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By Paolo Heiniger

The aim of this paper is to present the operative solutions devised and then adopted to implement the underexcavation (soil extraction) of the Tower of Pisa, by means of soil extraction. The intervention has been performed by the Consorzio Progetto Torre di Pisa, a joint venture made of five qualified Italian companies (Trevi S.p.A. , Rodio S.p.A., Italsonda S.p.A., Ismes -Enel Hydro S.p.A., Bonifica S.p.A.), selected for their experience in the field of monitoring and restoration of monuments, structural design, foundation engineering and specialised works in underground conditions. Since 1991 the Consorzio has been charged with the specific task of implementing, within the contractual frame of a Concession, all the decisions made by the International Multidisciplinary Commission appointed by the Italian Government the previous year, with the aim at solving the «problem» of the Tower, strengthening the structure and stabilising its foundation. The Trevi Group, which is represented by Trevi S.p.A. in the above mentioned Consorzio, has given and is giving its direct and constant contribution and is engaged in supplying the special equipment to the operation and the drilling technology which has been successfully adopted to date.

Jan 1, 2000

By J. X. Wu

An investigation on the seismic damage to buildings with pile foundations in Tianjin region, was conducted after the earthquake which hit Tangshan in 1976. It showed that most pile-founded buildings have an excellent aseismic capacity. In this paper, several pile-founded projects suffering the seismic damage are introduced as examples, simplified calculations are made of the vertical bearing capacity of pile foundations and of the horizontal seismic force, and suggestions are presented in conection with the design of pile foundations in the liquified ground soil. The paper shows a frame structure which has a plie foundation with a box-shaped base. Analyses if its response to the earthquake has been carried out in accordance with the F.E.M. and results have been obtained.

Jan 1, 2010

By Hal W. Hunt

Heavier loading and more efficient equipment is helping to keep driven piles competitive in America. Better Knowledge and testing of soils and support materials make it practical to use higher stresses; this is being strongly promoted by those directly concerned with timber, steel and concrete piles. Readily available point protection is increasingly used to assure penetration of piles without damage to full load bearing capability. Fabric drains are being installed with pile equipment to speed consolidation of soils. Sheet pile configuration has changed; production has been reduced largely because of imports. Dynamic checking of representative piles for load carrying capability is replacing conventional load testing of just a pile or two ? at much lower cost.

Jan 1, 1987

By Giovanni A. Bonita

The United States Capitol Visitor Center (USCVC) is one of the largest underground structures ever constructed in the Washington, DC, metropolitan area. The 600,000 ft2 (55,750 m2) structure is entirely underground and immediately adjacent to the shallow foundations of the existing U.S. Capitol building. Interior building columns for the USCVC were supported on 186 drilled shafts that varied in diameter from 4 to 9 ft (1.2 to 2.9 m) and in length from 15 to 45 ft (4.6 to 13.7 m). The vast majority of the building utilities were located beneath the basement floor slab. It was decided at the onset of the project to proceed with construction prior to completion of the design drawings, and coordination between the underslab utilities and the drilled shafts had not yet been finalized at the onset of drilled shaft installation. Given depth and location restrictions of the outlets, relocation of the bulk of the utilities was not possible. Almost half of the drilled shafts were affected, leaving redesign as the most feasible remedial solution. The redesign involved adjustments to the shaft length, diameter, and bell. It took place on a case-by-case basis, sometimes only minutes before installation began. Coordination between the field and design team was excellent, and delay associated with the redesign efforts was minimal. In addition, the detailed, high-quality field records kept by both the contractor and field engineers allowed for accurate and fair estimations of the added drilled footage and concrete volumes placed. The additional service fee, which was minimal, was settled quick and fair.

Jan 1, 2006

By Cassandra A. Wetzel

Rock socketed mini-piles are a desirable foundation alternative when design capacity is more than 40 tons and there is limited access. In this case history mini-piles were designed to support between 75 and 200 kips at 12 locations adjacent to a perimeter wall, a party wall and at cast iron column piers. Limited geotechnical information, low overhead clearance, and active building population tested the creativity of the team to get the piles installed. The key geotechnical concern during installation of the mini-piles was the presence of a glacial till layer above the bedrock surface that restricted the seating of the casing into bedrock with a track mounted drill rig. Soil loss during the advancement of the rock socket using an air hammer was excessive and increased the risk of subsidence. Over a three week period the engineer worked with the contractor to modify the design, means, methods, and materials to install piles with adequate load capacity. This paper will present the changes in design and construction methods that were required.

By Sastry Putcha, Vamshi Vemula, Aneesh Goly, Kumar Allady

Current dynamic testing practice to obtain pile total capacity will not yield optimum capacity due to the strain incompatibility between the side and tip resistances during driving. Superposition of end of initial drive- static tip capacity and the peak static skin capacity during beginning of restrike and adding them is the preferred method. The FDOT method determines independent pile static tip and skin capacities in real time analyzing appropriate blows from the embedded tip and top data of the Embedded Data Collectors (EDC). This data is collected through a wireless radio transmitter, receiver, and laptop software. The approach utilizes EDC tip and top data and nonlinear single degree of freedom system to satisfy force and energy equilibrium with a global genetic inversion analysis. Top impacted energy equals at pile tip as sum of Static, Damping and Inertial energy providing independent tip resistance. With EDC sensors as boundary conditions, pile is divided into desired segments and using global inversion techniques one dimensional equation is solved for independent skin friction for every blow. EDC data compared close static load test results. The EDC - FDOT method has enabled cost effective 100% testing of driven piles cost effective. INTRODUCTION Historical documentation has shown that not only driven piles have a long history of usage but also continues to advance unceasingly till today. Historians placed the first pile driving using timber piles in the 4th century BC. While modern pile driving systematically started around nineteenth century, the credit for conceiving the idea of the applicability of wave equation to driven piles goes to David Victor Isaccs of Australia. His 1931publication “Concrete Pile Driving Formulae” provides the basis for modern pile driving using stress wave theory. He felt that the dynamic formulae then in use lacked the capability of detecting integrity and hence developed stress wave theory. This work was further developed starting in 1938 by W.H. Glanville and colleagues of British Building Research Board as they developed the first solution to the wave equation. But these early efforts have really taken off only with the advent of computers. E.A.L. Smith (1960) published ‘Pile Driving Analysis with the Wave Equation’ and provided first numerical solution to the wave equation. Within few years, the FHWA funded research and in due course this effort ushered the era of externally instrumented pile driving.

Jan 1, 2018

By Brian Isherwood

TransCanada Pipelines, Calgary (TCPL) is one of North America's leading transporters of natural gas through its energy transmission business. TransCanada also operates significant complementary businesses in energy marketing and energy processing in North America and internationally. The main trunk pipeline crossing Canada comprises as many as six pipes, 30" to 48" diameter delivering up to 7.8 trillion cubic feet of natural gas per day. To maintain the maximum operating pressure of 1000 psi, it is necessary to provide compressor stations at 60 to 100 km spacing. One such station is located at Potter, in northern Ontario, some 80 km north of Timmins, referred to as Station 102. The station contains two compressor plants, 'A' and 'B' Each incorporates a gas turbine driven centrifugal compressor unit. 'A' Plant uses an aero-derived gas generator (jet engine) rated at 15 MW (19,000 HP).

Jan 1, 1997

By Alexander Nikolic

The paper presents the foundation design and construction of a landmark urban redevelopment scheme in central London, UK. The scheme comprises the new Tottenham Court Road Underground station, Crossrail interchange box and associated over-site commercial development. The paper focuses on the design, procurement and construction of large diameter bored piles, up to 68m in depth, which form the foundation support system for the over-site commercial development at Denmark Place. The congestion below ground required an intricate foundation design solution which has been a catalyst for developing innovative load transfer arrangements and has resulted in the advancement of pile construction technology in the UK. The foundation system was also designed to cater for the construction of two significant elements of proposed below ground infrastructure. Selected large diameter piles have been constructed within 1.1m of live underground railway tunnels. An innovative D-shaped pile was constructed in a zone subject to particular spatial constraints. The proposed Crossrail tunnels will be bored within 1m of selected over-site development piles. In addition, a 30m deep excavation forming a new escalator box will be constructed in direct contact with the over-site development piles. The stakeholder engagement process is described together with the foundation design development and buildability assessment. The benefits from early collaboration between the designers and specialist contractors are highlighted. From an analytical design perspective, the entire foundation construction sequence was modelled in detail in order to assess the soil structure interaction and any potential adverse effects on existing elements of underground infrastructure. The results from the three dimensional numerical modelling simulation are compared with field monitoring data.

Jan 1, 2011

By C. Y. Liu

This paper principally deals with the application of caisson foundation in the Chinese bridge building industry, the different types of caisson foundation adopted, and their spheres of application. Caisson foundation has been used and speedily developed for bridge works in New China, and a number of new innovations have been made in its design. Especially in deep water foundation, the Nanjing Bridge over Changjiang has attained one of the deepest bridge foundations in the world. There are six types of deep caisson foundation being now in use in China, namely:

Jan 1, 2010

By Paul W. Mayne

Axial pile performance can be rationally evaluated within an elastic continuum framework using field results from seismic piezocone tests (SCPTu). Adopting a versatile Randolph-type elastic pile model, the approach can be applied to either traditional top down loading using an anchored reaction beam or the newer Osterberg cell that simultaneously pushes the base and shaft in opposite directions. The axial load distribution within the shaft is also evaluated. For site-specific data at a given site, the SCPTu is an optimal means for collection of subsurface information because it combines penetrometer readings and downhole geophysics in one sounding. The results obtained are at opposite ends of the stress-strain-strength curves, specifically the peak strength for capacity interpretations and the small-strain stiffness (Emax) for evaluating the initial deformations. Axial pile capacity can be analyzed using both direct and indirect CPT methods. As such, the approach allows for a complete representation of the axial load-displacement-capacity curve for pile response. Case studies are presented for deep foundations situated in stiff clays at two national geotechnical test sites located in Houston and College Station, Texas, using top down loading, as well as a third case study of a drilled shaft in clay till loaded by O-cell in Alberta.

Jan 1, 2009

By P. Bermingham

A new approach to load testing of high capacity piles is presented. The method is mobile, inexpensive, repeatable and non-destructive allowing for multiple pile testing at a single site. A reaction mass is placed over a pressure chamber situated atop the pile to be tested. The test method is significant in that it can produce linearly increasing forces of high magnitude (over 5.0 MN) with durations of up to 80 milliseconds. This represents pulse durations an order of magnitude longer than achieved using a drop hammer. The accelerations the pile undergoes are less than one g, (conventional dynamic methods = 50 to 100 g). These effects combine to produce pile behaviour no longer dominated by the action of stress wave, instead the pile is under high levels of stress through its length during the force input. This is representative of the situation when static loads are applied, thus the method may be considered quasi-static. Further advances introduced with this method are that pile deflection and transmitted force are measured directly by means of a laser beam and load cell. This allows accurate correlation of event load displacement histories without the error associated with zero shift (acceleration integration) or non-homogeneous materials (strain measurement). The load displacement histories emulate those obtained for static load testing.

Jan 1, 1989

By Tracy Brettmann

? Hollow Stem Auger ? Drill Bits ? Leads/Torque Arm ? Hydraulic Gearbox ? Hydraulic Power Unit ? Grout Pump ? Crawler Crane

Jan 1, 2001

By Mark Maday

As part of the I-94 North-South Corridor reconstruction program, the Wisconsin Department of Transportation (department) is reconstructing the Mitchell Interchange in Milwaukee, Wisconsin. Located on the south side of Milwaukee near Mitchell International Airport, The Mitchell Interchange interconnects I-94, I-43 and I-894. Reconstruction began in 2009 with the letting of the first advance contract for local crossroad bridge reconstruction. A second advance contract for construction of collector-distributer roads on each side of the I-94 mainline was completed in 2010. The main contract involving reconstruction of the core of the Mitchell Interchange was let in the summer of 2010, and is scheduled to be completed by the end of 2012. The core contract includes construction of three cut and cover tunnels along two system interchange ramps. Construction of the three tunnel structures is on the critical construction path. The contract includes an interim contract completion date that requires the tunnels to be open to traffic by the end of 2011. A top down method of construction using drilled shaft secant piles for the sidewalls of the cut and cover tunnel structures was selected as the preferred structure type to address subsurface and construction schedule challenges. The department identified in pre bid coordination that no cost reduction incentives would be reviewed or accepted for changes in tunnel wall type. A major component of the tunnel structures requires the installation of 1,500, 4-foot diameter secant piles. This paper presents mitigation strategies to manage construction risks associated with the installation of the secant piles including; prequalification of the secant pile subcontractors, requirement for use of full depth temporary casing, a site specific quality control plan, specifying drilling equipment, and developing a geotechnical baseline report for this critical component of the Mitchell Interchange reconstruction project.

Jan 1, 2011

By Muhannad T. Suleiman

Temperatures below freezing significantly enhance the soil shear strength and stiffness and to a lesser extent increase the compressive strength of concrete as well as the yield and ultimate strength of reinforcing steel. Consequently, the lateral load resistance of bridge columns supported by drilled shafts becomes dependent on seasonal weather conditions. To investigate the effects of seasonal freezing on the behavior of bridge columns supported by drilled shafts, large-scale field lateral load tests were conducted at 23°C (73.4°F) and -10°C (14°F) on two identical units at an field test site, which consisted of glacial till soil classified as low plastic clay. The bridge column-drilled shaft systems were subjected to cyclic lateral load with the maximum lateral column top displacements reaching approximately ±30 cm (±11.8 in.). The soil at the test site was characterized at different temperatures using unconfined compression tests in the laboratory as well as in-situ Cone Penetration and Pressuremeter Tests. Using these test results, the lateral load behavior of the column-drilled shaft systems were analyzed utilizing numerical models that consisted of beam elements representing the concrete column and the shaft and lateral springs representing nonlinear p-y response of soil. This paper focuses on comparing the calculated responses of test units with different p-y curves that were developed for the soil near the ground surface using the laboratory and in-situ tests. From the experimental study, the response of the unit tested at -10°C (14°F) was found to show 44% increase in lateral force resistance and 0.84 m (2.76 ft) upward shift of the maximum moment location compared to the response of the identical unit tested at 23°C (73.4°F). Theoretical behavior that included the temperature effects on soil, concrete and steel properties provided good correlation with the measured responses when the soil near the ground surface was modeled using the unconfined compression test or the Cone Penetration Test data, but not the Pressuremeter test data.

Jan 1, 2006

By Javier Rodriguez

Adaptive re-use of existing structures in urban environments has become very common due to lack of available space in our cities and requirements for increased structural capacity. Often, it involves retrofitting existing foundations to support increased loading. In such cases, Engineers face the need to review existing deep or shallow foundations for their true load carrying capacities in order to determine the required magnitude of retrofit work, if any. To accomplish this, the engineer must track down and cull through the existing construction documentation to determine what was actually constructed, complete an investigation to confirm these conclusions, possibly sample the foundation elements for strength properties, and on occasions complete non destructive or full scale load testing of indicator elements. This paper describes the typical procedure followed by the authors for design of retrofit schemes for existing buildings in the Washington DC metropolitan area. Three case histories are presented that illustrate various issues encountered during design.

Jan 1, 2006

By Nuno Cruz, Saúl Rodríguez

"When executing offshore bored piles there are several specific factors and problems to consider in order to guarantee excavation stability. One of the methods employed to carry out this type of work consists in setting up a floating work platform, typically a barge, and implementing a soil stabilization system that combines a partial steel guiding casing with third generation polymeric drilling fluids. The main aspects to take into consideration when performing offshore pile boring works are soil stabilization, project design, work methodology and operational aspects. An example of a work methodology problem arises before any pile boring work takes place as the steel guiding casing contains water, sometimes salt water. What to do with this water in order to replace it by an adequate polymer fluid will determine the stabilization capacity as soon as the shaft advances below the protection of the casing. Another example of operational problem may derive from barge movements while executing boring activities. This study is the result of extensive field data collection and concrete logging analysis from marine projects using polymers in different continents. The bored pile stability target was set ranging between 2% to 15% of concrete overbreak. Values above 15% or below 2% mean that there is a stability problem. Then the off-target pile’s data is collected, analyzed and classified under categories. Thus, a direct correlation is established between the problem category and the final results. Modifying steps in the pre-established construction methods or operational variables guarantees target results without the need to replace the approved construction methods. As a general conclusion, the worldwide experience in large diameter marine works, allows to provide truthful information and solutions for these problems. In knowing how to follow a logical sequence of work and applying adequate work methodology will be the key for success.GENERALBackgroundTo carry out the drilling process of offshore bored piles there are two main options to take into consideration: drilling the pile by using full guiding casing until final depth; or using a combined system of partial steel guiding casing and support drilling fluids.The knowledge and situations described in this paper come from the experience acquired in different projects where the second method was employed. This construction method consists in installing a steel guiding casing by vibration and thus covering the water table and further stabilizing the soil below it with polymeric fluids until reaching the pile’s final depth. The Fig. 1 schematic shows an example of this method where H corresponds to the length of the steel guiding casing whereas the remainder of the shaft’s length is stabilized by polymer fluid. The entire bored length is full of slurry up to top of casing.In most cases this kind of civil works results from the need to build a bridge or executing port structures in places where the creation of temporary artificial peninsulas with fill material is impracticable or not allowed. Hence the need to use floating work platforms, commonly referred to as barges."

Jan 1, 2017

By Fabian Kirsch

Cyclic behaviour of axially loaded piles has been an issue since studies revealed that the capability to transfer skin friction into the ground is highly depending on the level and the number of load cycles the pile is subjected. It has been shown that degradation of skin friction due to axial cyclic loading leads to accumulating displacements and a severe reduction in pile capacity. In Germany the DIN 1054 as well as the Recommendations of the Working Group 2.1 ?Piles? of the German Geotechnical Society (EA-Pfähle) require the consideration of cyclic loading for the assessment of both the displacements and the capacity. Up to now no broadly accepted design method exists, which enables the engineer to give a reliable judgement on the pile capacity under axial cyclic loading and the displacements respectively. Instead numerous design charts make it possible to distinguish between stable and instable loading levels in order to ensure a design on the safe side. A newly developed design approach based on engineering models is presented which delivers a calculation algorithm for the remaining axial pile capacity after a defined number of load cycles to allow for the analysis of stability of the foundation. Furthermore the computation of accumulating displacements is made possible. The results are verified with pile load tests undertaken at Dunkirk, France and showed that the axial capacity after cyclic loading calculated with the newly developed design approach predicts actual capacity with an accuracy of ±20%.

Jan 1, 2011

By Robert A. Field

Static-Load Piledriving utilizes a hydraulic push to facilitate the installation of a pile. The pile is not rotated, impacted or vibrated. A smooth pushing force advances the pile incrementally into the ground. Static-Load devices must have a reaction mass to push against. The most simple form of a Static-Load device is a jack; more advanced equipment, such as the Still Worker, also utilizes this approach. This paper focuses on the use of the Still Worker on three challenging projects. In each case, the existing site conditions made it risky, or unattractive, to utilize conventional impact, vibratory, or drilled-shaft equipment.

Jan 1, 1997

By G. Noce

The ever more present necessity for greater precision in foundation structures on vertical piles subject to horizontal forces applied to the heads, in the light of of the latest knowledge about the elastic-plastic behaviour of the soil has led to the use of numerical calculation for the formulation of a general resolution method for the problem. The calculation method that will be set out, applicable to piles with inertia moments variable discreetly along their axes is especially useful when studying steel structures for medium and large tonnage vessels for which the metal piles are often constructed for the assembly of section of equal external diameter but different thickness and therefore different inertia moments. Two examples are given of constructions whose foundations have been projected with these calculation tools, one in the railway sector (foundation pile for the river Nera viaduct - Italy) important for the limitation of horizontal relative deck displacement, the other maritime (Dolphins of the petroleum pier of the port of Bandar Abbas - Iran).

Jan 1, 1989

By F. Castelli

A simplified non-linear method to predict the behaviour of a single pile and/or pile group under horizontal loads is presented in the paper. The evaluation of the non-linear lateral deflection is based on a procedure taking into account the decrease of the model stiffness with the increasing of the applied load. The solution derived firstly for the single pile, was extended to the case of a pile group introducing the p-multiplier (fm) concept proposed by Brown et al. (1988).

Jan 1, 2006