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By Shawna Munn, Jakub Hudler

This paper outlines the use of tunneling headwall softeyes for transit construction projects in the Greater Toronto Area (GTA) over the past decade. Due to spatial constraints, tunnel boring machines were used to construct the underground tunnels requiring the design of launch and exit shafts with headwall softeyes to facilitate tunneling operations. Variable ground conditions and shaft geometries lead to the development of innovative headwall and tunnel softeye design applications using fiber reinforced polymer (FRP) elements (beams, reinforcing bars, and tiebacks). This paper outlines the challenges and benefits associated with designing and constructing shafts using various systems. Lessons learned throughout design and construction of more than 20 structures over the past 10 years are outlined. The constructability challenges with using FRP and design performance are also discussed. For over a decade, the City of Toronto has been expanding its metropolitan transit network with a variety of new transit construction projects. Two recent projects in the Greater Toronto Area (GTA) for underground infrastructure include the Toronto York Spadina Subway Extension and the Eglinton Crosstown Light Rail Transit project. These add a total of 31 new stations and 18.6 km (11.5 miles) of underground transit (TTC 2017) (EllisDon 2016). Due to ground conditions and spatial constraints of existing surface infrastructure, these projects utilized tunnel boring machines (TBMs) to construct the underground tunnels requiring the design of various types of shafts and headwalls to facilitate underground tunneling operations. To allow for tunneling through the headwalls, these shafts were designed with “softeyes” - a section of the wall without metal reinforcement that allows the TBMs to tunnel through.

Jan 1, 2018

By Flor De Cock

The paper reflects part of the work from the European Regional Technical Committee on Piles (ERTC3) during its mandate between 1994 and 1999, and, in particular, describes the find­ings from an International Seminar held in 1997 in Brussels on European practice for design­ing axially loaded piles. The seminar included contributions from 17 European countries, each of which provided a synopsis of their respective national design approaches. This paper pays particular attention to the design methods based on laboratory and in-situ test data for both bored and displacement piles.

Jan 1, 2002

By Darrell L. Beddard

Pile driving started October 29, 1993 and was completed on January 27, 1994. Field work included driving piling from ground surface at one site and at or near proposed footing elevations for the remainder. Piles were driven to specified tip elevations or the elevations directed by the Project Manager. In an attempt to address what installation technique(s) performed the best, several methods were used, including varied predrilled depths, open ended piles, closed ended piles, and the use of both impact and vibratory hammers. Piles were driven closed ended where possible to study the feasibility of this option to reduce construction costs associated with pile cleanout. Piles were driven to different depths to measure capacity variations. The 24-inch (610 mm) diameter piling were driven in one piece while the 42-inch (1.07 m) diameter piling was driven in two segments. A total of 79 piles were driven for the four sites, 74 of the 24-inch (610 mm) diameter and 5 of the 42-inch (1.07 m) diameter. Various hammers were used to determine which hammers provided viable solutions to the potential problems anticipated in the design phase. Hammer selection was based on the driveability studies. Equipment included a 175 ton (1.56 MN) crane, support crane for pile stabilization, crane mounted auger drill, offshore leads, Delmag D30-32, D46-32, and D62-22 diesel hammers, an HPSI 2005 single acting hydraulic hammer, a Foster IHC S-90 double acting hydraulic hammer and a Kencho VM2-25000AII vibratory hammer with the weights set to produce 17,500 pound-inch (1.98 kN-m) of eccentric moment.

Jan 1, 1996

By Donald A. Bruce

Pin Piles are small diameter, bored, cast-in-place piles used to underpin structures. They were first employed over 40 years ago in Italy, and have been used in the U.S. since the late 1970's. However, it is only in the last few years that their full potential in terms of load holding capacity has been exploited: whereas 100 kip working loads typified former practice, ultimate loads approaching 700 kips have recently been recorded for Pin Piles founded in sand. In order to better understand the actual performance of these piles, fundamental research has been conducted by a consortium of industry and academia. This paper describes the advances made in the laboratory and full scale field testing programs. In particular, the extensive field tests have been conducted in a variety of materials in which different pile configurations have been cyclically tested to failure. By using this test method, the elastic performance of the piles has been examined and so the progressive interfacial debonding phenomenon has been studied. This has led to the development of the Elastic Ratio concept which is proving extremely useful in analyzing and predicting Pin Pile performance. Data are provided from the full scale Test Pile Programs conducted at Mobile, AL and Port Vancouver, WA. Given that Pin Piles are usually installed in areas of low headroom or restricted access, and through difficult, occasionally contaminated soils, the paper also describes key aspects of construction.

Jan 1, 1993

By Patrick J. Hannigan

A comparison of 40 statically and dynamically load tested piles was performed to evaluate the variation between testing methods. This evaluation indicated an agreement of 10% to 15% could be obtained when the available static resistance is fully mobilized by both methods and when time dependent capacity changes are minimized. Dynamic pile testing recommendations for minimum induced impact force, ram weight to pile weight ratio, and considerations for time dependent capacity changes are presented.

Jan 1, 1987

By David E. Albus, Bidjan Ghahreman

A single-family home constructed on the side of a slope in Los Angeles, CA, was subjected to lateral forces due to soil slope creep on the pile foundation supporting the home. Impacts to the property included cracking and separations in the street, retaining walls, exterior concrete flatwork, and decorative concrete features in the rear yard area. The home was supported by concrete piles that penetrated the surficial soil mantle and were embedded in underlying bedrock. However, the home exhibited minor distress that suggested even the home was being affected by soil creep. Selected points on the home were monitored with an optical survey method and manometer over a period of two years to assess if the home was undergoing vertical or lateral movement. Monitoring data indicated the home was in fact moving down slope in a manner consistent with slope creep. As a result, the authors were concerned that continued movement due to slope creep could result in over-stressing of the piles that support the home and ultimately lead to failure of the foundation system. An evaluation was then undertaken to evaluate the behavior of the foundation system due to forces from slope creep. Research was performed during the course of evaluating the conditions to consider various approaches to modeling pile behavior of the piles supporting the home. Some research has been performed to field measure creep displacement of soils and rock in slopes. These previous works have found a diverse behavior of the soil displacement with depth (velocity profile) indicating the process is very complex. An example of various velocity profiles measured in field experiments is depicted in Figure 1. Other research focused on theoretical models of velocity profiles and exhibited similarities to some of the field measured cases.

Jan 1, 2018

By Melvin I. Esrig

Lime Cement column stabilization of soft clay and sand in Salt Lake City, Utah and in San Francisco California is described and discussed. Stabilization permitted the construction, in a single stage, of a 14 m MSE wall on "medium" clay in Salt Lake City. It was used to mitigate the potential for liquefaction in San Francisco and to stabilize the Young Bay Mud beneath the BART extension to San Francisco Airport. These applications are described and the field measurements of performance are reported.

Jan 1, 2000

By Jorj O. Osterberg

The Osterberg (O-Cell) Method makes it possible to separate the side shear resistance (skin friction) from end bearing. The O-Cell is placed on or near the bottom of a drilled shaft and after the concrete is poured and cured, an equal upward and downward pressure is applied. From the test, the load-upward deflection curve in side shear and the load-downward deflection curve in end bearing are drawn. Typical curves are shown where the ultimate load in side-shear is reached and where the ultimate load in end bearing is reached. Several examples of tests in which the test load reached ultimate loads far in excess of what was expected are shown. The side shear in rock sockets is shown to be much larger than generally estimated. Examples are given of where side shear is smaller than expected and the reasons discussed. Disturbance of the sides of drilled holes due to poor construction techniques and ways to avoid these conditions are considered. Examples of bottom hole disturbance are given and ways to prevent the disturbance are discussed. A graph showing the actual measured capacity of drilled shafts compared to the estimated capacity as a function of the hardness and strength of the soil or rock is presented.

Jan 1, 1999

By Fawad S. Niazi

Ever since the use of the cone penetration test (CPT) in geotechnical practice, attempts have been made to correlate CPT parameters with pile capacity components of unit end bearing (qb) and unit shaft resistance (fp), thus deriving multiple CPT-based pile design methods. These methods focus on "capacity" only without consideration to complete axial pile load-displacement (Q-w) response. Estimated capacities from these methods also exhibit considerable scatter without any consensus on their consistency. In addition, load-displacement curves obtained from axial load tests on highly expensive and extensively instrumented piles can exhibit different shapes. Nevertheless, a single value from the curve so obtained dictates the design capacity. Currently, there are at least 42 different criteria defining capacity with considerable variation in the values obtained thereof. The Randolph elastic solution, which provides a framework for analytical evaluation of pile load-displacement response, requires the profiles of soil stiffness. The fundamental soil stiffness defined by the small-strain shear modulus (Gmax) can be obtained from shear wave velocity (Vs) readings via seismic piezocone tests (SCPTu). The secant stiffness (G), which softens from Gmax corresponding to operational load levels, can be obtained by generating stiffness reduction curves from back analysis of load tests. Then, using appropriate G values, the Q-w curve can be defined for conditions similar to the database from the pseudo strain (w/d). Thus, a complete framework for optimal integration of SCPTu data, Randolph elastic solution and back-analysis of field operational stiffness can be established for complete axial pile foundation analysis.

Jan 1, 2011

By Phil Wilkinson, Sam Whitaker

"The installation of large (XL) diameter monopiles offshore typically requires expensive and specialist plant, equipment and vessels. Due to the increasing size (weight, diameter and length) of the foundations, in order to mitigate installation risk, the use of large diameter drills is becoming an increasing requirement.Project developers often try to avoid drilling operations due to the time associated with the drilling process. This restricts projects in terms of location and it also overlooks the additional engineering benefits drilling can bring to monopile foundation design e.g. reduced foundation material and better fatigue design life.By comparing the lessons learned of three milestone overwater drilling projects; methods of maximising drill speed and decreasing drilling process time is established. Particular emphasis is put on pile internal relief drilling in a process known as Drive-Drill-Drive (DDD).The milestone overwater drilling projects are North Hoyle Offshore Wind Farm (OWF) (2003); Flamanville EPR cooling water outlet shaft (2008); and Gwynt-y-Mor OWF (2014).By evaluating the effect of foundation pile diameter on drilling process times, example foundation installation costs are derived and used to show that incorporating drilling as part of a process may not be cost prohibitive to projectsContinued advances in drill technology, and drilling rates of penetration, combined with an integrated approach to foundation design, challenge whether hammering only is always the optimal solution for XL monopile installation."

Jan 1, 2017

By Bengt H. Fellenius

"ABSTRACTAn example from a guidelines document for the Eurocode is discussed that addresses design for geotechnical strength of piled foundations in settling soil, generating drag force and downdrag. A modified example of geotechnical response is then analyzed in a failure mode, Ultimate Limit States (ULS), and stationary long-term state, Serviceable Limit States (SLS). It is shown that the Eurocode principles, when applied to correctly determined forces, results in an irrational and costly design. The results of the analysis of the modified example are applied to eight different codes pertaining to piled foundations from USA, Canada, Europe, and other countries. Several of the codes require that the drag force be included as a load in a ULS design, which an absurd and costly requirement, in some codes, in one case made even worse by combining drag force with live load. A major weakness of almost all codes is their minimal treatment and sometimes total absence of aspects of settlement of piled foundation. In contrast, my main argument is that design for capacity, whether in working stress approach, or by LFRD or ULS approaches, is not always safe unless a thorough settlement analysis shows that the design also meets the requirements of the SLS.1. INTRODUCTIONFirst, there were analysis, design, and construction establishing a State-of-Practice, SOP. Then, came codes and specifications summarizing the SOP, as interpreted by a committee. When the state-of-art, SOA, was not understood by that SOP-interpreting committee, the codes and specifications are uneconomical and, sometimes, also unsafe.The paper first presents an example quoted from two commentaries on the Eurocode 7 on design for geotechnical strength by the Eurocode (1997). The example is then modified to a more realistic case and analyzed in failure mode (ultimate limit states, ULS) and in the context of settlement (serviceability limit states, SLS). The analysis results are then applied to eight codes addressing piled foundation design and changes necessary for the referenced codes and specifications to be closer to the SOA are identified."

Jan 1, 2014

By Roy Peratrovich

An innovative cost-saving design for a 1,100 ft bulkhead on the Tanana River at Nenana in central Alaska won Alaska Construction & Oil magazine's Construction Achievement Award. The designers utilized materials available nearby at low cost. They planned sheet pile enclosures, self-anchored back into shore without cell closures. They made it practical for inexperienced local workers to do the building. And they completed the project on time and below a reduced budget.

Jan 1, 1985

By Aly M. Mohammad

The Delaware River Tramway will link civic and retail developments in Philadelphia, Pennsylvania and Camden, New Jersey. Twin 300-foot towers will anchor the cables at either side of the river. Four high capacity drilled shafts designed by the Geotechnical Department of DMJM+HARRIS support each of the towers. At the Philadelphia tower, each 6-foot diameter shaft extends 130 feet deep and terminates with a 30-foot rock socket. The shafts are situated within the footprint of an existing relieving platform, which complicates the typical construction sequence. Also, the subsurface conditions at the site provide a unique challenge in both the design and construction of the drilled shafts. During the construction of the four-drilled shafts for the Philadelphia tower, a 6000-ton Osterberg load test was performed on the first shaft to verify design assumption and confirm the shaft capacity. The results of the test were utilized to establish load transfer characteristics and develop foundation design parameters suitable for the site conditions. By doing so the Design Engineer was able to reduce the length of the rock sockets on the remaining production shafts by approximately 5 feet per shaft. As a result, the test provided a significant cost saving to the Owner by eliminating 15 feet of rock drilling from the construction costs. This paper presents a description of the unique design and construction methods adopted for the foundations, also on the Osterberg load test including equipment used, number and locations of strain gages, and interpretation of results. The results and findings presented in this paper could benefit both the design and construction industries because it provides a comparison between geotechnical design assumption and actual field measurements; which has always been a challenge particularly for rock formation.

Jan 1, 2002

By Ting Chinsu

Diaphragm wall with tie-back cable is widely used for deep excavation, especially in the area with high density of buildings. This paper presents the measured earth pressure distribution on diaphragm wall during excavation. The earth pressure cells used in field were successfully installed in deep slurry trench by a new type of simplified manipulator. The sizes of the deep excavation are 26m X 36m on plane and 9m in depth. The construction site is located between two multistorey buildings at the main business section of Beijing city. In this paper the field measurements of earth pressure distribution and the analyses based on the comparison between calculation and measurement are very valuable to improve the current calculation method for diaphragm wall design.

Jan 1, 1991

By Lok M. Sharma, Deep K. Khatri, Bradfield. Brett

"A shored enclosure was required to access a control structure upstream below the dam of a deep lake. The shoring involves the interaction of the structure, soil, and water and the loads imposed include the hydrostatic forces of the water, soil pressures as well as dynamic forces due to currents and waves. Deep excavation support systems have traditionally been designed using classical methods that involve direct computations of earth pressures. However, traditional analysis does not take into account soil-structure interaction. Numerical modelling offers better means to analyze soil-structure interaction. This paper presents a 2D finite element (2D-FE) analysis of a deep excavation support structure that was required to remove and replace a control structure at the upstream toe of a dam. The sheet-piling shoring was designed to withstand the lateral pressures from 14 m deep free water and 5.5 m deep excavation below the free water to reach the required excavation level to replace the gate structure. Elastic-plastic analyses were performed to predict the stresses and deformations of the complicated shoring structure and excavation bottom. The soil parameters, procedures used to develop the 2D-FE model, and the results are discussed in this paper. The shoring system is currently under construction.INTRODUCTIONA deep shoring system enclosure is required to keep out water and soil and to provide a support for unbalanced loadings due to dewatering and/or, excavation in order to permit construction of the permanent structures in the dry. A braced shoring system consists of a single wall sheet piling which is driven into the ground to form a “box” around the excavation site and is braced on the inside. After bracing the sheet piling, seal concrete is placed into the bottom to prevent water from seeping into the open excavation from underneath the sheet piling, and the water is pumped out to provide the dry work area. The braced shoring involves the interaction of the structure, soil, and water and the loads imposed include the hydrostatic forces of the water, soil pressures as well as dynamic forces due to currents and waves. Deep excavation support systems have traditionally been designed using classical methods that involve direct computations of earth pressures, (active, passive, or apparent pressures). There have been some uncertainties regarding the actual distribution of earth pressures due to influence of the support wall flexibility, as these traditional methods do not take into account soil-structure interaction. Numerical modelling offers better means to analyze soilstructure interaction."

Jan 1, 2017

By Yogesh Prashar

Three conventional uplift tests and 12 Rapid Pile Load Tests (RLT) were performed on total of fifteen 16-inch square pre-cast concrete driven piles at a test site in Emeryville California in December of 2000. The uplift tests were performed in accordance with ASTM standards, and the RLTs were performed using a FUNDEX RLT. The RLT is carried out by dropping a mass of 25-tons on top of the pile, thereby inducing a force that is measured by a load cell. An optical lens records the vertical deflection of LED's that are mounted on the pile. Ultimate uplift and compression capacities of each of the fifteen piles were determined using the Davisson method. Soil parameters were calibrated by back-calculation (cohesion and internal angle of friction) using both the results of conventional uplift load versus deflection curve, as well as the results of the triaxial compression tests. A two-dimensional finite difference model including soil elements, and structural elements representing the test pile was setup using the computer program Fast Lagrangian Analysis of Continua (FLAC). FLAC was used to simulate both the uplift as well as the RLT. Strength increase of cohesive material was also accounted for in the analysis. Numerically simulated and theoretically computed pile capacity curves and axial deformation variation with applied load curves are in close agreement to the observed curve during the field test. Conclusions are made from this test site regarding the factors influencing results of RLT.

Jan 1, 2002

By Eugene Mirsky, Eloy Ramos, May ElKhattab, John Wise, Terrence Carroll, Jose Torres

In 2017, Nicholson Construction Company completed a $72.1 million design-build contract for Miami Dade Water and Sewer Department to replace an existing 54-inch diameter pre-stressed concrete force main that runs from the Virginia Key Central District Wastewater Treatment Plant, under the Biscayne Bay at Norris Cut, to Fisher Island. In order to install the new sewer pipe below the bottom of Biscayne Bay, a tunnel boring machine (TBM) was launched from a 42ft diameter and 89ft deep shaft on Virginia Key and a precast segmentally lined tunnel was constructed towards a 28ft diameter and 72ft deep retrieval shaft on Fisher Island. Both shafts were constructed through sand and highly permeable limestone, primarily the Fort Thompson Formation which is part of one of the most permeable aquifers in the United States and two different techniques were used to ensure a water-tight shaft at each end of the tunnel drive. The launch shaft structure was built using the secant pile technique, wet excavation and a tremie plug. For the tunnel break-in a soil freeze block was installed after the ground was treated with low mobility grout. The retrieval shaft was built using the Deep Soil Mixing (DSM) technique and excavated in the dry. Precedence of any other structure built this deep through hard layers (UCS over 3,000 psi) using this technique was not found. This case study addresses the challenges of constructing watertight underground structures in highly porous ground for launching and retrieving a TBM. Design challenges from complex asymmetric loading, selection and comparison of the construction techniques, the installation and excavation of both shafts, and their performance are also discussed herein.

Jan 1, 2018

By Gordon Demetrick

3900 Yonge St. was not a typical site on which to build a condominium apartment. A steep hill covered the majority of the site. In order to use as much of this site as possible, the rear of the building was to have nine stores cut into the face of the hill. A permanent shoring system was required as the building structure was not designed to provide sufficient stabilizing elements to support the total earth pressure. The total excavation depth required was 36 m (120'-0") with the upper 12 m (40'-0") to be backsloped. The vertical face of soil to be supported was 24 m (80'-0'). The shoring system originally designed by the Structural Engineer was to support this face by installing soldier piles and inclined earth anchors. During bid preparation it became evident to us that the system as designed would be difficult and expensive to install due to wet soil conditions. An innovative design was required to overcome these problems. Anchor Shoring hired John Stephenson Consultants Ltd. to aid them in accomplishing this goal. After extensive investigation together with The Trow Group, a unique design was proposed which provided a practical solution to the shoring problem.

Jan 1, 1987

By Roy A. Bell

A 200-foot diameter, 72-foot high petroleum storage tank was built in a hillside ravine where a portion of the site contained soft clay fill. Soil-cement piles, 40 inches in diameter and up to 38 feet long, were installed to support the tank shell and ringwall, and a portion of the tank floor by drilling into the stiff to hard underlying soils and weathered bedrock. The goal was to provide a strong enough foundation to resist the seismic tank shell loading and to minimize differential settlement of the tank shell to avoid out-of-round clearance problems between the shell and floating-roof. A cantilevered retaining wall up to 8 feet high was constructed around a portion of the tank perimeter by inserting steel H-beams into soil-cement piles. The cantilever soldier piles for the retaining wall were installed from a temporary earth embankment on the hillside directly over the top of the wall. The temporary embankment was then removed and the tank pad was cut to grade in front of the soldier piles. Some of the soil-cement piles for both the tank foundation and retaining wall could not be advanced to design depth because the drill/mixing tools could not penetrate to the required depth in the hard soils/bedrock. Smaller diameter borings (22 inches in diameter) were drilled through the centers of the short-of-design soil-cement piles to the design depth and then backfilled with concrete.

Jan 1, 1997

By Colin Curtis

In recent years, Manchester Airport has undergone expansion including the construction of a second runway, a new terminal building (Terminal 3) and extensions to the existing Terminal 1. Manchester is Britains third largest airport and ranked 20th in the world for international traffic. Arup (Manchester) was engaged as consulting engineer in a multi-disciplinary role for the terminal works. Part of this was a geotechnical commission including site investigation and pile design followed by supervision. This paper reviews the piling for the old, new and terminal extensions. In total, five pile types have been utilised over the years. The original 1950's Terminal 1 was founded on driven cast in situ piles, with a later 1970's extension utilising rotary augured piles. The recent piling comprised continuous flight auger piles (CFA), driven steel tube and tripod bored; the latter in areas of restricted access or low headroom. The ground conditions are Made Ground over thin Alluvial and Glacial drift, in turn, over a generally weak to moderately weak gypsiferous mudstone. All the piles were socketed into the mudstone. In terms of the new CFA piles, quality control using the instrumentation monitoring was problematical, but a substantial static load and integrity test programme resolved pile performance. Part of the work is matching new pile performance with previously installed piles and the continued use of older piles with new loads. Research provided some data on the older piles, including some static load test data, which enabled back analyses of their design and likely behaviour. Differences in design methods, installation techniques and pile behaviour based on load tests will be discussed.

Jan 1, 2001