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By Rudolph P. Frizzi

The current trend of increasing augered cast-in-place (ACIP) pile diameter, length, and load carrying capacities demonstrates improvements in installation equipment, increased acceptance, and that quality control is being successfully implemented by the parties involved in the ACIP pile construction process. Quality control is essential for ACEP piles since 24- to 36-in-dia (610-to 915-mm-dia) piles are currently being constructed to sustain design compressive loads of 800 to 900 kips (3555 to 4000 kN). This paper presents a summary of ACIP pile quality control procedures and methods beginning in the design and bid process, through ACIP pile installation, to post-construction. The results of a recent survey of contractors, engineers, equipment suppliers, and researchers routinely involved with ACIP piles in the United States, Europe, and the Middle East are included to address current trends in ACIP piles and quality control.

Jan 1, 2001

By Heinrich Majewski, Rob Jameson

"Careful review of site conditions and constraints is essential to select the appropriate shoring system for each project. Key evaluation criteria include the geotechnical profile, groundwater and environmental conditions, adjacent buildings and utilities, schedule and any project specific access or other constraints. Typical earth retention schemes range from rock or soil nail walls, through conventional anchored pile and lagging walls to deep internally braced cut-off systems. The Owner’s design team will often develop the conceptual approach under their design studies, and this is refined with Contractor input through Design-Build or Design-Bid-Build procurement. In downtown San Francisco, underground construction must accommodate a unique combination of variable fill, soil, rock and groundwater conditions, potential for severe seismic loadings, and constrained sites within a dense urban environment. The quarter square mile of San Francisco’s Transbay and Rincon Hill districts has seen repeated cycles of development, destruction and re-building through earthquakes and the economy, and has been intensely redeveloped over the last decade. Over 50 acres of this land has been reclaimed from the Bay since the Gold Rush and within 3 city blocks the bedrock slopes from over 250 FT depth below the fills up to outcrops over 100 FT above sea level. A series of project examples from within this small area illustrate how varied shoring systems have accommodated the highly variable subsurface conditions while offering best value in terms of cost, schedule and appropriate protection of adjacent facilities.INTRODUCTIONA walk of 3 blocks from Rincon Hill on San Francisco’s Harrison Street, north through the Transbay area to Mission Street will traverse an urban zone which has been reinvented twice within its 150 year history in response to major seismic events. This small area highlights the range of subsurface conditions and urban environments which are encountered and accommodated in shoring schemes throughout the city. This route down the north side of Rincon Hill overlies a steep bedrock slope, outcropping over 100 FT above sea level at its south end and dropping to over 250 FT below sea level at Mission Street. A complex overburden soil profile, shaped by seismic activity and changing sea-levels has created layered soils ranging from soft estuary muds, dense sandy strata and deep clay layers, in turn topped with urban fill, frequently contaminated with debris from the Great 1906 earthquake. This route runs parallel to, and 350 yards inland of, the San Francisco shoreline resulting in groundwater elevation close to sea level with almost limitless recharge within granular layers. On the higher slopes of Rincon Hill, groundwater is typically observed flowing on top of and periodically within the fractured bedrock formation. The Transbay and Rincon areas were developed early in the Gold Rush era of San Francisco. After destruction in the 1906 earthquake and fire, they became a transit gateway into the city throughout the 20th Century. Demolition of the Embarcadero Freeway in response to earthquake damage and social pressure has opened this large area to redevelopment within the last 20 years, creating a new commercial and residential hub for the city. In its latest wave of building, planners are developing taller structures with deeper basements, in turn creating new construction challenges. Selection of shoring systems appropriate for these developments requires detailed evaluation. The process must address both the rapid spatial changes in subsurface conditions and the constraints surrounding, and specific to, each site in order to define shoring performance requirements. This paper presents an overview of the subsurface conditions and land use development of the Transbay and Rincon Hill areas, with examples of the shoring systems selected to meet site-specific conditions and requirements. The projects cited range from soil nail wall"

Jan 1, 2017

By A. Paviani

The subject of this session is "Equipment Installa­tion, Recent Developments". This is a subject which is not usually addressed at conferences of Foundation Engineering. It is rare to find sessions dealing with the technological side of deep foundations, a subject which only recently seems to have aroused sufficient interest at national and international conferences. It is therefore natural for the subject of "Equipment", or the tools used to implement the various "technologies", to be over­looked or mentioned only occasionally during the discussion of other issues. At conferences, most of the attention is attached to research and to the theoretical interpretation of the performance and behaviour of deep foundations, as well as to establishing the most suitable calculation algorithms and approaches for the study, design and control of foundation structures. It is almost as if the subject of equipment is felt to be less important or, perhaps, that it is considered to belong more strictly to mechanical engineering than to civil engineering.

Jan 1, 1994

By Alexander Filotti, Richard Kalson

"In the last decade, the construction industry has witnessed significant changes in the project delivery systems and contractual relationships between the general contractors (GC) and Deep Foundation Specialty Contractors. The Deep Foundation industry, especially including industry specialty subcontractors, have experienced a significant increase in requests that project risks be transferred through contract documents to subcontractors and suppliers with a decrease in margins for the industry. GCs regularly revise their form subcontracts to take into account recent experiences/contractual trends and newly issued judicial precedent, an exercise that is less frequently undertaken by subcontractors and suppliers. These contradictory trends are at the base of the ethical analysis of subcontracts that comprises the subject matter of this paper. Using contracts as a risk management tool in order to mitigate the general contractor’s risks in the context of dynamic changes in the legislative environment will also be addressed. Furthermore, another possibility for risk mitigation for the industry is to actively promote the introduction of the latest technical developments into the contract documents.CONTRACTS’ ETHICSFor thousands of years, ethics have been a constant presence in our lives and have been debated by different branches of philosophy. In modern times, ethics in business started to be an imperative for the success of a globalized economy.“Ethics are standards by which one should act based on values. Values are code beliefs such as duty, honor, and integrity that motivate attitudes and actions.” (Rumbaugh 2004). Some of these values and actions have been carved in legislation in general and in business legislation in particular. More and more, unethical business practices (e.g., corruption) are identified as the root cause of poverty, underdevelopment, and war around the world. In the context of contract ethics, three aspects are of interest:•,Ethics of contract construction•,Ethics of contracting processes•,Ethics of risk allocation in contracts"

Jan 1, 2016

By David H. Sanders, Ramin Motamed, Fahim M. Bhuiyan, Raj V. Siddharthan

Large-diameter drilled shafts (DS) are a critical part of a seismic-resistant system, and therefore it is important to be able to accurately model lateral resistance. To undertake the lateral load analysis of largediameter DS, a finite-difference p-y analysis program, NVShaft, is being developed at the University of Nevada Reno. Validation of the new program involved numerous p-y analyses using commercially available programs. Subsequent comparisons suggested the program's ability to yield reasonable predictions for typical diameter DS. Based on the I-15/US 95 load test program carried out in Las Vegas, NV, this study presents the evaluation of NVShaft in Nevada’s subsurface condition. Lateral load analyses of a 2 ft and an 8 ft diameter DS were attempted using NVShaft. The location of the applied lateral loads and the presence of cemented soil-layers were incorporated in the modeling. A good agreement between NVShaft prediction and the measured response was found for the 2 ft diameter DS. For the 8 ft diameter DS, a stiffer response was predicted. The inspections of the moment-curvature characteristics at different load levels suggested cracked response of the concrete due to prior axial load testing may be one of the reasons behind the deviation.

By Ricardo Dobry, Alain Pecker, George E. Leventis, Ralph B. Peck

"This year’s DFI Outstanding Project Award is for the design and construction of the foundation scheme for the largest cable-stayed bridge in the world. In 1993, Gefyra, SA (a French/Greek consortium led by VINCI of Paris, France) was awarded a €750 million ($1billion+ USD) Concession Contract to design, build, fi nance, operate and maintain a three-span cable-stayed suspension bridge connecting the Peloponnese, Greece’s southernmost peninsula, with the mainland across the Gulf of Corinth. The contract extends over a 42-year period, 7 years for design and construction and 35 years for operation. The project was fi nanced through a combination of public funds, private equity and bank loans. Alternative foundation concepts that were considered included traditional driven piles, deeply embedded caissons and soil improvement. PROJECT CHALLENGESThe extreme technical challenges faced included:??Weak foundation soils composed of soft alluvial deposits consisting of interbedded layers of granular and cohesive materials with thin layers and lenses of gravel and liquefi able sand pockets; rock is believed to be at a depth of 1,000 m (3,500 ft) or more.??A very deep seabed exceeding 60 m (200 ft).??The requirement to withstand the collision of 180,000-ton tankers traveling at 16 knots.??Maximum wind forces of 250 km/hour (155 mi/hour).??Design seismic forces corresponding to Richter magnitudes of 7.0+ with peak ground accelerations of 0.48 g at seabed.??Design tectonic movements of 2 m (7 ft) in any direction between any two adjacent bridge pier foundations/pylons.Considering subsurface conditions and local seismicity and water depths, foundation design and construction methods were the key drivers for this project. In large part, the success of the project is owed to the unprecedented partnering and collaboration between all partners involved fostered under the leadership of Jean Paul Teyssandier and Gilles De Maublanc of VINCI Group (France) who served as lead Concessionaire and General Contractor. The joint venture’s lead Greek partners were Elliniki Technodomiki/AKTOR and J&P/AVAX. Alain Pecker of Geodynamique et Structure (France) served as lead Geotechnical Consultant/ Designer while Buckland and Taylor (Canada) served as Design Checkers with Ralph Peck and Ricardo Dobry (U.S.) as Special Advisors on foundation issues, Langan International/Langan Engineering and Environmental Services P.C. (George E. Leventis, Gregory Biesiadecki and Diane Fiorelli) served as Technical Advisor on geotechnical, geodynamic and foundation/marine construction issues."

Jan 1, 2007

Jan 1, 1998

By Dimitrios Polantzas P. E., Collin E. Sweeney E. I. T., Franklin M. Grynkiewicz P. E., Leili Javidanian P. E.

In the latest AASHTO design specifications, the Load and Resistance Factor Design (LRFD) method is prescribed for the design of retaining walls. However, inconsistencies arise when LRFD is used for retaining wall design versus the traditional Allowable Stress Design (ASD). Required toe embedment and wall loading demand vary greatly when the two design approaches are compared, all else being equal. This is due to application of linear load factors to properties that vary non-linearly in the design. These inherent inconsistencies are further intensified when introducing factors such as layered soil profiles, different wall types, groundwater elevation, and surcharge requirements. When applied correctly, these two design approaches, in theory, should lead the designer to the same result with little discrepancy, as they do with steel structure design. However, the use of the current AASHTO LRFD method for various geostructural retaining wall designs yields contradictory results that suggest existing retaining walls that have been successfully designed and constructed are unstable. Fundamentally, LRFD should be built on reliability-based calibrations; the successful past performance of existing retaining structures designed using ASD suggests that the LRFD approach requires considerable modification. The authors of this paper recommend that the current LRFD load factors be reviewed and revised based on more comprehensive wall performance data and wall type such that the difference between retaining structures designed using LRFD and those designed using ASD is eliminated.

Oct 1, 2022

By Antonio Marinucci, Robin Mao

The new Hangzhou West Railway Station, which is currently in the early stages of construction, will be located in the city of Hangzhou, China. To accomplish the ambitious goals of the project, the construction work and station building was divided into three project areas. The original design utilizes 1,580 drilled shafts with diameters of either 800 mm or 1000 mm (32 or 40 inch) to support the new Station and its various ancillary structures. The drilled shafts will be tipped into the moderately weathered argillaceous siltstone a distance between 5 and 15 m (16.5 and 49 ft), resulting in an effective pile length ranging from 35 to 43 m (115 to 141 ft), respectively. For the first phase, approximately 550 production drilled shafts will be installed. Eight (8) sacrificial drilled shafts each with a diameter of 1000 mm (40 inch) were installed to a depth ranging from 50 to 57 m (164 to 187 ft), and were tested to confirm the design parameters used for the first phase, to evaluate the contractor’s installation means-and-methods, and to provide guidance whether redesign is warranted for the subsequent two phases. Bi-directional static load testing was performed using a donut-shaped Super Cell to apply unidirectional axial loads up to 13,200 kN (2,970 kip). This paper will describe the bi-directional testing and select results obtained therefrom. The axial compressive and uplift resistances determined from the testing verified that the available axial resistance of a single drilled shaft exceeded the minimum design requirements.

By W. G. K. Fleming

The general history of piling is traced up to the present time with regard to the evolution of methods and materials. The processes have been strongly influenced by developments in basic equipment and industrial change. It is noticeable that in the twentieth century more progress has taken place than in the many previous centuries. It has been strongly influenced by the general development of Soil Mechanics. Test loading is probably the most effective way to assess the success of designs and many empirical relationships have been challenged through it. As we approach a new century it appears that it will be an age of rapid equipment development, with much enhancement of understanding of what has been done. Processes of automatic construction and testing will becoming commonplace. These changes will narrow the limits of conventional scatter that have come to be accepted and to a large extent will be driven by political efforts to curtail energy consumption, to raise standards of quality and reliability, and to conserve the environment. 1. Ancient history. Piling is an ancient art. Its first mention in history is from Herodotus, the first person to commit an account of his times to the written word in the years 557 to 479 BC. He evidently had a strong interest in engineering matters because he wrote of building, brick making, reinforced brickwork, river training, canal building, bridge construction, tunnelling and its acoustic detection and piling. The piling reference comes from Book 5 at paragraph 16.

Jan 1, 1999

By Marco D. Boscardin, Benjamin H. MacKinney, Kenneth R. Allard, Kenneth A. Pidgeon, Adriane G. Boscardin

This paper presents a case history for a unique application of a system of vertical micropiles with horizontal soil nail bracing and shotcrete facing for underpinning. The system was used to support and protect an existing 2-story hospital building during demolition and renovation. The goal was to limit building movements and have the building remain in use during construction of an abutting addition. Soils at the site consisted of clean, loose to dense, sand and gravel. The original underpinning design was revised after the initial excavation revealed unsuitable soil conditions for traditional underpinning pits. An alternative system consisting of vertical micropiles (hollow bars) through the footing, combined with shotcrete and soil nails was proposed, accepted by the owner, and successfully constructed. Excavation depths were up to 15 feet (4.6 m) below the existing footings. Wall movements were monitored at regular, horizontal and vertical intervals along the hospital wall, and less than 0.6 inches (15 mm) of settlement and 0.1 inches (3 mm) of horizontal displacement throughout underpinning and construction were reported. The challenges with the original proposed support of excavation design and other alternative approaches considered will also be discussed.

Oct 1, 2022

By Timothy C. Siegel

Given that piles are composed of different materials and installed using a variety of methods, ASTM D 1143/D 1143M-07 Standard Test Methods for Deep Foundations Under Static Axial Compression is justifiably general so that it has as many applications as reasonably possible. There are aspects of the test setup, the test procedures, and data interpretation for instrumented piles (some of which are specific to augered cast-in-place piles) that are either not discussed in detail in this ASTM standard or are not addressed at all. Specifically, the use of variable time hold times can obscure the shape of the conventional load-deflection curve, as well as, influence the interpretation of the ultimate pile capacity. Unload-reload cycles induce additional non-uniform internal axial loads within the pile which complicate interpretation of the strain gage data and increase the potential for errors. Attempts to maintain a constant top load during the hold period can lead to operational difficulties in taking measurements and are technically unnecessary. Residual load has been shown to develop in cast-in-place piles and can significantly influence the axial load distribution as interpreted from strain gage data. The stiffness of cast-in-place piles has been observed to vary with the measured strain, and a constant modulus, as provided by correlation with the unconfined compressive strength of the grout, may lead to a significantly different interpretation of the axial load distribution.

Jan 1, 2010

By Anthony L. Reynolds, Clifford J. Wren

"The adoption of a significant pile testing regime, the use of Eurocode 7 as the design standard, the development of lean construction techniques, and lateral thinking in overcoming some considerable construction challenges allowed Stent Foundations to construct the foundations for the new Wembley Stadium, London, on time and within budget. In addition to the piling works for the main stadium, and after significant design development, a large number of extra piles were required to raise the new iconic roof Arch to its final position some 133 metres above the ground. A 1,400m long contiguous bored pile wall was also constructed to allow for excavation and formation of the new pitch. INTRODUCTIONHjstorjcal lntrodyctionWembley Stadium is the 'home of English football'. As long ago as the 1880's, Wembley Park leisure grounds had football pitches and running tracks.In 1918 the British Government began planning a British Empire Exhibition with a stadium as its centrepiece. The Exhibition area covered 219 acres and the area on which a former abandoned tower called Watkins Folly had stood was chosen as the site for the new stadium (http://www.wembleystadium.com).The Empire Stadium, as it was originally known, was designed by architects Sir John Simpson and Maxwell Ayerton and the engineer Sir Owen Williams. It took just 300 days to complete at a cost of £750,000 ($1.4m), and was built using 25,000 tons of ferro concrete, 1,000 tons of steel, and over half a million rivets.The Empire Exhibition was a remarkable event, containing fountains, lakes, gardens, and many pavilions, each representing the architectural style of the countries exhibiting. It was opened on 23rd April 1924 and the final attendance was over 27 million, with 4.5 million admissions to the Empire Stadium alone."

Jan 1, 2005

By Gerald Verbeek, Erick Baziw

Cone penetration testing (CPT) is a popular and cost effective tool for geotechnical site characterization. CPT consists of pushing at a constant rate an electronic penetrometer into penetrable soils and recording cone bearing (qm), sleeve friction (fs) and dynamic pore pressure (u) with depth. The measured qm, fs and u values are utilized to estimate soil type and associated properties based predominantly on empirical correlations. The cone bearing measurements are highly susceptible to additive measurement noise for sandy, silty and gravelly soils. This measurement noise results in high peaks due to interbedded gravels and stones and low peaks due to softer materials or local pore pressure build-up. To date there has been little progress in filtering this additive noise aside from ad hoc techniques, which include discarding qm measurements and smoothing/averaging qm measurements. This paper outlines a qm filtering technique which attempts to put structure into the estimation problem. In this case, the dynamics of the cone bearing measurements are modelled within a state-space mathematical formulation and a Kalman filter (KF) is then utilized to obtain optimal estimates of qm. The mathematical details of the qm KF algorithm are outlined in this paper along with the results from a challenging test bed simulation.

Sep 8, 2021

By Gerald Verbeek, Erick Baziw

Cone penetration testing (CPT) is a popular and cost effective tool for geotechnical site characterization. CPT consists of pushing at a constant rate an electronic penetrometer into penetrable soils and recording cone bearing (qm), sleeve friction (fs) and dynamic pore pressure (u) with depth. The measured qm, fs and u values are utilized to estimate soil type and associated properties based predominantly on empirical correlations. The cone bearing measurements are highly susceptible to additive measurement noise for sandy, silty and gravelly soils. This measurement noise results in high peaks due to interbedded gravels and stones and low peaks due to softer materials or local pore pressure build-up. To date there has been little progress in filtering this additive noise aside from ad hoc techniques, which include discarding qm measurements and smoothing/averaging qm measurements. This paper outlines a qm filtering technique which attempts to put structure into the estimation problem. In this case, the dynamics of the cone bearing measurements are modelled within a state-space mathematical formulation and a Kalman filter (KF) is then utilized to obtain optimal estimates of qm. The mathematical details of the qm KF algorithm are outlined in this paper along with the results from a challenging test bed simulation.

Oct 1, 2021

By Dario Libano

"The Line 5 Extension, in Sao Paulo, Brazil, is currently the most important investment in public transportation by Sao Paulo’s state government. It will connect the south part of the city to the city center, crossing through four other major Metro lines and stations; all currently in operation. The total extension of the line is 11 km (6.8 mi), and includes a new parking yard for the trains and 11 new stations. The Brooklin Station, one of the new stations due to be open and operating in 2016, has a unique geometry of five secant shafts.The original design included constructing five secant shafts stabilized by two plastic slurry walls using conventional grab technology. One slurry wall, along the Santo Amaro Avenue, was to contain the contamination plumes, and another was for temporary support to enable the excavation of the shafts. The final retaining wall design was changed to a concrete structural diaphragm wall that reduced the construction time of the shafts by half, allowing the contractor to meet the construction schedule. This solution also avoided dewatering effects in a geological region characterized by Quaternary sediments and environmental contamination plumes. It was the first time that a hydromill was used in such a situation in Brazil. The hydromill, by overcutting the panels, increased the quality of the joints, and decreased the probability of having seepage into the shafts. The hydromill also created a seepage barrier and avoided movement of the contaminated plumes.The GeologyLocal geology is composed of a superficial Quaternary soil, basically soft organic clays and sands and gravels. From the depth of 8 m (26 ft) until 18 m (59 ft), geology is composed by tertiary medium compact sand with thin silt-clay layers. From 18 m (59 ft) down, there are alternations between compact silt-sands layers with very hard clays layers. Each is approximately 5 to 10 m (16.4 ft to 33 ft) thick.The Initial Basic DesignThe original basic design of the Brooklin Station was to be constructed from five 40 m (131 ft) diameter intersecting circular shafts, all in a line along the axis of the Metro tunnel, in 555 days. In the excavation sequence, the odd shafts were first excavated, waterproofed and had part of their inside cast-in-place structure built before the even shafts were excavated. During the excavation of the even shafts, part of the odd shaft’s support was demolished and connected with the even support. A 0.8 m (2.6 ft) thick plastic slurry wall, acting together with the wire mesh reinforced shotcrete support, ensured the excavation stability around the five shafts."

Jan 1, 2014

By Ronnie Melker, Joel Webster, Daniel Belardo, Thomas Hyatt

Quality assurance of drilled shafts is highly dependent upon the construction practices used during the excavation and concrete placement process. When performed under slurry, challenges are presented in maintaining borehole stability and placing a uniform and continuous concrete column. An integral part of the construction operation is to evaluate the as-built integrity to verify the drilled shaft is capable of safely transferring the required loads to the subsurface. One such case is exemplified by a project involving the expansion of an existing public transit rail line. The expansion required the construction of a new bridge bent supported by seven 5-ft diameter drilled shafts of various lengths. The specifications for the project required both Cross-Hole Sonic Logging (CSL) and Thermal Integrity Profiling (TIP) for drilled shaft integrity evaluation. Both of these post-construction non-destructive tests (NDT) are designed to detect anomalies or the presence of regions with reduced concrete quality. However, the implementation and methodologies of performing each of these NDT methods are significantly different. Cross-Hole Sonic Logging uses ultrasonic signals emitted from a transmitter in one access tube to a receiver in another access tube. Thermal Integrity Profiling measures elevated concrete temperatures during the curing process using embedded thermal wires. Both test methods require different access details and therefore have different costs associated to the contractor or owner to perform. This paper provides a detailed comparison of these NDT methods as performed on these seven drilled shafts. The associated financial and time costs to perform each method are compared and the results are discussed in detail. INTRODUCTION Drilled shafts are a fundamental deep foundation element that can be designed to resist large bending moments as well as to transfer large compressive axial loads through weaker upper soils to competent soils or rock below. Often times when the upper soils are very soft, lateral support by casing or slurry, or a combination of both, may be used to hold back the softer soils from collapsing into the hole before concrete has been placed. Due to the blind nature of drilled shaft construction and the qualities issues that may arise during the placement process, it is essential for design engineers to specify non-destructive testing (NDT) to assess the quality of the as-built drilled shaft. CSL and TIP testing are two NDT methods designed to detect areas of lower quality concrete or soil inclusions throughout the length of the drilled shaft and determine its overall quality. Each method uses different technologies and methods to achieve the results required to determine the as-built condition of the drilled shaft.

Jan 1, 2019

By Alok Bhowmick

The most uncertain and challenging part of a bridge design and construction is the ‘Choice of foundation’. During the planning and conceptual design stage, it is extremely important to choose the right type of foundation. Wrong choice can lead to disaster for the project. This paper will present three interesting case studies of past bridge projects, to demonstrate how correct choice of foundation can help to meet the project commitments while the wrong choice of foundations can led to huge delay in project completion, leading to time and cost overrun.

Nov 1, 2022

Jan 1, 1984

By Mario A. Terceros Herrera, Mario Terceros Arce, Antonio Marinucci

A Smart Cell is a closed-type tip post-grouting device that is attached to the bottom of the steel reinforcement cage of a drilled shaft and is used to enhance performance and to reduce uncertainty thereof. Control of the grout is maintained within the device during injection and a uniform stress is imparted across entire base area simultaneously, inducing a pre-mobilization load into the shaft as well as the soil. This paper describes the construction and tip post-grouting of drilled shafts from two bridge projects in the Santa Cruz, Bolivia region along the Paraí River. During the grouting process at each project site, there were noticeable differences in the grouting pressures achieved and responses observed, even within short distances between shafts. For this project, the greater benefit of using the Smart Cells was the reduction of risk and uncertainty of performance due to the highly variable soil conditions. Ultimately, since the response of each shaft was observed during grouting and because a “minimum” value of shaft resistance (i.e., pre-mobilization of load) was measured, there is a greater reliability with the anticipated performance of the shafts when axial loading is eventually applied.