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By Jeff Wilkinson, Brandon Walter

"A&N Electrical Cooperative provides electrical service to the counties of Accomack and Northampton along Virginia’s Eastern Shore and to Smith Island in Somerset County, Md.A&N recently worked to improve the efficiency of power distribution to a small island community and marina on Tangier Island in the Chesapeake Bay. This improvement consisted of upgrading the existing distribution substation with a new 25 kV 2-bay box distribution structure. Earth Contact Products (ECP) collaborated with PowerServices, Inc. (PSI) to design and install a helical foundation support system as part of the substation upgrade. Feasibility EvaluationThroughout the design process, A&Nworked with its partners PSI (design) andT&D Solutions (installation) to identifycost-effective alternatives. Foundationsystems considered included cast-in-placereinforced concrete caissons, precastconcrete foundations, driven steel piles and helical piles. In evaluating all of theoptions, the greatest concern was gettingthe material onto the island, followedclosely by the availability of the equipmentto install the foundations. Clearly, cost,more specifically the installed cost, was asignificant consideration and decisionfactor throughout the process.There were several limiting factors that had to be considered during the design process, the most significant of which was that all of the material had to be barged to the site. With traditional reinforced concrete deep foundations in mind, the cost for installing these piles was projected to be nearly $2,000/cu yd ($262/cu m) of installed concrete. Given that approximately 5 to 6 cu yd (3.8 to 4.6 cu m) of concrete would be required for this structure, the cost was significantly high for this project. What’s more, because the components of the concrete mix would have to be barged and then hand mixed on site, there was concern regarding both the time required to complete the piles and the quality of the installed concrete. For the driven pile alternative, the availability, or lack thereof, of equipment and material cost resulted in a total cost estimate that was more expensive than that of the concrete piling alternative. The high material cost for the piles, which was more than double than the cost of concrete, was due to the number and size of piles needed to resist the overturning moment. Ultimately, the team selected the helical pile alternative. The decision to a use helical pile foundation system was based on many factors, not the least of which was the remote location of the project site and the difficulties associated with getting material, equipment and construction personnel to the project site."

Jan 1, 2017

By Willie M. NeSmith

The use of drilled (screwed) displacement piles is an emerging sector of the United States deep foundation industry. During installation of these systems, a Ko to Kp environment is created in the materials surrounding the pile immediately prior to casting, and this condition results in increased shaft and toe resistance in soils where displacement leads to densification. Current continuous flight auger and drilled shaft design methodologies in the United States assume a Ko to Ka condition in the vicinity of the pile, and are thus an inappropriate starting point for static capacity analysis of drilled displacement piles. This paper examines constructability issues, and the sensitivity of performance to installation, and offers an empirical design methodology for drilled displacement piles. The proposed design process has been based on evaluation of 40 load tests, primarily in granular materials, and in a variety of geologic settings, and includes modification for soil types within the coarse-grained range.

Jan 1, 2002

By Hitoshi Ogura, Koichi Kobayashi, Sadao Yabuuchi

"In Japan, most pile foundations using pre-cast concrete piles are installed by the bored pre-cast piling method, wherein pre-cast piles are installed in holes that have been excavated beforehand and filled with cement milk (term used for cement water slurry in Japan). The bored pre-cast piling method with enlarged base, in which the portion near the toe is enlarged during boring operation, is widely used because of the cost benefits and the increased vertical bearing capacity that this method offers.The EX MEGATOP method, further developed as an improved bored pre-cast piling method with enlarged base, is reported here. The features of this method are: (1) High vertical bearing capacity; (2) High degree of freedom in design; (3) Excellent workability; and (4) Friendly to the environment. In particular, high vertical bearing capacity can be obtained using nodular piles and by enlarging the area at the pile toe and shaft. This method can gave a vertical bearing capacity coefficient at the toe of a=430, more than twice the corresponding value of a = 200 of a conventional bored pre-cast pile. Moreover, the shaft resistance can be several times larger than that of a conventional bored pre-cast pile. This report gives an overview of the EX MEGATOP method, evaluation of vertical bearing capacity, and examples of application of the method.1.lntroductionMost pile foundations in Japan are installed by the bored pre-cast piling method, that is, in holes that have been excavated beforehand and filled with cement water slurry, referred to as 'cement milk'. The ""bored pre-cast piling method with enlarged base"" is frequently used. In this method an enlarged excavation is used near the pile toe to increase the vertical bearing capacity.The EX MEGATOP method is a variation of the bored pre-cast piling method. Its features include the use of nodular piles and a long, enlarged excavation. The vertical bearing capacity of the EX MEGATOP method is described in this report."

Jan 1, 2005

By C. O. Riggs

Geotechnical exploration in North America, in particular, exploration for deep foundations analyses, is currently and generally performed following the most basic sampling and insitu testing methods and techniques. Some would surely say that the state-of-practice severely lags the state-of-the-art. Probably more than 90% of all deep foundations, both driven piles and drilled piers, installed in North America are initially analyzed and designed, i. e. geotechnically, on the basis of either the soil penetration resistance obtained by performing the "Standard Penetration Test" (SPT), or from laboratory shear tests performed on samples obtained using 76-mm (3-in.) nominal diameter, thin wall, "Shelby tube" samplers. The use of design data obtained with other exploration methods and devices, such as bore hole pressure meters, flat plate dilatometers, even cone penetrometers, occur on the fringes of practice and often in conjunction with the use of the two simpler methods of analysis. This basic approach probably represents an attempt of the profession to use, as much as possible, common, easily understood and easily communicated procedures in all geologic environments. The characteristics of drill rigs with the required drilling and samplng tools vary somewhat from region to region in North America according to the physiography of the area of use, the types of exploration data required on a day-to-day basis, the philosophy of the engineers and geologists that use the exploration data and the financial resources of the drill rig owner. The physical capability of the exploration drill rig used on a project can have a significant effect on the quality of samples or insitu tests. The physical configuration and the quality of the drill and the drilling, sampling and testing tools not only provide the mechanical capability to obtain data but affect the attitude of the field exploration crew and the quality of work. This complete presentation is taken, for the most part, from a book in preparation for publication: "Geotechnical Exploration and Site Characterization" by C. Riggs, A. Hatheway and N. Schmidt. The book is scheduled for completion during 1987.

Jan 1, 2010

By Adel Hanna

Earth pressure acting on piles driven in sand is playing a major role in estimating pile capacity. In literature, researchers entertained simplifying assumptions in estimating the earth pressure acting on the pile's shaft, ignoring the effects of pile installation and pile size. Empirical formulae were introduced based on laboratory or field test results, where major discrepancies can be found among these formulae. In this paper, the theory of cavity expansion and the finite element technique will be used to establish the effects of pile installation technique and pile's diameter on the earth pressure acting on the pile's shaft and accordingly on the values of the existing coefficient of passive earth pressure and overconsolidated ratio. It is of interest to note that pile driven technique and pile's diameter have significant increase on the earth pressure acting on the pile's shaft and accordingly on the overconsolidation ratio in case of loose or medium sands, while they may cause crushing and dilation in case of dense sand. Keywords: Single pile, Cavity expansion, Cohesionless soil, Driven piles, Numerical modelling, Finite element technique, Earth pressure.

Jan 1, 2003

By Michael W. Oakland

Weidlinger Associates was retained to evaluate the foundations supporting ten oil storage tanks at a tank farm on the east coast. The tanks were constructed over the site of a landfill which was underlain by deep organic deposits. The tanks were typically 48 ft. in height and ranged in diameter from 60 to 150 ft. The tanks were supported on both wood and steel pipe piles. After more than 35 years of service, an inspection found that up to 25 percent of the piles had separated from the mat foundation. The operations at the facility were temporarily stopped pending further investigation. Weidlinger developed comprehensive finite element models of the foundations for each tank and used random generators to conduct Monte Carlo simulations the range of scenarios of detached support conditions since it was not possible to survey all the piles below the tanks. To confirm the modeled performance and verify stability, each tank was also load tested using water with electronic instrumentation installed by Geo-Instruments. The instrumentation provided real time, web based monitoring during testing in areas which would otherwise be inaccessible during loading. Through inspection, complex modeling and sophisticated load testing, Weidlinger and Geo-Instruments were able to show that all but one of the tanks could safely be put back into service. This paper details the analysis, Monte Carlo simulations and instrumentation and load testing performed for this unique project.

Jan 1, 2009

By Ed Kase

Cross-hole sonic logging (CSL) has become the universal standard, nondestructive testing (NDT) method used in evaluating the integrity of foundation structures to maintain quality assurance and quality control (QA/QC) of transportation facilities and infrastructures. Tomography, based on three-dimensional cross-hole sonic logging data processing technology, offers an improvement over the techniques currently used to characterize the interior structure of drilled shafts. The underlying concept for seismic tomography is based on the principle that acoustic waves propagate at different velocities through different types of material or the same material with different physical properties. Three-dimensional velocity tomographic images provide greater detail of the interior structure, making defects easier to classify with respect to size and location within the foundation structure. By accurately classifying these defects, an engineer has the information necessary to accurately assess whether these structures meet the applicable design requirements, allowing them to repair or replace inadequate foundation structures. The end result is that the foundation structures will meet the safety and service life requirements for their project. This paper will present applications of seismic tomography, illustrating how seismic imaging can provide accurate information regarding the integrity of foundation structures.

Jan 1, 2003

By G. Ranjan

The designers and the practicing engineers have started using latest and cost effective techniques of ground improvements which utilise the weak and poor sub-soil deposits efficiently for the civil engineering construction. In the present investigation, a new concept of 'skirted granular piles' has been advocated. An effective method of construction of granular piles as an economical alternative to vibroflot, and the skirt has been developed. The construction technique is based on indigeneous know how which effectively utilises the man-power technology avoiding import of costly equipment suiting to the developing countries. Full scale insitu tests have been carried out at four sites, having different soil conditions, on virgin weak sub-soil, and improved ground by casting plain and skirted granular piles. Effectiveness of different types of skirt has been demonstrated through insitu tests. A simple analytical approach has been proposed to predict the ultimate pile capacity. The predicted values of ultimate capacity have been found to demonstrate a good correspondance. Granular pile behaviour in terms of pile depth, diameter, spacing and stress deformation characteristics of the improved ground have been discussed. A significant improvement in ultimate capacity in improved ground has been noted. This is further augmented when granular pile group is skirted.

Jan 1, 2010

By G. W. Plant

This paper describes the design philosophy and construction details of piles between 25m and 32m deep to support 160m high and 110m base diameter cooling rowers for a major power station. It is sited on deep expansive soil where a vast plantation of Eucalypts had been felled. The depressed water table is expected to rise, leading to swell of the soil and uplift forces on the piles. These forces, combined with the complex loading from the cooling towers, led to design tensile loads up to 20MN (2 000 tons) per pile. When competent stable material was present hand excavated underreams 3m in diameter were constructed for the piles sup-porting the shells. However, in some areas it was not possible to form an effective underream and an innovative solution was sought. This comprised unstressed dowels in the underlying sandstone which were formed by percussion drilling through void formers cast into the piles.

Jan 1, 2010

By Matthew Janes

The RC Harris Filtration Plant, which treats the majority of the fresh water for over 2.5 million Torontonians, is a Canadian Architectural Heritage site demonstrating a classic example of Art Deco Architecture. The facility is undergoing an expansion to install an underground sludge treatment capability. Perched atop a bluff on the North shore of Lake Ontario the structure enjoys a commanding presence on the Lake Ontario shoreline. A series of underground tanks were proposed for the hillside below the structure, which when covered would preserve the building?s architectural presence. However, the plan required two, stepped excavations 12 m and 10m deep into compact, wet sands over stiff clays and clayey silts. Concerns regarding the original structure influenced designers to set the lateral deflection limit for the front footing of the existing structure at 4 mm, (0.03% excavation depth). The design-build team indicated at the time of tender that the movement criteria was unattainable using the tender design. Analysis indicated installation effects and overall elastic movement of the soil mass beneath the building would result in movements of 7 to 9 mm at the structure. Through extensive FLAC analysis and a novel construction geometry the design-build team crafted an alternative that produced significant savings over the original concept. Based upon the analysis the design-build team negotiated a new deflection criteria dictating a maximum of 2.0 mm of movement across the critical expansion joint between the Filter Building front footing and the tank slab beyond. The contractor invested in additional pre tender soils investigation to support the refined design process. The FLAC analyses indicated the Filter Building movements would be elastic and distributed up to 50 m back beneath the front footing of the structure. An extensive precision monitoring program proved construction related movements of 6 to 10 mm horizontal at the front footing. Extensometers placed at two locations over the critical interior tank expansion joint showed no measurable movements. The overall monitoring program, including inclinometers, tilt meters, tie back extensometers (smart cables) and tie back load cells indicated a good match between recorded movements and loads and those predicted by FLAC Analysis.

Jan 1, 2006

By E. W. Raabe

The paper discusses the increasing role of specialist grouting techniques to form water seals or cut-offs for deep basement construction. Raabe and Toth discuss the various grouting methods available for sealing applications and then concentrate on the use of Soilcrete Jet Grouting, a system particularly well suited to ground water control. The Soilcrete processes, suitable soil types and quality control methods are fully described, particularly with regard to the formation of cut-off walls and sealing slabs to prevent the progress of ground water or leachates. The authors have included case histories detailing their experience on designing and installing Soilcrete seals for various projects in West Germany. These include an underground rail project in Dortmund and a discharge structure for the Alz Canal at Burghausen.

Jan 1, 1989

By Abolfazl Eslami, Fatemeh Valikhah

"Complexity in soil-foundation interaction and subsoil nonlinear behavior cause difficulties and uncertainties in evaluating the actual values of foundation design factors such as settlement. The acquired continuous records of Cone Penetration Test (CPT) can be used to determine the soil profile and characteristics those are applicable in the geotechnical design. In this paper, it has been attempted to present a new non-linear stress-strain approach to estimate the foundations settlement by using CPT data in the form of soil behavior classification charts. This new approach is based on Janbu method (1960s and also 1998). Instead of using fixed and constant values for stress exponent (j) and modulus number (m), continuous coefficient variations can be used. The proposed approach also can be used as a new method to predict pile group settlement. A data bank has been compiled containing twenty-two practical case histories to investigate the accuracy of the predictions made by the proposed and available common methods. The comparisons indicate that the proposed approach is relatively able to predict the settlement close to their real values. Therefore, it can be considered as an alternative method based on valuable CPT data and nonlinear stress-strain approach for foundations and pile groups settlement estimation.INTRODUCTIONComplexity in soil behaviour for settlement analysis is the result of non-linear and time dependent stressstrain behaviour of soils, their elasto-plastic performance under loading and unloading situation and also effects of stress history (Holtz et al., 2011; Fellenius, 2015). Hence, many relations and equations have been proposed to predict foundation settlement, where most of them are based on typical different parameters such as soil stiffness (E), foundation width (B), contact pressure (q) and pressure developing in depth (Janbu, 1967 also 1998; Briaud and Gibbens, 1999; Uzielli and Mayne, 2012).The Janbu approach for settlement estimation, proposed by Janbu in the early 1960s, combines the basic principles of linear and non-linear stress-strain behaviour of material. The method is applied to all types of soils. The relation between stress and strain is a function of two non-dimensional parameters which are unique for any soil: a stress exponent, “j”, and a modulus number, “m”. The Janbu relations are derived from the definition of tangent modulus by the following expression:"

Jan 1, 2017

By Roderic A. Ellman

The new Woodrow Wilson Bridge (WWB) will replace the existing bridge over the Potomac River to connect Alexandria, Virginia to Prince Georges County, Maryland. The new WWB will extend approximately 1.1 miles across the river, with a 367-ft long bascule span in the main river channel where the water depth is about 36 ft. The bridge is primarily comprised of fixed spans in relatively shallow water and a bascule span over the navigation channel. The subsurface soil profile was quite variable along the bridge alignment. In Virginia, there was fill over soft Alluvial deposits underlain by dense Terrace deposits, as well as remnant foundations from a former ship yard. At the bascule span, there was up to 50 ft of a soft organic silty clay layer underlain by a deep deposit of stiff Cretaceous clay. Along the Maryland approach, there were Alluvial deposits over dense Terrace deposits over stiff Cretaceous clays and dense Cretaceous sands. The variation in subsurface conditions led to the selection of alternative deep foundations that suited the specific conditions and were based on the design phase testing program, from which ultimate design capacities were determined. During construction, there were instances of unexpected pile performance, notably different than that experienced during the design phase testing, requiring changes to the contract installation criteria and re-design. This paper will present the types of deep foundations used for the project, the performance criteria assumed during the design, the measured performance and difficulties encountered during construction, and the resulting remedial actions, i.e., changes to contract installation criteria and/or re-design due to the unanticipated field conditions.

Jan 1, 2009

By Theodore W. Vogelpohl

Augered cast-in-place piles have proven to be effective, adaptable and economical for projects throughout the Ohio River Valley. Specifically, they have been used extensively for high-rise structures, sports stadia and large commercial developments along the Cincinnati, Ohio and Northern Kentucky Riverfront. They have been designed and utilized as relatively short toe resistance piles in bedrock, and intermediate to long toe and shaft resistance piles in granular outwash deposits above the bedrock. They have been designed for large axial compression loads as well as moderate axial tension loads and lateral loads. This paper presents a few load test results that demonstrate the range of capabilities of augered cast-in-place piles in the variable subsurface profile along the Cincinnati, Ohio/Northern Kentucky Riverfront.

Jan 1, 2005

By Les R. Chernauskas

Driven pipe piles are commonly used for near and offshore structures due to their omni-directional bending resistance, large surface area, and ease of installation. However, these piles typically cannot be driven deep enough to develop significant and sustained uplift capacity, and in some cases do not generate enough end-bearing resistance before being overstressed during driving. When driven closed-ended, their relatively light weight to cross-sectional ratio, and when driven open-ended their tendency to prematurely plug, are some installation short comings. Spin Fin® piles are traditional pipe piles fitted with flat, steel plates (?fins?) attached at a slight angle over the lower few feet of the pipe. Their design development dates back several decades for projects associated with harsh, limited weather window, offshore Alaskan oil field work. These projects required a pile type that could generate high and sustained capacity in both compression and tension, at relatively shallow depth. During pile driving, a relatively short, high capacity pile translates into more rapid installations with smaller and more efficient equipment. In this type of environment, where pile capacities are large, cyclic loading is typical, and relatively high pile movement is tolerable, the Spin Fin® pile is a superior solution. This paper describes the experience of using Spin Fin® piles on several recently completed Massachusetts Steam Ship Authority projects.

Jan 1, 2011

By Michael T. Lambert

The purpose of the this paper is to demonstrate the benefits of using additional instrumentation during load tests of auger-cast-in-place piles. Traditionally, only load and butt displacement are determined during load tests. The results from and methods used to instrument 15 auger-cast-in-place (ACEP) piles as part of six projects are included herein. By instrumenting the piles, the distribution of load along the pile length and load transfer can be determined, allowing the pile capacity to be adjusted or the length/diameter of the pile to be adjusted for the a given required load. The majority of the piles tested were designed as end bearing piles on either shale or limestone bedrock. No discussion of Geotechnical Instrumentation can be started without acknowledgement of the "Red Book." The actual title of the book is Geotechnical Instrumentation for Monitoring Field Performance, by Mr. John Dunnicliff, John Wiley and Sons, 1993. Anyone undertaking an instrumentation program should thoroughly review the Red Book, paying particular attention to Chapters 3 and 4. Instrumentation should not be done just because it can be done. There must be an unanswered question or questions that can be answered with measured data before instrumentation should be considered.

Jan 1, 2000

By Jack Hayes

The design and construction of deep foundations involve many uncertainties. For the designer there are uncertainties regarding soil and ground water variability, regarding sampling and lab testing, regarding analytical techniques and regarding construction technique. The latter being the uncertainty over which the engineer has least control and which may have the greatest impact on capacity. Foundations with a high design factor of uncertainty can be very costly. Foundations designed with a high factor of uncertainty may have a low factor of safety, which can be even more costly.

Jan 1, 2000

By Alan Alhadeff

Why is mediation being hailed as the wave of the future? The high cost of putting on a trial, over-crowded court calendars and long trial delays have resulted in what prominent attorneys and leading jurists are calling a litigation crisis. In no segment of the legal world are these pressures greater felt than in the trial of the serious construction case. Furthermore, the siege mentality of both the plaintiff and defense bar often leads to a reluctance by either side to make the first reasonable offer for fear of showing weakness. Attorneys operating in the serious construction case arena express concerns that there exist insufficient opportunities for the parties to meet, tell their stories, and negotiate settlement prior to the eve of trial. Mediation, by opening lines of effective communication and encouraging meaningful settlement negotiation, has proven to be a very effective antidote to the litigation crisis.

Jan 1, 1990

By Georg Breitsprecher

The technique of Stabilising Columns (product names are for example "Stabilisierungssaulen" (STS) or "Coplan Stabilisierungs-verfahren" (CSV)) is gradually becoming well accepted for ground improvement. The installation, dimensioning and quality control are standardized by DGGT (German Association for Geotechnique), working committee 2.8, of which until now only part one exists for dry columns. This paper describes the installation and testing of stabilising columns for a ground improvement project. To achieve comparable results in testing both ready mixed concrete and dry binder had been used for production.

Jan 1, 2006

By Andrzej Tejchman

A method of improvement of a subsoil under bored pile base by injection is presented. The method employs a special chamber attached to the reinforcement at the bottom of the drilled borehole. The chamber is made of semi-permeable textile bag. The injection entered under high pressure into the bag, causes prestressing of subsoil under the pile base. The results of load tests of piles improved in this manner have shown a substantial increase of their capacity together with simultaneous reduction of settlements. This technology has been implemented for four constructions such as trestle bridges in Gdynia and Warszawa and the bridges in Szczecin and Gdansk. The injection effects are shown based on the load test results.

Jan 1, 2002