Methods of determining pile toe capacity for both small displacement driven steel piles and drilled sockets were collected. Working in conjunction with a local consulting firm, records of previous pile driving sites were collected. A process to determine quality data for use in this work was developed by the author including information from geotechnical site investigations, pile driving records and pile driving analysis records. By plotting unconfined compressive strength of rock versus measured ultimate pile toe capacity of these piles, a best fit line of 7.5qu and a series of confidence intervals were established for the site records. This best fit line was compared to all of the previously reviews design methods for calculating ultimate pile toe capacity. Rehnman and Broms (1971) was determined to be the most effective existing method while most of the methods for drilled sockets were overly conservative when applied to small displacement driven steel piles.

Ever since the use of cone penetration testing (CPT) in geotechnical site investigations, efforts have been made to correlate its readings with the components of static axial pile capacity: unit base resistance (qb) and unit shaft resistance (fp). Broadly, the pile capacity analysis from CPT data can be accomplished via two main approaches: rational (or indirect) methods, and direct methods. The rational methods require a two-step approach, whereby CPT data are first used to provide assessments of geoparameters that are further utilized as input values within a selected analytical framework to enable the evaluation of the pile capacity components. In contrast, direct CPT methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to obtain fp and qb for full-size piling foundations. The evolution of the CPT from mechanical to electrical to electronic versions and single-channel readings (i.e., measured tip resistance, qc) to the piezocone penetration test (CPTu), that provides three readings of point stress (qt), sleeve friction (fs), and porewater pressure (u1 or u2), has resulted in the concurrent development of multiple CPT-based geotechnical pile design methods. It is noted, however, that current CPT-based methods focus only on an estimate of "axial pile capacity", corresponding to a limiting load or force at full mobilization. A more comprehensive approach is sought herein utilizing the CPT readings towards producing a complete nonlinear load-displacement-capacity (Q-w-Qcap) on axial pile response. In particular, the seismic cone penetration test (SCPT) provides the profile of shear wave velocity (Vs) that determines the fundamental small-strain shear modulus: Gmax = gt?Vs2, where gt = total mass density of soil. With the penetrometer readings useful in assessing foundation capacity, the stiffness Gmax finds application within elastic continuum solutions towards evaluating the load-displacement (Q-w) response. In this study, a concise review of the deep foundation systems is presented, including pile types and characteristics, various arrangements of axial pile load testing in static mode, and interpretations of the load test data. In addition a comprehensive state-of-the-art review of CPT-based rational and direct methods of pile capacity evaluations is compiled. It is recognized that the direct methods offer more convenience in their straightforward approach in estimation of the pile capacity. The piezocone-based UniCone direct method proposed by Eslami and Fellenius (1997) is selected for further refinements, as it utilizes all three CPT readings in its design formulations. Concerning the analysis of pile deformations under axial loading, a brief review covers designs employing empirical formulations, analytical solutions, load-transfer (t-z) methods, numerical simulations, variational approaches, and those using hybrid methods. Specifically, the analytical elastic solution by Randolph and Wroth (1978; 1979) is covered in more detail since it is simple and convenient in application with extended applications to uplift and bidirectional O-cell types of loadings. This elastic approach also serves well in modeling a stacked pile solution for layered soil profiles. The last part of the review covers various shear modulus reduction schemes, since evaluation of the applicable stiffnesses is considered to be the most delicate phase in the nonlinear Q-w response analysis of axially loaded piles. It is identified that the most appropriate scheme applicable to static axial loading of pile foundations is the one that can be derived from the back-analyses of actual load tests within the framework of analytical elastic solution. In order to conduct a comprehensive research study on the axial Q-w-Qcap response of deep foundations from CPT readings, a large database is compiled. This includes 330 case records of pile load tests at 70 sites from 5 continents and 19 different countries of the world, where pile foundations were load tested under top-down compression or top-applied uplift (tension) loading, or both, or by bi-directional Osterberg cell setups. All test sites had been investigated using CPT soundings; in most cases by the preferred SCPTu that provides all four readings from the same sounding: qt, fs, u2, and Vs. In a few cases, sites were subjected to CPT or CPTu and the profiles of shear wave velocities were obtained by other field geophysical techniques, otherwise by empirical estimations. Results of the new correlation efforts are offered to derive coefficients Cse for shaft component and Cte for base component of the axial pile capacity from CPTu data. The UniCone type of soil classification chart is refined by delineating 11 soil sub-zones along with their respective Cse, in contrast to the 5 zones originally proposed. The CPT material index, Ic (Robertson, 2009) is then used to establish direct correlations linking Cse vs. Ic and Cte vs. Ic. Statistical relationships offer continuous functions for estimating the coefficients over a wide range of Ic values, thereby eliminating the need for use of the soil classification chart as well as improving the reliability in the evaluations of fp and qb. The effects of the pile loading direction (compression vs. uplift) and loading rate are also incorporated in the proposed design formulations. New sets of shear stiffness reduction curves are developed from the back-analysis of pile load tests and Gmax profiles obtained from the SCPT data. Alternative functions formats are provided in terms of hyperbolic tangent expressions or exponential curves, developed as normalized shear stiffness (G/Gmax) vs. logarithm of percent pseudo-strain (gp = w/d, where w = pile displacement and d = pile diameter). These charts offer convenience in the axial Q-w analysis of different pile categories within the framework of analytical elastic solution. The results also account for the plasticity characteristics of the soil formations within the database. A stacked pile model for Q-w analysis is presented in which certain adaptations are proposed in the elastic continuum solution. These adaptations enable plotting of separate modulus reduction curves (G/Gmax vs. gp) as function of depth for each layer, and treating pile as a stack of smaller pile segments embedded in a multi-layered soil media. The solution can be used to address the question of progressive failure with depth in a multi-layer soil media that exhibits nonlinear soil stiffness response. Finally, the closed-from analytical elastic pile solution for predicting the Q-w response is decoupled and modified to account for different setup cases and multi-stage loading of bi-directional O-cell tests. The decoupling accounts for separate assessments of the response to axial loading for different segments of pile shaft and different stages of loading, while the modifications include: (1) reduced maximum radius of influence for the upward displacements of the upper shaft segment, and (2) modeling the non-linear ground stiffness from the back-analysis of a well-documented dataset of O-cell load tests.

<p>In the last two decades, there has been significant improvements in pile design methods. These methods include variables that have been studied using laboratory and full-scale experiments. Refined understanding of the underlying mechanisms controlling pile response to loading enables introduction of variables in the design equations that reflect observations made in high-quality experimental data.</p><p>The mechanisms involved in the mobilization of the pile resistance (both base and shaft resistance) are studied in this thesis using a large-scale model pile testing facility consisting of a half-cylindrical calibration chamber with image analysis capabilities, instrumented model piles, and data and digital image acquisition systems. The thesis focuses on the effect of the pile surface roughness on the mobilization of tensile shaft resistance, the effect of the pile base geometry on the mobilization of base resistance, the analysis of possible mechanisms responsible for time-dependent increases in pile axial capacity, and particle crushing produced by pile installation. </p><p>A set of model pile tests were performed to study the effects of three different surface roughnesses on the shaft resistance of model piles jacked in the half-cylindrical calibration chamber. Digital images of the model piles and surrounding sand captured during tensile static loading were analyzed using the digital image correlation (DIC) technique. The base and shaft resistance measured for the instrumented model piles and the displacement and strain fields obtained with the DIC technique show that an increase in the roughness of the pile shaft results in an increase in the average unit shaft resistance and in the displacements and strains in the sand next to the shaft of the pile. Guidance is provided for consideration of pile shaft surface roughness in the calculation of the tensile limit unit shaft resistance of jacked piles in sand.</p><p>Base geometry effects were studied using jacked and pre-installed model piles with flat and conical bases tested in the DIC calibration chamber. The results show that the mobilized base resistance of a model pile with a conical tip was less than that of an equal pile with a flat base, all other things being equal, by a factor ranging from 0.64 to 0.84. The displacement and strain fields obtained with DIC also show that the slip pattern below the pile with a conical base differs from that of a pile with a flat base. </p><p>Finally, the degree of crushing of silica sand particles below the base of model piles jacked in sand samples is studied. The particle size distribution curves are obtained before and after pile installation. Relationships between the load mobilized at the base of the model piles and two well-known breakage parameters are proposed. This work also provides detailed measurements of the trajectories followed by crushed and uncrushed particles during pile installation, and characterizes the typical particle crushing modes produced by piles jacked in silica sand.</p><div><br></div>

Deep foundations, including driven piles, are used to support vertical loads of structures and applied lateral forces. Many pile supported structures, including bridges, are subjected to large lateral loads in the form of wind, wave, seismic, and traffic impact loads. In many practical situations, structures subjected to lateral loading are located near or in excavated and fill slopes or embankments. Full-scale research to examine the effects of soil slope on lateral pile capacity is limited. The purpose of this study is to examine the effects on lateral capacity of piles located in or near cohesionless soil slopes. A full-scale lateral load testing program was undertaken on pipe piles in a cohesionless soil at Oregon State University. Five piles were tested near a 2H:1V test slope and located between 0D to 8D behind the slope crest, where D is the pile diameter. Two vertical baseline piles and three battered piles were also tested in level ground conditions. The cohesionless backfill soil was a well-graded material with a fines content of less than 10% and a relative compaction of 95%, meeting the Caltrans specification for structural backfill. Data collected from the instrumented piles was used to back calculate p-y curves, load-displacement curves, reduction factors, and load resistance ratios for each pile. The effects of slope on lateral pile capacity are insignificant at displacements of less than 2.0 inches for piles located 2D and further from the crest. For pile located at 4D or greater from the slope crest, the effect of slope is insignificant on p-y curves. A simplified p-multiplier design procedure derived from back-calculated p-y curves is proposed to account for the effects of soil slope. Comparisons of the full-scale results were made using proposed recommendations from the available literature. Lateral resistance ratios obtained by computer, centrifuge, and small scale-models tend to be conservative and overestimate the effects of slope on lateral capacities. Standard cohesionless p-y curve methods slightly over predict the soil resistance at very low displacements but significantly under predict the ultimate soil resistance. Available reduction factors from the literature, or p-multipliers, are slightly conservative and compare well with the back-calculated p-y curves from this study. / Graduation date: 2012

In an effort to obtain 100-year level hurricane protection for southeastern Louisiana, the U.S. Army Corps of Engineers (USACE) has implemented design guidelines that both levees and structures shall be designed to. Historically, USACE has used concrete piles or steel H-piles as the foundations for these structures. Because of the magnitude of obtaining 100-year level hurricane protection, limited resources, and a condensed timeline, spiral welded pipe piles can be manufactured as an alternative to either the concrete piles or steel H-piles. This research will provide the necessary background for understanding pile foundations, will compare the behaviors of spiral welded pipe piles to that of other piles with respect to geotechnical concerns through a series of pile load tests, and will offer a current cost analysis. This background, testing, and cost analysis will show that spiral welded pipe piles are a viable alternative for USACE structures from a geotechnical and economic perspective.

A utilização de estacas helicoidais como fundação de linhas de transmissão de energia elétrica tem aumentando significativamente no Brasil. No entanto, em alguns casos de obra, a camada de solo adequada para se instalarem as hélices da estaca encontra-se em profundidade economicamente inviável para o uso deste tipo de fundação. Esta foi a razão que motivou a presente pesquisa, que tem como objetivo avaliar soluções para a instalação de estacas helicoidais mais curtas, ancoradas em solo de capacidade inferior à necessária para atender às cargas de projeto. Nesta dissertação, foram avaliadas duas soluções alternativas para o aumento de capacidade de carga de fundações por estacas helicoidais, para os casos de carregamento de tração e compressão. A primeira alternativa verificada foi a injeção de calda de cimento em torno das hélices da ponta da estaca. A segunda solução testada foi o preenchimento com argamassa em torno da haste da estaca acima das hélices. Foram realizadas na presente pesquisa nove provas de carga (cinco de tração e quatro de compressão): três em estacas helicoidais convencionais, quatro em estacas helicoidais com injeção de calda de cimento e duas em estacas helicoidais com fuste de argamassa. Após a realização de provas de carga nas estacas, estas foram exumadas para se verificar a forma da coluna de argamassa e as formas de bulbos resultantes das injeções realizadas com calda de cimento. A partir dos resultados dos ensaios, foi verificado que a capacidade de carga da estaca á tração pode ser aumentada usando-se as alternativas testadas. Porém, são necessários mais ensaios para avaliar a eficiência destes procedimentos em diferentes condições de solo e configuração de estacas. / The use of helical piles as foundation for transmission lines has increased significantly in Brazil. However, in some sites, the soil layer suitable for installing the pile helices are considerably deep and it is economically unviable to use this type of foundation. This reason motivated the current study, which aims to evaluate solutions for the installation of helical piles anchored in soil with low capacity. In this research, it was evaluated two alternative solutions to improve the helical pile capacity. The first alternative is injecting a water/ cement mixture which is delivered to the ground throught holes, placed between the upper and bottom helices. The second alternative solution is helical piles with a mortar shaft. Nine pile load tests were performed for the present investigation (five in tension and four in compression): three on conventional helical piles, four on helical piles with injection, and two on helical piles with mortar shaft. After that, the helical piles were exhumed for the verification of the shaft shape and the forms of the bulbs resulting from injections performed with cement mixture. The results of these tests indicated that the uplift capacity of helical piles can be increased by using the alternatives tested. However, more tests are needed to evaluate the effectiveness of these procedures, in different soil conditions and pile configurations.

A utilização de estacas helicoidais como fundação de linhas de transmissão de energia elétrica tem aumentando significativamente no Brasil. No entanto, em alguns casos de obra, a camada de solo adequada para se instalarem as hélices da estaca encontra-se em profundidade economicamente inviável para o uso deste tipo de fundação. Esta foi a razão que motivou a presente pesquisa, que tem como objetivo avaliar soluções para a instalação de estacas helicoidais mais curtas, ancoradas em solo de capacidade inferior à necessária para atender às cargas de projeto. Nesta dissertação, foram avaliadas duas soluções alternativas para o aumento de capacidade de carga de fundações por estacas helicoidais, para os casos de carregamento de tração e compressão. A primeira alternativa verificada foi a injeção de calda de cimento em torno das hélices da ponta da estaca. A segunda solução testada foi o preenchimento com argamassa em torno da haste da estaca acima das hélices. Foram realizadas na presente pesquisa nove provas de carga (cinco de tração e quatro de compressão): três em estacas helicoidais convencionais, quatro em estacas helicoidais com injeção de calda de cimento e duas em estacas helicoidais com fuste de argamassa. Após a realização de provas de carga nas estacas, estas foram exumadas para se verificar a forma da coluna de argamassa e as formas de bulbos resultantes das injeções realizadas com calda de cimento. A partir dos resultados dos ensaios, foi verificado que a capacidade de carga da estaca á tração pode ser aumentada usando-se as alternativas testadas. Porém, são necessários mais ensaios para avaliar a eficiência destes procedimentos em diferentes condições de solo e configuração de estacas. / The use of helical piles as foundation for transmission lines has increased significantly in Brazil. However, in some sites, the soil layer suitable for installing the pile helices are considerably deep and it is economically unviable to use this type of foundation. This reason motivated the current study, which aims to evaluate solutions for the installation of helical piles anchored in soil with low capacity. In this research, it was evaluated two alternative solutions to improve the helical pile capacity. The first alternative is injecting a water/ cement mixture which is delivered to the ground throught holes, placed between the upper and bottom helices. The second alternative solution is helical piles with a mortar shaft. Nine pile load tests were performed for the present investigation (five in tension and four in compression): three on conventional helical piles, four on helical piles with injection, and two on helical piles with mortar shaft. After that, the helical piles were exhumed for the verification of the shaft shape and the forms of the bulbs resulting from injections performed with cement mixture. The results of these tests indicated that the uplift capacity of helical piles can be increased by using the alternatives tested. However, more tests are needed to evaluate the effectiveness of these procedures, in different soil conditions and pile configurations.