Pile Penetration Research Articles

Model Tests on Verticality Correction using Individual Length Control Method for Lifting Cable during Suction Pile Penetration

The suction pile can be installed in a slope when it is penetrated in the seabed owing to the inhomogeneity of the ground. Therefore, a method for the verticality correction of suction pile is required. In this study, to correct the verticality of the suction pile while using the suction penetration process, the concept to control the length of the lifting cable was devised and a model test was performed. The results showed that in the case of individual cable control technique according to the slope condition, the verticality was corrected by inducing rotation due to the difference in tension in the individual cable. It was 0.1° when the suction pile finished penetration. Furthermore, the penetration velocity did not reduce while correcting the verticality during the penetration process. Keywords: Suction Pile, Lifting Cable Control, Verticality, Penetration Velocity

Discrimination of Particle Breakage below Pile Tip after Model Pile Penetration in Sand Using Image Analysis

Particle breakage is a common phenomenon in granular soils and has been well observed during laboratory and in-situ pile studies. In this paper, an image analysis approach was developed to investigate the particle breakage behavior below a flat-ended pile tip, with special attention given to the location of particle breakage. The color difference between the original silica sand (light gray) and its coated surface (black) allows particle breakage to be distinguished based on the gray level variation. Larger gray values corresponded to a higher degree of breakage that occurred within the target area, which provides a new approach for quantitative assessment of the particle breakage extent. First, sequential images of the subsoil at different depths below a loaded pile tip were digitally recorded, and the degree of particle breakage was subsequently evaluated based on the gray level of the images. Then, the layered images at different depths were assembled to form a quasistereoscopic graph, and the slice image at any profile could be obtained. Accordingly, the zone of particle breakage below a flat-ended pile tip was graphically illustrated. The results of this study are beneficial for further clarifying the mechanism of particle breakage and provide a fundamental basis for accurate assessment of the ground-bearing capacity considering soil crushability.

Lateral-bearing behaviour of vibratory driven monopiles in different model test set-ups

This paper presents a comparison between two different but dependent model test set-ups to investigate the vibratory pile penetration and lateral loading behaviour in sand. Relevant considerations ...

Model tests on open-ended concrete pipe piles jacked in sand

An experimental study of the performance of concrete pipe piles during installation under different penetration speeds and static load tests on the piles in sand is presented. The applied jacking force, the amount of pile penetration, length of soil plug formed and ultimate bearing capacity were measured during the model tests. The results showed that the concrete pipe piles were partially plugged and the behavior of the soil plug was significantly affected by the penetration speed. The lower the penetration speed, the larger the soil plug formed which in turn leads to a greater ultimate bearing capacity. The size of soil plug can be evaluated by the m value defined as the ratio of the volume of the soil plug to that of the penetrated pile wall. The relationship between the m value and the penetration speeds can be used to estimate the amount of soil plug and the depth of penetration for an open-ended concrete pipe pile jacked into sand.

DEM modelling of screw pile penetration in loose granular assemblies considering the effect of drilling velocity ratio

Screw piles have been widely used as foundations for various types of structures. Drilling velocity ratio, the ratio of rotational velocity to driven velocity, is a critical parameter that affects the driven behaviors of screw piles. Three dimensional discrete element method, with a particle refinement method to enhance computation efficiency, is used to study the driven behaviors of screw piles to compare with the laboratory mini screw pile test results achieved by Shi et al. (Rock Soil Mech 39(6):1981–1990, 2018). The driven behaviors of a mini screw pile (900 mm long and 40 mm shaft diameter) with a variable diameter auger into loose granular assemblies under 0.5, 1 and 1.5 critical drilling velocity ratios are studied. The variation of stress distribution in the assemblies, particle movement around the piles, and evolution of void ratio in the assemblies are investigated. The results indicate that particles around the piles behave differently under different drilling velocity ratios. The reduction of driven force with the increase of drilling velocity ratio can be explained using the direction of particle movement around the piles and the vertical force acting on the screw blades. It was found that under high drilling velocity ratio, higher downward vertical force can be provided by the blades.

Determining the dependence of marine pile driving sound levels on strike energy, pile penetration, and propagation effects using a linear mixed model based on damped cylindrical spreading

Acoustic recordings were made during the installation of four offshore wind turbines at the Block Island Wind Farm, Rhode Island, USA. The turbine foundations have four legs inclined inward in a pyramidal configuration. Four bottom mounted acoustic recorders measured received sound levels at distances of 541-9067 m during 24 pile driving events. Linear mixed models based on damped cylindrical spreading were used to analyze the data. The model's random effects coefficients represented useful information about variability in the acoustic propagation conditions. The received sound levels were dependent on the angle between pile and seabed, strike energy, and pile penetration (PP). Deeper PPs increased sound levels in a frequency dependent manner. The estimated area around the piles where auditory injury and disturbance to marine life could occur were not circular and changed by up to an order of magnitude between the lowest and highest sound level cases. The study extends earlier results showing a linear relationship between the peak sound pressure level and per-strike sound exposure level. Recommendations are made for how to collect and analyze pile driving data. The results will inform regulatory mitigations of the effects of pile driving sound on marine life, and contribute to developing improved pile driving source models.

A finite element benchmark study based on experimental modeling of vibratory pile driving in saturated sand

The present study reports the approach and extensive results of FE back-calculations of model tests on vibratory pile installation in saturated sand. The model tests represent a half model setup with a half-pile driven into the soil body along an observation window. Due to this test setup, the soil displacements in vicinity to the penetrating pile have been successfully evaluated by application of high-frequency image recording and Digital Image Correlation (DIC) techniques. Additionally, an extensive instrumentation has enabled the measurement of pile motion, penetration resistance and pore water pressure during the penetration process. An axisymmetric model which incorporates the pile-oscillator system in contact with the soil has been developed in the FE-software Abaqus/Standard for the simulation of the tests. The dynamic analysis of water-saturated soil is based on a u-p formulation using a user-defined element. A hypoplastic constitutive model with intergranular strain has been selected to describe the mechanical behavior of the soil. The various comparison opportunities establish a comprehensive and quantitative validation benchmark of the numerical calculations. The generally good agreement between the results confirms that the pile installation process can be satisfactory reproduced numerically.

Evaluation of 18 Direct CPT Methods for Estimating the Ultimate Pile Capacity of Driven Piles

Cone and piezocone penetration tests (CPT, PCPT) are widely acknowledged to be useful and powerful in-situ tests for soil classification and characterization, and for evaluating different soil properties, such as strength and consolidation parameters. Due to similarity, between the cone and the pile penetration, CPT data have been used effectively for estimating ultimate pile capacity. Researchers have developed various direct CPT methods to estimate the ultimate capacity of piles ( Qp) from CPT/PCPT data (tip resistance and sleeve friction) with depth. In this study, the measured ultimate pile capacities ( Qp) obtained from static load tests on 80 square precast prestressed concrete piles in Louisiana were used to evaluate 18 direct pile-CPT methods for estimating ultimate pile capacity. Two approaches were used. In the first approach, three criteria (best fit line, arithmetic mean and standard deviation, and cumulative probability of Qp/Qm) were adopted, and the sum of ranking of all criteria was used to determine the final ranking of each method. A second approach, multidimensional unfolding, was used to display the ranking data in a two-dimensional space. This approach helps to reveal the typical ranking of the pile-CPT methods, the extent of agreement between the piles, the existence of outliers among the piles, and the similarity between the CPT methods. Based on the results of this study, Bustamante and Gianeselli (LCPC), probabilistic, UF, Philipponnat, CPT2000, UWA, De Ruiter and Beringen, and Schmertmann were found to be the best CPT methods (in order) for estimating the ultimate pile capacity of driven PPC piles.

Influence of relative acceleration in saturated sand: Analytical approach and simulation of vibratory pile driving tests

In this work, 1 g model tests on vibratory pile driving in saturated sand are simulated, using different coupled element formulations in conjunction with a hypoplastic constitutive model. Owing to the high frequency of the vibrator in the model tests, the influence of the relative acceleration between the solid and water phases cannot be neglected a priori. The frequently applied u-p formulation assumes the relative acceleration to be zero; hence, two additional element formulations (the u-U and u-p-U approaches) are applied. A general investigation regarding the relative acceleration is first conducted using a semi-analytical approach, based on which the impact of the relative acceleration can be expressed by the wave frequency and hydraulic conductivity alone. Further, a threshold level of applicability of the u-p formulation is established. A comparison of the different element formulations used in the simulation of the vibratory driving model tests reveals that the relative acceleration has little impact, and the frequency threshold level obtained by the analytical solution holds. The simulations exhibit strong accordance with the experimental data in terms of pile penetration and pore pressure development. Different numerical aspects of the element formulations are discussed, including problems regarding volumetric locking and conditioning of the stiffness matrices.

A study on particle breakage behavior during pile penetration process using acoustic emission source location

Particle breakage is a common occurrence in granular systems when the external stress exceeds the individual particle strength. A large number of experimental evidences suggested that particle breakage may significantly influence the soil behavior. In the case of pile foundations, the subsoil below the pile tip experiences considerable high stress and consequently prone to break. Due to the lack of sufficient understanding on particle breakage mechanism, there is currently no consentaneous theoretical background for particle breakage analysis during the pile penetration process. This study aims to clarify the location of particle breakage and its evolving characteristics with the aid of acoustic emission (AE) source location method. The spatial distribution of AE hypocenters is interpreted to be associated with the mechanism of particle breakage. Results showed that the AE sources were not uniformly distributed, but concentrated within certain zones below the pile tip. This AE concentration zone was pushed downward with the advancing pile tip, and its distance from the real time pile tip position decreased after certain depth of pile penetration. The location of particle breakage interpreted from AE source location was verified with posttest excavations and the insights on the particle breakage evolution zone were further discussed.

Durability and microstructure of steam cured and autoclaved PHC pipe piles

Effects of two different curing regimes (steam curing and autoclaved curing) on durability of pre-stressed high-strength concrete (PHC) pipe piles with fly ash (FA) had been investigated. The chloride penetration, salt and frost resistance performances of PHC pipe piles with these two curing regimes were tested. The results showed that the chloride ion permeability coefficient of steam cured sample at 85 °C for 4.5 h was decreased by 97.13% compared with that of autoclaved one, these steam cured sample could stand 150 times of salts (5% Na2SO4 + 3.5% NaCl solution) corrosion tests and 550 times freeze-thaw tests. The pore structural and micro-cracking analysis of samples with three water to binder ratios (0.21, 0.23, 0.25) revealed that the mean total porosity values of these steam cured sample were about 5%, which was less than half of that of autoclaved samples. The dipping dyeing test showed that the mean micro-cracks width, length and the density of the steam cured samples were less than that of the autoclaved samples. The results supported that by optimizing the mix ratio and curing regime the PHC pipe piles could be prepared with satisfied mechanical and durability performances. So a feasible low-carbon manufacturing technology for PHC pipe piles was provided.

Centrifuge Modeling of Stress and Pore Pressure Responses Due to Closed-Ended Pile Jacking in Silty Clay

Abstract A series of centrifuge model tests were performed to examine the short-term soil stress responses around closed-ended displacement piles during jacking in Shanghai silty clays. Miniature transducers were placed near the piles to monitor the evolution of the total radial soil stress and pore pressure at different positions, which were closely associated with the progress of pile penetration. The results show that these stresses accumulated when the pile approached and decreased when the tip (or shoulder) passed, which indicates that the transducers experienced a loading and unloading process. The maxima of the soil stress or pore pressure increased with the initial depth of the observation positions and decreased with the horizontal distance to the pile axis. Compared with the total radial stress, the arrival of the peak pore pressure had an obvious hysteresis. Three typical modes to describe the stress variations during the pile installation process were summarized. Furthermore, the cumulative total stresses and pore pressures at a given location because of the installation of two piles were investigated.

CAPACITY ANALYSIS OF SINGLE PILE BEARING CAPACITY BASED ON STATIC METHOD AND N-SPT TEST ON PILE DRIVING ANALYZER TEST (CASE STUDY OF PT. ASAHI FORGE INDONESIA PHASE II PROJECT)

Soil investigation has an important role before building a building. The carrying capacity of the soil obtained from the results of soil investigations is very influential on the shape and dimensions of the foundation itself. In the PT.Asahi Forge Indonesia Project, the SPT test data is out of sync with the actual piling results related to embedded pile penetration. The design plan for piles with a length of 7 m based on the N-SPT test turned out that in the field, the piles achieved a bearing capacity at a depth of 9 meters. The final project aims to analyze and compare the carrying capacity of a single pile based on static methods and N-SPT test on the Pile Driving Analyzer. The method used in this research is the study method of laboratory test results and N-SPT. Work steps include; preparation, literature study, data collection, carrying capacity analysis, and comparison of analysis results. The results of the analysis of the carrying capacity of the piles based on the static method by the (Vijayvergiya & Focht, 1974) method amounted to 549,201 kN; The (McClelland, 1974) Method of 426,292 kN; The U.S Army Corps Method is 459,545 kN and the Tomlinson (1977) Method is 474,191 kN. While the results of N-SPT were bearing piles bearing capacity with the Mayerhof (1956) method of 738,645 kN and the Schmertmann (1967) Method of 451,327 kN. Based on these results, the N-SPT test based on the Mayerhof (1956) Method of 738,645 kN was the closest to the PDA test results of 755,116 kN. The comparison of the results of the analysis between the static test, N-SPT and PDA test is 19: 24: 30. This means that the carrying capacity of the static pile and PDA test has a difference of 37% while between the N-SPT and PDA test has a difference of 20%.

Numerical evaluation of buckling in steel pipe piles during vibratory installation

The buckling of steel pipe piles during installation is numerically studied. Generally, numerical simulation of installation processes is challenging due to large soil deformations. However, by using advanced numerical approaches like Multi-Material Arbitrary Lagrangian-Eulerian (MMALE), such difficulties are mitigated. The Mohr-Coulomb and an elastic-perfectly plastic material model is used for the soil and pile respectively. The pile buckling behavior is verified using analytical solutions. Furthermore, the model is validated by an experiment where a pipe pile is driven into sand using vibratory loading. Several case scenarios, including the effects of heterogeneity in the soil and three imperfection modes (ovality, out-of-straightness, flatness) on the pile buckling are investigated. The numerical model agrees well with the experimental measurements. As a conclusion, when buckling starts, the penetration rate of the pile decreases compared to the non-buckled pile since less energy is dedicated to pile penetration given that it is spent mainly on buckling.

Numerical simulation of XCC pile penetration in undrained clay

This paper presents large deformation analysis of X-section Cast-in place Concrete (XCC) pile (a type of non-cylindrical pile) penetration in undrained clay using the Coupled Eulerian-Lagrangian (CEL) numerical technique. The main objective of this study was to investigate the shape effect of XCC pile cross-section on the penetration mechanism, such as the plastic zone around pile shaft and stress developed in the soil. The discrepancy of the stress mechanism between the circular and XCC piles are captured. The results show that the shape effect has insignificant influence on the plastic zone surrounding penetrated XCC pile. The shape effect only influences of the radial stress distribution around a rough XCC pile, while it can be neglected for smooth interface case. In addition, the radial stress, radial stress gradient and vertical stress around the smooth XCC pile shaft in θ=0∘ profile is larger than the one in θ= 45∘ profile. Moreover, the radial stress near the ground surface in θ= 45∘ profile is nearly equal to zero, while the radial stress near the ground surface in θ=0∘ profile sharply increases with the increasing of soil depth. The presented analysis provided a basis for developing design method for XCC pile in the future.

High Frequency Acoustic Emissions Observed during Model Pile Penetration in Sand and Implications for Particle Breakage Behavior

High Frequency Acoustic Emissions Observed during Model Pile Penetration in Sand and Implications for Particle Breakage Behavior

Analytical model for evaluating XCC pile shaft capacity in soft soil by incorporating penetration effects

The derivation of a new analytical model for predicting the soil displacement of X-section cast-in-place concrete (XCC) piles installed vertically into soft clay as well as for predicting limit shaft resistance during loading phases is presented in this paper. The analytical model is formulated by assuming that the XCC pile penetration process is an X-shaped cylindrical cavity expansion process. Based on the theoretical framework of the Strain Path Method (SPM), the strain, displacement and stress induced by X-shaped cavity expansion can be obtained. The proposed analytical model is validated by comparing the degenerate solution of this study with that of conventional circular (cylindrical) cavity expansion theory. Analytical model-based design methods are then proposed for evaluating soil displacement and XCC pile shaft capacity. Theoretical predictions are compared with field test measurements to verify the suitability of the proposed design method. The proposed new analytical model reveals the fundamental penetration mechanics of XCC piles and gives improved design methods for determining XCC pile shaft capacities.

Formation of soil plug in open-ended pipe piles in sandy soils

Open-ended pipe piles are commonly used for the foundations of offshore jacket platforms, mooring piles, offshore wind turbines and, in general, for pile foundations like micro piles, etc. Driveability of open-ended piles is greatly affected by the formation of soil plug during the driving, particularly in sandy soils. In order to study the behaviour of formation of soil plug during driving, open ended model piles were driven into uniformly graded sand in a calibration chamber in the laboratory scale as well as in the field. The influence of the pile diameter, hammer energy and pile penetration depth were studied. The results of the model pile tests showed that the incremental filling ratio (IFR, which indicates the degree of plugging) during driving decreased with pile penetration and increased with increase in hammer energy. IFR has also increased with increase in pile diameter. A correlation between plug length ratio (PLR, percentage plug height with respect to total penetration) and IFR is proposed based on the laboratory experiments.

A novel analytical approach for predicting the noncylindrical pile penetration‐induced soil displacement in undrained soil by combining use of cavity expansion and strain path methods

SummarySince development of cavity expansion theory and strain path method, almost all the conventional analyses of pile penetration problem have been based on circular cross section penetrometer. However, noncylindrical pile (with noncircular cross section) is also required in geotechnical engineering such as rectangular cross‐sectional pile, X‐sectional cast‐in‐place concrete pile, H‐shaped steel pile, prefabricated vertical drains, and flat dilatometer. This paper presents a novel and general analytical approach for capturing the soil deformation mechanism around the pile with arbitrary cross section. The penetration problem is simulated by a new 2‐dimensional (radial and circumferential) cavity expansion model. Based on the theoretical framework of strain path method, the kinematics (velocity field) of the noncylindrical cavity expansion is reduced to solve the Laplace equation with arbitrary velocity boundary conditions by using the conformal mapping technique. Then, solutions for the strain and displacement, which could consider the large deformation effect, are obtained by the integration of the strain rate and velocity along the streamline. The analytical solution is validated by comparing the degenerate solution of this study with conventional circular (cylindrical) cavity expansion theory. Subsequently, typical numerical examples for the deformation mechanism of elliptical and rectangular cavity expansion are presented to prove the advantage of the proposed new solution particularly in capturing the noncylindrical symmetric displacement field. A brief application of the proposed new analytical solution to the interpretation of the smear effect of prefabricated vertical drain installation confirms its useful in geotechnical engineering.

Numerical modeling of pile penetration in silica sands considering the effect of grain breakage

Current numerical platforms rarely consider the effect of grain breakage in the design of sandy soil foundations. This paper presents an enhanced platform for large deformation analyses which considers the effect of grain breakage during pile penetration in silica sand. For this purpose, a model based on critical state theory has been developed within the framework of multisurface plasticity to account in the same constitutive platform the effect of stress dilatancy and particle fragmentation. Furthermore, to implement the underlying constitutive equations into a finite element code, a stress integration scheme has been adopted by extending a cutting plane algorithm to the model with multiple yielding mechanisms. A laboratory model test and a series of centrifuge tests of pile penetration are simulated to verify the performance of the selected constitutive approach in terms of pile resistance and grain breakage distribution, with the parameters of sand calibrated through a set of drained triaxial compression tests from low to very high confining pressure. Some extra features of the enhanced platform are also discussed, such as: i) the effect of sand crushability on pile resistance and ii) the nonlinear relation of pile resistance to sand density. The proposed findings demonstrate the capability of this numerical platform to proper design of pile foundation in sandy soils and highlight the interplay between stress dilatancy and grain breakage mechanisms during pile penetration processes.