Jacked Pile Research Articles

Evolution of mechanical properties of soils subsequent to a pile jacked in natural saturated clays

The mechanical properties of soils adjacent to a jacked pile significantly affect the bearing capacity and settlement of the pile. This paper investigates the evolution of the mechanical properties of the remolded soil surrounding a jacked pile by considering in-situ properties of natural clays, pile installation effects and variable coefficient of consolidation. The pile installation process is modeled by the undrained cylindrical cavity expansion. The distribution of excess pore pressures around the pile is derived by adopting the K0-based anisotropic modified Cam-clay (K0-AMCC) model, which can incorporate the initial stress anisotropy and the initial stress-induced anisotropy of natural clays. The Terzaghi's radial consolidation theory is further developed by introducing a variable coefficient of consolidation to the governing equation, which is solved by the variable separation method. The predicted results are in good agreement with the published test data. The variations of the mechanical properties of the remolded soil are studied with different variable coefficients of consolidation and the in-situ properties. The calculated results show that the variable coefficient of consolidation plays a significant role in the dissipation rate of excess pore pressures. The undrained shear strength considering thixotropic effect and the shear modulus of the remolded soil increase more rapidly with larger values of the introduced parameter α (related to the variable coefficient of consolidation). Moreover, the overconsolidation ratio has a pronounced effect on the undrained shear strength and the shear modulus of the remolded soil after pile installation.

MODELING OF THE JACKED PILE STATIC LOAD TEST WITH PLAXIS 3D / SPAUSTINIO POLIO BANDYMO STATINE APKROVA MODELIAVIMAS PLAXIS 3D

In this article jacked pile installation technology and its current processes, altering the base physical and mechanical characteristics are discussed. For the jacked pile static load test simulation Plax 3D software was selected, the opportunities and developments were described. Model building, materials, models, model geometry, finite elements, boundary conditions and assumptions adopted in addressing problems described in detail. Three different tasks formulated and load-settlement dependence a comparison of the results with the experiment given. Conclusions are formulated according to the modeling results. Šiame straipsnyje aptarta spaustinių polių įrengimo technologija ir ją taikant vykstantys procesai, keičiantys pagrindo fizines ir mechanines charakteristikas. Spaustinio polio bandymui statine apkrova modeliuoti pasirinktas PLAXIS 3D programinis paketas ir aprašytos jo galimybės bei raida. Detaliai nupasakotas modelio kūrimas, medžiagų modeliai, modelio geometrija, baigtiniai elementai, kraštinės sąlygos ir priimamos prielaidos sprendžiant problemą. Suformuluoti trys sprendžiami uždaviniai ir apkrovos bei nuosėdžio priklausomybe pateikiamas rezultatų palyginimas su eksperimentu. Atsižvelgiant į modeliavimo rezultatus suformuluotos išvados.

Soil Deformations During Casing Jacking and Extraction of Expanded-Shoe Piles, Using Model Tests

A small-scale 1-g transparent soil model was employed to investigate soil deformations caused by casing-assisted pile jacking of plastic tube cast-in-place concrete piles. The transparent soil was made of fused quartz and a refractive index matched blended oil. Models were sliced with a laser light sheet and digital images were employed to record jacking and extraction of the casing, allowing the use of digital image correlation to derive the generated displacement fields, non-intrusively. The effects of the shoe shape as well as use of a casing to jack the pile were investigated. It was found that under unconfined conditions, soil response to jacking is significantly affected by the pile shoe shape, with displacements adjacent to a conical shoe markedly smaller compared to a flat shoe. Moreover, casing extraction results in recovery of some of the soil deformation that takes place during pile jacking.

Field study of residual forces developed in pre-stressed high-strength concrete (PHC) pipe piles

A large-scale field testing program for the study of residual forces in pre-stressed high-strength concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m in embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with fiber Bragg grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual force on the interpretation of the load transfer behavior is discussed. The field data show that residual force along the installed pile increases approximately exponentially to the neutral plane and then reduces towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles significantly affect the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane and underestimate the shaft resistance at positions below the neutral plane, and the toe resistance for an open-ended PHC pipe piles founded in stratified soils.

원심모형 실험을 이용한 압입말뚝에 대한 동적 p-y 곡선 산정

본 연구에서는 말뚝 설치 방법에 따른 동적 p-y 곡선의 차이를 분석하기 위하여, 1g 상태에서 지반 조성 전 설치한 말뚝과 지반 조성이 완료된 후에 1g 상태에서 압입하여 설치한 말뚝, 그리고 40g의 원심 가속도 조건에서 압입시킨 말뚝에 대해 동적 원심모형 실험을 수행하였다. 실험 결과로부터 얻은 각 모형 말뚝의 동적 p-y 곡선의 최대지반반력을 이용하여 동적 p-y 중추곡선(Backbone curve)을 쌍곡선 함수로 나타내었다. 말뚝 설치 방법에 따른 동적 p-y 중추곡선 분석 결과, 40g 조건에서 압입한 말뚝이 1g 상태에서 압입한 말뚝 및 지반 조성 전 설치 말뚝에 비해 말뚝에 작용하는 지반반력이 크게 평가되었으며, 이러한 지반반력의 차이는 깊이가 깊어질수록 작아지는 것으로 나타났다. 일련의 p-y 곡선 결과를 바탕으로 기존에 제안된 현장타설말뚝에 대한 동적 p-y 중추곡선의 적용성을 평가하고, 이를 수정한 압입 및 항타 말뚝에 대한 동적 p-y 곡선 산정식을 개발하였다. In this study, dynamic centrifuge tests in dry sand were conducted in order to evaluate the effect of pile installation on the dynamic p-y curve. According to the result of the pile installation effect on the dynamic p-y backbone curves, the subgrade resistance of a jacked pile in 40 g was found to be greater than that of a jacked pile in 1 g and a preinstalled pile in 1 g. It was also found that differences of the subgrade resistance decrease with the depth of the pile. Applicability of dynamic p-y backbone curve for the bored pile proposed by preceded researcher was evaluated by comparing with the result of centrifuge tests. In addition, dynamic p-y backbone curve for jacking/driven pile was developed by modifying that for the bored pile.

Application of Fiber Bragg Grating Strain Sensors to a Centrifuge Model of a Jacked Pile in Collapsible Loess

The use of traditional sensors in a geotechnical centrifuge model test usually causes deviations in the monitoring data. This is because of the mutual interference among centrifugal field electromagnetic waves that is caused by the independent transmission lines. In recent years, the development of fiber Bragg grating (FBG) sensing technology has substantially improved the accuracy and reliability of monitoring the strain and temperature in geotechnical centrifuge model tests. This study follows a series of centrifuge model tests carried out on a 60 g-ton geocentrifuge, with FBG sensing technology used for monitoring the strain on a static pressed pile; the strain is caused by soil collapse around the pile. During the test, an improved packaging and installation method of the quasi-distributed FBG sensor system was employed to monitor the strain of a jacked pile in a loess field with immersion collapse. The model test results show that the proposed FBG-based sensor assembly monitored the strain distribution of the jacked piles effectively, proving that it is a promising solution for strain monitoring in a geotechnical centrifuge test.

Large deformation finite element analysis of undrained pile installation

Abstract In this paper, a numerical undrained analysis of pile jacking into the subsoil using Abaqus software suit has been presented. Two different approaches, including traditional Finite Element Method (FEM) and Arbitrary Lagrangian–Eulerian (ALE) formulation, were tested. In the first method, the soil was modelled as a two-phase medium and effective stress analysis was performed. In the second one (ALE), a single-phase medium was assumed and total stress analysis was carried out. The fitting between effective stress parameters and total stress parameters has been presented and both solutions have been compared. The results, discussion and verification of numerical analyzes have been introduced. Possible applications and limitations of large deformation modelling techniques have been explained.

Discussion of “Examining Setup Mechanisms of Driven Piles in Sand Using Laboratory Model Pile Tests” by Z. Zhang and Y. H. Wang

The authors conducted a pressurized chamber test, which was equipped with an advanced bender element system and tactile pressure sensors to examine the mechanisms of pile setup in sand. The findings of the paper are of significant interest and the discussers would like complement these findings with those from other experiments on this subject. The authors conclude that, in line with Axelsson (2000), the changes of stationary radial and hoop stresses in close proximity to the pile shaft during setup are minor and the soil stiffness and its corresponding rate of growth following pile installation are significantly higher. The same conclusion was drawn by Lim and Lehane (2015) from field experiments on instrumented jacked piles, which recorded a very small variation of stationary radial stress (σ 0 rs) over a period of 72 days after installation. A comparison of the measured variations of shear stress with radial effective stress during the last installation pushes and during subsequent load testing indicated a significant time dependence of the radial effective stress change during shearing (Δσ 0 rd). The authors suggest that additional loading imposed on the surrounding soil because of pile insertion triggers the subsequent aging (or creep) process. While soil displacement (and thus the additional loading induced to the sand) could broadly explain why setup is observed in driven piles but not bored piles, and why the rate of setup is higher on large-displacement piles than on small-displacement piles, field experiments reported by Lim and Lehane (2014a) show that cycles imposed during installation and the nature of the installation process also need to be considered. In the discussers’ experiments (summarized in Fig. 1), the closed-ended driven piles induced a large displacement to the sand but also required a very significant number of blows/shearing cycles. These piles exhibited a very low capacity shortly after driving but the capacity then increased substantially over the aging period. The short term capacity of the driven open-ended (pipe) piles was not as low as they were easier to drive and also imparted lower levels of displacement to the soil. In addition, the closedended jacked piles were installed relatively gently using a hydraulic system and these showed a higher initial capacity but very little gain in capacity with time. The discussers also conducted laboratory chamber tests to investigate the effects of pile setup in sand (Lim and Lehane 2014b). Despite a more basic experimental setup than the authors’ version, these tests offer some useful additional qualitative information concerning parameters influencing the aging phenomenon. Apart from significant setup on driven piles that was captured in the experiments, the absence of setup in buried piles (which impart no disturbance to the in situ sand) was also modelled successfully. The original aging during the compression period as described by the authors was considered by Lim and Lehane (2014b) as an undesired sample aging effect. This effect was minimised by extending the sample compression period to 7 days (characterized by the changes of miniature cone tip resistance measured at different time intervals) before piles were installed so that its interference with the setup effect would be negligible. One limitation of the authors’work is the very short setup period (80 h) employed in the experiment. To utilize the benefits of aging effects for foundation construction, the performance over a longer period of time (weeks to months) needs to be established. Experimental observations reported by Lim and Lehane (2014a), in conjunction with several recent full-scale pile tests (Jardine et al. 2006; Gavin et al. 2013; Karlsrud et al. 2014) presented in Fig. 2, show that the complete evolution of pile setup may involve a delay or a lower rate of setup during the initial period after installation and a plateau when equilibrium under the new environment following pile installation is close to being reached. Therefore, simple extrapolation using basic semi-logarithmic or power-law functions from a short-term observation is not appropriate. It would be

Approximation of pile installation effects: a practical tool

This paper presents a novel technique to describe the installation effects around a jacked pile without simulating the penetration process. With the proposed technique, a jacked pile can be modelled as wished-in-place, and corresponding installation effects, such as stress and density change, can be imposed. In order to obtain a trend for parameters affecting the installation effects, different pile diameters (D), penetration depths (L) and soil densities (Id) are investigated. A mesh sensitivity analysis is performed to assess the possibilities and limitations of transferring the installation effects (stress and density). Model functions are proposed to approximate stress components and void ratio distribution. After finding geometrical functions for each variation by employing non-linear regression analyses, a generalised form based on D, L and Idis proposed. Finally the generalised formulations are validated by a centrifuge test.

Measuring horizontal stresses during jacked pile installation

Jacking is an installation technique for displacement piles which is commonly used onshore in urban environments owing to its low noise and vibration. During pile jacking, stress changes occur in the soil which are substantial close to the pile, but also extend a significant radial distance. These stresses are difficult to measure accurately owing to arching around stress sensors. In the field, stress measurements are commonly made by means of an adjacent pile whose stiffness changes the stress field within the soil. Accurate measurements of stresses due to the installation of a single pile under laboratory conditions are needed in order to quantify this error. In this paper, null gauges that do not suffer from membrane deflection are used to measure horizontal stress changes during the jacked installation of a cylindrical pile in dry sand. Stresses are measured by means of both an adjacent pre-installed square pile and in-soil sensors. The paper also presents a comparison between the centrifuge results and the radial stress distribution estimated using conventional methods, such as Boussinesq's elastic analysis and elasto-plastic spherical cavity expansion.

Optimisation of water injection nozzles to aid pile jacking

Utilising water injection to aid pile installation is becoming increasingly widespread. Water injection reduces installation loads in a variety of soil conditions, making pile jacking possible at hard ground sites. Previous work has focused on understanding the mechanisms governing water injection but the aim of this paper is to investigate the effect of nozzle geometry on the efficacy of the technique. A series of centrifuge model experiments were completed using a closed-ended tubular pile in saturated fine sand to complete a parametric study of a variety of base-exiting and side-exiting nozzles. Base injection has a large effect on base resistance and a minor effect on shaft resistance, whereas side injection behaves in the opposite manner. Load testing of the model piles showed a permanent reduction in the shaft resistance when using side-exiting nozzles, an effect not observed for the base-exiting nozzles. A set of mechanisms is proposed to match the observed differences in the experiments and compared with the results of another study in silt to demonstrate that the theoretical mechanisms are relevant in various soil types.

Simplified numerical modelling of pile penetration - the press-replace technique

This paper presents a simplified finite element analysis technique, the ‘Press-Replace’ technique, to model pile penetration problems in geotechnical engineering, particularly, pile jacking. The method is employed in standard finite element analysis software. The method involves a straining and a consequent geometry update phase. First, a cone penetration test in (undrained) clay is modelled and compared with the results of analytical, semi-analytical and more advanced finite element techniques. The model sensitivity for the step size and mesh is investigated using a hypoplastic constitutive model. An optimum way of modelling based on the numerical performance is shown. Copyright © 2015 John Wiley & Sons, Ltd.

Numerical Estimation of the Pile Toe and Shaft Unit Resistances During the Installation Process in Sands

Abstract Numerical simulations of a pile jacking were carried out. A Coupled Eulerian-Lagrangian (CEL) formulation was used to treat with large deformation problems. An Abaqus, a commercial Finite Element Method software suit, was used as a computing environment. The Mohr-Coulomb constitutive model was applied and the Coulomb model of friction was used to describe pile-soil interaction. Calculations were made for three different pile diameters. Toe and shaft unit resistances versus depth for each pile were investigated and plotted. CPT-based solutions were compared with the results of numerical simulations.

Discussion of “Shaft Resistance and Setup Factors for Piles Jacked in Clay” by Prasenjit Basu, Monica Prezzi, Rodrigo Salgado, and Tanusree Chakraborty

Discussion of “Shaft Resistance and Setup Factors for Piles Jacked in Clay” by Prasenjit Basu, Monica Prezzi, Rodrigo Salgado, and Tanusree Chakraborty

Closure to “Shaft Resistance and Setup Factors for Piles Jacked in Clay” by Prasenjit Basu, Monica Prezzi, Rodrigo Salgado, and Tanusree Chakraborty

Prasenjit Basu, A.M.ASCE; Monica Prezzi, A.M.ASCE; Rodrigo Salgado, F.ASCE; and Tanusree Chakraborty, A.M.ASCE Assistant Professor, Dept. of Civil and Environmental Engineering, The Pennsylvania State Univ., University Park, PA 16802 (corresponding author). E-mail: pbasu@engr.psu.edu Professor, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47907. E-mail: mprezzi@ecn.purdue.edu Professor, School of Civil Engineering, Purdue Univ., West Lafayette, IN 47907. E-mail: rodrigo@ecn.purdue.edu Assistant Professor, Dept. of Civil Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India. E-mail: tanusree@civil .iitd.ac.in

Application of a Coupled Eulerian–Lagrangian approach on pile installation problems under partially drained conditions

A numerical technique for modeling the soil as a two-phase medium by means of a user material subroutine is presented. The approach is applied to a classical FE analysis in a Lagrangian formulation using an explicit time integration rule and to a Coupled Eulerian–Lagrangian approach. The application of these two approaches to the problem of pile jacking into fully saturated soil under partially drained conditions is investigated and compared to the solution obtained by use of an iterative equation solver. The influence of the installation process as well as the influence of the permeability on the surrounding soil is investigated.

In-flight Simulation of Pile Installation in Slopes in Centrifuge Model Tests

A new device was developed to simulate the in-flight installation of jacked displacement piles in slopes using centrifuge model tests. In the modularization-based design of this device, the pile installation process is divided into combinations of five-axis movements, which are realized by corresponding electric motors. New structures consisting of combined cubes and cylinders are proposed for the pile top and the picking-up unit. In addition, this device utilizes a series of techniques, such as the use of linear guideways, to increase digital control and the local stiffness of key structures. These measures provide a high degree of automation with good accuracy in determining the locations and vertical extents of piles during installation. The structures and electric motors in the device were optimized to provide high capacities for the load (10 kN) and displacement (260 mm). This device was designed with hollow components to control the size and mass of the entity (only 50 kg) and to satisfy rigorous requirements regarding the allowable deformation and stability levels during centrifuge model tests. The effectiveness of the device was verified using pile installation tests under various conditions. The test results were compared with results that were obtained using pre-flight pile installation. Overall, the pile installation method influenced the responses of the pile-reinforced slopes. For example, the loading-induced displacement of the slope with piles installed in-flight was considerably greater than that in the slope with piles installed at the 1g level when the load was near the limit.

Shear Zone around Jacked Piles in Clay

AbstractAs the most important feature of jacked open-ended concrete pipe piles, shear zone has fluence of crucial importance during installing and after penetration. This study conducted a field test in silt deposit to observe the physical phenomenon of shear zone after installation and investigated soil parameter differences from undisturbed soil through laboratory tests. Direct observation on shear zone reveals that the boundary between shear zone and in situ soil is evident. The average soil thickness in the shear zone falls between 6 and 30 mm, which are closely related to natural water content and void ratio in different layers. Laboratory tests on the shear zone show evident compaction during installation, and the soil parameters in the shear zone are sensitive to the jacking installation procedure. Some soil parameters decrease, whereas others increase because of excess pore water dissipating after installation. The extent of the shear zone is helpful in understanding interface friction on pretensi...

Reducing driving forces for pressed-in piles

Pile jacking techniques use static loading to install sheet piles with minimal environmental effects, such as noise and ground vibrations, which are often associated with other methods of driven piling. This paper describes a series of 20g centrifuge tests conducted to investigate two methods of reducing the large driving forces that can be associated with jacked sheet piles in stiff clay. In practice, pre-auguring at the clutch positions and water jetting techniques are routinely carried out prior to the installation of sheet piling in order to reduce the driving forces. However, these methods are known to contribute to ground movements and can detract from the advantages of jacked sheet piles. The tests involved driving model sheet piles, which were modified either by installing driving shoes to the base of the pile, or by ribbing the profile of the pile shaft. The driving forces of the modified piles were compared with those of a plain pile. The tests showed that the use of driving shoes and ribs can lead to the reduction of driving forces at greater depth.

Structural Analysis and Design of Slipway Floor with Anchor Jacked Piles

The rapid advance of shipbuilding industry generates greater demands on port and waterway engineering. The reconstruction and maintenance of infrastructure supporting shipbuilding industry also has aroused extensive attention. Since the tonnage of ship increases, the bearing capacity of slipway floors can’t meet the working requirement with the moving load of ships. As for the bearing capacity insufficiency, grouting, anchor jacked piles and bored piles are generally used. However, the anchor jacked pile has better practicality and applicability for easier to control construction quality and smaller damage to the original slipway floor. At present, methods based on Winkler foundation model have been more popular in the engineering practice. But Winkler foundation model can’t consider the interaction between pile and soil, the calculated structural internal force of slipway floor is far from the truth. In order to correct Winkler foundation model imperfections in this aspect, this paper provided the method of equivalent bedding value. In terms of area weighted means, the equivalent bedding value of pile and soil in the influence area would be got. Then this weighted area of pile and soil and other areas of soil could be equivalent to springs with different stiffness coefficients for calculating the structural internal force of slipway floor. To some degree, this method reduced the stress concentration on the top of piles and was closely to the reality, remedying some weaknesses of Winkler foundation model. This method may have definite reference value for foundation plate design in engineering application.