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By Mark X. Haley

Foundation design and construction in Boston has changed dramatically during the past 10 years. Prior to 1985, the primary foundation element in Boston, where deep foundations are required, was driven end-bearing piles. Since 1985, drilled or excavated high capacity foundation elements have been utilized more frequently. This paper will provide a historic perspective of their use and a summary of design parameters for elements installed and founded in the bedrock. TOPOGRAPHY Boston was founded in 1630 by the Massachusetts Bay Company of John Winthrop and his hearty band of Puritans. The settlement was chosen for: ? its safe harbor, ? abundant source of fresh water, and ? peninsula setting offering protection of the ocean on almost all sides with high ground for fortification. These three factors were a direct result of past geologic processes that created the Boston Basin by erosion of the soft bedrock underlying this area as compared to the harder granite rock to the north, west and south. As the glacial ice sheets melted and moved northward, various soil types were deposited. During ice sheet re-advancement the hills and islands of Boston took on their precolonial shapes. The Trimont, consisting of Beacon, Mt. Vernon and Pemberton Hill, rose to 150 ft above sea level with the smaller Copps and Fort Hill to the north and south.

Jan 1, 1994

By Seung-hoon Lee

The use of piled raft foundations has been considered as an economical alternative to conventional piled foundations because a portion of the applied load is carried by the raft in the design of piled raft foundation. In analyzing the behavior of a piled raft foundation as a settlement reducer, an accurate estimate of settlements of the system should be made on the basis of the understanding of nonlinear behavior of piles in layered soils as well as the interaction between the raft, soils, and piles. Although the 3-dimensional finite element method and simplified analysis methods have been used for the design of piled raft foundations, these methods were found to be inadequate for the practical purpose or could not consider the interactions properly. This study developed an approximate hybrid method of analysis to be used for the practical design of piled raft foundations considering pile-soil, raft-soil, pile-soil-pile and raft-soil-pile interactions. In the presented method of analysis, the settlements of the system are estimated satisfying the compatibility of two separate models which are the flexible raft model consisting of 2-dimensional finite elements supported by springs representing soils and piles, and the group-pile model embedded in layers of soil having different properties. Comparisons with other analytical methods as well as a 3-dimensional FEM program were made to verify the sufficient capabilities of the proposed hybrid model for application to practical design and analysis of piled raft foundations.

Jan 1, 2008

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 Y. El-Mossallamy

The piled raft foundation was extensive applied in the last two decades in different soil conditions e.g. in soft to stiff clay as well as in medium to dense sand and even in highly weathered rock. The piled raft is now applied not only to control the foundation settlement but also to minimize the required raft thickness to reach the most economic foundation design. An innovative application of the piled raft is its special adjustment to cases of foundations with large load eccentricities or very different loaded parts of buildings to avoid the need of settlement joints, which are especially complex below ground water table. Recently, the piled raft is applied for foundations of highway and railway bridges with special serviceability requirements regarding the allowable total and differential settlement as well as tilting. Actually numerical analyses are the mostly used design methods for piled rafts. For all day design practice a simple and modest design method is highly needed -at least in the first design stage- to check the feasibility of the piled raft on the specific project conditions. In this paper, a general overview on the recent innovative applications of piled rafts in Germany will be presented in a short overview. The results of the simple design method will be discussed and compared with the results of more enhanced numerical methods.

Jan 1, 2006

By Abhijit Saha

"The stone columns improve the performance of foundations on soft and loose soil due to the ability of composite ground to sustain increased structural loads under reduced settlements. The interaction between the two basic elements: the ambient subsoil and installed column, present a complexity of behaviour, both in terms of applied stresses and resulting strains. Moreover, as the same is provided in-group in a regular array beneath foundations, the performance of an individual column is likely to be influenced by the presence of neighbouring columns. The present paper addresses this very issue. Analysis of reported field hydro-test data of large diameter oil storage tanks in soft ground in reference to some existing theories led to the development of the stone-column ‘group efficiency factor’. In order that such factor is of general use, it was felt necessary to examine the applicability of the factor to different sizes of groups under varied subsoil conditions. With this in view, some model test results reported in literature of single and group of columns have been analysed and in the process an explicit relationship regarding the stone-column ‘groupeffect’ could be established.INTRODUCTIONThe field application of the stone column technology has gained momentum than the intricate design methodology due to its simplicity in installation and intuitive performance. The ground improvement is due to the complex interaction within the ‘unit-cell’ comprised of the installed column in ambient ground under sustained vertical stress; in association with the interdependence of problem geometry and material properties of the two different soils-one 'native' and the other 'back-filled'. The beneficial effects are increased load capacity, reduction in total and differential settlements, minimization of post construction settlements effected by accelerating consolidation, reduced risk of soil liquefaction, aiding in improvement of slope stability of embankments and natural slopes and effecting changes in the dynamic response. The ‘unit-cell’ concept of a tributary soil cylinder encapsulating an installed column with some reasonable assumptions and boundary conditions (Aboshi et al, 1979; Balaam & Booker, 1981; Van Impe & De Beer, 1983; Priebe, 1976; Saha & De, 1994; Saha; 2005, 2006, 2007, 2011, Saha & Das; 2007) deals with the load-settlement behaviour of the composite system. The present investigation is based on published field data from literature & validated with experimental study reported in literature. The study addresses the effect of group interaction of stone columns beneath a large area loading on ground settlement. The hydrotest load-settlement data of 12 large diameter oil storage tanks founded on stone column reinforced soil at Haldia1 and Kandla2 refinery sites in India; reported by Som (1997), has been analysed to quantify the group efficiency. The results as obtained are compared with experimental study on 2, 3 and 4 stone column groups at different spacing-diameter ratios in soft clay3 reported by Rao et al (1997) to validate the above analysis. A unique relationship between the column spacing and group efficiency has been obtained."

Jan 1, 2015

By Jean J. Abiassi

The Boston Marine Industrial Park (BMIP) VENT 6 project is a cut and cover tunnel, part of the Central Artery / Tunnel (CA/T) in the city of Boston. The BMIP job will serve as the south approach to the Third Harbor Tunnel crossing. The alignment is approximately 2500 Ft long and is made up of four sections starting from west to east: 1. West Tunnel 2. Boat Section 3. East Tunnel 4. Tunnel inside Vent 6 Cofferdam and connection to the Third Harbor Tunnel. The support of excavation (SOE) system for the West Tunnel, Boat Section, and East Tunnel are all a part of this project whereas the SOE for Tunnel inside the Vent 6 Cofferdam was a part of the contract for the Third Harbor Tunnel.

Jan 1, 1994

By Reza Y. Khaksar

Presented is a rigorous solution for the three-dimensional stability analysis of vertical shafts (excavations) subjected to the self-weight of the soil based on the upper-bound theorem of limit analysis approach. A rigid-block translational collapse mechanism is assumed, with energy dissipation taking place along planar velocity discontinuities. This mechanism is optimized to obtain the critical failure mechanism giving the lowest factor of safety for stability of shafts. Based on comparisons with other solutions, the method is generally found to be accurate in predicting the stability of vertical cuts.

Jan 1, 2006

By S. Kanai

Nodular piles is to be piles provided with several nodular projections along the pile shaft, as shown in Fig. 1. Nodular piles are usually installed through either driving method with hammer or preboring method. This paper presents that the bearing capacity installed through each method is considerably higher than that of cylindrical pile without nodules. This paper also proposes the statistically analyzed unique formulae of the bearing capacity of nodular piles.

Jan 1, 1989

By Jean Balech

This paper presents some results of dynamic loading tests performed on concrete piles driven in soft clay formation. The load transfer mechanism, measured in the dynamic increasing energy test (DIET), under blows of growing energy, is described in terms of mobilized normal forces diagrams and unitary local friction and displacements. It was observed that the lateral skin friction grows up to a maximum, in the soft clay layer and, gradually diminishes to a residual value when the system presents the maximum mobilized resistance. It may be concluded that the rupture load is not equal to the maximum mobilized point resistance plus the maximum mobilized local friction as suggested by most of static bearing capacity formulae.

Jan 1, 2002

By Vahid Tajdar

The behavior similarity between pile and cone penetration test, has guided the researchers to use the CPT results in prediction of piles bearing capacity. In this article, artificial neural networks have been used to study about relation between cone tip and sleeve friction strength obtained from cone penetration test and ultimate pile bearing capacity, obtained from static pile load test. Artificial neural networks "ANNS" is a form of artificial intelligence. ANN tries to dramatize the human nerves & brain system biology structure in self-structure. In this article, the results of relevant studies about the prediction of ultimate pile bearing capacity in especial area of soils are presented by use of back - propagation neural networks. The results of static pile load test up to failure on 63 piles with closed end and CPT test results in the place of construction these piles use in order to confirm and creation ANN model. Comparing predicted ultimate pile bearing capacity by utilizing ANN with the numbers which are predicted by 5 common traditional methods shows that using of artificial neural networks is a suitable method for predicted ultimate pile bearing capacity in identified area of texture of soil moreover it has a better operation in comparison with common traditional methods.

Jan 1, 2006

By Emad Farouz

The resistance of very dense glacial outwash formations consisting of sand, gravel and cobble formations can be quite high, and techniques for measuring the strength and deformation properties often cause engineers to underestimate the strength of these layers in drilled shaft design. More realistic measurements of this dense formation can be achieved with slotted steel casing pressuremeter tests. To minimize disturbance and achieve accurate measurements, drilling a pilot hole prior to probe insertion is necessary. Characterizing geologic formations that contain significant amounts of gravel and cobbles is challenging because of scale factor. Inserting a standard pressuremeter probe into this formation without damaging the membrane is difficult. This paper presents a case study for the IR-75 project in Dayton, Ohio, USA, where these dense materials were characterized using a slotted casing pressuremeter, optimizing design by providing more realistic properties of these materials.

Jan 1, 2006

By Helen S. W. Chow

The use of piled raft foundations for tall buildings has been increasing in this decade as it is an economical alternative to conventional piled foundations. Piled rafts are composite structures comprised of the piles, raft and soil and so soil-structure interaction is important in computing the behaviour of the foundation. In this paper, the behaviour of piled rafts subjected to non-uniform loadings will be examined where the raft is supported by piles of different lengths. Finite layer techniques are used for the analysis of the horizontally layered soils and finite element techniques are used for the analysis of the raft and piles. This method accounts for the soil-structure interaction and the lateral resistance of the soil on the piles and raft. Results provided from the present method are compared with the results of a full 3D finite element analysis.

Jan 1, 2006

By Robb L. Swenson

Construction of foundations for the Skyway Segment of the San Francisco Oakland Bay Bridge required innovative techniques due to the mass of the structures being inserted and the unique subsurface of the Bay. Twenty of the pier structures required large sheet pile cofferdams. Eight other foundations were installed in open water without cofferdams at the deeper part of the Bay. This narrative will present the initial planning, as well as the stages of installation, for each type of foundation. The first section will discuss foundation constructability modifications made during the initial planning phases of the project. Considerable effort was expended by Caltrans, the owner, T.Y. Lin the designer, and KFM (Kiewit/FCI/Manson) the contractor in modifying the design to assure that required tolerance would be maintained during the installation of the foundations. The final section will describe the steps required for installation including: initial access dredging, installation of cofferdams, preparation required to install the footing boxes, footing box installation, foundation support pile installation, and pile to box connections.

Jan 1, 2005

By Wen-Chieh Cheng

Two bored piles with base grouting are loaded axially and the results are used to compare with numerical analyses. One compressive pile with a diameter of 2 meters is drilled through clay deposit and into bedrock to a depth of 13.7 meters. One tensile pile with a diameter of 1.5 meters is drilled through the same clay deposit and into bedrock to a depth of 17 meters. Both piles are installed with monitoring system such as rebar strain meters, concrete strain gauges and extensometers. The monitored data during pile load test are used to obtain average frictional stress (t) a displacement (z) curve, pile tip bearing (q) as well as pile head load (p) and a displacement (s) curve. FLAC3D is used to simulate the pile loading and base grouting. The soil and bedrock are modeled with Mohr-Coulomb. The parameters of the constitutive law are established from soil biaxial tests and rock bore hole deformation tests. The pile is assumed as an elastic body. The interface element is used to simulate the pile/soil interface and pile/rock interface. The numerical results are compared with the pile load test in terms of t-z curve, q-z curve and p-s curve. Finally, the pile base grouting is simulated and the uplift is analyzed. The result from this study is promising and the numerical modeling is successful.

Jan 1, 2006

By A. Verghese Chummar

The paper presents a field study where the effect of negative drag caused the failure of a pile foundation system. Utilising the field observations the probable negative drag that acted on the piles is worked which gives an insight into the effect of negative drag on deep foundations.

Jan 1, 1996

By R. H. Wright

This paper describes the design philosophy and methods employed in constructing the foundation elements for the Little Britain Project in the City of London. The Contract is a design and construct package for the foundations of a 3-storey basement which will be built using "top-down" construction techniques and is to be carried out by Fairclough Piling and Marine on behalf of Wimgrove Nominees. The Project includes 8000 sq.m. of diaphragm wall and barrettes 139 No. large diameter piles ranging from 900mm to 3000mm in diameter and up to 45m deep, and 9 No. cruciform barrettes for the heaviest column loads. Major factors influencing the design of these foundations include differential settlement, heave analysis and a fast track construction approach. Little Britain will provide 43000 sq.m. of space in two linked buildings which will bridge a new road joining London Wall to Newgate Street. The foundation contract is well advanced and the building is due for completion in the Summer of 1990.

Jan 1, 1989

By Ground Improvement Committee

The evaluation of earthquake-induced liquefaction has become a routine part of geotechnical engineering design. For a given project, if an analysis identifies a potential for liquefaction and the consequences of liquefaction are deemed unacceptable, then some form of hazard mitigation is required. Mitigation efforts may consist of removing the liquefiable soils, bypassing the liquefiable soils with deep foundations, structurally accommodating the deformations or strength loss caused by liquefaction, or preventing the onset of liquefaction through ground improvement. The fundamental ground improvement mechanisms for liquefaction mitigation include densification, drainage, and reinforcement. When evaluating, recommending and specifying various ground improvement methods for liquefaction mitigation, practitioners should understand the fundamental mechanics involved and applicability and limitations of the various methods. The DFI Ground Improvement Committee offers a review of the fundamental mechanics and commentary on the applicability and limitations of each method to provide clarity and guidance on the issues related to ground improvement for liquefaction mitigation.

Aug 1, 2013

By Harry K. Weatherbee

The paper presents a design case study for a four-story correction facility addition in south Boston, Massachusetts, supported on friction piles driven into the Boston Blue Clay. 356 mm (14-in.) square prestressed-precast (PSPC) concrete piles were selected as they were found more effective and economical. A static load test was performed where the pile was brought to "failure". The load test data were evaluated to estimate the Ultimate Pile Capacity as well as the Ultimate Unit Skin Friction (Adhesion) to serve as a design tool for friction pile projects in the south Boston Area.

Jan 1, 2003

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 Michael P. Balducci

Urban deep foundation projects contain unique risks that must be recognized by the parties involved. Common pitfalls must be recognized and avoided or addressed through contractual relations and corresponding insurance coverage. By understanding these pitfalls, examining the risk-apportioning clauses and corresponding insurance obligations, may the parties? desires and expectations be met.

Jan 1, 2008