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By Tony Mazzo

It has often been said by consulting engineers that foundation contractors are in the business of taking risks. One would agree that the mere fact a foundation project can be budgeted, planned, engineered and executed solely on the reliability of eight test borings made at a proposed site having an area of approximately 19,000 square feet, is a risky proposition, in and of itself. Now imagine that this site is actually one half of a city block located in an urban setting in an old, congested, historical neighborhood, surrounded by narrow city streets and historic landmark buildings. And suppose that the required depth of excavation for the construction of the new building on this site is approximately 35 feet and the natural groundwater table is at a depth below existing grade of only 25 feet. Given the difficult site conditions outlined above, one could certainly add the words "challenging" and "complicated" to the inherent word "risky" when describing the construction techniques involved to undertake a foundation project of this magnitude. This case study will discuss in detail how the excavation, sheeting, dewatering and underpinning work was accomplished as well as the problems overcome along the way.

Jan 1, 2003

By Sudip Basack

"The topic of pile foundation subjected to lateral cyclic load is an age-old problem confronted by Geotechnical Engineers. The environment prevalent in ocean and shorelines necessitates the piles supporting offshore and onshore structures to be designed accounting for the lateral cyclic loading resulting from the effects of sea waves. The quasi-static nature of this type of loading induces remarkable deterioration in the interactive performance of the soil-pile system. This can be manifested as progressive loss in pile capacity associated with increased pile head deflection. The work reported herein is aimed towards conducting rigorous theoretical analysis using finite difference technique so as to analyze the lateral cyclic loading response of a single, vertical pile embedded in cohesionless soil. The theoretical results are compared with the experimental results and reasonably good agreement is noted. This paper presents a brief description of the theoretical analysis carried out with some typical results and the relevant conclusions drawn therefrom. 1. INTRODUCTIONOffshore structures, namely, quay & harbour structures, jetties, tension leg platforms, oil drilling platforms, etc. are largely supported on pile foundations. Apart from usual loads from superstructures, these piles are subjected to continuous action of wave loading. This type of lateral loading is quasi-static cyclic in nature which results in considerable degradation in the interactive performance of the pile-soil system initiating progressive reduction in pile capacity associated with increased pile-soil stiffness. This may ultimately lead to disastrous consequences.Amongst limited research works in this field, the major contributions are made by Matlock (1970), Idriss et al (1978), Poulos (1982), Vucetic et al (1988), Long & Venneste (1994) and Basack (1999). A brief review of these works indicates that the degradation of the pile-soil system under lateral cyclic loading mainly depends upon the following parameters: number of cycles, frequency (cycles per unit time), cyclic load level (ratio of cyclic load amplitude to the lateral static ultimate pile capacity, in case of loadcontrolled mode) and cyclic displacement level (ratio of cyclic displacement amplitude applied at the pile head to the external pile diameter, in case of displacement-controlled mode). As pointed out by Poulos (1981 & 1982), the degradation is mainly due to: 1) partial to zero dissipation of excess pore water pressure generated during cyclic loading in progress, 2) destruction of interparticle bond with particle realignment and 3) rearrangement and gradual accumulation of permanent plastic deformation around pile"

Jan 1, 2005

By Shamsher Prakash

Equivalent spring constants for analysis of footings is a function of Young's modulus of pile material (Ep), shear modulus of soil (Gs), and geometry of the footing and/or piles. Shear modulus is strongly strain dependent in soils. Therefore, the spring constants are strain dependent, which is acceptable to the Geotechnical engineers. However, structural engineers prefer to use spring constants as a function of displacement, rather than strain. In order to develop these relationships, appropriate relationships between strain and displacement are needed. Also, modulus degradation with strain needs be built into these relationships. Description of spring constants kx , ky, and kz in x, y, and z direction and k?, k?, k?, about x, y, and z directions are relatively simple. However, description of kxø and ky?, the cross-coupling spring constants depend on 2 - components of displacement and rotation. Thus, there are 8 spring constants and likewise there are 8 damping constants. Approximate strain-displacement relationships on which displacement dependant k's and c's are based are presented with appropriate equations, and a numerical example is included illustrating k's and c's as functions of displacement.

Jan 1, 2002

By Dennis Wrixon

It was a little bit exceeded. The decision was the uniform settlement is measured at each one corner and the highest one corner is the important one. And in addition there is a differential settlement of 2.1 mm allowed. So we reached about 7.8 or 7.9 mm with the highest corner and in addition 2.1 so it was a little too much. But behind there is a very difficult calculation of the authorities where all of the displacements are combined together and there are of course some more factors of safety in these settlements.

Feb 10, 2003

By Dennis Nottingham

"Increased interest in seismic soil liquefaction and preventative soil stabilization sets the stage for improved deep compaction methods using pile driving techniques. In 1971, L.B. Foster Company personnel patented a method of deep compaction using a vibratory pile hammer and pile probe. The technique had some success, but did not produce consistent results and thus found its way to obscurity. Other patents attempted to modify the technique by various probe modifications, but again without measurable improvement from a practical point of view. Solutions to economical deep compaction up to 100-foot depths particularly in saturated granular soils would have a great impact on the construction industry and new bulkhead structures being developed, thus PND was prompted into related research and development. The advent of higher horsepower vibratory hammers, coupled with PND engineers’ experiments, observations and measurements, led to an “H” pile probe design which has produced measured soil density improvements up to 250% using SPT “N60” values as a measure. Case histories of two projects involving extensive SPT soil sampling comparative measurements will be discussed along with findings that led to the compaction success. Applications to numerous modern “Open Cell” bulkhead projects will be presented and discussed.INTRODUCTIONNecessity often is the basis for innovation and such was the case for needed cost-effective deep soil fill compaction in Open Cell bulkheads where granular fill below water levels was often placed.Open Cell bulkheads were developed by PND Incorporated starting in 1980, for the express purpose of meeting client demands for an economical, easily constructed, extremely strong structure. Earth-filled structures historically have had a long history of problems with stability, scour and settlement.Open Cells are flexible steel sheet pile membranes supported by soil contact with embedded tail anchor walls.This concept creates an integral reinforced soil system. The result is a structure that can withstand large settlement and support a variety of very large loads. In effect, viewed from above the structure becomes a series of U-shaped horizontal membranes that require no toe embedment for stability. The Open Cell bulkhead is constructed of only three components: flat sheet piles, fabricated connector wyes and anchor piles. Compared to alternative structures, several cost savings are realized from this land based construction such as, reduced sheet pile area, greater construction tolerance, minimal pile penetration, and simplified backfilling procedures. In seismic regions or weak soils, the tail walls can be extended as required to guarantee fill mass stability."

Jan 1, 2005

By Michael J. Garlich

Steel sheet piling has a long history of use in a variety of permanent and temporary structures. Current engineering practice uses numerous publications and standards for design guidance. U.S. design guidance is fragmented, with numerous inconsistencies between design guides. To improve current U.S. design practice, the North American Steel Sheet Piling Association has initiated a project to produce a design standard that will unify design procedures and provide specification guidance for engineers and users of steel sheet piling. The wide range of uses for sheet pile structures presents a challenge in developing such a standard. Load factors or allowable stresses acceptable for a temporary retaining wall in soil may reasonably vary from those for a river cofferdam or a dockwall located in sea water. However, it is still possible to provide consistent and rational guidance for such varying uses. The standard also can address sheet pile design aspects often neglected in U.S. publications, such as vertical load capacity and resistance to loads applied parallel to the sheeting.

Jan 1, 2008

By Tsuyoshi Honda, Kazuhiro Kaneda, Masayuki Imai, Kazuo Konishi, Kunio Higashinaka

"In recent years, the demand for measures to control liquefaction of existing airport runways and harbor structures has increased. However, from the perspectives of constructability and cost, application of grid-form deep mixing walls to these types of structures requires the formation of wider grid spacing as compared with conventional designs. In this research, we focused on the extent of liquefaction and ground surface settling when grid spacing is made wider than conventional designs. We conducted centrifuge model tests, and confirmed the liquefaction suppression effect when grid-form modifications involving wide grid spacing are adopted under asphalt pavement. The tests were conducted under conditions that included changing the grid spacing and groundwater level. When the groundwater level was high, an increase in water pressure was observed, even within the grid. However, when the groundwater level was low, the increase in water pressure inside the grid was suppressed. We also found that if the generation of water pressure can be suppressed, the amount of settling due to liquefaction can also be controlled.INTRODUCTIONOne construction technique used as a countermeasure to liquefaction is grid-form deep mixing walls. Grid-form deep mixing walls are a construction technique for which improved grid-shaped wall bodies are built into the ground below the surface using a deep mixing method. This construction technique minimizes shear deformation by surrounding liquefied ground with improved wall bodies, thereby preventing liquefaction (Fig.1). With conventional designs, grid-form deep mixing walls determine the grid spacing that can deter liquefaction based on a ratio of the grid spacing L to the improved depth H (ratio = L/H). Ordinarily, designs are implemented with an L/H ratio of 0.8 or less (PWRI, 1999).In recent years, a demand for measures to control liquefaction of existing airport pavement and harbor structures has increased. However, when liquefaction countermeasures are implemented at these types of facilities and structures, the construction work must be implemented while the facilities and structures remain in service. Therefore, temporal and spatial constraints must be considered. In addition, unlike conventional liquefaction countermeasures, performance requirements are such that, even if some degree of liquefaction is allowed, the performance is acceptable as long as the amount of settlement is within a predetermined value. Therefore, if grid-form deep mixing walls are applied to these structures, grid spacing that is wider than conventional standards is desired."

Jan 1, 2015

By Craig H. Olson

"A new ship dock at a Philadelphia area refinery will be capable of docking the largest tanker to travel the Delaware River, the Stena V-MAX, which will induce significant lateral loads. The loads at the dock, a system of mooring dolphins and platforms, will be resisted by over 150 pipe piles, including some 20- and 30-in diameter, reinforced, concrete-filled pipe piles and H-piles. Construction included driving the pipe piles to the required ultimate capacity, flushing the pipe pile casing clean of overburden materials, followed by drilling rock sockets into the underlying Wissahickon Formation. The Wissahickon Formation is a complex subsurface that includes variations in depth to bedrock, rock quality, degree of weathering and the presence of very hard quartzite lenses or inclusions. Because of the problematic subsurface, the designers and client requested extensive pile dynamic analysis (PDA) testing by TRC Engineers (TRC).Before beginning, the contractor requested that TRC perform the WEAP (wave equation analysis program) to evaluate the proposed hammer (APE D30-32 open-end diesel) to drive the piles into the proposed bearing strata while maintaining allowable compression stress levels. The WEAP provided a prediction of blow counts and stresses for various ultimate capacities, and showed that for the HP14x89 piles with a required ultimate capacity of 480 kips, a blow count of at least four blows per in at a stroke of 8.0 ft was necessary.New Approachway RampThe PDA testing began at the new dock approachway ramp, parallel to the existing one. The new structure is a 300-ft-long by 21- ft-wide concrete deck supported on seven bents; each has two 24- ft-diameter steel open-ended pipe piles. Every pipe received an HP 14 x 89 x 80-ft pile that was later driven beyond the pipe pile tip to create a composite pile. The pipe piles were later cleaned of overburden materials and finally filled with concrete and rebar. At each bent, a cap was installed on top of each pair of pipe piles, and then a prefabricated concrete deck was added."

Jan 1, 2008

By Craig H. Olson

"Anew ship dock at a Philadelphia area refinery will be capable of docking the largest tanker to travel the Delaware River, the Stena V-MAX, which will induce significant lateral loads. The loads at the dock, a system of mooring dolphins and platforms, will be resisted by over 150 pipe piles, including some 20- and 30-in diameter, reinforced, concrete-filled pipe piles and H-piles. Construction included driving the pipe piles to the required ultimate capacity, flushing the pipe pile casing clean of overburden materials, followed by drilling rock sockets into the underlying Wissahickon Formation. The Wissahickon Formation is a complex subsurface that includes variations in depth to bedrock, rock quality, degree of weathering and the presence of very hard quartzite lenses or inclusions. Because of the problematic subsurface, the designers and client requested extensive pile dynamic analysis (PDA) testing by TRC Engineers (TRC).Before beginning, the contractor requested that TRC perform the WEAP (wave equation analysis program) to evaluate the proposed hammer (APE D30-32 open-end diesel) to drive the piles into the proposed bearing strata while maintaining allowable compression stress levels. The WEAP provided a prediction of blow counts and stresses for various ultimate capacities, and showed that for the HP14x89 piles with a required ultimate capacity of 480 kips, a blow count of at least four blows per in at a stroke of 8.0 ft was necessary. New Approachway RampThe PDA testing began at the new dock approach way ramp, parallel to the existing one. The new structure is a 300-ft-long by 21- ft-wide concrete deck supported on seven bents; each has two 24- ft-diameter steel open-ended pipe piles. Every pipe received an HP 14 x 89 x 80-ft pile that was later driven beyond the pipe pile tip to create a composite pile. The pipe piles were later cleaned of overburden materials and finally filled with concrete and rebar. At each bent, a cap was installed on top of each pair of pipe piles, and then a prefabricated concrete deck was added."

Jan 1, 2008

By Wu Jie Mei, Li Yao Liang, Franz-Werner Gerressen, Arthur Bi

Diaphragm walls (D-walls) are known as underground structural elements commonly used for retention systems and permanent foundation elements. In addition, they are also quite often used as deep groundwater barriers, called Cut-Off-Walls (COW). Shanghai ranks third among the most densely populated metropolises in the world. In 1990, only eight million people lived there. Today, Shanghai has about25 million inhabitants. The increasing demand to accommodate the infrastructure of growing megacities like Shanghai pushes the required depth for subway, sewage and foundation projects to the limit. Future projects will demand excavation depths of more than 100 m (328 ft) on a regular basis. Already carried out reference projects will be described and a general outlook for upcoming projects will be given. The paper also explains the installation process in general focusing on the use of trench cutter technology. INTRODUCTION D- walls are known as underground structural elements, commonly used as retention systems for excavation pits and shafts as well as permanent foundation walls or elements. It is anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm wall usage in even more difficult conditions and with increasing depth. The trench cutter is the most important tool for performing this work. The hydraulic grab, a well-known and valuable excavation tool for d-walls reaches its limits in terms of depth and when cutting rock. Therefore the trench cutter technology will be in the focus of this paper. The trench cutter itself is a reverse circulation excavation tool. It consists of a heavy steel frame with two drive gears attached to its bottom end, which rotates in opposite direction around the horizontal axis. Cutter wheels are mounted onto the drive gears. As they rotate, the soil beneath the cutter wheels is continuously broken up, removed, mixed with the bentonite slurry in the trench and moved towards the opening of the suction box of the pump? A centrifugal pump located right above the cutter wheels conveys the slurry via a hose system up to a desanding plant. There the slurry loaded with soil and rock particles is cleaned and returned into the trench.

Jan 1, 2018

By Matthew Runion, Christopher Lawler

The Aeolus – Jim Bridger Transmission Line Project is located in southern Wyoming, home to some of the largest coal seams in the world. Coal seams present unique challenges to underground construction, as they are at high risk of coal-seam fires and do not provide a reliable bearing stratum. Accurate identification of these hazards was essential for reliable design and successful construction of foundations on this project; however, environmental restrictions and other protections created short time frames to access several sites. Coupled with a firm construction deadline, this meant that a comprehensive geotechnical investigation prior to construction would not be possible. This paper presents the project as a case study, and details how an Engineer-Procure-Construct (EPC) contracting format supported by a comprehensive Quality Assurance (QA) program provided a solution to the defined challenges. It describes the initial design process using incomplete geotechnical data and explains how the developed QA program verified design assumptions and reduced geotechnical risk through early identification of geologic conditions during construction. Specific examples will be given, and industry implications will be discussed.

By Soorkty Elarabi

The aim of this paper is to discuss the impact of end bearing plate on the capacity of micropile. Preliminary studies have been made in Sudan in specific area of cohesive soil. Experimental works were carried on a number of micropiles with and without end bearing plate. Same diameters, lengths and techniques of placing cement grout are considered, there after the axial load test applied to find out the capacities of micropiles in both cases. Deduced results in each case show that the end bearing plate has no positive impact on micropile capacity.

Oct 1, 2022

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 Karl A. Higgins

In 1976, Prof. G. G. Meyerhof published a famous article in the Journal of Geotechnical Engineering titled ?Bearing Capacity and Settlement of Pile Foundations?. This article presents the authors opinions on calculating pile capacities in clays and sands, group capacities and pile settlement. A portion of the article presents correlations of shaft friction and end bearing to the Standard Penetration Test (SPT) N-value. Subsurface exploration via the Standard Penetration Test is the most widely used exploration tool in the United States, so correlations of pile capacity to N-value are significant to the practice of geotechnical engineering. Meyerhof?s SPT-N correlations are relatively simple calculations compared to other pile capacity computation methods presented in the article or found in other text books (such as the a-method, b-method, Nordlund, Vesic, Meyerhof?s semi-empirical, others) and therefore are popular amongst practicing geotechnical engineers. At the time these correlations were published by Prof. Meyerhof, utilization of dynamic testing with the Pile Driving Analyzer (PDA) was not widespread in geotechnical engineering practice. Prof. Meyerhof?s correlations appear to be based upon conventional static pile load testing of instrumented piles. Dynamic pile measurements to estimate a pile?s static capacity provides certain advantages over conventional static load testing, namely the determination of unit shaft friction values at discrete intervals along the pile, and the unit end bearing support value. The author has compiled a database of driven, displacement piles tested with dynamic methods (ref. ASTM D4945, Test Method for High-Strain Dynamic Testing of Piles). The data was collected between 2002-2010 and is comprised of displacement piles driven into coastal plain sediments in the mid-Atlantic states of Virginia, Maryland and the District of Columbia. In layered soils, dynamic testing in particularly helpful as it reveals the differences in unit shaft friction for varying soil types. One hundred ninety (190) piles are included in the database, with a corresponding 1,373 discrete shaft friction and 190 end (toe) bearing measurements. The pile type typically consisted of 12 and 14 inch square, prestressed, precast concrete piles; however, a significant number of piles were steel HP 12 or 14 inch sections. The database was sorted based upon soil type, and then correlations of shaft friction and end bearing were derived in the same or similar manner as Meyerhof?s original 1976 publication. The new correlations are compared to Meyerhof?s original values.

Jan 1, 2011

By Richard Stone, Rouzbeh Afsharhasani, Moses Karakouzian

"Caliche, a hardened sedimentary deposit of calcium carbonate that occurs worldwide, generally in arid or semiarid regions, is frequently encountered in Las Vegas, Nevada. The presence of a caliche layer in a soil profile affects the response of deep foundations to axial load. This paper studies the stiffening effect of caliche layers on the elastic settlement of a pile foundation. In order to evaluate the response in a layered soil-caliche profile, finite element analyses were performed on a typical-sized single pile and a pile group, both having constant diameter and length of the pile. The results indicate that the stiffening effect from the caliche is noteworthy, and a layer with a relative thickness of at least one pile width, regardless of its location, reduces the pile settlement for both single piles and group of piles systems by at least 50%.IntroductionThe presence of cemented materials in the soil profile influences the settlement response of foundations. One type of cemented material that can be found in arid places around the world is a sedimentary deposit of calcium carbonate called caliche. Caliche, a hardened sedimentary deposit of calcium carbonate, is common in arid and semi-arid urban areas, such as Las Vegas, Nevada (Wyman, et al. 1993).Caliche is mostly observed in lacustrine, river, and alluvial fan deposits (Jr.C.C 1970). It is also found in Central and Western Australia, the Kalahari Desert, the High Plains of the Western U.S., and the Sonoran Desert of the U.S. and Mexico.Some conditions required for the formation of caliche are that country or basement rocks must be a carbonate type, carbonate must be present in the soil zone of the area, climate regime is semi-arid to arid, there exists widespread capillary activity, and carbon dioxide (CO2) is present in the environment. As a result, caliche occurs as a product of the carbonization process (Atabey, Atabey and Kara 1998). In such areas where foundations are constructed on thin rock layers (caliche), special geotechnical design conditions should be considered, particularly if the supporting rock layer is underlain by a weaker material."

Jan 1, 2015

By Steven L. Anderson

A cut-off wall has been designed and is currently under construction along the Back Dam of the existing tailings impoundment at Red Dog Mine, Alaska. The cut-off wall, which will be in the order of 5,000 ft long and up to 150 ft deep, when complete, is being excavated using a 40 metric ton Bauer trench cutter head mounted on a Liebherr crawler crane, in combination with a closed loop slurry pumping and de-sanding system. The tailings impoundment is situated in an area of warm permafrost and high potential seismic activity. Design incorporated an assessment of rock jointing to define the final depth of the wall along the alignment requiring the use of plastic concrete backfill to address the concerns associated with potential cracking of the wall due to settlement and during seismic activity. The results of the geotechnical investigation program, particularly with respect to variation in rock hardness along the wall alignment are discussed, as are the design criteria for the plastic concrete backfill, the challenges faced during construction, including scheduling of the work with the on-going dam raise activities of the mine, and the lessons learned with respect to potential productivities and selection of cutter wheels and teeth. Also described are the requirements for and advantages of utilizing a slurry boosting system to meet pumping requirements, re-design of the plastic concrete mix to consider workability and optimization of cutter teeth configurations to reduce wear through highly varied rock hardness.

Jan 1, 2010

By Racquel Nottingham, Freddy Lopez, Ole Gadermann

The ongoing urban development is a global phenomenon, placing has high demands on urban infrastructure (housing, public services, transportation, telecommunications, etc.). Micropiling is one of the most successfully implemented deep foundation technologies in urban interventions, and in densely populated and built-up areas. The use of micropiles enabled the implementation of several solutions within short time frames, with minimal disturbance to the daily activities of the population. Since urban interventions usually represent a very important investment and have an economic impact, special attention should be paid to the serviceability of the urban infrastructure in the middle and long term. For the foundations, the design loadbearing capacity of the used structural elements needs to be guaranteed during the planned life time of the structures. In the case of micropiles, it must be ensured that the steel load bearing elements are effectively protected against corrosion. This paper presents the structural design of permanent self-drilling micropiles, subject to tension due to uplift loads. For the case study, different micropile systems - available worldwide - will also be evaluated. For the afore mentioned micropile systems, the design considerations regarding the durability of the reinforcement, based on their corrosion protection approaches, will be presented in this paper.

By Adnan A. Malik, Tadashi Maejima, Jiro Kuwano, Shinya Tachibana

"The helical piling system provides solution to many geotechnical related problems due to its quick installation, higher compressive and pullout resistance, no wastage of material, workable in limited areas and reusability. However, its use as a foundation for bridges and high-rise buildings is still limited as compared to other piling methods. In the present study, the performance and load settlement behavior of screw and straight pile is investigated under cyclic compressive load in dense ground conditions. To achieve the set objectives, pile load tests were conducted in a cylindrical steel container. The model ground was compacted with dry sand at relative density of 80%. It is observed from the test results that screw and straight pile resistance reduced when the cyclic load is applied at allowable pile resistance state. The reduction in the ultimate pile capacity is more in straight pile than in screw pile. However, straight pile showed higher ultimate pile capacity than screw pile under similar pile tip diameter. The effect of helix bending deflection on load settlement behavior and ultimate pile capacity increases under cyclic loading.INTRODUCTIONScrew pile is one of the new developments in deep foundation, which is growing tremendously fast because of its quick installation technique, less noisy operation, no wastage of material and involvement of minimum manpower. Screw piles have an edge on straight pipe piles due to its high bearing capacity and uplift resistance. The installation mechanism of screw pile is different from straight pile. Torque and pressure is required to install the screw pile whereas hammering, pressure and vibration is required to install straight pile. As the installation mechanism is different between screw and straight pile, therefore, the ground disturbance that is produced during their installation is also different. The ground disturbance produced during the installation also depends upon the pile tip condition i.e. open or closed ended. Sakr, (2009) stated that the compressive capacity of screw pile in 3 to 5 times higher than driven piles having the same shaft diameter and length. The reason for this increase in pile capacity is due to helix, which is generally 2 to 2.5 times the pile shaft diameter. Larger helices can give higher end bearing capacity but it requires very powerful machinery to install in dense grounds. For instance, if large helix screw pile is installed in a dense ground then helix-bending deflection will start affecting the end bearing capacity (Yttrup and Abramsson, 2003; Malik et al. 2013 and 2015). According to Malik (2015), the equations of thin plate (Young and Budynas, 2002) with uniformly distributed load on the plate can give reasonable estimation of helix deflection due to dense ground conditions."

Jan 1, 2016

By Max Gwynn, Tony Suckling

"The new Wembley Stadium is the most spectacular soccer stadium in the world, built to the highest specifications, using the latest technology and offering visitors an unrivalled match-day experience. Wembley Stadium is the home of English soccer, dating back to 1918 when the British Government began planning a British Empire Exhibition with a stadium as its centrepiece. The Empire Stadium, as it was originally known, was completed in 1924 in just 300 days and cost £750,000 ($1.4m). It was finally closed in 2000.The new Wembley Stadium, which opened in 2006, features fully covered seats for 90,000 fans and a striking arch that sits above the northern half of the stadium. With a span of 315 m (1040 ft), the 133-m (440-ft) tall arch is the longest single-span roof structure in the world. It supports the entire weight of the northern roof and 60% of the weight of the southern retractable roof. This means there is no need for columns within the stadium and ensures unobstructed views.Multiplex Constructions (UK) Ltd. employed Stent Foundations Limited to construct the £10m ($19m) foundations package for the new stadium. The scope of works for the foundation package included the design and construction of all foundations, including all main works piling, temporary works piles for the arch and roof, and tower crane piles. The scope also included trial piling and pile testing, setting out and removal of spoil.Piles were constructed by using bored cast-in-place techniques with both hydraulic and traditional crane-mounted rigs. Stent also installed sheet-piled walls at three locations to the site’s northern boundary. In addition to the main contract works, Stent constructed a £2m ($3.8m) contiguous bored-pile retaining wall within the demolition and earthworks package (Figure 1). This work was carried out as a subcontractor to Griffith McGee."

Jan 1, 2008

By Rick Ellman, Ian Chaney

"The Hampton Roads area encompassing the Norfolk, Virginia Beach and Newport News metropolitan region experiences some of the worst traffic congestion in Virginia. With continued growth of the ports and increasing demand, the Virginia Department of Transportation (VDOT) initiated the Downtown Tunnel/Midtown Tunnel/MLK Expressway Project, a complex undertaking critical to addressing the Hampton Roads area’s transportation needs. The project is a $2.1 billion Design/Build/Finance/Operate (DBFO) endeavor most notably involving the construction of a new two-lane vehicular tunnel utilizing the Immersed Tube Tunnel (ITT) method. The tunnel will pass under the Elizabeth River parallel to the existing Midtown Tunnel between Norfolk and Portsmouth, Va. It will be the largest design-build project constructed in the history of the Hampton Roads District.The New Midtown Tunnel will extend approximately 6,450 ft (1,966 m) along the north side of the existing tunnel where it ties into the existing Midtown Tunnel approaches in Norfolk and Portsmouth. It is being installed in a pre-excavated trench of which approximately 2,250 ft (686 m) required bracing on the Portsmouth side and approximately 1,000 ft (305 m) required bracing on the Norfolk side. The remaining 3,200 ft (975 m) of trench excavation was open cut dredging with laid back side slopes, optimized to reduce dredging, disposal and backfill quantities while also reducing the risk to the existing tunnel. The braced excavation portions of the tunnel alignment were divided into distinct segments which include: Portsmouth Approach Boat Section, Portsmouth Approach Cut-and-Cover Section, Portsmouth Dredge Section, Norfolk Dredge Section, Norfolk Approach Cut-and- Cover Section and the Norfolk Approach Boat Section. All “approach” excavations were performed in the dry and all “dredge” excavations were performed in the wet. Eleven ITT segments are being fabricated in the Sparrows Point Dry Dock facility in Baltimore, Md., and each 14,000 ton (12,700 tonne) segment is being towed approximately 220 mi (354 km) to the site. The ITT segments will extend under the Elizabeth River, with the deepest crossing 90 ft (27 m) at the Federal Navigation Channel. Once beyond the channel limits the ITT rises at an approximate 4.5% slope. Controlled screeding and element lowering operations will be performed primarily from floating barges."

Jan 1, 2014