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By Safwan Labanieh

An experimental set-up is specially designed to study the behavior of a friction pile of 3 cm diameter in contact with the soft clay of Mexico City in a small calibration chamber (CC) of 30 cm diameter and 50 cm height. The consolidation of this compressible clay is accomplished using a special system adapted to the CC itself to insure a good knowledge of the initial state. Loading results of the pile under a consolidation pressure of 50 kPa indicate an elastic mobilization of shear stresses at the shaft of the pile (?3 kPa for 1mm displacement) followed by a hardening plastic type behavior. Unloading-reloading results indicate a mobilization of shear stresses of the same type and of the same order of values obtained from the virgin loading stress path. Cyclic loading (?40 cycles) between 0 and 1 kPa (1/3 of the failure value) give similar results to those obtained from virgin loading.

Jan 1, 2002

By John Y. L Chen

This paper presents full-scale instrumented pile static compressive and tensile load tests to be conducted in the area of Pearl Harbor, Hawaii. Thousands of piles have been installed to support the existing piers and wharves in the Pearl Harbor area. Due to the absence of bedrock within practical depths, most of the piles use combined friction and end bearing. A new 925 feet (282 meters) long and 50 feet (12 meters) wide reinforced concrete wharf supported on pile foundation is planned. This paper will present results of soil investigation, laboratory testing, dynamic load tests during indictor pile driving and static pile load tests. The subsurface conditions consist of soft harbor sediment, young alluvium deposit, volcanic tuff rock formation and stiff old alluvium deposit. The load test piles consist of 20-inch (508 mm) square and 24-inch (610 mm) octagonal pre-stressed, pre-cast concrete pile and instrumented with embedded strain gauges. The length of the piles ranges from about 50 to 125 feet (15 to 38 meters). The test pile program consists of probing, driving indictor piles, dynamic load tests during indictor pile driving and static load tests. The standard loading procedure method was used during static pile load tests.

Jan 1, 2002

By Walter Ensinger

Special foundation works is one of the most innovative sectors in civil engineering and construction. Both engineering techniques and construction machinery are undergoing continu­ous further development. These developments are providing ways to meeting the world-wide requirement for special geotechnical works even faster, even better and more efficiently. Unfortunately, accident prevention organisations have had to realise that the figures on in­dustrial accidents in special foundation works are still above average in number. The Safety & Environmental Working Group of the EFFC thereupon started to carry out a survey on acci­dents occurring in this sector and used this information as a basis for the preparation of acci­dent statistics and an accident analysis. The objective of this undertaking is to determine key accident occurrences and their causes and to consequently determine measures for improved health and industrial safety.

Jan 1, 2002

By Bauduin C. Besix

The Eurocode 7 "Geotechnical Design" is based on "Limit State Design", tackling the uncertainties as much as possible at their source through: - selection of characteristic values of variables (loads, soil properties, pile resistance,...); - partial factors applied on the characteristic values; - model factors to account explicitly for uncertainties of the calculation rule if necessary. Eurocode 7 will propose three "design approaches". The selection of one of them will be by National Determination. For pile design, the approaches are: - approach 1 is a "material factoring approach" at load side and a "resistance factoring approach" at resistance side. The structural and geotechnical design are checked for both of two separate sets of partial factors. - approach 2 is a "load and resistance factoring approach" and is in several aspects close to a deterministic approach. The design is checked for one set of partial factors. - approach 3 is a material factoring approach, at load as well as at resistance side. The design is checked for one set of factors. The aim of this paper is to introduce to the design of pile foundations based on pile load tests and on ground test results (semi-empirical and analytical methods) in the frame-work of the three design approaches. Detailed attention is devoted to: - the selection of the characteristic value of the pile resistance, accounting for spatial variability and stiffness of the structure; - the reliability of the prediction of the pile resistance using analytical or semi-empirical methods which may be accounted for through a "model factor". The results of a large test campaign on screw piles in OC Clay and a calculation example illustrate the proposed procedure when calculation rules using CPT results are used.

Jan 1, 2002

By Mark R. Svinkin

Construction vibrations may adversely affect surrounding buildings and their effects range from human discomfort and disturbance of sensitive devices to visible structural damage. There is no unique conclusion regarding the effect of construction vibrations at every site. Measurement is usually made to monitor vibrations and control them with the vibration thresholds for disturbance of sensitive objects as well as damage to structures. To prevent potential litigation and mitigate the vibration effects on sensitive devices, people and structures, it is necessary to manage and minimize vibration problems before the beginning of construction activities or installation of vibrating machine foundations, and during construction. Pre-construction damage survey and engineering vibration investigations, including the prediction of anticipating vibrations, have to be made at most construction sites in advance of construction activities. Vibration monitoring and control have to be provided during construction. The instrumentation feedback of vibration prediction, monitoring and control provide the basis for choice of measures to prevent or mitigate vibration problems and settlement damage hazards.

Jan 1, 2002

By Robert E. Fosse

Driven 14-inch-square concrete piles were used as the foundations of Genentech Hall at the new University of California, San Francisco Mission Bay Campus. The five-story, steel eccentrically-braced frame building is currently under construction at a 43-acre property located in a former large shallow marshy inlet from San Francisco Bay. The piles were driven through 10 to 25 feet of fill and 20 to 60 feet of soft compressible Bay Mud into an underlying dense sand layer. Pile design capacities were developed for traditional allowable stress design, load factor and resistance design, and ultimate design criteria. The ultimate level capacities were for checks of loads occurring when the links in the eccentrically-braced frame yield during an earthquake. A load test program was performed to confirm pile design recommendations. Two test pile locations were selected for compression, tension, and lateral load tests to evaluate pile capacity and pile/soil stiffness under long-term, short-term and rapid loading conditions. Maximum test loads were 1000 kips downward, 350 kips uplift and 50 kips lateral. Foundation construction began by driving 34 indicator piles with a Delmag D46-32 diesel hammer of 113 foot-kips maximum rated energy. All indicator piles were monitored during initial driving using the Pile Driving Analyzer. Restrike data, obtained several days after initial driving, indicated significant pile-soil setup and typical pile capacity increases from 750 to 1000 kips. The majority of the 1242 production piles were then driven to acceptance criteria of 75 blows per foot and a minimum embedment of 10 feet into the dense sand bearing layer. Piles driven to full length without achieving the blowcount criteria were evaluated on a case-by-case basis. Acceptance of these piles was established by evaluating restrike data.

Jan 1, 2002

By Jiwei Duan

The deformation and load transfer behavior of a single soil-cement column are studied with the finite element method. The results show that there is an effective length for a soil-cement column. Beyond this length, the settlement of the column is approximately equal to a constant. The effective pile length is introduced to the concentric cylinder approach (Randolph and Wroth 1978), and an analytical formula for estimating the settlement of a single flexible pile is presented. A second analytical formula for determining the effective pile length of a soil-cement column is obtained and an example shows that the calculated and measured results are in quite good agreement.

Jan 1, 2002

By Alp Gokalp

The aim of this article is to present an application of jet grouting technique in stiff clays for foundations of the natural gas combined cycle power plant, under construction in Aliaga, Turkey. The plant site is in the Aegean coastal region and 60 km north of Izmir. The foundation soil is composed of quaternary alluviums on top and tuff base rock. The thickness of the alluvium varies between 16 m to 30 m. Groundwater was observed 2.5 m below the ground level. At the design stage, settlement analyses were carried out for the various buildings and facilities in the power plant. Based on the analyses, it was predicted that total and differential settlements are not tolerable, thus jet grouting is implemented as a ground improvement under the majority of the foundations of the power plant. This paper also describes the selection of jet grouting technique, application type and details of the process parameters such as injection pressure, number and size of nozzles, lifting and rotation speeds. Prior to the commencement of the jet grouting works, a number of preliminary parameter tests and preliminary pull-out tests were carried out throughout the site in order to define and verify the jet grouting process parameters to achieve the required diameter of 600 mm and minimum jet grout strength of 3.2 MPa. Moreover as part of the comprehensive quality control and quality assurance program pursued in the project, a number of tests; such as continuous coring, integrity testing, installation of confirmatory jet grout columns, were carried out during the production of jet grout columns.

Jan 1, 2002

By Alan B. Wagner

The River Tower is a proposed 27-story condominium building in the heart of downtown Milwaukee, Wisconsin (USA). The tower will be over 100 m tall, and will have a ground area measuring 15 m by 40 m. The structure will be constructed of cast-in-place reinforced concrete. Certain transfer girders and stabilizing diagonals will be constructed of post-tensioned concrete. Vertical loads will be transmitted through an arrangement of columns, bearing walls, and elevator and stair cores. A mat foundation will be used to connect and integrate these load-carrying elements. The site's geologic profile includes 8.4 m of compressible estuarine (organic) deposits. To control settlement, the mat will be pile-supported. These deposits are underlain by moderate-strength inorganic deposits that extend to bedrock at 32 m.

Jan 1, 2002

By Kyle M. Rollins

To improve our understanding of lateral resistance of pile groups, a series of lateral load tests were performed on a full-scale pile group using both static and dynamic loads. The pile group consisted of nine 0.6 m-diameter steel pipe piles driven into clay. During the static tests, the load was cycled fifteen times to evaluate the drop in lateral resistance that would occur due to repeated loading and the formation of a gap. The peak load typically decreased by about 15% from the initial cycle to the last cycle. The load carried by each pile was also measured and there was a significant drop in resistance for the piles in the trailing row relative to the leading row. The dynamic force was applied using the Statnamic loading system which produced a lateral force of 3500 kN (787 kips) in about 0.1 seconds. In two cases, dynamic loads were applied following application of 15 static load cycles. In these cases, the dynamic lateral resistance was about the same as the static resistance, likely due to gaps around the pile. In three other cases, the dynamic force was applied prior to the cyclic loading. In these cases, the dynamic resistance was 30 to 60% higher than the static resistance. Simplified analyses suggest that the difference in resistance could be attributed to damping produced by the soil surrounding the piles during the virgin loading.

Jan 1, 2002

By Carl D. Ealy

Work is being done to web enable the FHWA Deep foundation Load Test Database. Originally designed to function in the client server environment via modem, access to the database both for data maintenance and user queries has been upgraded to take advantage of the Internet and current and future information technology innovations. The DFLTD will be part of an Automated Geotechnical Information and Design Aid System, the object of which is to assist those involved with managing and maintaining our nation's highway infrastructure. The system will also meet the needs of university and other research institutions for a statistically meaningful source of high quality data for the development and verification of improved analysis methods, in-situ testing methods, etc.

Jan 1, 2002

By Wolfram Groh

New underground floors comprising the complete footprint area of the building structure, were constructed under an existing building in sand, located in the Verdun district of Beirut / Lebanon. The works for the rehabilitation and extension of the Verdun 528 building were carried out between December 1999 and August 2000. A restriction of differential vertical movement of existing load bearing walls and columns had to be respected throughout the construction phase of the new basements. Support measures for the building were taken based on a underpinning system with Bauer SVV preloaded micropiles. The specialty of this underpinning job was that the building loads at the time of preloading and excavation of new basements was substantially less than at final stage. The design of the preloading system was particularly challenging in view of the transition from temporary to final load transfer under variable load conditions. Load transfer was based on the Bauer SVV micropile head system applied in several technical variants. Monitoring of levels of structural elements performed throughout the construction works confirmed that the differential movements of adjacent load bearing columns and walls were maintained within the specified limits.

Jan 1, 2002

By José Carlos A. Cintra

This paper addresses a new experimental procedure to measure the shaft friction and the base resistance of bored piles during static load tests. It is proposed that a set of polystyrene foam discs, placed between the shaft and the base of the pile, be used instead of the usual instrumentation. Throughout the initial stages of the loading test, the foam discs will allow only the mobilization of the shaft friction. The load x settlement curve clearly shows that the shaft friction vanishes at low settlement values. As the load test proceeds, the base resistance is also mobilized. This procedure was used in two belled piles bored at the Experimental Foundation Field of the University of São Paulo, at São Carlos, Brazil. Both piles were 8 m long and had a shaft diameter of 0.6 m. The enlarged base had a diameter of 1.5 m and a height of 0.9 m. Twenty foam discs with a thickness of 20 mm each were placed between the enlarged base and the shaft of the pile. The load tests indicated ultimate shaft frictions of 28 and 30 kPa for measured settlements of 8.98 and 7.39 mm. Base resistance values at failure were 617 and 499 kPa, for a chosen settlement of 10% of the pile base diameter. The proposed approach seems to be straightforward, efficient and inexpensive.

Jan 1, 2002

By David R. Black

Foundation problems due to collapsible and expansive soils are well known throughout the arid western United States. Millions of dollars are spent annually to counteract the effects of such soils for both new foundations and existing foundations suffering from settlement or heave. Over the last 20 years helical screw piles have come into wide-spread use as a permanent deep foundation element for these problem soils, especially in the arid western United States where, in some areas, they are a standard of practice. Independent research resulting in recognition by every national building code in the United States has legitimized helical screw pile technology. Once thought of in terms of light structural underpinning, helical screw piles of today are designed to take heavy structural loads, vertical and lateral, tension or compression, including seismic loads. With proper pile grouping, design capacities for column loads over 4,500 kN (1,000 kips) are attainable. This paper discusses design considerations specifically dealing with collapsible and expansive soils: soil investigation parameters, predicted settlement and long-term creep, heave in expansive soils, downdrag in collapsible soils, shaft slenderness buckling, maintaining shaft alignment during installation, refusal condition, water migration along the shaft, lateral loading, cyclical loading for seismic loads and machine foundations, corrosion, helix durability during installation, the installation torque vs. capacity equation, and design methodology. The paper concludes with several case histories where helical screw piles were used for new structural foundations and to underpin existing failed foundations in St. George, Utah, Cedar City, Utah, and Denver, Colorado, USA, sites of some of the most expansive clay and collapsible soil in North America. Soil descriptions and performance histories are presented.

Jan 1, 2002

By Christopher J. Pacitto

This paper presents a case history of an engineered, monitored, and tested program that provided an effective and satisfactory basis for the completion of pile foundations for Twin Dolphins 1 at La Peninsula Condominiums located in the Isles of Capri in southwest Florida, U.S.A. An 8-story building (withl-story parking underneath) along with recreational facilities (such as a swimming pool and tennis courts) had been planned for final construction. Following an evaluation of various foundation alternatives, a precast prestressed concrete (PPC) pile-supported system was selected. The building foundations were designed for pile capacities of 445kN (50 tons) and 890kN (100 tons) in compression and 133kN (15 tons) in uplift. A test pile program was performed to provide site-specific pile driving data, verify design assumptions, determine production pile lengths, and evaluate pile driving criteria. A total of 24, 356 mm (14-in.) square, 19.8 m (65 ft) PPC concrete piles were driven and dynamically load tested utilizing a Pile Driving Analyzer (PDA) within the building limits. Dynamic monitoring during probe pile installation and restriking was performed to estimate the ultimate capacity of the piles and to evaluate driving stresses during installation. CAPWAP analyses were preformed on PDA data to better estimate pile capacity, resistance distribution, and predict pile freeze (increase in pile resistance with time) and thus optimized the production pile lengths. Upon completion of probe pile installation, 12 of the probe piles were tested using the Pile Echo Tester (PET) function of the Pile Integrity Sonic Analyzer (PISA). PET testing was performed to evaluate the integrity of piles which had exhibited high driving stresses during PDA testing. Information gathered during the probe pile driving program was effectively utilized as part of the overall quality control program to install a total of 539 PPC piles (including 24 probe piles) within the building limits at the project site to depths ranging from 9.1 to 19.8 m (30 to 65 ft) below the existing ground elevation as part of the foundation support system. Prior to installation of probe or production piles, a termination criterion was established using 1-dimensional wave equation analyses in addition to the design pile embedment requirement. The predicted pile capacities compared very well with the capacities from the CAPWAP analysis for probe piles. Use of geotechnical instrumentation and PDA assisted technology enabled each foundation support element to be constructed to its optimum capacity and at optimum cost. Furthermore, by using PDA the consultant was able to quantify a difficult to measure geotechnical phenomenon termed "pile freeze" which eliminated costly overdriving and unnecessary splicing of piles.

Jan 1, 2002

By Michel Bustamante

The original Cistercian Lure abbey situated in eastern France and built in the second half of the 16th century, has become nowadays an administrative building. Because it has been founded on poor ground conditions and inadequate foundation scheme, the abbey has suffered severe structural distortion. In 1992 an inspection revealed new extensive damages which led to a general refection together with a foundation underpinning. Micropiling was the selected method. Movements recorded over a period of 6 years after underpinning completion are presented.

Jan 1, 2002

By Chu E. Ho

Field load tests on deep slurry stabilized bored piles have shown that end bearing resistance was unreliable due to soft toe conditions caused by debris accumulation at the bottom of the hole during pile installation. This is true whether bentonite or polymer slurry was used. Skin friction resistance was less affected by the slurry and is more reliable. A design strategy is proposed which ensures that an adequate factor of safety against the ultimate shaft resistance is maintained for any chosen design working load, such that a pile settlement of 12mm would not be exceeded.

Jan 1, 2002

By Dan Brown

Two drilled shaft foundations were subjected to axial load tests in order to measure the influence of drilling fluid on performance. Other than the differing drilling fluids, the shafts were constructed with great care to ensure identical conditions. The results indicate superior performance in both side shear and base resistance of the shaft constructed using a polymer over that of the shaft constructed using bentonite drilling slurry.

Jan 1, 2002

By Chris D. Thompson

In Southern Ontario, Canada, piles are frequently driven through competent clayey soils to obtain end bearing on extremely dense till or bedrock. One reason for this is the difficulty at assessing the adhesion of the clayey soils. This is illustrated by texts, such as the Canadian Foundation Engineering Manual, which is the standard of practice in Canada, that indicate that theoretical analysis of the adhesion values of such soils are unreliable. In this paper, the results of high strain dynamic testing have been used to estimate the shaft resistance of 11 closed end pipe piles driven in overconsolidated very stiff to hard clayey tills at four sites by means of the CAPWAP wave equation analysis. More than twenty-five years of experience with bearing capacity predictions by such means have developed considerable confidence in its accuracy. The results were found to correlate reasonably with the average Standard Penetration Resistances of the clays at the sites. There was a linear relationship between an adhesion of 64 kPa at 20 blows per 300 mm and 192 kPa at 60 blows per 300 mm. At one site, 6 piles were tested and found to have a wide range of Standard Penetration Resistance and estimated adhesion in the same stratum. While there was significant scatter of the results, piles would have been safe at design loads obtained from the relationships established by the analysis carried out for this paper after applying appropriate factors of safety.

Jan 1, 2002

By Colin Curtis

The City of Manchester is hosting the 2002 Commonwealth Games. A world class Stadium with a 38,000 capacity was commissioned for a site located close to the City Centre. The Stadium location is in an area that was derelict and in need of regeneration and it is envisaged that the Stadium will be the spur for this. The industrial and residential history of the site has left a legacy of buried foundations together with chemically contaminated soils. This Made Ground deposit overlies Glacial Deposits which in turn overlie bedrocks of the Central Manchester Coalfield. Coal mining has taken place from at least 1761 leaving several worked seams and shafts. In order to support the stadium, 1159 conventional augured piles of 600 to 1200mm diameters were used. This paper will deal primarily with the piling operations and testing, but will also discuss the coal seam treatment with respect to piling. A substantial trial pile test programme was carried out together with 11 static load tests on contract piles. The results of the pile tests will be discussed and conclusions drawn.

Jan 1, 2002