Jacked Pile Research Articles

Penetration mechanism of open-ended pipe piles under jacking and driving methods

Different pile penetration methods will cause different pile penetration results. Therefore, it is very necessary to study the pile penetration mechanism under different pile penetration methods. In this paper, numerical simulations using the discrete element method (DEM) are carried out to investigate the meso-scopic mechanism of pipe pile penetration under jacking and driving methods. The mechanism is comprehensively compared and analyzed in terms of particle movement, changes in the force chain, displacement changes, resistance of penetration pile, soil lateral stress and soil vertical stress. Results show that the height of the soil plug in the jacked pile is lower than that in the driven pile. The degree of contact force chain at the bottom of the soil plug in the driven pile is slightly higher than that at the bottom of the soil plug in the pile of the jacked pile. The total resistance of the driven pile greater than that of the jacked pile. Within a certain distance below the pile tip, the jacked pile affects the vertical stresses of the soil in this area to a greater extent than the driven pile. Then, parametric sensitivity analysis is performed, which captures the effects of the penetration velocity in the jacking method and the hammering frequency in the driving method. This study can provide a reference for the selection of the penetration method of pipe piles in actual projects.

Model Tests on Jacked Pile Penetration Characteristics Considering a Static Press-in Piling Machine

This study incorporates a static press-in piling machine into the conventional laboratory model tests for jacked piles. By conducting a comparative analysis between two tests, one involving the static press-in piling machine and the other focusing solely on pile jacking, this study aims to unveil the variations in penetration characteristics with pile sinking depth during the process of pile jacking under the constraint imposed by the static press-in piling machine. When considering the impact of the piling machine, the pile pressing force, pile sinking resistance, pile axial force, and unit side friction resistance of the pile body are higher compared to test results that only focus on pile jacking. There is an acceleration in the total side friction resistance within the depth range of 20 to 30 cm. Additionally, the reduction rate of axial force during the entire pile jacking process is 2% higher, with a general reduction in the “side resistance degradation” phenomenon. The soil pressure around the pile exhibits an initial increase followed by a decrease. The authors believe that the model box test of the jacked pile, considering the pile machine, would be more aligned with engineering practice.

Effect of Permanent Load in Gresik Alluvium on Friction Pile Embedment Depth

Hydrostatic load, approximately 250-35 kPa (i.e., water of 2.5m-3.5m high), has been applied in the project area for about 25 years; hereafter, it will be referred as permanent load. Recently, this permanent load including its perimeter embankment, is demolished for which a new facility will be built. The upper 2-4m soil layer in this area consists of fill soil (mainly cohesionless material) overlying thick Gresik alluvium layer. A bearing layer was not found (down to an investigation depth of 50m). The initial design of pile embedment depth refers to the legacy soil report, pile embedment information from the surrounding area (not being subjected by permanent load), and preliminary soil investigation data (from the surrounding area); in this case, the projected embedment depth is 20-23m with the friction pile design concept. Due to the proximity of project location with existing facilities, the jacking-driven pile method, with HSPD (Hydraulic Static Pile Driver) machine, is selected for installing the precast spun pile. The pile jacking works indicate that piles can only be driven down to a depth of about 12m (far less than the projected depth). This paper provides an analysis on the changes of soil properties due to permanent load, which in turn increasing the pile shaft capacity and effectively reducing the pile embedment depth. The analysis is supported by data from pile jacking record, PDA test, and instrumented test pile. Discussion regarding the conservatism in pile design is also presented.

Lessons learned from large-scale physical modeling of tapered jacking piles: HSDT

To provide an improved understanding of the behavior of screw piles in disturbed soil, as a series of companion papers, laboratory tests with full scale tapered jacking piles were performed in the current study. The designated tapered pile has the similar dimensions, material properties and cone-shaped bottom, with the exception of threads eliminated.
 The main objectives of this paper are to: (1) establish the robust and efficient simple high strain dynamic testing (HSDT) requirements for validating displacement tapered piles capacities while exploring the installation effect; (2) determine a correlation between static and dynamic bearing capacity in compression for steel tapered piles installed by jacking in sand with various relative densities.
 Out of nine large-scale laboratory expriments at Aalborg University Offshore Geotechnics Laboratory [1-3] with the tank filled with Aalborg University Sand No.1, this research exclusively presents some lessons learned from an exemplar tapered jacking pile installation (Test 4) in dry sand (relative density and its response to monotonic and impact loadings. The selected piles have diameter of D=76 mm and 89 mm with length of 2.07 m. The layout of the miniature CPTs carried out to measure soil state is shown in Fig. 1, with four CPTs performed following each jacking installation campaign to study the soil state after the installation of the piles (Fig. 1). In order to fulfill the objectives, the piles are installed by a static compression load that includes an unloading/reloading step, followed by dynamic testing in order to facilitate the determination of the bearing capacity (Fig. 2). The hammer test was carried out on both piles, by a hammer from increasing drop heights of 218, 418, 618, 818 and 1018 mm (Fig.3). The hammer consists of a sleigh with multiple attached steel plates weighting 19.31 kg on average and the sleigh itself weighs 18.55 kg. Tapered pile jacking resulted in dilation extending to a depth of 2.8when diameter exceeds from 76 mm to 89 mm. By contrast, in the region around pile P76, the soil was entirely densified. The tendency to densify the soil near tip area due to jacking installation is observed in both tests, where the initial viod ratio varied from 0.67 to 0.59 and from 0.63 to 0.57 corresponding to piles P76 and P89, respectively (Fig.4).
 Subseuqntluy, Danish Pile Driving Formulas (DDR) introduced by [4] was ustilised which is according to the required potential energy from a hammer stroke to exceed the pile penetration resistance. The mass of the hammer G is defined by:
 where elastic settlement =, A is cross-sectional area, E is the Young’s modulus, l is the installed length of pile which is approximately 1.9 m, and is the maximum static force required to install the pile. The efficiency factor is set as 1. During the impact loading tests, the settlement of the pile is measured with a 1 mm accuracy for each hammer stroke, and the limiting settlement, s was set to yield a certain level (0.1D) when the drop height is 618 mm. Thus, the dynamic bearing capacity = , and ratio= are shown in Table 1.

Axial cyclic performance of a jacked pile in structured clays: A semi-analytical solution approach

Cyclic loads resulting from environmental factors such as wind, waves, trains, and construction activities pose a potential hazard to the stability of piled structures. These loads can cause the performance degradation of piles, including cumulative settlement and weakening of bearing capacity. This paper presents a semi-analytical solution for evaluating the axial cyclic behavior of jacked piles in structured clays. The solution employs enhanced nonlinear load-transfer models that effectively capture the stress-strain hysteresis and interfacial cyclic degradation characteristics. The key factors influencing pile behaviors are incorporated within the analytical approach, encompassing pile installation, subsequent soil equalization, and the static and cyclic loading encountered during service. The validity of the current solution is established through model pile tests conducted in artificially structured clays under static and cyclic loading conditions. Extensive parameter studies are performed using the proven theoretical approach to emphasize the influence of soil structure and cyclic loading on pile behavior. The results demonstrate a favorable agreement between the theoretical and measured values in static and cyclic pile response analyses. Compared with the response of jacked piles in reconstituted clays, the pile response in structured clays with a cement content of Aw = 4%, including penetration resistance, final ultimate bearing capacity, and the convergence speed of permanent settlement, has been substantially improved. The parameter studies indicate that soil structure and cyclic loading patterns significantly influence the axial cyclic performance of jacked piles in natural clays.

Influence of residual stress and soil dilatancy on the load capacity of jacked pile

ABSTRACT Pile jacking is one of the commonly adopted techniques for installation of displacement piles. The present study investigates the evolution of residual stresses during the pile jacking process and its subsequent impact on the pile load capacity with a particular emphasis on the soil dilatancy angle. The simulations have been carried out following an updated Lagrangian-based finite element framework employing ABAQUS. The magnitude of radial to vertical residual stress ratio coincides with the passive earth pressure coefficient within a radial zone of 6D and reduces to the at-rest coefficient beyond 20D. Owing to the enhanced stress-state, the load capacity of jacked pile is markedly higher than the in-place one with a predominant contribution from the shaft resistance. A small increase in soil dilatancy results into significant enhancement of residual radial stress and extent of influence zone, which further leads to increased load capacity in jacked pile through enhanced shaft resistance.

Investigation of the time-dependent bearing capacity of a jacked pile in saturated structured clays

Natural clay setup significantly contributes to the improvement of the bearing performance of a jacked pile. This paper presents a semianalytical solution to predict the time-dependent bearing capacity of a single pile in natural clays. The proposed solution properly incorporates the initial structure and stress-induced structure degradation of soils and the subsequent thixotropic and reconsolidation of disturbed soils. Pile penetration is simulated using the cavity expansion method (CEM) based on the Modified Structured Cam Clay (MSCC) model. The governing equations computing stress components during consolidation are established using a variable relaxation gradient function and are numerically solved by combining initial boundary conditions. A functional relationship between the ultimate strength and stress state of soils is presented according to critical state soil mechanics theory. The predicted results are validated against the results from the existing analytical approach, published centrifuge model tests, and laboratory model tests in structured clays. The excellent agreement between the measured and predicted values demonstrates that the method can properly predict the time-dependent bearing capacity of jacked piles in structured clays. Considering the impact of soil structure on soil setup plays a significant role in quantitatively evaluating the time-dependent bearing capacity of piles in natural clays.

DEM study of particle scale effect on plain and rotary jacked pile behaviour in granular materials

The capacity of open-ended piles strongly depends on the potential plugging occurring during installation. The Discrete Element Method (DEM) is particularly suitable to the study of pile plugging, as it can model large soil deformation. However, DEM simulation of the 3D boundary value problems is computationally expensive, and particle upscaling is usually used to reduce the number of particles modelled. In this paper, two granular beds were created with the same average porosity, initial stress field and contact parameters, but different particle scales. Two pile geometries were installed by plain and rotary jacking. Normalised results show that the pile penetration mechanism is strongly affected by the particle scale. Larger particles lead to earlier pile plugging, higher shaft resistance and require a greater force to penetrate the ground. This effect can be linked to a modified penetration mechanism, with larger shear zones and less well defined “nose cone” under the pile tip for larger particles. Changing particle scaling has a neutral effect on the total penetration resistance of a rotary jacked pile, but reduces the base penetration and increases the plug resistance. Maximising the ratio of particle scale to wall thickness is key to adequately capturing the pile coring mechanism.

Laboratory Test Study on Pile Jacking Penetration Mechanism Considering Different Diameter and Length Based on Photoelectric Integration Technology

Model tests are carried out on the jacked single piles of different diameters and pile lengths under the model pile of different diameters and pile lengths in clayey soil, which aims to investigate the penetration mechanical mechanism. How to accurately test the pile end resistance and pile side resistance during jacked pile sinking is particularly important. In this paper, a full-section spoke-type pressure sensor, a double diaphragm temperature self-compensating fiber Bragg grating (FBG) earth pressure sensor and a sensitized miniature FBG strain sensor are jointly applied to a single pile penetration model test to test a single pile driving force, pile end resistance and pile body stress during penetration. The test results show that the load transfer performance of test piles will be affected by different diameters, and the axial force transfer capability of a large diameter in the depth direction is better than that of a small diameter since the compacting effect is more obvious. The unit skin friction of the pile increases gradually as the depth increases, which is larger due to the lateral extrusion force increasing as the diameter increases. At the same depth, the unit skin friction of two different diameter piles demonstrates “friction fatigue”, which also decreases obviously as the depth increases. Under the conditions of this test, the maximum frictional resistance of the pile TP1 pile side is about 27.7% higher than that of the test pile TP2. In the static pile sinking process of three test piles in cohesive soil, 50% is end bearing; therefore, there is 50% friction, and the diameter influences the end bearing and the length influences the friction.

Distribution and dissipation laws of excess pore water pressure based on pile-soil interface during pile-sinking in saturated clay

PHC pipe pile cooperated with jacked method is widely used in recent years. The excess pore water pressure of pile-soil interface caused during jacked PHC pipe driving would produce important effect on jacked pile construction and bearing characteristics. Two full scale jacked-in piles are penetrated into the clayey soil and studied by monitoring the law of generation and dissipation of excess pore water pressure. The law of excess pore water pressure with penetration depth and time is also analyzed. From this test results, excess pore water pressure of the pile-soil interface increases to the peak and then begins to decrease, but it remains large. The excess pore water pressure of S1 test pile pile-soil interface decreases from 201.4 kPa to 86.3 kPa, and decreases from 374.1 kPa to 114.3 kPa for S2 test pile. The excess pore water pressure of pile-soil interface rises first at the initial stage of consolidation, and it dissipates when the hydraulic gradient between pile-soil interface and soil around the pile disappears. The dissipation degree of excess pore water pressure reaches from 75% to 85%. The proposed solution provides certain engineering significance for jacked pile construction and bearing capacity design in the clayey foundation.

Construction technologies and mechanical effects of the pipe-jacking crossing anchor-cable group in soft stratum

In this study, an open-cut approach using steel-sheet piles and jet grouting piles for waterproofing was proposed to resolve the problem that ordinary pipe-jacking equipment cannot cross areas with existing anchor cables in soft stratum. The case history of a pipe-jacking project of a sewage treatment plant in the Jinan East Railway Station area was investigated. The mechanical properties of steel-sheet piles, horizontal displacement of piles, and ground surface settlement in the anchor-cable crossing area were investigated based on in situ observations. Numerical investigations were performed using the finite element method (FEM). The effects of existing anchor cables on the mechanical behaviors of retaining structures, deformation variation of the ground, and stability of the excavation were studied. The results indicate that the composite supporting structures of steel-sheet piles and jet grouting piles have a positive effect on waterproofing and deformation control in areas with existing anchor cables. When the steel-sheet pile touched the anchor cable during pile jacking, the compressive stress at the pile cap increased rapidly until it reached 62.8 MPa (the maximum pressure provided by the pile-pressing machine), which is twice the pressure under ordinary conditions. The maximum horizontal displacement of the retaining pile, δv, increased linearly with the excavation depth He. Existing anchor structures behind the excavation can restrain the deformation of the ground and retain the structure to a certain extent. The δv value of the pile with existing anchor structures behind is 6.5 mm or approximately 0.01% of the He value, which is 70% of that of the retaining pile without existing anchor structures. “Groove type” ground surface settlements are found on both sides of the excavation. The maximum ground settlements δh are 0.29% He and 0.05% He, respectively. The plastic zone at both sides of the excavation bottom extends to the ground surface with an angle of about 45°. When an excavation fails, the plastic zone range in the ground with existing anchor cables is significantly larger than it is in the ground without anchor cables. The key contribution of this research is to provide an effective and low-budget treatment for pipe-jacking crossing through an anchor-cable group region. The findings from this study also provide industry practitioners with a comprehensive guide regarding the specific applications and mechanical performance of the crossing excavation for obstacle treatment.

A Field Study of Soil Plugging of Jacked Pile and Its Effect on the Pile Resistance

Both a static pile load test and cone penetration test were conducted in a field to investigate the effect of soil plugging on the ultimate bearing capacity of a pile. Both the force equilibrium method and Terzaghi’s method were adopted for the theoretical analysis of the soil plugging effect during the pile setting process. Consequently, a new equation was proposed for the estimation of the height of soil plugging. It is observed that the process of pile settlement can be divided into three stages: (i) the soil plugging is initially formed; (ii) the soil plugging reaches its maximum height; and (iii) force equilibrium is reached with a constant soil plugging height. The proposed method in this paper provides an alternative method for the assessment of the height of soil plugging and its effect on the ultimate bearing capacity of the jacked pile.

Study on time effect of residual pressure and bearing characteristics of jacked pile in saturated silt foundation

The history of stress in soil mass and pile surface roughness significantly impacts the time effect of residual pressure at the pile end and bearing characteristics of the jacked pile. In this study, the impacts of soil over-consolidation ratio and pile surface roughness on the time effect of residual pressure and bearing characteristics of jacked pile end in saturated silt foundation are explored. Through the independently developed model test device for the vertical bearing characteristics of jacked pile, the driving of jacked pile with different pile surface roughness and static load tests at different resting phases are carried out on saturated silt foundations with different over-consolidation ratios. The model box is cylindrical in shape with a size of 40 cm × 48 cm (inner diameter × height) and is made of transparent tempered glass. The results show that: the increase in surface roughness of jacked pile in saturated silt foundation causes not only the increase in the pile side friction but also the increase in the pile end resistance during the static pressure sinking pile; the change laws on the residual pressure of pile end and limit friction resistance of pile side for jacked pile in saturated silt foundation vary with over-consolidation ratio of soil mass and the pile surface roughness.

The Effects and Vertical Bearing Capacity of Two Jacked Model Piles in Sand

The effects and vertical bearing capacity of two jacked piles in sand are still not well understood, and the mechanism of the adjacent pile’s uplift caused by the jacking pile in a double pile system is especially unclear, but these facets are important to the stability of the jacked pile. In this paper, a series of tests is performed on jacked model piles in sand, where in the influences of the pile length and the driving pile’s speed on the effects and vertical bearing capacity of two jacked piles were studied. The results revealed that the effects and vertical bearing capacity of the two jacked piles were mainly in relation to pile length and influenced by the driving speed. The horizontal displacement of the top of the first jacking pile during the installation of the post-jacking pile was caused by the difference in the stress state of the first jacking pile between the side of the pile’s face and its back side, in which the uplift displacement of the first jacking pile was also involved. The radial stress of the pile increased nonlinearly with the depth under different pile lengths and gradually converged to the passive earth pressure. The ultimate capacity of the double pile is approximately twice that of a single pile, and the ratio of the ultimate capacity of a single pile to the final jacking pressure was approximately 1.04.

Research of jacked pile penetration test based on airbag loading

In view of the problem that the model test of pile jacking cannot reproduce the soil's self-gravity and thus cannot truly reflect the pile jacking force, this paper developed an airbag loading system. The airbag is used to pressurize and simulate the overburden soil weight. The method of subsection pile jacking and coupling is ingenuously adopted to achieve long pile penetration. Because the airbag and pressure can be controlled well, it is convenient to simulate the cohesive soil foundation. The size of the model pile used in the test is larger than that of the usual centrifugal model test pile, so it belongs to large scale model test. The experimental results using this system show that the pile jacking force increases with the increase of penetration depth. The degradation of pile lateral resistance has little impact on pile jacking force. After modification based on the degradation theory of pile lateral resistance, the overall variation law of pile lateral resistance is good, and the difference value generated at the joint of pile segments is basically 0. With the increasing of pile depth, the pile lateral resistance is gradually exerted. The pile end resistance fluctuates with the depth, and accounts for a relatively high proportion of pile jacked force, which is maintained above 50%. The method of pile jacking with airbag loading in this paper provides a new idea for the study of the penetration characteristics of jacked pile.

Experimental measurement of particle crushing around model piles jacked in a calibration chamber

During installation of driven or jacked piles in sand, particle crushing occurs in a region below the base of these piles. Quantification of the degree and extent of particle crushing during driving or jacking in sand is necessary to improve current design methods. To study the effects of particle crushing on the capacity of piles jacked in uniform silica sand samples, a model pile was jacked and tested in a half-cylindrical calibration chamber with transparent observation windows in its front wall. Annular samples of crushed sand 3 mm in thickness were recovered after testing from several locations along the shaft and the base of the model piles and used to assess particle gradation changes and to calculate breakage parameters. Relationships between the load mobilized at the base of the model piles and three breakage parameters are proposed. Furthermore, the number of jacking strokes (ranging from 1 to 32 in this research) has a negligible effect on the degree of crushing produced during installation and on the measured stresses at the base of the model pile. Analyses of the digital images captured during pile jacking indicate that the silica sand particles in the path of the model pile crush mainly along irregularities and sharp edges. Different zones are identified below the model pile according to the degree of particle crushing. Digital images taken during static loading of the model pile allowed tracking of the displacement paths of individual sand particles during loading.

Analysis on the piling mechanism of the jacked pile in layered soil

Analysis on the piling mechanism of the jacked pile in layered soil

Numerical study on the installation effect of a jacked pile in sands on the pile vertical bearing capacities

The installation effect of a jacked pile in silica sand is investigated numerically. A simplified state-dependent dilatancy model is used to model the sand behavior and the sand grain crushing effect is considered by modifying the critical state line at large confining pressures. The Arbitrary Lagrangian-Eulerian (ALE) technique is adopted to model the pile penetration and the load-displacement behavior at the operational loading stage is simulated using standard finite element method with the initial states being the equilibrium of the pile-jacking-disturbed soil stress and void ratio fields and a free pile head. The numerical procedure has been verified against some calibration chamber tests and centrifuge tests. Simulations of wished-in-place piles are performed for the quantitative study of the installation effect. The results show that the capacity ratios between the jacked and wished-in-place piles become higher for long piles in dense sand. Linear fittings have been applied to obtain the capacity ratios as functions of the relative density and the penetration length-to-diameter ratio, which can be used for a quick estimation of the bearing capacity difference between jacked and wished-in-place piles.

Closure to “Field Experiments on Cyclic Behaviors of Axially Loaded Piles Jacked in Soft Clay” by Ren-Peng Chen, Chun-Yin Peng, Jian-Fu Wang, and Han-Lin Wang

Closure to “Field Experiments on Cyclic Behaviors of Axially Loaded Piles Jacked in Soft Clay” by Ren-Peng Chen, Chun-Yin Peng, Jian-Fu Wang, and Han-Lin Wang

Discussion of “Field Experiments on Cyclic Behaviors of Axially Loaded Piles Jacked in Soft Clay” by Ren-Peng Chen, Chun-Yin Peng, Jian-Fu Wang, and Han-Lin Wang

Discussion of “Field Experiments on Cyclic Behaviors of Axially Loaded Piles Jacked in Soft Clay” by Ren-Peng Chen, Chun-Yin Peng, Jian-Fu Wang, and Han-Lin Wang