Jacked Pile Research Articles

Pile response in sand: experimental development and study

Pile response in sand remains an important issue in the field of foundations. The influence of such parameters as the consolidation stress, the density ratio, the direction of loading (tension or compression) and the installation method significantly affects pile behaviour. As part of the Forever research project on micropiles in France, a parametric study was undertaken in a calibration chamber to analyse the influence of these parameters on pile response. A pile was designed with specific instruments independently to measure the tip resistance and shaft friction for a given pile segment. Two installation methods were tested: displacement piles (DPs) and non-displacement piles (NDPs). Significant differences in tip resistance were associated with the two installation methods. The shaft friction exhibited a stiffer response during the compression tests of the NDP, but the difference in capacity was less distinct. The effect of loading was highly symmetrical for the NDP, but for the jacked pile the shaft friction was smaller under tension loading. A comparison of the results with data presented in the literature (laboratory and field tests) showed satisfactory agreement. In addition, hyperbolic transfer laws were proposed for the tip resistance and the shaft friction and validated for the experimental results.

An investigation into the use of push-in pile foundations by the offshore wind sector

This paper presents the results of a field test performed to study the effects of installation method on the load–displacement response of piles used to support the offshore wind turbines. An instrumented open-ended model pile was installed by jacking in a deposit of medium-dense sand. Pile jacking has environmental benefits over the traditional method of pile driving which can cause noise and vibration damage to the marine mammals. Pile installation by jacking was shown to enhance the pile-soil stiffness response during compression loading. Residual stresses, generated during the installation process, caused the pile to exhibit a relatively soft stiffness response during tension loading. Environmental loading caused by wind and waves which causes piles that support jacket structure to experience tension loading and the serviceability limit state of the foundation to these loads governs the design.

Water supply to a geotechnical centrifuge

The supply of water to a centrifuge experiment has always been important. This paper details a new system which has been successfully commissioned for use on the geotechnical centrifuge at University of Cambridge. High water pressures and large flow rates were delivered to an experimental package, for the modelling of water injection-aided pile jacking. The practicalities of such a system are discussed in relation to existing alternatives, in addition to the precautions taken to ensure safe centrifuge operation. A method for calculating water pressures in the system away from instrumented locations is also proposed, using a linear relationship between energy per unit volume and the flow rate squared. Experimental data are presented to support these relationships.

Experimental Study on the Time Effect of the Jacked Pile

Based on the strain-holding test by using GDS stress path triaxial apparatus, the changes of pore water pressure and stress of soil around the pile were simulated during and after pile jacking. Test results show as follows: excess pore water pressure and effective stress increment increase with strain and initial stress rising at the stage of strain applied. And at the stage of strain holding, effective stress increment increases with rising of strain and initial stress. For the total effective stress increment, the proportion of effective stress increment is large at the stage of strain applied. And at the stage of strain holding, the proportion of effective stress increment is small.

Shaft Resistance and Setup Factors for Piles Jacked in Clay

Installation of a displacement pile often involves complex loading modes that cause substantial changes in the state of the soil surrounding the pile. When a displacement pile is installed in saturated clay, significant excess pore pressure develops. As the excess pore pressure dissipates over time, the effective stresses in the soil surrounding the pile and the pile capacity increase. This paper investigates jacking of piles into clay using finite-element analysis. A two-surface plasticity-based constitutive model for clays was implemented in the finite-element code Solid Nonlinear Analysis Code. Based on the numerical results, equations are developed for quantifying the effects of undrained and residual shear strength on the shaft resistance of jacked piles in clay. The gain in shaft resistance over time is assessed and setup factors are proposed that can be used to estimate the gain in shaft resistance as a function of time after installation of a jacked pile in clay. Good agreement was obtained between the shaft resistance values calculated with the proposed equations and the data available in the literature.

Centrifuge tests investigating the influence of pile cross-section on pile driving resistance of open-ended piles

Soil plugging in open-ended piles not only leads to an increase in compressive bearing capacity but also influences pile driving resistance. Numerous factors affect the tendency for soil plugging, for example pile geometry, penetration depth and installation method. In this study, the influence of the cross-sectional geometry of different open-ended piles (tubular, U- and sheet-piles) on the internal and external stress state at the pile toe is investigated. The underlying data were obtained from tests of pile installation (pile jacking) into dry silica sand conducted using a geotechnical beam centrifuge. During pile penetration the internal and external horizontal stresses at the pile toe were recorded to obtain the stress state inside the open-ended piles. The results are discussed with respect to the influence of the pile's geometrical properties (diameter of tubular piles, base width of U-piles and opening angle of sheet-piles) on the plugging tendency or the pile driving resistance. To conclude, a simple analytical approach based on equilibrium analyses is presented to predict the pile's bearing capacity.

Research on Soil Deformation due to Pile Jacking in Saturated Soil

According to the theoretical formula of compacting displacement field due to jacked pile in semi-infinite soil, calculation of displacement field produced during construction process of precast pile was carried out. And the changing trends of radial displacement with depth of pile penetrating, the maximum radial displacement with normalized distance r/D and vertical surface displacement with normalized distance r/D were analyzed in this paper. Then the Comparison between theory calculation results and the field test data was presented. The results show that the theoretical formula will fit with the actual situation of the site, when the soft soil properties around the pile are homogeneous and saturated. The further solving of compacting displacement field due to pile jacking was put forward.

Cyclic axial behaviour of piles and pile groups in sand

Piled foundations are often subjected to cyclic axial loads. This is particularly true for the piles of offshore structures, which are subjected to rocking motions caused by wind or wave actions, and for those of transport structures, which are subjected to traffic loads. As a result of these cyclic loads, excessive differential or absolute settlements may be induced during the piles’ service life. In the research presented here, centrifuge modelling of single piles and pile groups was conducted to investigate the influence of cyclic axial loads on the performance of piled foundations. The influence of installation method was investigated and it was found that the cyclic response of a pile whose jacked installation was modelled correctly is much stiffer than that of a bored pile. During displacement-controlled axial load cycling, the pile head stiffness reduces with an increasing number of cycles, but at a decreasing rate; during force-controlled axial load cycling, more permanent settlement is accumulated for a bored pile than for a jacked pile. The performance of individual piles in a pile group subjected to cyclic axial loads is similar to that of a single pile, without any evident group effect. Finally, a numerical analysis of axially loaded piles was validated by centrifuge test results. Cyclic stiffness of soil at the base of pre-jacked piles increases dramatically, while at base of jacked piles it remains almost constant.

Research on Time Effect of Bearing Capacity of Jacked Pile in Soft Soil

Through the study on the characteristics of bearing capacity of jacked pile in soft soil, it is found that the increment of ultimate bearing capacity of the single pile is mainly determined by pile side resistance. The end resistance has little influence on the time effect of bearing capacity of pile. The relationship between ultimate bearing capacity and time can be expressed with logarithmic curve. According to penetration mechanism of jacked pile, the expansion of a series of spherical cavities in semi-infinite space is used to simulate the process of pile installation. Soil is assumed as Mohr-Coulomb material. Based on the theory of spherical cavity expansion, estimating formulas were proposed to calculate the ultimate side frictional resistance. Then the ultimate bearing capacity of single pile in different time can be obtained. Analyses show that the calculation results are close to the measured data and the error between computed and measured value is little. So it is acceptable for the formula to forecast bearing capacity of jacked piles.

Ground Movement during Concrete Pipe Piles Jacking in Silt Deposit

In this study a comprehensive field test program was carried out to closely monitor the ground responses during open-ended concrete pipe piles jacking into a deposit mainly consisting of silt soils. The horizontal soil movement due to pile jacking was of depth-dependent characteristic that cylindrical cavity expansion models were unable to capture. The magnitude of displacement decreased rapidly with depth, and no discernible deflection was measured below the depth of the pile tip. The maximum displacement along the depth occurred at clayey-silt layer with relative lower permeability. The rebound of soil movement may be attributed to the setup effect following the piling stage.

Research on the Relationship between SPT and the Ultimate Vertical Bearing Capacity of Jacked Pile in Shenyang District

Though the wide applications of jacked pile in engineering in Shenyang district, the problem is also exist in engineering for the capacity of the jacked pile is hard to account. The relationship between the standard penetration test and the ultimate vertical bearing capacity of jacked pile is established in this paper; also an empirical formula is put forward for calculating the ultimate vertical bearing capacity of the jacked pile in this district with blow count of standard penetration test (SPT). The engineering examples indicated that the empirical formula is feasible because the calculating bearing capacity of the silent pipe pile is coincided with the static load tests. The calculated results satisfy the engineering requirement andt can be concluded that the method is also convenient to choose the diameter and length of the pile during the initial stage of design.

Numerical Simulation of the Successive Penetration of Jacked Pile in Layered Cohesive Soil and Sand

Different constitutive models is piecewise adopted including modified Cam clay model in cohesive soil and Drucker–Prager model in sand in order to simulate the penetration of jacked piles with ABAQUS more reasonably in layered soil particularly in interactive cohesive and sandy layered soil. Simultaneously, a series of other measures are taken including smoothing the angular corner between the tip and the shaft of a pile in the penetration process, allowing elastic slip even local detachment in pile-soil interface, making the initial stress equilibrium in layered soil come true by means of unconventional multiple calculation and so on. Combining with engineering example, the process of successive penetration of jacked pile in layered soil of having significantly different properties and stiff soil-interlayer in soft soil is simulated and calculated successfully, reflecting the abrupt change phenomenon of stress around pile and jacking resistance. And so the conclusion of numerical analysis is consistent with the in-situ observations.

Simulation for the Complete Uninterrupted Penetrating Process of Jacked Pile

The FEM mehods for simulating the penetration of jacked pile were summarized. Using the displacement penetration method, the complete uninterrupted penetrating process of jacked pile was simulated with the finite element method based on ANSYS. The soil’s displacement and stress field were obtained, and compared with the field test. The elastoplastic constitution law, large deformation, soil’s gravity field and pile-soil friction contact were taken into account. The difficulties and skills in the simulation were indicated, so it might be helpful to the other researchers.

Analysis of shaft resistance of jacked piles in sands

AbstractIn recent years, pile jacking has become a viable alternative installation method for displacement piles. Pile jacking produces minimal noise, vibration and air pollution during installation. In addition, it is possible, at the end of jacking, to have a good estimate of the ultimate static capacity of the pile. In this paper, the shaft resistance of piles jacked into sand is studied using one‐dimensional finite element analysis. The finite element simulations, using a two‐surface plasticity model, demonstrate the effects of relative density and confinement on the unit shaft resistance of piles jacked in sand. The impact of the number of jacking strokes on the unit shaft capacity is also assessed. Based on the numerical results, we developed equations for shaft resistance quantifying the effects of relative density, initial confinement and number of jacking strokes. Predictions using these equations are compared with data obtained from centrifuge tests and field tests. Copyright © 2010 John Wiley & Sons, Ltd.

Influence of pile installation on adjacent structures

AbstractPile installation leads to significant changes in the main state variables of the surrounding soil. In addition, the installation process may have an influence on adjacent or intersecting structures such as pile grillages. In this paper, three‐dimensional numerical analyses are presented to investigate the effects of pile driving with open or closed cross‐sections on the surrounding soil and on adjacent structures. Two different installation methods are used: quasi‐static pile jacking and vibratory pile driving. The numerical models are evaluated and verified using data from field tests performed in situ during the construction of the quay wall at the container terminal CT4 in Bremerhaven.Two case studies are presented to characterize the main influence factors for additional loading on adjacent structures due to pile installation.Finally, a parametric study is conducted showing the influence of the installation method, pile cross‐section and distance of a pile from an existing structure on the additional loading for this structure. Copyright © 2009 John Wiley & Sons, Ltd.

Field study of construction effects in jacked and driven steel H-piles

INTRODUCTION The nuisance of noise and vibration caused by percussive piling of displacement piles has limited the use of driven piles in Hong Kong. As an alternative, pile jacking is quiet and free of strong vibration in use. Recently, pile jacking was introduced to the construction industry in Hong Kong (Chan et al., 2002; Li et al., 2003). Li et al. (2003) and Zhang et al. (2006) described termination criteria for jacked pile construction, and Yang et al. (2006) and Zhang et al. (2006) reported behaviour of several jacked piles. Jacked piles were not previously a recognised type of pile foundation (Buildings Department, 2002), local regulations required that piles be installed by jacking to their approximate founding levels and then driven by hammers to confirm that their final sets were similar to those of equivalent driven piles (Chan et al., 2002). In order to satisfy prescribed final set criteria for driven piles, usually derived from Hiley’s formula, a minimum of 7 m of pile section had to be driven after pile jacking in order to achieve the same nominal pile capacity. In other words, in identical soil conditions the length of a jacked pile is smaller than that of a driven pile to satisfy the same capacity requirement. Several questions on the past practice can be asked by engineers. What are the differences between the stress conditions around a jacked pile and a driven pile? What are the differences between the load-carrying behaviour of jacked and driven piles? Why does final driving on a jacked pile cause a considerable change in the pile behaviour? The objective of this note is, through field tests, to study and compare the construction processes, the stress conditions caused by construction, and the load-transfer behaviour of jacked and driven piles.

Closure to “Termination Criteria for Jacked Pile Construction and Load Transfer in Weathered Soils” by L. M. Zhang, C. W. W. Ng, F. Chan, and H. W. Pang

Closure to “Termination Criteria for Jacked Pile Construction and Load Transfer in Weathered Soils” by L. M. Zhang, C. W. W. Ng, F. Chan, and H. W. Pang

Discussion of “Termination Criteria for Jacked Pile Construction and Load Transfer in Weathered Soils” by L. M. Zhang, C. W. W. Ng, F. Chan, and H. W. Pang

Discussion of “Termination Criteria for Jacked Pile Construction and Load Transfer in Weathered Soils” by L. M. Zhang, C. W. W. Ng, F. Chan, and H. W. Pang

Termination Criteria for Jacked Pile Construction and Load Transfer in Weathered Soils

Pile jacking is a piling technique that provides a noise- and vibration-free environment in the construction site. To improve termination criteria for pile jacking and to better understand the behavior of jacked piles, two steel H piles were instrumented, installed at a weathered soil site, and load tested. A set of termination criteria was applied to the test piles, which includes a minimum blow count from the standard penetration test, a specified final jacking force, a minimum of four loading cycles at the final jack force, and a specified maximum rate of pile settlement at the final jacking force. The two test piles passed all required acceptance criteria. Punching shear failure occurred at the failure load for both piles and the shaft resistance consisted of approximately 80% of the pile capacity. Based on the results of field tests in Hong Kong and Guangdong and several centrifuge tests, a relation between the ratio of the pile capacity Pult to the final jacking force PJ and the pile slenderness ratio is established. The Pult∕PJ ratio is larger than 1.0 for long piles but may be smaller than 1.0 for short piles. A regression equation is established to determine the final jacking force, which is suggested as a termination criterion for jacked piles. The final jacking force can be smaller than 2.5 times the design load for very long piles, but should be larger than 2.5 times the design load for piles shorter than 37 times the pile diameter.

Field measurements of the stiffness of jacked piles and pile groups

INTRODUCTION This Technical Note presents a back-analysis of the axial response of some field-scale tubular displacement piles installed by jacking. This study was motivated by the recent development of large pile-jacking rigs. These rigs are sufficiently strong to offer an alternative to bored piling in urban areas where conventional dynamic methods of displacement pile installation are not permitted (White et al., 2002). The most notable feature of the axial response was the very high stiffness. Some pile jacking machines ‘walk’ along the pile wall under construction, so all piles must necessarily be installed at close centres, or indeed touching. This geometry is in contrast to conventional design guidance, which suggests that a separation of typically two or three diameters is required between piles, to prevent harmful interaction effects (BSI, 1986; GEO, 1996). Load test results from jacked piles installed closer than this recommended minimum spacing are presented. The study comprised a series of field tests carried out in Kochi, Japan. Full details are provided by Yetginer et al. (2003), and brief details are repeated below. Test piles were installed singly and in groups forming a ‘cell foundation’, comprising jacked piles at close centres around an enclosed soil block. In this Technical Note, pile group efficiency is defined as the average performance per pile (strength or stiffness) when a group is loaded in unison, divided by the performance of a single pile tested alone. Using this definition, the behaviour of trial piles installed prior to the main group can be linked to the group response. This definition is used by Vesic (1969) and Fleming et al. (1992), and is shown in equation (1) for strength and stiffness. Group strength efficiency, GROUP, is defined in equation (1a), where QSINGLE and QGROUP represent the capacity of a single (isolated) pile and the capacity of a group of n piles respectively. Group stiffness efficiency, GROUP, is defined in equation (1b), where KSINGLE and KGROUP represent the stiffness of a single (isolated) pile and the stiffness of a group of n piles respectively.