Pile Installation Effects Research Articles

Performance Analysis of Pile Group Installation in Saturated Clay

In offshore pile engineering, the installation of jacked piles generates compaction effects within soil, thus further affecting previously installed adjacent piles. This study proposes a three-dimensional numerical model for pile group installation, soil consolidation, and loading analysis. Subsequently, the effect of pile spacing and pile length-to-diameter ratio on the deformation, internal forces, and vertical bearing capacity of adjacent piles are investigated. The results indicate that with an increase in pile center distance, the peak lateral displacement of the adjacent piles decreases, whereas the peak vertical displacement increases. As the pile length-to-diameter ratio increases, the peak vertical and lateral displacements of the adjacent piles are enhanced. In addition, the peak axial force of the adjacent piles initially decreases and then increases with the penetration depth of the subsequent pile, whereas the peak bending moment initially increases and then decreases. The vertical bearing capacity of the subsequent pile is significantly superior to that of the adjacent piles. Therefore, the effects of pile installation on adjacent piles should be included in pile engineering. The impact of the subsequent pile installation on the bearing capacity of adjacent piles can be significantly reduced by increasing the pile center distance and pile length-to-diameter ratio. The findings provide useful guidance for pile group engineering.

3D FE simulation of PISA monopile field tests at Dunkirk using SANISAND-MS

This paper presents an investigation into the suitability of the SANISAND-MS model for the three-dimensional finite-element (3D FE) simulation of cyclic monopile behaviour in sandy soils. In addition to previous work on the subject, the primary focus of this study is to further assess the model's capability to reproduce the accumulation of permanent deflection/tilt under cyclic lateral load histories. To this end, experimental data from the PISA field campaign are employed, particularly those emerged from the medium-scale cyclic tests conducted at the Dunkirk site in France. The methodology adopted herein involves calibrating the SANISAND-MS model's parameters to align with 3D FE simulation of a selected monotonic pile test reported by the PISA team using a bounding surface plasticity model partly similar to SANISAND-MS. Subsequently, the soil parameters governing SANISAND-MS’ ratcheting response are calibrated using only minimal information from published PISA field data. While representing the first attempt to simulate the reference data set using a fully ‘implicit’ 3D FE approach, this paper offers novel insights into calibrating and using advanced cyclic models for monopile analysis and design – particularly, with regard to the quantitative influence of pile installation effects and sand's microstructural evolution under drained cyclic loading.

Lateral loading response of monopiles in sand considering installation effect

The effect of pile installation is a critical issue in the analysis and design of pile foundations but it is commonly ignored due to various numerical difficulties. In this paper, the installation process of an open-ended pipe pile into a sand deposit is simulated by using the zipper technique combined with the Arbitrary Lagrangian-Eulerian (ALE) method in the framework of three-dimensional (3D) finite element modeling. The subsequent lateral load response of the pile is also simulated and compared with that without consideration of the pile installation. The state dependent behavior of sand in associated with the pile installation and the subsequent lateral load is described using an advanced constitutive model. The study shows that for a relatively loose sand deposit, the sand surrounding the pile exhibits contraction and the disturbance zone takes the form of a trapezoid, whereas for a dense sand deposit, the sand near the pile will dilate and the disturbance zone takes the form of an inversed trapezoid. Furthermore, the deformation mode of the surrounding sand under the lateral load differs to some extent from that without consideration of the installation effect. Particularly, the location of the rotation point for the laterally loaded pile tends to move downwards when the pile installation process is considered.

Evaluation of Pile Driving Effects on Slope Stability in Clay

Pile driving can trigger slope failure, specifically in sensitive soil deposits or marginally stable slopes. Cases of slope failure during pile installation have been reported in countries such as Norway, Sweden and Canada where soft sensitive clay deposits are prevalent. Although a few approaches have been suggested to assess the factor of safety of a slope during pile driving, there is currently no standard method recognized by the geotechnical society to account for the reduction of safety factor of a slope as an effect of pile installation. Some approaches suggest using the excess pore pressure generated during pile driving to account for the reduction in soil strength (by reducing effective stresses), neglecting the change in total stresses. This paper discusses the accuracy of stability analysis methods currently in use for this problem by looking at stress changes in the soil during pile driving as well as using numerical analysis results. Importantly, the paper identifies the shortcomings regarding these approaches, thus allowing geo-engineers to understand the limitations of their analysis and the uncertainties in the models.

Case study for effects of pile installation on existing offshore facilities in brownfields

New prop structures are meant to be used to strengthen existing ageing offshore platforms in brownfields. This technical note aims to assess the possible effects of pile installation of new prop structures on existing offshore facilities, specifically existing platform piles and nearby pipelines. Based on the case study presented, this work investigates the down-drag and interaction effects of installation-induced vibrations of new piles on the load-displacement response of existing piles, namely pile load-bearing capacity and settlement, as well as assessing vibration levels in the vicinity of existing pipelines.

Numerical modelling of laterally loaded piles driven in low-to-medium density fractured chalk

Chalk’s sensitive, variable nature poses difficulties for foundation designers. It can present as weak rock and yet be de-structured to very weak putty by dynamic or high-pressure loading. The development of multiple offshore wind farms at north European chalk sites led to the recent ALPACA Joint Industry Programme, which undertook intensive material characterisation and large-scale field testing at St Nicholas at Wade (SNW), Kent, UK to capture and better understand the behaviour of piles driven in fractured low-to-medium density chalk. Noting that lateral loading response is a vital design concern for monopile and jacket supported structures, this paper focuses on 3D Finite Element (FE) modelling of ALPACA’s monotonic lateral loading field tests on open-ended driven tubular steel piles. The brittle chalk is modelled with a strain-softening Mohr-Coulomb model combined with nonlocal regularisation, calibrated meticulously against the ALPACA characterisation dataset. A second, simpler modelling approach, adopting a perfectly-plastic Mohr-Coulomb model, is also explored as a simplified practical alternative. Both approaches can match field lateral capacity and bending moment distributions, after taking due account of pile installation and chalk fracturing effects. The analyses indicate how robust, accurate and cost-effective lateral loading design may be approached for low-to-medium density fractured chalks.

Numerical simulations of displacement piles in a tropical soil

The behavior of pile foundations under axial loading is directly influenced by the effects that its installation process induces in the surrounding soil. Consequently, the consideration of these effects is essential for the correct numerical modeling of these geotechnical structures. In the present study, numerical simulations of driven cast-in-situ piles under axial loading have been carried out using finite element analysis. Three 3.5 m long piles with diameters ranging from 114.3 to 219.1 mm were analyzed. The pile installation effects have been considered indirectly by employing two distinct approaches, both based on the concepts of cylindrical cavity expansion. The behavior of the tropical soil profile is described with the Hardening Soil constitutive model. The load-displacement response and load distribution along the pile obtained with the numerical simulations have been analyzed and compared with in-situ load tests results. In the failure conditions, both approaches accurately predicted the bearing capacity of the piles, with an average error of only 2% compared to the measured values. The results in terms of load distribution over depth were also satisfactory. The difference between measured and numerical ultimate base resistance values ranged from 0% to 30%. The good agreement between the numerical and experimental results indicates that the proposed numerical approaches have been effective in simulating the piles installation process and reinforces the importance of considering the installation effects in the numerical modeling of these geotechnical structures. Both approaches can also be used to predict the bearing capacity of displacement piles.

Effects of full displacement pile installation on the stress and deformation state of surrounding soil: review

Effects of full displacement pile installation on the stress and deformation state of surrounding soil: review

Finite element modelling of helical pile installation and its influence on uplift capacity in strain softening clay

This study investigated the effect of helical pile installation in undrained softening clay using a coupled Eulerian-Lagrangian (CEL) finite element modelling approach. A previously published strain softening soil constitutive model was used to evaluate soil disturbance. The influence of two key strain softening parameters was considered to assess installation-induced soil disturbance. The CEL-predicted remoulded soil strength field was then imported into a finite element limit analysis (FELA) to evaluate the subsequent influence on uplift capacity. The CEL results showed that helical pile installation caused a significantly disturbed zone of soil that measured approximately 1.4 helix diameters in plan and extended the full length of the pile. When the disturbed soil strength field was imported into FELA calculation, it was found that the solutions reported in previous literature had significantly overestimated the ultimate uplift capacity for softening clay. The numerical output informed the development of a new closed-form analytical approach to predict uplift capacity considering the influence of the installation process. The design method was shown to provide a high-fidelity representation of the numerical results.

Performance analysis of a jacked-in single pile and pile group in saturated clay ground

When a pile is installed into saturated clay ground, the “setup” effect may occur due to ground consolidation, which changes pile performance. Although this phenomenon has been observed both in the field and laboratory, its numerical simulation is still challenging. In this work, pile installation effects on the behaviors of jacked-in piles were investigated through three simulation techniques by a three-dimensional finite element analysis program, PLAXIS 3D. A constitutive model called the soft soil creep model was used to describe the soil behavior based on soil parameters obtained from laboratory tests. The behaviors of single piles were first investigated with or without the consolidation process after pile installation to evaluate the pile setup effect. Then, a pile group comprising 4 piles was analyzed using the consolidation process to verify the applicability of the three simulation techniques. The calculated results were compared with the corresponding experimental results. The calculated results using three techniques generally agreed well with the experimental results in terms of initial stiffness and pile shaft resistance. Both the measured and calculated results indicate that ground consolidation caused by pile installation significantly increases the pile bearing capacity and especially, the pile shaft resistance. Therefore, the pile setup effect can be reasonably simulated by the three proposed techniques.

Theoretical analysis of long-term setup of driven piles considering soil anisotropy, destructuration and creep effects

The soil adjacent to the pile suffers a severe destructuration during pile installation and then regains its strength during the setup stage. This paper presents a theoretical approach to evaluate the long-term setup of driven piles in soft sensitive clays. An advanced elastic-viscoplastic model that accounts for fabric anisotropy, particle bonding and viscosity, is used in both stages of pile installation and setup. A semi-analytical solution for the undrained cylindrical and spherical cavity expansion in soft sensitive clays is developed to capture the pile installation effects. The changes in the stress state and fabric anisotropy of the soil adjacent to the pile caused by pore pressure dissipation and sustained service loads are analyzed. The evolution of soil mechanical behavior is incorporated into the load-transfer models of shaft friction and base resistance. Comparisons between measured and predicted results of field tests at three different sites demonstrate the applicability of the proposed approach. The calculated results illustrate that the ultimate bearing capacity increases steadily with time during the long-term setup stage. An extensive study is carried out to evaluate the effects of soil's initial anisotropy and bonding on the load-settlement behavior of driven piles.

An elastoplastic solution for cylindrical cavity expansion under constant water content conditions in anisotropic unsaturated soils

In this paper, an elastoplastic solution is developed for cylindrical cavity expansion in anisotropic unsaturated soils under constant water content conditions. The most prominent features of the solution can be attributed to 1) the stress–strain behaviour of unsaturated soil is subtly coupled with the saturation-suction behaviour; 2) both the mechanical and hydraulic behaviours are modelled as elastoplastic processes; and 3) an anisotropic critical state soil model for saturated soil is extended to an unsaturated situation to consider the effects of the initial stress anisotropy and stress-induced anisotropy of the natural unsaturated soils. The problem is formulated as a system of first-order differential equations and solved as an initial value problem. A numerical code that can judge the hydraulic yield condition of soil particles during the cavity expansion process is developed based on the Runge-Kutta algorithm to solve the governing equations. Parametric analyses, which cover a wide range of suctions, overconsolidation ratios, degrees of initial stress anisotropy, are conducted to investigate the effects of these important factors on the expansion responses in unsaturated soils. The proposed solution could potentially be applied to interpret pressuremeter tests and model pile installation effects in anisotropic unsaturated soils.

Effects of Pile Installation on Existing Tunnels Using Model Test and Numerical Analysis with Medium Density Sand

Vital underground structures such as sewers, power transmission lines, subways, and underpasses are potentially vulnerable to adverse effects from aboveground construction. In this study, the influence of pile installation on nearby existing tunnels was investigated. Both a laboratory model test and finite-element numerical analysis were conducted. Twelve different combinations of horizontal and vertical offsets between the pile and the tunnel were investigated. Different surcharge loads (allowable and ultimate) were also considered. In this way, the appropriate separation distance between the existing tunnel and the piles was established for sandy, medium-compaction soil. Although this study considers simple ground conditions, it facilitates safe construction by confirming the appropriate separation distance and comparing the areas that cannot be penetrated by the structures of each standard.

Cavity Expansion–Contraction-Based Method for Tunnel–Soil–Pile Interaction in a Unified Clay and Sand Model: Drained Analysis

This paper proposes an analytical method based on drained solutions of cavity expansion and contraction in a unified clay and sand model to investigate tunnel–soil–pile interactions. Cavity expansion analyses are used to evaluate the effects of pile installation on ground stresses and to determine pile end-bearing capacity and the distribution of shaft friction. Cavity contraction methods were adopted to replicate the tunnel convergence–confinement response using the singularity and image method for ground loss and ovalization of a shallow tunnel in a semi-infinite medium. A 2D model was developed that evaluates changes in mean stress and specific volume during pile installation and tunnel excavation. Outcomes from the developed analytical approach are compared against data from centrifuge tests in silica sand; results demonstrate that trends in pile load capacity degradation, mobilized safety factor, and tunneling-induced pile settlement can be satisfactorily predicted for the case of a tunnel excavated beneath a pile with a constant service load. Criteria based on pile capacity, safety factor, and settlement are proposed that can be used to determine a critical tunnel volume loss or evaluate pile safety level. The paper contributes to the understanding of tunnel–soil–structure interaction mechanisms and provides an efficient means of conducting a preliminary risk assessment of tunnel–pile interaction.

An elastoplastic solution to undrained expansion of a cylindrical cavity in SANICLAY under plane stress condition

Although cylindrical cavity expansion under plane stress condition is commonly encountered in geotechnical problems, most currently available solutions have been developed for cavity expansion under plane strain condition. This paper develops a novel elastoplastic solution for undrained expansion of a cylindrical cavity in SANICLAY under plane stress condition. The SANICLAY model, which could well represent the mechanical behaviour of the anisotropic soil and overconsolidated soil, is employed in the present solution to model the responses of the soil around the expanded cavity. The problem is formulated as a system of first-order differential equations with the unknown variables as the functions of an auxiliary coordinate, which are solved as an initial value problem. The expansion responses under plane stress condition are comprehensively compared with those under plane stress condition to highlight the unique expansion responses under plane stress condition. The results show that the present solution could well reflect the unique expansion responses under plane stress condition, which are totally different from those under plane strain condition. It is expected the proposed solution could provide a reasonable approach to interpret the pressuremeter test and model pile installation effects near the surface of the natural anisotropic clays.

Expansion responses of a cylindrical cavity in overconsolidated unsaturated soils: A semi-analytical elastoplastic solution

This paper presents a semi-analytical elastoplastic solution for cylindrical cavity expansion in overconsolidated (OC) unsaturated soils under constant water content condition, in which both the OC features and the coupled hydro-mechanical behaviour of soils are properly addressed. The unified hardening model for OC unsaturated soil is further coupled with a void ratio-dependent soil-water characteristic curve to model the coupled hydro-mechanical soil responses during expansion. With the aid of an auxiliary variable, the coupled hydro-mechanical constitutive matrix for the investigated problem is finally formulated as a set of first-order ordinary differential equations in terms of Lagrangian description, with the three net stress components, the suction, and the void ratio as the basic unknowns. The governing differential equations are solved as an initial value problem with the code developed based on the Runge-Kutta algorithm. Parametric studies show that both the overconsolidation ratio and the suction have remarkable impacts on the expansion responses, including the distribution of stress components, the change of degree of saturation as well as the expansion pressures. The proposed solution could provide a reasonable tool for interpretation of the pressuremeter tests and prediction of pile installation effects in overconsolidated unsaturated soils.

Effects of screw pile installation on installation requirements and in-service performance using the discrete element method

Existing guidance on the installation of screw piles suggest that they should be installed in a pitch-matched manner to avoid disturbance to the soil that may have a detrimental effect on the in-service performance of the pile. Recent insights from centrifuge modelling have shown that installing screw piles in this way requires large vertical compressive (or crowd) forces, which is inconsistent with the common assumption that screw piles pull themselves into the ground requiring minimal vertical compressive force. In this paper, through the use of the discrete element method (DEM), the effects of advancement ratio, i.e., the ratio between the vertical displacement per rotation to the geometric pitch of the helix of the screw pile helix, on the installation resistance and in-service capacity of a screw pile is investigated. The findings are further used to assess the applicability of empirical torque capacity correlation factors for large diameter screw piles. The results of the investigation show that it is possible to reduce the required vertical compressive installation force by 96% by reducing the advancement ratio and that although over-flighting a screw pile can decrease the subsequent compressive capacity, it appears to increase the tensile capacity significantly.

Long-term setup of a displacement pile in clay: An analytical framework

This paper integrates the effects of pile installation, reconsolidation, pile loading and soil ageing into an analytical framework to predict the long-term setup of a displacement pile in clay. The increase of mean effective stress and the decrease of void ratio of surrounding clay during reconsolidation and soil ageing are determined to quantify the changes in undrained shear strength and shear modulus, which are the two key soil parameters controlling load carrying behaviours of piles. The bearing capacity factors and load-transfer curves are developed by incorporating the developed soil parameters. The analytical framework is then proposed and validated by predicting a well-documented pile field test. Good agreements between the analytical results and the measured data demonstrate that the pile setup can be reasonably predicted by the proposed framework. Comprehensive parametric studies are conducted to investigate the influences of overconsolidation ratio, secondary compression index and pile loading on the pile setup. The results indicate that a displacement pile in clay with a smaller overconsolidation ratio or a larger secondary compression index, or subjected to a larger load, exhibits a larger long-term bearing capacity.

Settlement of jacked piles in clay: Theoretical analysis considering soil aging

This paper develops an analytical approach to estimate the long-term load-displacement behaviors of jacked piles in clayey soils. Apart from considering the effects of pile installation, subsequent re-consolidation and loading, the proposed approach properly considers the effects of soil aging on the long-term behavior of the surrounding soil so as to determine the load-displacement response of the jacked pile in the long run. An elastic-viscoplastic soil model is incorporated into the load transfer method to predict long-term soil properties. The comparison between the predictions from the presented approach and the data measured from the field pile loading test shows the validity of the proposed method. Parametric studies are conducted to illustrate the effects of the in-situ overconsolidation ratio, internal friction angle and the secondary consolidation coefficient on the long-term load-displacement behaviors of old piles. Results show that the proposed approach not only is capable of predicting the short-term set-up of jacked piles, but also could yield reasonable long-term load carrying behavior. The three parameters pertaining to the strength and stiffness of soil have significant impacts on the long-term load-displacement curve of the pile.

Assessment of disturbance impact of hydraulic jacked-in pile penetration in artificial clayey soil

The jacked-in pile method provides a substitute procedure that permits the installation of pre-formed piles with negligible vibration in a noiseless manner, thereby reducing noise impacts in marine and urban environments. This research was carried out by using a small-scale physical modelling approach to examine the movement of soil during pile installation. The model soil was formulated from a mix of amorphous silica and mineral oils; the resulting mixture was subjected to consolidation in a transparent chamber. The model pile was driven vertically down the mid-point of the soil model at different vertical speeds using a strain control device. The array of soil displacement dispersal was obtained by utilising the close-range photogrammetry and particle image velocimetry techniques. The deformation of soil during pile installation was found to decrease with progressive increase of the penetration rate. This result can be employed in the assessment of the disturbance effects of pile installation on underground services and archaeological relics beneath the ground in both urban and marine environments.