variable Stack Load

Objectives: To study the structural behavior of the components of berthing structure subjected to variable stack load with and without mooring force conditions. Methods/Statistical Analysis: Linear static analysis was performed on the berthing structure subjected to variable stack load with and without mooring effects. Based on this study, equations related to bending moment and axial force of structural members of berthing structure has been obtained. A Monte Carlo simulation method was adopted for generation of random numbers using MATLAB software. From the obtained results, analysis was performed to obtain characteristics of load effects of the components of the berthing structure. Findings: The influence of variable Stack load has an effect on the Bending Moment and Axial Force of structural components of the berthing structure. It was also found that there was a significant variation of results of load effects between with and without mooring force condition in case of Vertical Pile (VP) but there was no significant variation of results of load effects on Main Cross Head Beam (MCHB), T-shaped Diaphragm Wall (TDW) and Raker Pile (RP) due to stack load. Applications/ Improvement: This study helps to predict the behavior of berthing structure subjected to varying stack load caused due to lack of awareness of end user on the loading specifications that have been assessed by the designer

Lateral pressure on piles due to horizontal soil movement

This paper presents the results of 1g model tests on single piles and pile rows loaded laterally by horizontal soil movements in soft kaolin clay. In soft soil layers, vertical piles are frequently loaded laterally by horizontal soil movements caused by eccentric loading or unloading of the ground surface around the piles. In many cases, the lateral pressure acting on piles due to horizontal soil movements is calculated using empirically or analytically based approaches. The model tests investigate the influence of the roughness of the pile–soil interface, the pile size, the pile shape, the displacement rate of the soft soil flowing around the pile and the pile spacing on the lateral pressure acting on the piles. During the model tests, the soil movements were analysed with the particle image velocimetry method. The results of the model tests show possible influences on the resulting pile loads.

Model load tests on battered pile foundations and finite-element analysis

Behaviours and resistance mechanisms of pile groups and piled rafts with or without batter piles were investigated through a series of load tests on foundation models at 1g field. Three-pile pile foundation models were used in the experiments. Dry silica sand having a relative density, Dr, of ∼82% was used for the model ground throughout the experiments. A series of triaxial CD tests of the sand were carried out to characterise the sand behaviour. Close-ended model pipe piles having a length of 255 mm and an outer diameter of 20 mm were used in the foundation models. The results of the load tests are presented and discussed in detail, focusing mainly on the horizontal load tests. Numerical analyses were conducted for cases of the piled rafts subjected to horizontal load to confirm the experimental results and to get a deeper insight into the resistance mechanisms of the piled raft foundations. It is shown from the results that the foundations with batter piles have advantages over the foundations with only vertical piles in aspects of resistance and settlement reduction.

Run-up on vertical piles due to regular waves: Small-scale model tests and prediction formulae

In wave-structure interaction, one of the most important phenomena clearly identified is wave run-up on offshore structures. In this study, wave run-up on a slender pile due to non-breaking regular waves is investigated by means of small-scale experiments performed in the 2m-wide wave flume of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI) in Braunschweig, Germany. The test programme is designed to generate a comprehensive data set covering a broader range of wave conditions including not only deep and intermediate water conditions but also nearly shallow and shallow water conditions, which are missing in the available laboratory studies on wave run-up on piles. The relative wave height (H/h), relative water depth (h/L) and slenderness of pile (D/L) are identified as the key parameters governing the relative wave run-up (Ru/H). Based on these parameters, new formulae covering the range of tested conditions (0.028≤H/h≤0.593, 0.042≤h/L≤0.861, 0.003≤D/L≤0.206) are developed to predict regular non-breaking wave run-up on single piles using a combination of the M5 model tree and nonlinear regression techniques. Using statistical accuracy metrics such as agreement index Ia, squared correlation coefficient R2 and scatter index SI, the performance of the developed formulae is evaluated. It is shown that the new formulae outperform the current formulae in predicting regular wave run-up on single piles. This success is in part due to the explicit account for the water depth in the new experiments and formulae. The proposed model is valid for a wider range of wave conditions and, therefore, more appealing for engineering practice compared to those available for the estimation of regular wave run-up.

Dynamic soil–pile interactions for machine foundations

To achieve the satisfactory performance of a machine foundation, the dynamic amplitude should be limited to a few micrometres. In using piles for the foundation, the interaction of the pile with the surrounding soils under vibratory loading will modify the pile stiffness and will generate damping. The results of a three-dimensional, finite element model of a soil–pile system with viscous boundaries were used to determine the dynamic stiffness and damping generated by soil–pile interactions for a single vertical pile subjected to a vertical harmonic loading at the pile head. The pile was embedded in a linearly elastic, homogeneous soil layer with material damping of the hysteretic type. A parametric study was undertaken to investigate the influence of the major factors of the soil–pile system that affect the vertical vibration characteristics of the pile response. These were found to include the dimensionless frequency, ao, soil properties, pile properties, and length and axial load on the pile head. Equations were developed to determine the range of such influence. Two general equations that include all of these parameters and can be used to approximate the stiffness and damping of the pile were developed so that a finite element analysis does not have to be made in every case.

Scour around vertical piles due to random waves alone and random waves plus currents on mild slopes

This paper provides a practical stochastic method by which the maximum equilibrium scour depth around a vertical pile exposed to random waves plus a current on mild slopes can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Battjes and Groenendijk (2000) wave height distribution for mild slopes including the effect of breaking waves, and using the empirical formulas for the scour depth on the horizontal seabed by Sumer and Freds e (2002). The present approach is valid for wave-dominant flow conditions. Results for random waves alone and random wave plus currents have been presented and discussed by varying the seabed slope and water depth. An approximate method is also proposed, and comparisons are made with the present stochastic method. For random waves alone it appears that the approximate method can replace the stochastic method, whereas the stochastic method is required for random waves plus currents. Tentative approaches to related random wave-induced scour cases on mild slopes are also suggested.

Centrifuge modeling of batter pile foundations under earthquake excitation

Although batter pile foundations are widely used in civil engineering structures, their behavior under seismic loadings is not yet thoroughly understood. This paper provides insights about the differences in the behavior of batter and vertical piles under seismic soil-pile-superstructure interaction. An experimental dynamic centrifuge program is presented, where the influences of the base shaking signal and the height of the gravity center of the superstructure are investigated. Various seismic responses are analyzed (displacement and rotation of the pile cap, total shear force at the pile cap level, overturning moment, residual bending moment, total bending moment and axial forces in piles). It is found that in certain cases batter piles play a beneficial role on the seismic behavior of the pile foundation system. The performance of batter piles depends not only on the characteristics of the earthquakes (frequency content and amplitude) but also on the type of superstructures they support. This novel experimental work provides a new experimental database to better understand the behavior of batter pile foundations in seismic regions.

Study of static lateral behavior of battered pile group foundation at I-10 Twin Span Bridge using three-dimensional finite element modeling

In this study, the static lateral behavior of a battered pile group foundation was investigated using three-dimensional finite element (FE) analysis. The FE model was used to simulate the static lateral load test that was performed during the construction of the I-10 Twin Span Bridge over Lake Pontchartrain, La., in which two adjacent bridge piers were pulled against each other. The pier of interest was supported by 24, 1:6 batter, 34 m long piles in a 6 × 4 row configuration. The FE model of the battered pile group was developed in Abaqus and verified using the results from the field test. The model utilized an advanced constitutive model for concrete, which allowed distinct behavior in tension and compression, and introduced damage to the concrete stiffness. The soil domain comprised of several layers in which the constitutive behavior of clay layers was modeled using the anisotropic modified Cam-clay (AMCC) model, and for sands using the elastic perfectly plastic Drucker–Prager (DP) model. FE results showed good agreement with the results of the lateral load test in terms of lateral deformations and bending moments. The results showed that the middle rows carried a larger share of lateral load than the first and the last rows. The pile group resisted a maximum lateral load of 2494 t at which the piles were damaged within a 6 m zone from the bottom of the pile cap. The edge piles carried larger internal forces and exhibited more damage compared to the inner piles. The soil resistance profiles showed that soil layering influenced the distribution of resistance between the soil layers. A series of p–y curves were extracted from the FE model, and then used to study the influence of the group effect on the soil resistance. The p–y curves showed that the group effect reduced the soil resistance in all rows, with the lowest resistance in the third row. Finally, the p-multipliers were calculated using the extracted p–y curves, and compared to the reported p-multipliers for vertical pile groups.

A new analytical cone model for laterally-loaded vertical piles in cohesionless soil

ABSTRACTLaterally-loaded vertical piles are commonly designed by p-y curves or two-dimensional (2D) analytical methods. The former are vaguely correlated while the latter are oversimplified and conservative. Three-dimensional (3D) analysis can be used, but it is time consuming for practical applications. An improved analytical cone method is thus developed using spreadsheets. Subject to the lateral load under greenfield condition, the soil in front of a vertical pile is under constant volume plastic compression, heaving at the free boundary on top. Stress release occurs in the soil behind the pile. These mobilised soil masses are idealised as inclined right circular cones. The pile below the cone is subjected to the direct compression at the back and shear at the sides. Thus, the pile behaves as a simply-supported beam with one movable support at the loading point. This enables the rational prediction of the pile length required to satisfy the vertical tangent and the “zero-toe-kick” criteria. By plane of...

A method to compute the non-linear behaviour of piles under horizontal loading

The empirical evidence for vertical piles under horizontal or lateral loading is firstly reviewed. The load–deflection relationship is nonlinear from the early stages of loading, while the load–moment relationship is nearly linear. Moving from the available experimental evidence, typical design issues are addressed and a validation of the widespread Broms’ method is then carried out. To predict the pile–soil interaction, a computer code, NAPHOL, based on a hybrid BEM approach, is fully presented and discussed. A limiting pressure profile, coupled with a cut-off procedure, allows the method to cope with the nonlinear behaviour. Simple guidelines and equations, to calibrate the model parameters, are derived on the basis of the back-analysis of a significant number of case histories. The program is finally used to throw light on the mechanism of the pile–soil interaction under horizontal loading.

The Analysis of The Direct Foundation With Energy Foundations On The Basis of The Office Building “A4 Business Park” In Katowice At Francuska Street

Abstract Resources of geothermal energy range from the shallow ground to hot water and hot rock were found a few kilometres beneath the Earth’s surface, and down even deeper to the extremely high temperatures of molten rock called magma. The paper shows the analysis of the public building foundation with the usage of shallow geothermal system (closed loop systems using the vertical energy piles). In the soil and groundwater conditions the change of the way of public building foundation was suggested from direct (setting of pads, strip footings and foundation plate according to the basic project) into indirect one with the use of drilled piles in a casing pipe with the possibility of their cooperation with vertical ground collector. Calculations have been conducted in accordance with effectual standards. Both the quantity of energy piles in a single foundation pile coped with the foundation plate and the quantity of energy foundations in the whole building have been determined for the analysed building. Moreover, approximate heating power of the whole system has been calculated. An economical analysis of the proposed solution is presented in a summary.

Centrifuge modeling of batter pile foundations under sinusoidal dynamic excitation

Batter pile (or inclined pile) foundations are widely used in civil engineering structures. However, their behavior under dynamic loadings is not yet thoroughly understood. This paper presents an experimental work on the behavior of batter and vertical piles considering dynamic soil-pile-superstructure interactions. A series of dynamic centrifuge tests were performed using sinusoidal excitations. The influence of the base shaking (frequency content and amplitude) and of the height of the center of gravity of the superstructure is investigated. Seismic responses are analyzed considering the pile cap displacements and forces (total base shear, overturning and residual moments, axial forces). It is found that in certain cases batter piles play a beneficial role on the dynamic behavior of the pile foundation system. This novel experimental work provides an important database on the behavior of batter pile foundations under dynamic loadings.

Limit equilibrium analysis of seismic stability of slopes reinforced with a row of piles

SummaryAn approach based on the category of limiting equilibrium analysis is proposed to consider the reinforcing effect of one row of vertical piles on slope under seismic conditions. The approach is based on an uncoupled formulation in which the pile response and slope stability are considered separately. Closed‐form equations are derived, allowing the yield acceleration coefficient to be determined for giving pile characteristics. Results were compared with those obtained using another limit equilibrium method. The effects of pile location on the effectiveness of increasing seismic stability of the slope–pile system were elucidated. It was found out that the piles should be installed in the middle–upper part of the slope to achieve greatest safety, but the pile length and other possible failure modes should be checked carefully in design. Copyright © 2015 John Wiley & Sons, Ltd.

Numerical Investigation of Solitary Wave Interaction with a Row of Vertical Slotted Piles

ABSTRACT Jiang, C.; Yao, Y.; Deng, Y., and Deng, B., 2015. Numerical investigation of solitary wave interaction with a row of vertical slotted piles. This study numerically investigated tsunami-like solitary waves propagating over a row of vertical, slotted, cylindrical piles. Existing studies using depth-integrated models, such as shallow-water equations, could not adequately resolve the wave dynamics over water depth. An alternative three-dimensional, numerical model, based on OpenFOAM® software, was developed for this study. The Navier-Stokes equations for two-phase, incompressible flow, combined with methods of large eddy simulation (LES) for turbulence closure and volume of fluid (VOF) for tracking the free surface, were solved. Laboratory experiments were performed on the measurements of flow near the piles and the dynamic pressures on the pile surface. The model was then validated with the laboratory data as well as data in the literature, and good agreements were found for wave, flow, and dynamic ...

Seismic Dynamic Damage Characteristics of Vertical and Batter Pile - supported Wharf Structure Systems

Seismic Dynamic Damage Characteristics of Vertical and Batter Pile - supported Wharf Structure Systems

A hypoplastic macroelement for single vertical piles in sand subject to three-dimensional loading conditions

This paper presents a novel macroelement for single vertical piles in sand developed within the hypo-plasticity theory, where the incremental nonlinear constitutive equations are defined in terms of generalized forces, displacements and rotations. Inspired from the macroelement for shallow foundations of Salciarini and Tamagnini (Acta Geotech, 4(3):163–176, 2009), the new element adopts the “intergranular displacement” mutuated from Niemunis and Herle (Mech Cohes Frict Mater, 2:279–299, 1997) to reproduce the behavior under cyclic loading. Analytical and numerical strategies are provided to calibrate the macroelement’s parameters. Comparisons with experimental results show the performance of the macroelement that while being simple and computational fast is suitable for finite element calculations and engineering design.

Experiment of single screw piles under inclined cyclic pulling loading

The ultimate pullout capacity under inclined dynamic loading is an important measure of the destruction degree of vertical screw piles (anchors) under dynamic actions. Based on the static and dynamic tests on two kinds of model screw piles, the ultimate bearing capacity was researched considering different distance-width ratio of blade (D/W) and preloading ratio. The results compared well with other experimental data available in the literature. This research reveals that D/W might determine the failure model of the piles (anchors), for example D/W

Vertical vibration of an elastic pile embedded in poroelastic soil

We present an analytical study on the vertical vibration of an elastic pile embedded in poroelastic soil. The poroelastic soil is divided into a homogeneous half-space underlying the pile base and a series of infinitesimally thin independent layers along its shaft. The dynamic interaction problem is solved by extending a method originally proposed for an embedded rigid foundation. The validity of the derived solution is verified via comparison with existing solutions. Arithmetical examples are used to demonstrate the sensitivity of the vertical pile impedance to the relative rigidity of the two soil parts.

Acoustic emission characteristics of subsoil subjected to vertical pile loading in sand

The response of the subsoil subjected to pile loading is crucial to clarify the bearing mechanism of pile foundations. This study presents a novel acoustic emission (AE) method to monitor the subsoil behavior in a model pile testing system. The AE testing aims to capture the “micro-noises” released from sand grain dislocation and crushing around the pile shaft during penetration. The correlations between the pile settlement and the AE characteristics including count, amplitude and energy are revealed and discussed, highlighting that the ground density and the shear zone formed during pile penetration mainly affect the AE behavior. The results also suggest that the yielding of ground can be determined based on the development of the AE activity. The technique shows promise as an in-situ methodology for monitoring of subsoil behavior during the process of pile loading.

Soil–pile interaction considering structural yielding: Numerical modeling and experimental validation

In the present study the accuracy of an efficient beam formulation for inelastic analysis of pile-foundation systems is validated against a series of Laboratory Pushover tests on vertical single piles embedded in dry sand under different load paths to failure in M–Q space conducted in the Laboratory of Soil Mechanics/Dynamics (LSMD) in NTUA. The obtained results are also compared to those from a fully 3D Nonlinear Finite Element (FE) simulation. The proposed beam formulation is based on the Boundary Element Method (BEM) accounting for shear deformation effect. A displacement based procedure is employed and inelastic redistribution is modeled through a distributed plasticity (fiber) model exploiting pile material constitutive laws and numerical integration over the cross-sections, while the surrounding soil is modeled through independent inelastic Winkler springs. The efficiency of the beam formulation is verified through the good agreement between the measured and the calculated results.