Search Documents

By Trevor L. L. Orr

"AbstractThe background to the harmonization of geotechnical standards that has taken place in recent years in Europe has been the move to more economic and political integration following World War II that has led to the formation of the European Union. Prior to 2010 the standards used in the European countries for geotechnical design, investigation and testing and for the carrying out geotechnical work, such as the installation of piles, were the different national standards, which were not harmonized. The harmonization of geotechnical standards in Europe started in 1981 with work on a model Eurocode 7 for geotechnical design that led eventually to publication by CEN, the European Committee for Standardization, of the European Standard version of Eurocode 7 in 2004. In parallel with the work on Eurocode 7, a large number of associated harmonized standards have been, and are being, prepared by CEN and by the International Standards Organization (ISO) for geotechnical investigation and testing and for the execution of geotechnical works. Standards published by CEN must be adopted by the CEN member countries and all conflicting standards withdrawn. Hence all the CEN countries have adopted the same the harmonized text of Eurocode 7, but with National Annexes that allow national choice with regard to Design Approach and partial factor values. The adoption of Eurocode 7 and its associated geotechnical standards has removed the barriers to geotechnical activity in Europe due to the presence of different national standards. It has also enhanced the ability of EU firms to compete in the global market.Background to harmonization of geotechnical standards in EuropeThe initial moves towards the harmonization of geotechnical standards in Europe can be related to the economic and political developments that took place in the period immediately following World War II to revive the economies of Western Europe. Europe at that time was divided by a political and, in many places, a physical barrier, known as the Iron Curtain, into two very different and separate zones: communist in the east and non-communist in the west. In 1952 the European Coal and Steel Community (ECSC) was formed, linking 6 countries: Belgium, West Germany, France, Italy, Luxembourg and the Netherlands, and establishing a common market in coal and steel. The ECSC was the first international organization to be established on the basis of supranational principles whereby negotiated power is delegated to an authority by the governments of the member states. In 1957 the ECSC became the European Economic Community (EEC), also known as the Common Market in the English-speaking world, with the aim to bring about economic integration. With the addition of Denmark, Ireland and the UK in 1973 and Greece in 1981, followed by Portugal and Spain in 1986, this led to the formation of the European Union (EU) in 1993. East and West Germany were reunified in 1990, following the fall of the Iron Curtain in 1989. In 1995, Austria, Finland and Sweden joined the EU, and since then the numbers of countries in the EU has increased to 28, many of which are countries that were formerly behind the Iron Curtain."

Jan 1, 2014

By D. E. Sherwood

Recent developments in high torque hydraulic rotary rigs has lead to the construction of secant bored pile walls by rotary drilling methods in circumstances where earlier methods were difficult and in some cases impossible. The evolution of secant bored pile wall construction is described including classical, rotary drilled and continuous flight auger construction methods. The paper then details the restraints which have been created in recent inner city redevelopment, many of which were not relevant in the early days of the technique. Typical examples of walls are presented to show the adapatability and advantages of the secant bored pile wall method. A number of in-situ retaining wall construction techniques are then compared in detail with regard to relative cost, technical quality and practicality.

Jan 1, 1989

By Willie M. NeSmith, W. Morgan NeSmith, Alan Roach

"In 2013, Augered Cast-in-Place (ACIP) piles are a mature foundation technology throughout the United States. General guidelines for the design and construction of ACIP piles are available along with numerous references for design in specific North American geologies. In fact, the current generation of contractors and geotechnical practitioners might view ACIP piles as just another deep foundation option to be considered, along with driven piles, drilled shafts and others. This acceptance has developed, however, over a 60-plus year period.The term, Augered Pressure-Grouted (APG) pile is often used when referring to ACIP piles because the piles emerged out of construction processes at the Intrusion-Prepakt firm in the late 1940s. The company’s specialty was pressure grouting and preplaced aggregate concrete. The grouting was typically accomplished by driving a pipe to a target level and then injecting grout under pressure. In some soil conditions, it was necessary to use an auger to reach the desired grouting depth. In these circumstances, the grout pipe was driven beside the auger and grout was pumped as the auger was withdrawn. The grout pipe was then withdrawn as well. This was the genesis of the APG, or ACIP pile, and many piles were installed using this technique. The patent application, “Method for Forming Piles” was filed by Raymond Patterson of Intrusion-Prepakt in 1951, and the patent was granted in 1956. The process was eventually modified when a suitable hollow-stem auger was developed. Licenses were granted to the Lee Turzillo Contracting Company and Berkel & Company Contractors, Inc. in the late 1950s. Each of the three companies Patent, LicensesThe patent application, “Method for Forming Piles” was filed by Raymond Patterson of Intrusion-Prepakt in 1951, and the patent was granted in 1956. The process was eventually modified when a suitable hollow-stem auger was developed. Licenses were granted to the Lee Turzillo Contracting Company and Berkel & Company Contractors, Inc. in the late 1950s. Each of the three companies coined their own terms for the piling process: “Pakt-In-Place” for Intrusion-Prepakt, “Auger Pressure-Grouted” for Berkel and “Augercast” for Turzillo. Over time, “Augercast” was frequently used as a generic term for the system. The installation of these piles was, and still is, a highly nuanced process; “contractor dependent” is a term often seen today. Intrusion-Prepakt, Berkel and Turzillo all had personnel who were part of the original group that developed the system and who appreciated the craftsmanship involved in forming sound piles."

Jan 1, 2013

By Li Keqiang

This paper discusses the pile foundation of tall buildings in Shenzhen region. For 156 constructed tall buildings exceeding 18 storeys, about 86. 5 per cent of the sum. The two main types of foundation used are the semi?machine?bored/slurry drilled cast?in?situ pile and the excavation pile (hand ?dug caisson). The engineering geologiical condition in Shenzhen was analysed. In general, the bed rock level is not too deep. It belongs to hard rock, but the geologic structure is more complex and the tectonic fissures is plenty. According to experiences of the researches, tests, designs and constructions of pile foundation, we present the basic design principle of pile foundations for tall buildings as follows; (1) pile strength control to select the pile type and to choice the cross sectional dimen­sions, must be in compliance with the strength of the pile. (2) bearing stratum strongly weathered, moderartely weathered and slightly weathered rock may be used as the bearing stratum. (3) bearing pile bored /drilled cast-in-situ pile designed as an end bearing pile. (4) friction pile precast concrete pile, prestressed concrete tubular pile and driven cast-in-situ pile designe as a friction pile. In case, pile design is in compliance with these principles, it may be safe, economical and reasonable.

Jan 1, 1991

By Benoit Virollet

Over the last 10 years the diameter of unbraced, unlined and unanchored circular shafts has grown dramatically in many parts of the world. This progress has taken place through improvements in: construction methods; concrete rheology; and design capabilities. Excavation equipment has become more precise in terms of operator control and ability to correct alignment of digging elements leading to better alignment tolerances. Also contributing to the increases in shaft diameters is the evolution of design models. A better understanding of soil structure interaction is being incorporated into the analyses in terms of radial soil stresses and imposed loads on the shaft. This paper provides an overview of the recent progress made in circular shaft construction, the primary design considerations, and some innovative uses of efficient arc elements to develop unsupported structures of other shapes. In addition, a summary of recent circular shafts constructed worldwide is provided.

Jan 1, 2006

By John Kvinsland

"The Block 43 Project is the future home of the Paul Allen Institute for Brain Science located just off the southern shore of Lake Union in Seattle, Wash. The South Lake Union (SLU) district experienced considerable development over the last 10 years and Vulcan, Inc., which is headquartered in Seattle, is at the forefront of this transition. Once a light industrial/residential location, SLU has transformed into a hub of medical technology comprising new residential units and mixed-use buildings. Malcolm Drilling Company, Inc. constructed four shoring projects for Vulcan in this vicinity over the last year, beginning with Vulcan Block 44, which consisted of 42,000 sq ft (3,902 sq m) of soldier pile and tieback wall to support a below-grade parking facility. Block 44 construction began in February 2013 and ended in mid-April. The feature project, Vulcan Block 43, was in planning stages at the time and began construction in late fall 2013.Awarded by GLY Construction of Bellevue, Wash., in September 2013, Block 43 was the most complex of the block projects performed by Malcolm. Block 43 featured dewatering and ground improvement components along with a water-tight secant pile wall. Following the commencement of Block 43, Malcolm also began work on Vulcan Block 52 in December 2013. Block 52 consisted of 43,000 sq ft (3,995 sq m) of conventional shoring in conjunction with dewatering of 8 ft (2.4 m) of excavation located below the water table. The final Vulcan project was Block 45, which started in January 2014 for Turner Construction of Seattle and consisted of 41,000 sq ft (3,809 sq m) of conventional shoring and required dewatering to complete the final 15 ft (4.6 m) of excavation.Scope and Subsurface ConditionsBlock 43 involved a wide variety of drilling applications for the building to be constructed and properly founded. The primary scope of work involved shoring support for an underground parking structure requiring excavation of approximately 82,000 cu 3 yds (62,694 m ) of soil. The cuts for the excavation were up to 43 ft (13.1 m) in depth, and the excavation was bounded by city streets as well as the South Lake Union Light Rail on its perimeter. In order to excavate beneath the water table, an extensive, deep dewatering system was required to drain the upper fill and reduce the impact of the pressurized aquifer located beneath the excavation. In addition, drilled rigid inclusions, along with compaction grouting, were required for foundation support of the future structure."

Jan 1, 2014

This paper summarizes seven years of Italian ex­perience with the use of large calibration chambers for the calibration, under closely controlled stress and strain conditions, of some in situ testing devices which are used in sand deposits. At the present time two calibration chambers are operating in Italy, one at E.N.E.L.-C.R.I.S. (Milan) (*) and the other at I.S.M.E.S. (Berga­mo) (**). Both chambers can accomodate cylindrical samples 1.2 m in diameter and 1.5 m in height. A detailed description of these chambers can be found in Bellotti, et. al (1982).

Jan 1, 1987

By Jr NeSmith

"Drilled Displacement piles are a product of screw pile technology originally developed in Europe. The process involves rotating tool into the ground that displaces the soil laterally as it advances, then grouting or concreting through the hollow stem of the tool as it is withdrawn. They were first introduced in the United States in the 1990’s and have become a mature and accepted technology since that time. They are now used to support a variety of heavily loaded structures including electric power and LNG facilities, stadiums and arenas, airports and mid- to high-rise commercial and residential facilities. In urban environments, the technique has a number of advantages including, low noise and vibrations, no removal of the existing soil, and reduced pile material cost due to the improved stress state of granular soils after installation (smaller or shorter piles can be used). For these reasons, displacement piles have been used to support various facilities in Northeastern United States (US). The paper presents case histories of the performance of displacement piles in the Northeastern US including the use of full displacement elements as a settlement limiting ground improvement system.INTRODUCTION“Drilled Displacement” (DD) is an industry umbrella term for a number of proprietary or commercially available cast-in-place pile installation systems which involve a hollow-stem tool that laterally displaces soil as it advances and the placement of grout or concrete through the hollow-stem tool as it is withdrawn. The systems include grout/concrete placement methods by both sand-cement grout pumped under pressure and tremie grout/concrete placement through bottom-hole discharge. The system discussed in this paper includes grout pumped under pressure, also referred to as Auger Pressure Grouted Displacement (APGD). A schematic of the APGD tool is shown in Figure 1. The tools require significant torque and downward force to advance; a typical installation platform is shown in Figure 2."

Jan 1, 2016

By Michel Bustamante

The occasional substandard performances of continuous flight auger in particular soil conditions have prompted the drilling rig manufacturer to improve the standard CFA in order to reduce its negative effects. A real improvement of interest was the launching of the double rotary CFA system. The promising features of the latter have incited the authors to implement an extensive experimental research on pile constructed using this type of technique but in the specific context of cohesive soils. Short-term static load tests were carried out on a total of 9 test piles of various installation techniques in order to compare the respective performances. The promising features of the double rotary CFA have incited the LCPC & Durmeyer Company to implement an extensive experimental research on this type of pile technique but in the specific context of cohesive soils and more particularly in clayey marls. After load tests completion the research has been completed by an excavation of the double rotary CFA piles. All the collected data concerning the implemented program are reported.

Jan 1, 2002

By Dena Morgan, Emre Biringen

"Abstract This paper discusses the execution of pile installation and design issues at two environmentally challenging industrial sites in North America. Environmental regulations set constraints on the design and require versatility in choice of technology.For a proposed bridge, due to protected fish habitat, performing soil borings within 30 m of the creek embankment was prohibited. The limited subsurface profile indicated a thick upper layer of granular material, thus driving H-piles was considered. However, to limit generation of vibration and noise in the protected area, drilled piles had to be used. During execution, the subsurface profile differed from that in the borings 30 m away. Very soft, saturated silt was encountered at the bottom of the caisson and the length had to be redesigned very quickly while the contractor waited for instruction. For a new structure in uncontrolled fill area, performing soil borings was not allowed. It was known that a layer of peat was present in the area, but no information regarding the thickness and extent. The subsurface profile generally consisted of granular material overlying a thick compressible silt layer. Somewhere within the granular layer peat would likely be encountered. Franki piles were chosen to penetrate the peat and bear in the underlying granular material. During environmental sampling in the area, methane gas was encountered and Franki piles were no longer a viable option due to safety concerns. The foundation system was changed to steel H-piles driven to bedrock, which was more than 50 m below the ground surface and sloping. Rock shoes that would work to significant slopes had to be used in order to increase the likelihood of good embedment within the bedrock. Also, due to obstruction of an approximately 3 m thick debris field that was encountered in the upper granular soils, some of the piles had to be relocated and extra piling needed to compensate for such differences. The results of PDA testing to estimate compressive capacity and a series of lateral load tests are presented.INTRODUCTIONThe design issues that are encountered during construction can be quite problematic and have a significant impact on schedule. In order to avoid such impact on the project, a thorough subsurface investigation should be considered prior to design and construction. Better understanding of environmental regulations also prevents costly changes to the foundation design. This paper discusses the execution of pile installation and the design issues at two environmentally challenging sites in North America.BRIDGEDuring the subsurface investigation for a proposed industrial building complex, several boreholes were drilled within the footprint or in close proximity of various structures, with Standard Penetration (SPT) sampling of the upper coarse-grained soils (sand/gravel) and undisturbed sampling of the lower fine-grained soils (silt/clay). The SPT blow counts (N60) were corrected by a factor of 1.35 in order to incorporate the SPT automatic energy transfer ratio. When Modified California Sampler was used, a correction factor of 0.44 to 0.64 was also applied. N60 values were further corrected for gravel to avoid artificially high blow counts during the analyses due to spoon samples contact with gravel and cobbles, and the corrected values of (NG)60 (limited to a maximum value of 50 blows/300 mm) were used for design. The information from the SPT boreholes was then used to assess the subsurface conditions beneath the structures, as well as for a nearby bridge that was designed to cross over a creek. Since performing soil borings within 30 m of the creek embankment was prohibited due to the protected fish habitat, the investigation with regard to the bridge abutments was limited to two deep boreholes (B10-33 and B10-34) at the bridge location and two additional boreholes (B10-35 and B10- 36) located approximately 200 m upstream. The bridge location and two sets of boreholes are"

Jan 1, 2014

By Michael G. Batten, Brian D. Keaney

]The Virginia Department of Transportation (VDOT) and the harbors on the James River routinely use precast concrete piles founded in the Yorktown formation to support bridges and other coastal structures. However, axial pile resistances for large diameter piles in this area have been historically overestimated on past projects. This may be due to a common assumption that very large unit end bearing resistance will be developed for a large diameter displacement pile that is driven a significant depth. This assumption is integrated in the Nordlund (1963; 1979) method which is commonly used to estimate axial pile resistance for bridge foundations. A static and dynamic pile load testing program was implemented as part of the Hampton Roads Bridge and Tunnel Expansion project in Norfolk, VA in the James River. A primary objective of this program was to calibrate an axial resistance calculation method against the measured load test results. A method developed by Eslami and Fellenius (1997) that uses CPTu data directly was effective at calibrating to the measured load test results, and allowed for clearer interpretation of the unit resistance values than indirect, semi-empirical methods that require interpretation of soil friction angle and undrained shear strength.

Sep 8, 2021

By Kanagarajah Ravishankar

Drilled shaft (caisson) foundations are extensively used in the past. In the central part of New Jersey, the soils consist of silt and clayey silt overlying Triassic age shale bedrock. The shale is friable and generally severely weathered and highly fractured. The shale crumbles readily into small fragments. In general, the shale is encountered in shallow depth. Subsurface investigations indicated that the upper part of the shale is very soft, highly weathered, and able to advance through soil exploration methods. The underlain formation is relatively hard and required rock coring techniques for sapling. Individual core recoveries ranged from 10 to 100 percent and Rock Quality Designations (RQD) vary from 0 to 90 percent. Although several methods available to estimate the axial capacity of drilled shafts, it is a difficult task for the designer choose the suitable method due to self disintegrate nature of the shale. In the recent years several bridge foundations have been constructed using drilled shafts founded on shale rock in the vicinity of the central New Jersey. Based on load tests carried out on drilled shafts during construction, subsurface exploration, and laboratory tests, suitable methods for determining axial capacity of drilled shafts is analyzed. This paper presents the findings of the field tests and suitable methods to determine the axial capacity of drilled shaft founded on soft shale. Key words: Drilled shaft, axial capacity, Osterberg load test, shale.

Jan 1, 2006

By Khamis Y. Haramy

Curing temperature, density, and moisture significantly affect the velocity measured in the crosshole sonic logging, the rate of strength gain, and the final strength of concrete in drilled shafts and, thereby, affect their structure capacities. Non-destructive field measurements can enhance the QA/QC program by measuring temperature, density, moisture, and sonic velocity of curing concrete during the construction and curing of drilled shafts. The curing environment can greatly affect the concrete strength, and requires close attention during construction. This article shares the experience with the NDE technology used in the QA/QC program in the drilled shaft construction. To understand the mechanism by which a drilled shaft cures under field conditions, two newly constructed drilled shafts were monitored for up to seven days, immediately following concrete placement using the following geophysical logging methods: a) temperature logging; b) crosshole sonic logging; c) gamma-gamma density logging; and d) neutron-moisture logging. One additional drilled shaft was also monitored to a shorter duration. Temperatures were monitored using the sensor in access tubes and/or thermocouples embedded at the center of a drilled shaft and near its reinforcing cage. For a small shaft under 1m diameter, curing temperatures appeared to peak at 41° ? 68° C at different depths at around 24-hour curing time and decreased to and stabilized at around 23° ? 35° C in 6 days. The shaft curing rate varied with depth, shaft diameter, surrounding geo-material types, and the depth of ground water. CSL logging was performed in one shaft from top to bottom from six access tubes and limited monitoring in another shaft. The velocity increased with curing time till 4 to 7 days, and, at a specific time, the velocity appeared to be inversely correlated to curing temperatures. The gamma-gamma density log (GDL) results from 5 different depths were obtained at a source-detector separation of 355 mm. The average density was found to increase with curing time, but decrease slightly in 3 to 5 days. At a given time the GDL density curves seemed to correlate with the neutron monitoring logging (NML) moisture curve. The NML moisture was monitored from 1st to 6th day after concrete placement. The moisture was highest when surrounded by bedrock, then clay, and sand due to different hydration rates.

Jan 1, 2007

By Alan G. MacKinnon

The current piling practices in the U. S. have, to a great degree, been influenced by our founding fathers. When our constitution was written by the delegates from the original thirteen colonies, it was a document of compromise. Generally, the individual states retained their sovereign power over those duties that they had historically performed. The concept of States Rights has been tested throughout our history and has been preserved as of today. An example of the extent of this protection is occurring in the State of Ohio where I currently live. Each of the 50 states receives funds for highway construction from the federal government, approximately in proportion to its population. Congress, when it allocates the funds, quite often attaches amendments to the funding bill to exercise their authority. The major amendment prior to the most recent increase in the speed limit to 65 mph from 55 mph was to increase the legal drinking age to 21 from 18 years old. Embodied within the bill was the provision that the Federal government deduct a percentage from the allocation of any state that did not revise its legal drinking age law from 18 to 21. In the State of Ohio, this change in the law was put to a vote of the people and it was defeated. The federal government now is deducting funds

Jan 1, 1987

By Ting-Wei Wang, Yung-Wen Chen

Artificial ground freezing is commonly used globally during excavation of shield tunnels and for groundwater control. It is a special construction method for temporary ground improvement that involves introducing coolant into underground pipes to freeze water in the soil. The frozen soil is cemented together as a result to form a frozen wall, which provides high strength and low permeability. Once the thickness of the ice wall reaches design requirements, underground excavation can be conducted with the coolant removed afterward to return the soil to its original state. This technique is cost-effective in scenarios where complete groundwater cut-off and excavation support are required; where work is deep underground and faces difficult ground conditions and where access restrictions limit the use of other displacement-type ground improvement techniques. Due to the demand for shield tunnel construction for utilities in Taiwan, ground freezing has become an important soil stabilization method there. In this article, we will share two brine freezing case studies and an in situ liquid nitrogen experiment that was conducted to develop this technique.

Feb 1, 2022

By Frederick C. Rhyner

The United States government sponsored the construction of a new vehicular bridge over the Diyala River in Bubriz, Iraq. This paper describes the geotechnical engineering for design and construction of drilled shaft foundations for this bridge. An Iraqi geotechnical engineering firm made borings and laboratory tests while analysis and design recommendations were provided in the United States. Despite the severe challenges of engineering in a war zone, excellent cooperation was the key to a successful effort. Three drilled shafts designs were necessary to accommodate the different subsurface conditions: a) medium-compact to compact sands, b) stiff to hard clays and c) mixed soil profile. The alpha and beta methods were used to estimate capacities for a conservative design, recognizing that quality control during construction might be less than what is normally provided in the United States. Iraq has a high seismic risk and LPILE was used to estimate the drilled shaft response during earthquake loading conditions. Settlement estimates were made using FHWA methods. Construction was carried out entirely by local Iraqi firms, despite the challenges of working in an active conflict area.

Jan 1, 2009

By Dario Libano, Luis Carlos Tenuta, Juliano Penteado

"Subway Line Number 4 is one of the newest additions to the Rio de Janeiro subway network. Built for the 2016 Olympic Games, the 16 km (10 mi) subway line connects the south of the city, with the famous beaches Copacabana and Ipanema, to Barra da Tijuca, west of the city, where the Olympic Village and Park are located. This new line, which is estimated to cost USD 2.2 billion, is composed of six new stations: Jardim Oceanico, São Conrado, Gavea, Antero de Quintal, Jardim de Alah (JA) and Nossa Senhora da Paz Station.Brasfond participated in the construction of foundations and retaining structures for all the stations, and each presented unique challenges. This is not surprising considering the difficulties present in a highly-dense urban environment including utilities, nearby buildings, traffic limitations and noise.Of all the stations, JA Station was the most challenging to construct. It was located in the middle of an avenue between residential high rises supported on shallow foundations as well as below sea level in sands with high groundwater. The other five stations were located in small parks and squares, with no buildings in the immediate proximity.The interaction between designer, owner, and the general and foundation contractors during execution was key in safely reducing the construction schedule. This was significant given the unforeseen construction delays the client, Linha 4 Sul JV, faced due to permitting, utility and traffic relocation so that the owner could fulfill their final goal: making the line operational by the Olympic Games. The GeologyGeologically, the state of Rio de Janeiro is formed by Pre- Cambrian crystalline basement rock. Its geological formation is very old and comprises two major orogenic cycles, a Mid-Precambrian formation, called “Transamazonian” (Proterozoic Era), and an Upper-Precambrian to Cambrian called “Brasiliano” (Proterozoic-Paleozoic). The soil structure of the city of Rio de Janeiro is represented by a core of crystalline rocks, usually granite-gneiss, covered with a layer of residual soil and/or partially weathered rock.JA Station is located in a Rio de Janeiro neighborhood called Ipanema, between the Atlantic Ocean and Lagoon Rodrigo de Freitas. Local geology is composed of a superficial soil, consisting of medium to coarse grained sands. Top of rock varied significantly from 20 m (66 ft) deep on one side of the station to 33 m (108 ft) on the other. Water is at a depth of 3 m (10 ft)."

Jan 1, 2016

By Alan J. Lutenegger

Some years ago, a method was developed to incorporate a grout column around square-shaft helical screw-piles and anchors to increase shaft buckling resistance under compression loading. An additional benefit of this grouted shaft is to increase the load capacity in both compression and tension, depending on the geometry of the lead helical section and the soil conditions. Because of the unique construction procedure, the contribution of the shaft to the total capacity has largely been unknown. The behavior of grouted shaft helical anchors in clay was investigated by performing full-scale axial uplift (tension) load tests on a series of anchors installed at the University of Massachusetts Geotechnical Test Site. In order to isolate the contribution of the grouted shaft to the total load capacity, anchors were installed with a wooden dowel connection between the lead helical section and extension sections on three of the four anchors so that only the shaft resistance would be measured during the load tests. The grouted shafts ranged in length from 10 to 30 ft (3 to 9 m). Initial tests were performed approximately 5½ months after installation. Nearly four years after the initial tests were performed, the tests were repeated to evaluate any significant change in capacity with time and/or repeat testing (preshearing). The soil conditions at the site are presented along with the load-displacement curves for both the initial and repeat teats and a discussion of the analysis of the results. Repeat load tests showed an increase in capacity from the initial testing, however the percent increase was not the same for all depths. The results demonstrate that considerable shaft resistance can be developed in clays from the grouted shafts as might be expected. Depending on the L/D ratio of the shaft and the contribution of the lead helical section, at working loads the shaft capacity can dominate the behavior.

Jan 1, 2011

By Alfred H. Brand

New York City contains extensive deep deposits of glacial lake varved silt and clay, often overlain by organic soil. An 18 story building was proposed for Manhattan's upper East Side in one such area where bedrock is approximately 200 ft deep. Various pile and caisson alternatives were considered extending through the glacial lake soil to rock, but all proved beyond the project budget. Laboratory testing showed that the glacial lake deposits were preconsolidated. A test pile program using auger cast piles bearing in the glacial lake deposits proved that such piles could safely carry a load of 60 tons per unit. The auger cast pile scheme was estimated to be more economical than a deep pile alternative. A further benefit was that the vibration-free pile installation procedure posed less risk to adjacent structures which had been founded at shallow depth in fill above organic deposits and were stressed and cracked due to prior settlement. The project was designed with the anticipation that the glacial soils beneath the tips of the piles would produce a building settlement of 1 to 2 inches. The building was constructed in 2001 and 2002. It has been completed and is now occupied. Settlement data show that the building is performing as predicted. The auger cast pile scheme founded in a compressible stratum has proven to be successful and is a very unusual foundation alternative.

Jan 1, 2003

By Chaz Weaver, James Sheahan, Michael Mo

"The Virginia Department of Transportation (VDOT) undertook a program to replace four bridges along approximately 4 mi (6.4 km) of US 340 in Northwest Virginia. Two of these bridges, which span Compton Creek and the Norfolk Southern Railroad respectively, are the subject of this article. HDR provided roadway and structural design as well as geotechnical engineering services for the Norfolk Southern Railroad Bridge while their subconsultant, Saeed Associates, provided structural engineering services in support of the HDR roadway and geotechnical team for the Compton Creek Bridge.The project is located in the Valley and Ridge Geologic Province of Virginia, on an alignment that is adjacent to the Shenandoah River. The project lies within the Beekmantown Group consisting of limestone and dolostone that are prevalent and prone to karstic activity in a band that passes through the project area and north into Central and Eastern Pennsylvania. This area has been impacted by karst limestone conditions where caves and sinkhole activity is common. Caves at Luray and Front Royal, located to the south and north of the project, respectively, are popular public attractions.Since the potential for variability of subsurface conditions can be, and often is, greater in karst terrain, the need to develop a design that provides as much flexibility as possible during construction, and then to be prepared to efficiently review and respond to construction questions is heightened. Coordination and communication among the design staff, VDOT’s design and construction staff, and the contractor was a key factor in completion of this project.Compton Creek BridgeThe alignment for the new Compton Creek Bridge is located about 125 ft (38 m) west of the existing bridge, placing it between that bridge and the existing Norfolk Southern Railroad Bridge. No information about the foundations was available for the existing bridges. Borings in the Compton Creek valley encountered extensive voids (some clay filled and some open) with numerous boulders, rock ledges and pinnacles, particularly on the north side of the creek. Geophysical and geotechnical investigations indicated that below a poor and variable upper zone of rock was a layer of more competent and consistent limestone, which appeared to contain little or no voids."

Jan 1, 2017