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By Cem Akgüner

The displacements of axially loaded single piles are analyzed with an approach based on elasticity. Young?s modulus and Poisson?s ratio of the soil encompassing a pile are the unknowns required as input to obtain predictions based on the elastic method. Attention is directed towards Young?s modulus because the range and variability of Poisson?s ratio is not significant in displacement calculations. A database of axial pile load tests established for the California Department of Transportation (Caltrans) is investigated. All of the tested piles were driven into the ground. Measurements of displacements and loads were made only at the top of the pile. First the magnitude of displacements is determined up to loads that are half of the failure load measured from pile load tests. Various correlations for Young?s modulus are then employed to determine how accurately each predicts the actual measured displacement. The chosen correlations utilize the routinely available parameters of laboratory triaxial undrained shear strength for cohesive soils and standard penetration test blowcount for cohesionless soils.

Jan 1, 2008

By Saba Mohan

This study presents results based on the Pile Installation Demonstration Project (PIDP) that was conducted as a part of the East Span San Francisco-Oakland Bay Bridge Seismic Safety Project. For the three full-scale pile installations, two different high-energy hydraulic hammers were selected for the installation. However, these hammers may not have sufficient energy to drive these large diameter piles at their ultimate capacity following long-term set-up. Nevertheless, these hammers were selected because, soil plug behavior, the generation of excess pore pressures and remolding of soil during driving were expected to reduce the shaft and end bearing resistance, and therefore reduce the energy required to drive these piles to design penetration. Data collected during continuous installation driving and after a series of re-strikes at different set-up times ranging from 1 to 33 days were used as input data for CAPWAP. These results were used to estimate the soil resistance along the pile length and at the toe of the pile, and the soil pile set-up behavior. Validity of the procedures used to predict the soil resistance to driving and predicted blow counts were verified with the field observed blow counts and the energy that was delivered to the pile. Based on combined CAPWAP analyses, the soil pile set-up with time was estimated and compared with results of other methods currently available in the literature for predicting the soil pile set-up rate.

Jan 1, 2002

By Garland Likins

The Texas Department of Transportation, now considering using Augered Cast-In-Place (ACIP) Piles (also known as Continuous-Flight-Auger or CFA Piles) in their foundations, awarded a research project to Professor Mike O'Neill at the University of Houston (UH) to study the advantages and potential difficulties with ACIP/CFA piles. ACIP/CFA piles were installed on three sites for UH; they had extra instrumentation and additional measurements by UH staff during installation which are beyond the scope of this paper. Independent visual logging of the pile was done by an experienced inspection firm. The main advantages of ACIP/CFA piles are their speed of installation and their economy. Potential savings are substantial. Disadvantages include an unknown structural condition of the shaft. Inspection is critical, but many simultaneous observations make accurate inspection difficult. Because of resulting uncertainty, many engineers have avoided ACIP/CFA piles in the past.

Jan 1, 1998

By Daniel Ruffing, Charlie Krug

In recent years, the chain-style trencher has been proven a valuable tool for installing vertical walls on challenging sites where conventional methods may be less desirable. Like many tools, trenchers are most effective when used with the right application. Trenchers are commonly used for applications that could also be completed with conventional slurry trenching; low-permeability cutoff walls, collection trenches and permeable reactive barriers (PRBs). Drawing from a wealth of experience with conventional slurry trenching and the trencher, this paper compares and contrasts the technical considerations, treatability, installation, performance, and lessons learned for recent projects.

By Mitsuhiro Shibazaki

Generally, water-soluble polymers are effective in convergence of water jet ejected from a nozzle as they add viscosity to water. However, excessive additional polymers (added to keep water viscous) could increase friction on the contrary. Therefore, we have totally modified the jetting system from every possible aspect, such as the shape and upstream conditions of a nozzle in order to keep the flow spread to the minimum as stated in my presentation.

Feb 10, 2003

By G. Stuart Littlejohn

In spite of recent concerns in certain European countries, I believe that silicate-ester grouts will continue to be employed in practice, unless more cost-effective inorganic grouts are developed for the treatment of fine sands. It is also noteworthy that over the past 40 years, there has been a record of good experience where silicate-ester grouts have been used in ground improvement. Nevertheless, there is now a need via the European Standard EN 12715 (2000) "to assess the environmental impact, particularly the toxicity of the grout and grout components, and their effect on ground and drinking water should be considered before grouting." "When testing the grouting material for environmental impact, the following aspects should be considered: ? Whether during processing, transport or grouting, substance can be generated or released which could be hazardous to the environment or the grouting crew; ? Whether noxious substances can spread upon mixing with ground water; ? Whether reaction products can be produced or released which influence the water quality; ? The type of particles eroded from hardened grout; ? Chemical reactions between hardened grout and the ground water."

Feb 10, 2003

By Douglas Heenan

The fracture orientations were inferred based on theory and previous experience. The fracture pattern was not monitored during the project. Grout volume was recorded at each sleeve port and real time movement monitoring of the building foundation was performed.

Feb 10, 2003

By Marcus Daubner

This paper explains how BAUER Spezialtiefbau GmbH uses digital methods on projects - starting from work preparation to completion of works. More precisely, the advantages of BIM-based planning during work preparation and the automated and structured data management - both machine production data and the manually recorded quality-relevant reports - during execution phase are displayed. In this context, the benefit of the digital twin to optimize processes, to reduce defect costs, for a more effective reporting sys-tem, and the further usage of as-built information in the BIM or GIS process is described.

Sep 1, 2022

By Peter Deming

"PART 2 OF 2 (CONTINUED FROM SUMMER 2006 EDITION) CONSTRUCTION ISSUES (cont’d) The Influence of Ground Conditions on Collapse Sand and gravel strata provide frictional resistance to support active earth pressure. The angle of internal friction has only slight influence on computed stability. Sand and gravel material design parameters can be defined with SPT N-values. Silt strata should be analyzed using internal friction. Definition of soil parameters should be performed by laboratory testing. Cohesive materials, especially soft clay and peat, require careful definition for design. Shear strength should be determined by laboratory testing. Work platforms constructed over granular strata improve the ground resistance by increasing confining pressure. However, temporarily increasing overburden stress on cohesive ground reduces trench stability. If the ground contains soft cohesive deposits which are not normally consolidated to the construction overburden, these must be stabilized before attempting trench construction. Use of wick drains and surcharge fill to improve the ground is recommended. Ground stabilization work requires time, and should be performed by the Owner prior to trench excavation. The addition of cement, stone columns, or other measures to support trench excavation equipment is typically determined to be more expensive and less dependable than ground improvement. Excavation through peat can be especially problematic. Peat materials rapidly compress when earth pressures exceed preconsolidation stresses. Backfill materials provide a horizontal stress on the trench wall which can exceed the bearing capacity of peat. As the peat compresses, the trench becomes wider, and slurry levels drop and trench stability can rapidly deteriorate. If the peat is the closure layer, a shallow key is recommended. If peat is present on the trench wall, preconsolidation with surcharge is recommended. Bottom preparation and Backfill Placement Trench wall stability is a temporary condition which must be controlled by proper design and construction of work platforms and slurry features which influence ground support. Backfill materials and intimate contact of the backfill with the closure layer are permanent conditions which are the end goal of the work. The most common reason slurry trenches fail to provide working barriers is improper bottom closure. Either the closure layer is not engaged, or the backfill is not in intimate contact with the closure layer. This can result from construction problems associated with sidewall collapse described above, slurry performance and/or degradation, backfill placement methods, and failure to maintain the trench bottom clear of sediment prior to placing backfill."

Jan 1, 2006

By Mary Ellen Bruce

Let me first address the issue of the wet grab samples. The wet grab samples that were attempted to take on the Central Artery were hindered by the fact that the way the mixing was being done was only by injecting grout on the way out, during withdrawal of the mixing tools. They would auger down to the required depth (usually with some water being injected), which took anywhere from 45 minutes to an hour, and then when coming out, the grout would be injected with grout. That was leaving a column of grout in the center where the shaft had been (i.e. inside of the blades of the mixing tools), which would end up being something like a foot in diameter because the pipe that was used for the drill shaft was a foot in diameter. So we had 10 inches to a foot of almost pure grout in the middle of our column and then we had 2 feet on either side that was mixed soil cement. So when they went down with the wet grab sampler not knowing where that was in the column sometimes they/we were getting strengths of 1500 psi, and sometimes they/we were getting strength of 500 psi or 100 psi. So what was it that we were taking into the wet grab sampler? In those cases you don't really know, but it wasn't representative of the core samples we were taking. We were purposely not coring in the center because we knew that was going to be high cement content, almost pure grout. So the issue of wet grab sampling particularly on this project, the Central Artery Project, was that we didn't really know what we were sampling. What becomes an issue with wet grab sampling in other projects is that you have to have another device (machine) in most cases, a cherry picker crane or something similar that can raise and lower with a beam that is used to forces the sampler down into the freshly mixed soil-cement. And regarding economics, is it more economical to have that crane standing by with its operator or to have a drill rig to come along later and do the coring and take the material out that's fairly identical to what you're finding in situ? The complaint of micro-fracturing in the core samples as you're taking the cores was raised by Seiko as causing large strength reductions. But, if you're doing it carefully, then I don't think that's much of an issue anymore, on research basis perhaps but not on a practical level.

Feb 10, 2003

By Jim Bruce, Peggy Hagerty Duffy, Mary Ellen Large, Allen Cadden

"Over the past 40 years, Deep Foundations Institute (DFI) has executed its mission “to bring together multi-disciplined individuals and organizations to find common ground and create a shared vision and consensus voice for continual advancement in the deep foundations industry”. Like DFI, micropile technology began a significant growth path in the mid-1980s. This paper highlights how DFI’s mission was executed in the deployment and expansion of micropile technology.INTRODUCTIONMicropiles are small diameter foundation elements constructed using specialty drilling and grouting methods. Micropiles have evolved since their introduction into the North American market in the 1970s from being lightly loaded (less than 30 kips) elements used primarily for remedial applications, to today’s high-capacity, often hybridized foundation systems, for both remedial and new-build projects. Micropiles now occupy a substantial market segment in North America.For 40 years, DFI has aimed to be the forum for discussion of all issues related to deep foundations design and construction. DFI now supports 21 technical committees and working groups on all deep foundations technologies and has expanded to include regional chapters in Europe, India and the Middle East.Several key steps are required for the successful execution of DFI’s mission, including identifying a need, engaging dedicated and knowledgeable people, developing effective vehicles and resources for information sharing, cultivating stakeholder contributions and advancements, stimulating influence/impact on deep foundations market, and expanding approaches to continue progress. Pile drivers in New York City (the original organizers of DFI) positively affected their market using these same steps: they recognized a specific need, gathered the people who could affect change, convened a discussion forum (which is common today, but was innovative at the time), defined tasks to address the issues, and influenced their market by improving means, methods and owner perception of their services. These forward thinking, proactive members created a mechanism for communication among all related parties that would advance the profession by improving safety, quality and value of pile driving construction.Micropile technology has evolved in the United States and around the world for the past four decades. The accumulated efforts of DFI and other, similar organizations such as The International Association of Foundation Drilling (ADSC) have contributed to this evolution. The advancement of the micropile industry – and consequently the micropile market – has been intimately tied to the execution of the mission of DFI."

Jan 1, 2017

By J. P. Powers

Methods for dewatering and the control of ground water for construction and mining are discussed, including open pumping; predrainage with deep wells, wellpoints or other systems; cutoff or exclusion of water by steel sheet piling, slurry concrete walls and slurry trenching, grouting, ground freezing, compressed air, slurry shields and earth pressure balance shields. Criteria are given for the selection among the methods for a given project. Unwanted side effects of dewatering are listed, with procedures for evaluating and avoiding them, by cutoff or artificial recharge.

Jan 1, 2010

By M. Nomura

This paper describes the results and field measurements of two long-term observation tests and two short-term loading tests to confirm the effectiveness of NF piles in reducing negative skin friction. All the test piles were equipped with strain gauges, allowing measurement of the compressive axial forces in the piles. These test results prove that NF piles are effective in reducing the negative skin friction to an insignificant value. Some examples of the design procedures used in Hong Kong and Japan are also presented.

Jan 1, 2010

By D. Y. Peng

A Large Sub-structure with open top of S.Y.P. float line requires a 90m x 50m in plan and 13m-deep excavation in soft soil, Shanghai. The geological conditions in site are rather severe. The technology specifies that no permanent braces nor partition walls are allowed to be constructed inside. After a series of discussions the scheme of semi-gravity type cellular D-walling without any braces or earth anchors is finally adopted and successfully executed by SFEC. This paper deals with the technical problems in the design, construction and in-situ monitoring we met with in this difficult project.

Jan 1, 2010

By D. J. Ketkar

It is a frequent experience to find that the Sub-surface Investigation (S.I.) data is either inadequate or misleading. However, such cases are rarely reported. Nonetheless, the projects suffer on-account of delays, cost-over-runs, disputes and/or compromise of the safety norms. Many times S.I. is considered unnecessary or is carried out as a ritual, mainly due to (i) non-availability of good S.I. agencies, or (ii) absence of Geotechnical consultant, or (iii) shortage of time. Importance of S.I. cannot be over emphasised. Yet the profession is in a state of confusion - mainly because of lack of competent professional agencies and of well-defined roles/responsibilities of the concerned parties. In this paper, some suggestions are made to get better returns from the S.I. activity.

Jan 1, 1996

By L. Z. Xie

The results of the experimental study on the static behavior of single piles subjected to repeated and reciprocating axial loadings are recommended in this paper. Tests of four full-scale single piles of two different lengths under repeated loading and those under reciprocating loading have been conducted using the slow maintained load test method. All the eight piles were instrumented with strain gages located along the shafts. The study showed that for repeated loads below a certain critical value the total displacement of the pile top approached gradually a constant value. However, any repeated load greater than the critical value resulted a residual displacement per cycle, and that the reciprocating load capacity of a pile was dependent on the ultimate bearing capacity of the pile in tension and both were in the direct ratio.

Jan 1, 2010

By P. Davies

The Hillside Smelter presently under construction at Richards Bay, Republic of South Africa, will be, on completion, the fifth largest aluminium smelter in the world. The site selected for this plant is underlain by sandy soils of variable density to depths of 30m or greater. In order to firmly establish pile founding depths required for alternative pile types in the variable subsurface conditions prevailing across the site, a pre-construction test piling programme was conducted incorporating piles instrumented with resistance strain gauges. The results allowed analysis of the relative contributions of end-bearing and shaft friction to the overall bearing capacity of each pile type and permitted comparison with the predictions of conventional static bearing capacity analyses. Conformance with acceptance criteria in respect of allowable pile head movements for single piles was also examined.

Jan 1, 1996

By Hajialilue Bonab M.

The soil-pile interaction under lateral impact loads is not yet completely well known. Many tests on single piles under static lateral loads in centrifuge have been performed and P-y curves have been determined at different levels of the pile in soil. Following these static tests on piles, a large program is undertaken with the same piles submitted to impact loads. The pile equipped with various pile caps has been impacted under variable amplitudes of shock. The behavior of the pile under different impacts was studied and dynamic parameters of the soil-pile system have been determined. Many cases of loading constituting various load histories have been analyzed. They are resulting from parametric centrifuge tests run out, on the one hand with constant and cumulative impacts and on the other hand, variable and cumulative ones. The Influence of each type of loading was studied. Using a finite element method, a non-linear pile-soil system was conceived and a transient dynamic analysis have been performed. The results of the non-linear analysis and experimental data were compared giving a good agreement.

Jan 1, 2002

By Ali Bouafia

Five full-scale horizontal loading tests of piles carried out by the LCPC in France are interpreted in order to analyse P-Y load-transfer curves. The experimental piles are either bored or jacked into quite homogenous sandy soils and instrumented by strain gauges for measuring bending moments along the pile. Successive differentiation and integration of bending moment profiles have led to derive respectively lateral soil reaction and displacements then to construct the load-transfer P-Y curves. The initial horizontal lateral reaction modulus was derived from these curves and shows linear variation with depth in accordance with Gibson soils profiles. P-Y curves are validated by back-computation of the pile on the basis de these curves and the horizontal reaction modulus was compared to the recommendations frequently used in pile design practice.

Jan 1, 2002

By Barry C. Roth

A Real Time Automated Remote Reading Electrolytic Tilt Monitoring System was effectively deployed for monitoring an existing five story brick building during underpinning, shoring and excavation operations for a directly adjacent thirty-foot deep excavation. The monitoring system was comprised of four sets of uniaxial electrolytic tilt meters connected to a Campbell datalogger with multiplexer, cellular modem and solar power. The excavation was for the foundation and underground parking as part of a new 55 story tower complex. Challenges to the contractors and to our monitoring personnel which were addressed included a tight urban site contemplating property line to property line new construction with directly adjacent old existing buildings, buried concrete foundations from former site use, cohesionless pervious sandy soils and high groundwater. Highly variable and diurnal ambient temperature regimes due to adjacent building shadows required careful corroboration and application of temperature corrections to the raw data. Earth tides were suspected on a very small scale and investigated by correlation between the data and the local sinusoidal tidal ephemera. Incidental inadvertent contractor interference with the instruments during underpinning due to site constraints was readily detected.

Jan 1, 2007