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By Charles M. Wilk, Lori Tiefenthaler

"Information presented in this paper can be used to support deep soil mixing, subsurface grouting and slurry wall technology as sustainable construction technologies. Ordinary Portland Cement (OPC) is the default cementitious material used by Deep Foundation Institute (DFI) Members for geotechnical work. Owners, engineers and contractors can contribute to the sustainability of a geotechnical project by increasing the use blended hydraulic cements and industrial byproducts to replace some of the OPC in mix designs. Sustainability is defined as the quality of not being harmful to the environment or depleting natural resources. Production of cementitious materials consumes natural raw materials and energy while also generating air emissions and waste. Life Cycle Assessments can be used to compare the relative environmental impacts of one cementitious material to another. Blended hydraulic cements (BHCs) are interground (or blended) mixtures of Supplementary Cementitious Materials (SCMs) with OPC. Commonly used SCMs include fly ash, ground granulated blast furnace slag (GGBFS) and limestone. Examples of industrial byproducts commonly used in geotechnical work include coal combustion residuals (CCR) (aka fly ash), and ground granulated blast furnace slag (GGBFS). Much of life cycle impact of these SCMs and industrial byproducts have already been borne by the industries that generated them. There is increasing awareness to LCA and sustainability of different materials used on projects. This is evident in the application of the Leadership in Energy and Environmental Design (LEED) program. The savings in environmental impact with the use of SCMs and industrial byproducts can make proposed use of these materials in a geotechnical project more attractive in terms of sustainability. This paper presents (a) information that compares published life cycle assessment data of OPC, BHCs, and slag cement (SC) to illustrate the potential benefits to sustainability and (b) general strategies for positioning a geotechnical application, use, project design or cementitious material mix as a more sustainable alternative"

Jan 1, 2017

By Michael G. Batten, Brian D. Keaney

]The Virginia Department of Transportation (VDOT) and the harbors on the James River routinely use precast concrete piles founded in the Yorktown formation to support bridges and other coastal structures. However, axial pile resistances for large diameter piles in this area have been historically overestimated on past projects. This may be due to a common assumption that very large unit end bearing resistance will be developed for a large diameter displacement pile that is driven a significant depth. This assumption is integrated in the Nordlund (1963; 1979) method which is commonly used to estimate axial pile resistance for bridge foundations. A static and dynamic pile load testing program was implemented as part of the Hampton Roads Bridge and Tunnel Expansion project in Norfolk, VA in the James River. A primary objective of this program was to calibrate an axial resistance calculation method against the measured load test results. A method developed by Eslami and Fellenius (1997) that uses CPTu data directly was effective at calibrating to the measured load test results, and allowed for clearer interpretation of the unit resistance values than indirect, semi-empirical methods that require interpretation of soil friction angle and undrained shear strength.

Sep 8, 2021

By Eric S. Lindquist, Charles A. Luxford

The State of Texas recently adopted a master plan to expand the existing Capitol Complex in Austin. Phase 1 of this expansion will add two new State office buildings and five levels of underground parking to the existing Complex. Additionally, a landscaped pedestrian mall will be built atop a portion of the underground parking to enhance the area as a cultural destination. Capitol Complex website: https://www.tfc-ccp.org/ Brierley Associates was selected to provide detailed design of the entire Phase 1 earth retention system for an approximately 40-65 ft (12-20 m) deep, 500,000+ yd3 (380,000+ m3) excavation through overburden soils and limestone bedrock. To facilitate overall project coordination, all design packages were required to develop Revit models, including the retention system package. With the project located in an urban setting, this 3D model also facilitated coordination of the retention system with adjacent major structures and utilities. The retention system is a combination of soil nails, soldier piling with tiebacks and rock anchors with a shotcrete facing as a substrate for the below-grade blindside waterproofing system. Due to the substantial scope of excavation, a significant number of utilities had to be routed on a temporary span over the excavation. Brierley Associates designed this utility support structure, which required extensive coordination with the excavation support and existing utilities located directly underneath the structure’s foundations. Preconstruction geotechnical work identified a fault zone that might be encountered within the excavation; however, the fault feature was found to have a more adverse location and orientation than originally anticipated. This observation required that a portion of the temporary anchors be converted to higher-capacity, corrosion-protected permanent anchors.

By Glen R. Andersen

"Two of the greatest challenges we face in managing our aging infrastructure are to perform accurate condition assessments and to realistically predict the risk of non-action. The aim of this paper is to discuss common pitfalls we face in performing accurate condition assessments of our aging infrastructure using the case history of a recent near miss at the Lake Manatee Dam in Central Florida. The dam was placed into service in 1967 and was inspected every couple of years by dam safety engineers beginning in 1978. Although there was substantial and repeated evidence of a serious piping and internal erosion problem in each of these inspections, the problem was overlooked by most of the inspection teams. In 2012, the inspection team concluded that: “the Lake Manatee Reservoir Dam is well maintained and is in very good overall condition.” However, in 2013 a new team inspected the dam from an entirely different perspective, identified potentially serious conditions, performed an integration of the historical inspection data and concluded that: 1) the Lake Manatee Dam was in a severely distressed state; and, 2) without an immediate intervention there was a high risk of an uncontrolled release of the reservoir most likely following a large rainfall event and prolonged opening of the service spillway. This case history highlights human factors contributing to the near miss including group think and focusing on changes from prior inspections. The integration of historical inspection data is recommended for managing our aging infrastructure.INTRODUCTIONThe engineering analytical techniques most appropriate for assessing an aging infrastructure can be distinct from those used for the original design. To adequately manage our aging infrastructure it is necessary to change our perspective from anticipating failure mechanisms and designing to prevent them to assessing condition, detecting the presence of potential failure mechanisms, and assessing the potential risks. In many circumstances the failure mechanisms currently active may not have been anticipated by the original design team.We have developed a substantial body of experience in the design of our infrastructure. Full scale and laboratory testing coupled with the application of scientific principles to model behavior has led to many powerful design tools. The continued serviceability of our infrastructure as its elements reach their design lives stands as a legacy to our profession. However, under the sustained effect of limited resources for maintenance and rehabilitation parts of our infrastructure are in a highly deteriorated state. Unfortunately, the condition of some of these has not been properly assessed. This paper focuses on the Lake Manatee Dam in Central Florida and the process used to clearly identify its highly deteriorated state. While there are many factors that contributed to the lack of a proper assessment of its condition, the focus herein will be on human factors and in particular how “Group Think”, “Aversion to Bad News”, and “Condition Assessments Based on Changes to Prior Condition” may have contributed to not properly identifying the development of a serious failure mechanism."

Jan 1, 2017

By Mark D. Fuhriman, Parham Khoshkbari, Robert Fosse

Drilled displacement piles are becoming an increasingly common deep foundation choice for their relatively simple installation methods, applicability to a wide range of subsurface conditions, and versatility. The installation method includes drilling and displacement of the soil followed by delivery of fluid cement grout under pressure, and placement of steel reinforcing to complete the pile. Because the installation method uses blind processes that do not permit direct observation of the pile, it is desirable to employ redundant testing tools to complement good construction techniques and inspection practices to ensure integrity of the piles. This paper examines the use of a range of integrity testing tools used for pile installations at a major office campus development. Because the integrity of a drilled displacement pile and its performance depend to a large extent on the skill and experience of the installation crew, the paper explores how use of multiple practical tools, including automated monitoring tools on the pile installation equipment, thermal integrity profiling, and high-strain dynamic testing, ensure structural integrity of the completed piles and how redundant integrity testing methods complement good construction and inspection practices add confidence in the quality of the foundation system.

Sep 8, 2021

By Shawna Munn, Nadir Ansari, Allison Bennett

"This paper outlines how specification driven design has made Toronto Area transit infrastructure projects more expensive than similar private projects, and provides a case study of the results of an excavation at Launch Shaft 1 (LS1) for the Eglinton Crosstown Light Rail Transit project in Toronto, Ontario. The paper will describe the impact specification driven design parameters can have on design economy, constructability, and schedule and will suggest an alternative approach utilizing the Observational Method. As a result of the initial specification based design, Isherwood was retained by both the General Contractor and the Specialty Excavation Shoring Contractor to provide value engineering leveraging the Observational Method to improve constructability and construction schedule. By using well known, accepted design methods coupled with local experience in lieu of the specified design pressures and parameters, the redesigned bracing scheme reduced construction cost and schedule. This excavation case history can be a lesson learned for future transit projects.The City of Toronto has been developing its transportation network since the mid 1800’s. “Canada’s First Subway” along Yonge Street opened in March 1954 (TTC 1954), with a few additions to the subway network through to the 1980’s. The following two decades marked a long period of slow development due to recessions, budget cuts, and politics along with several cancelled projects. To fill the gap left by years of underfunding, several new transit projects are now under construction in the city as a part of Metrolinx’s $50B, 25 year, “The Big Move” initiative (Metrolinx 2013). The work on these types of infrastructure projects is highlighting a different and developing challenge within the tendering and design specification structure we will call Prescriptive Specification Design (PSD).PSD is a method used within contract specifications to control design risk on a project by applying conservative design methods, factors of safety, or other parameters to make a “fool proof” design. It is akin to requesting a colouring by numbers approach from a painter. There are inherent risks of using this method of tendering a project including increased project costs, longer construction schedules, and decrease of overall project economy. In PSD, the Owner “owns” all of the design risk on a project, including any additional costs due to changed site conditions. However, the Contractor commonly “owns” the risk of any deviations from the design specification they pursue, therefore making any improvements to the design, cost, or schedule less desirable from the Contractor’s point of view. The impact of this type of strict specified approach to design has been seen in transit infrastructure projects in the Toronto area. Figure 1 outlines the range of specified AEPD design pressures as a function of excavation height (H) specified for use in Toronto underground transit projects since the 1970’s to present day. A clear trend can be seen with respect to increased design pressures specified. The ranges shown for each project are intended to account for the potential differences in soil conditions for the highly overconsolidated glaciated soils in the Toronto area. The graph also highlights the typical range, in blue, for the industry practice in Toronto for comparison."

Jan 1, 2017

"1 INTRODUCTIONThe use of nondestructive testing (NDT) methods to evaluate the integrity of Augered Cast-in-Place (ACIP) and Drilled Displacement (DD) piles has been a subject of significant debate among engineers, contractors and NDT practitioners. This guideline document will illustrate the importance of reviewing all available information in conjunction with the NDT records. ACIP and DD piles have unique properties that must be considered when using a specific NDT method. Any evaluation of the integrity of an ACIP or DD pile must also include a thorough review of the detailed pile installation records and the site specific soil conditions. Long or theoretical descriptions of the methods have not been included in this publication. More detailed information about these NDT methods including their theoretical and historical backgrounds can be found in DFI’s Manual for Non Destructive Testing and Evaluation of Drilled Shafts (2004). Additional information can also be found in the more comprehensive textbook Nondestructive Testing of Deep Foundations by Hertlein and Davis (2006).1.1 PurposeThe intent of this guideline is to provide practical guidance for the proper interpretation of NDT results on ACIP and DD piles. Short descriptions of the main integrity methods available are provided along with several examples of how to use all of the information available to make sound engineering judgments about the results. This publication is a state-of-the-practice guideline to promote accurate engineering evaluations.For engineers inexperienced with NDT, these guidelines provide sufficient background information on NDT methods to help understand the limitations of the testing, assess the results presented to them, and formulate appropriate questions. This is particularly important for engineers charged with the responsibility to determine from those results what, if any, consequences there may be on the performance of the structure under construction."

Jan 1, 2016

By I. D. McPherson, Dominic P. Mahoney

The Metro Sports Facility is currently under development in Christchurch, New Zealand and is a key Anchor Project in the city’s post-earth quake recovery. When completed it will be largest indoor sports and swimming pool complex in New Zealand, with a building footprint in the order of 22,000m2. The site is underlain by poor performing soils comprising interbedded layers of soft compressible silts and loose liquefiable sands to over 20m depth. The site is typical for Christchurch with a shallow groundwater table and artesian conditions. The site performed poorly during the 2010-2011 Canterbury Earthquake Sequence with extensive liquefaction, and associated ground damage. To provide a resilient and economical foundation system for this key development project, deep ground improvement comprising of a uniform grid of some 7,200 stone columns in conjunction with robust shallow foundations has been adopted. This paper discusses the geotechnical site constraints, and ground performance under earthquake loading and describes the various options considered for the development. The foundation option selected, the design considerations of the adopted stone column ground improvement, and foundation solution are described in detail, as well as, construction observations. The paper aims to provide insight into an urban large-scale ground improvement project for the engineering practitioner.

Nov 1, 2022

By P. Seethalakshmi, Yatakuri Yaswanth Naidu

The use of a single pile, group of piles with pile cap, piled raft foundation system, etc., are prevalent in transferring the superstructure load from the soft soil layers to the firm underground layers to reduce the settlement and improve the bearing capacity. The recent development of disconnected piled raft foundation has gained greater importance in improving the load transfer mechanism among the pile, raft, and subsoil by reducing the vulnerability of the greatest axial force on the pile head which leads to pile failure. The present study aims at analyzing the performance of unreinforced and Geogrid reinforced disconnected piled raft foundations under vertical loading using the commercially available finite element software PLAXIS-3D. A parametric study was conducted on unreinforced and reinforced disconnected piled raft foundations to explore the effect of varying pile stiffness as well as the inclusion of Geogrid layer on the load vs settlement, the load sharing ratio of piles and raft, and the distribution of axial load and bending moment along the length of the pile. The Mohr-Coulomb model was used for the granular cushion layer while the Modified Cam Clay model was used for soft clay underlain the sand layer. Raft and piles were assumed to be rigid and linear elastic. The results showed that axial force taken by piles with higher stiffness was maximum while settlement at the bottom tip of the pile with higher stiffness was maximum in both reinforced as well as unreinforced disconnected piled raft systems.

Sep 1, 2022

By William Billiet

"The Dulles Silver Line Phase II is an 11.4 mile extension of the Washington Area Metro Transit Authority’s Silver line in northern Virginia. There are three miles of elevated guideway, which are supported on 188 large diameter mono-shafts founded within the Triassic Geologic Aged Culpeper Fault Basin. Three lateral load tests were performed on fully instrumented test shafts. The challenge in developing the load testing program was how to reproduce the effects of the extremely high design loads along the test shafts, considering the limitations of the load test equipment. Development, execution, and analysis of the lateral load test program is discussed.INTRODUCTIONPlans for Dulles Silver Line Phase II include two Aerial Guideway sections on elevated track, the Main Line and Yard Leads. The Aerial Guideways are supported on mono-shafts (single, largediameter drilled shafts) socketed into rock. Lateral loads are resisted primarily through the stiffness of the shaft and the geotechnical resistance of the rock socket. The monoshafts were designed in accordance with AASHTO LRFD 2014. Based on our preliminary analyses, the production mono shafts were expected to consist of 6.5, 7.5, and 8.5 foot diameter drilled shafts with rock socket lengths varying between 8 and 34 feet (averaging 14 feet). Table 1 summarizes the maximum service load combinations for each size production shaft along the aerial guideway alignment.GEOLOGYThe project is located within the Piedmont Province, a major physiographic province on the east coast of the USA extending from Alabama to Pennsylvania. Within the Piedmont, a number of Mesozoic basins formed in rift valleys. Dulles Airport is located in the Culpeper Basin, characterized by a relatively shallow siltstone rock surface compared to the adjacent areas underlain by Piedmont crystalline rocks. The geologic stratigraphy at the load test sites generally consist of residual soils and intermediate geo-material (IGM) overlying siltstone rock. IGM is a term used by Virginia Department of Transportation (VDOT) to describe residual material as it transitions between soil and rock. For the purposes of the load test, the siltstone rock is classified as fractured rock (RQD<50), and competent rock (RQD=50). Table 2 summarizes the stratigraphy encountered at each test site."

Jan 1, 2017

By Heman Manchanda, Sandeep Sharma

Several infrastructure projects are in various stages of construction and planning in India and almost all of them involves open ground excavation extending to varying depths. These structures are generally multipurpose and fulfil several needs of the society, their failure can be catastrophic. The design and construction of deep open excavations is generally associated with a high level of risks due to a whole series of uncertainties involved, and the success of such projects depends on various factors including appropriate evaluation of ground behavior and response to excavation stages, correct choice and analysis of construction supports, control of ground water flow during excavation, etc. One of the most critical amongst all these is ground water flow during construction and stability of underground excavation depends to a large extent on ground water control. This paper uses numerical studies for the assessment of the potential impact of ground water and ground water movement for the design of underground deep structures. The studies are being conducted using PLAXIS 2D finite element software and analysis all construction stages to which an open underground excavation shall be subjected. The paper discussed in detail the impact of water table fluctuations and comparative evaluation of different water flow conditions – a) Different Stages of excavation in line with the construction sequence (Phreatic), b) Coupled flow analysis (Transient- 1 year and 2-year duration) and c) Steady state flow conditions. The paper also covers seepage calculation and design of dewatering system.

Sep 1, 2022

By Hubert Law, Dan A. Brown, Kyle M. Rollins

"Soil mixing and jet grouting provide a means to significantly increase the lateral resistance of pile group foundations with relatively little investment of time, effort, and expense compared to the cost for additional piles necessary to produce the same increased resistance. Comparative field testing conducted on full-scale pile groups before and after treatment of small soil volumes showed significant improvement in lateral resistance. The lateral resistance of the pile group increased by 60% due to soil mixing and by 180% due to jet grouting. To provide additional understanding regarding the influence of the soil mix strength, depth of improvement and width of improvement, a series of parametric studies were performed using a 3D finite element model. This set of “virtual load tests” was then combined with the results from the actual field tests to help develop a simplified model to account for observed behavior. In general, the testing and analysis indicate the pile group and the surrounding improved soil block generally act as an equivalent “super pile”. The passive force, side shear and base shear on the improved soil surrounding the pile group itself increased lateral resistance. This increase in resistance from the soil block can be added to the lateral resistance of the pile group.INTRODUCTIONThe lateral resistance of pile groups is often critical to the design of bridges and high-rise structures subject to seismic, wind, wave and landslide forces. Typically, when analyses indicate that the lateral resistance of a foundation is inadequate, additional piles, drilled shafts or micro-piles are added to increase the lateral resistance. Furthermore, an expanded pile cap or connecting beam is often required to structurally connect the new piles to the existing pile group. While this approach provides the required lateral resistance, it may also be relatively expensive and time consuming. An alternative approach is to use soil improvement techniques to increase the strength and stiffness of the surrounding soil and thereby increase the lateral resistance of the pile group. The improved zone could potentially be relatively shallow because the lateral resistance of piles is typically transferred within 5 to 10 pile diameters. For example, the soil around the periphery of the foundation could be relatively easily improved for an existing foundation as illustrated in Fig. 1(a) using a variety of soil improvement techniques. Alternatively, the soil under the foundation could be improved for a new foundation or even for an existing foundation with a technique such as jet grouting (see Fig. 1(b)). Improving the soil under the foundation would have the potential for producing greater increases in lateral resistance because the improvement would reach interior piles. In addition, the process of creating a cemented “soilcrete” zone around pile foundations could potentially produce a zone which would behave like a reinforced “superpile” with increased structural stiffness."

Jan 1, 2015

By Stephan Fisch, Franz-Werner Gerressen

"The use of cut-off-walls (COW) for the open pit coal mines has been used for decades. They have been used to reduce the negative hydraulic impact to the surrounding area caused by the open pit mining. The pile-guided trench cutting system is a worldwide unique technique, originally developed by the engineers of the mining companies themselves. It guarantees a continuous, joint free, COW during a continuous installation process. At this specific site in Welzow, this technique has been pushed to new limits in order to address the local lake region. Depth capability has been designed to about 430 ft (130m), proven are already depth of about 360 ft (110m) at a constant trench width of 39 inch (1000 mm). This project is approximately. 6.8 miles (11 km) long of COW, scheduled to be completed in 12 years period. About 2.05 miles (3.3km) have been installed, which is equivalent of about 3.5 Million ft² (330,000 m²). The system flushes special clay which forms a filter crust at the inner surface of the trench. Only natural clay resources used, in order to achieve the cut-off effect (colmation effect). The paper explains the installation process of the cut-off-wall as well as the equipment systems developed specifically for this project. After a successful start of the first phase of the project, the next step in the advancement of the equipment is already underway to enable the installation of greater depth to approximately 490 ft (150 m +) and beyond. The next generation equipment system is scheduled to start operation around 2018 INTRODUCTIONThis Serbian saying “Bóh je stworil Lužicu a cert je zaryl brunicu – God created Lusatia and the devil buried brown coal underneath it.” captures local communities’ ambivalence towards lignite.Lusatia is an almost entirely flat stretch of land between the Elbe and Neiße rivers dominated by glacial sands. On the surface, the heathland and woodland is hardly noteworthy. However, three large lignite mining regions, two in Brandenburg and one in Saxony, in the east part of Germany, divert the attention to underground level, down to depths of up to 120 meters. Here, seams crisscross the earth like ribbons. They were formed in the Tertiary around 17 million years ago.The mining of the lignite started almost 200 years ago. To enable open pit mining, a suitable dewatering system was required. At first, wells and drainage system were used. With the increasing demand to go deeper to enable full use of the existing resources with greater mining depth, a decision taken back in the 60th of the last century, the amount of water which had to be pumped increased dramatically. In peak times, approx. 1.57 Billion cubic yards per year (1.2 Billion m³/year) had to be pumped. This led to a lowering of the groundwater level for up to 230 ft (70 m), impacting the regional lake landscape. In order to reduce the influence on the water balance, and bring the water level back to pre1970th, a first development took place to implement the use of specific COW system to depth of about 147 ft (45m)."

Jan 1, 2017

By Jarod McBride, Mike Johnston

Over the last decade the construction industry, particularly ground enhancement services such as Jet Grouting, have seen a dramatic rise in the cost of waste transportation and disposal services; increasingly representing a significant percentage of total job cost. As these costs increase and our industry continues making strides to become better stewards of the environment, one of the best ways we can contribute is by placing a priority on sustainability. Stage 3 Separation&rsquo;s unique solutions contributed to sustainability while creating new economic value. This was achieved by reducing waste, reusing materials, and accelerating production when compared to the traditional spoils pit management practice. Stage 3 Separation believes in bringing sustainable solutions to industry and was successful in teaming with HRBT South Island to meet the following project metrics: (1) reduce the overall disposal costs and associated liability, (2) recycle/reuse base materials where fit, (3) meet specified water quality for discharge, (4) do all of this in way that contributes to accelerating the production schedule in a critical job path. The HRBT South Island project overview consisted of over 650 columns, producing north of 150,000 yds3 of slurry.&nbsp; Our goal was to take the jet grout slurry waste stream and separate the liquids and solids; creating a water phase that met all environmental standards to be treated and disposed of directly into the environment and creating a dry stackable solid that could be sent directly to a landfill. Prior to Stage 3 Separation&rsquo;s deployment the Jet Grout contactor was being hampered by poor spoils management, long spoil cure times, and at the mercy of costly vac-trucks or less than partial solid loads.&nbsp; Within weeks of new process and the removal of these impediments production doubled, waste was cut in half, and numerous other efficiencies were gained. Keywords: Jet Grouting, Spoils Management, Sustainability, Waste Reduction, Production Performance

Oct 7, 2024

By Daniel Renosto, Crysthian Azevedo

This article presents a case study with field analysis and numerical tests of grillages and helical pile foundations used for tensile and compression loads of transmission line towers in Brazil. Through finite element analysis (FEA), the structural resistance of the pile will be evaluated using pre-established supports with the stiffness indicated in different types of soil along the profile of the transmission line. The variation in this resistance of the grillage-pile assembly depending on these supports will be evaluated. Elements such as couplers, shafts, leads, extensions, helices, welds, and screws are analyzed from the perspective of structural engineering with interaction with geotechnics. Actual structural safety factors are presented in this case study taking into account tensile, compressive, torque, and construction eccentricities loads. Within the scope of quality control of helical piles and grillages of this specific project, it will be possible to verify points of attention and suggestions for improvements for helical piles and grillages in terms of manufacturing, assembly, and execution. This article hopes to present the importance of a structural analysis of soil-structure interaction that is sometimes neglected in foundation projects based on a real case study carried out in Brazil.

Oct 7, 2024

By Carlandrea Albonico, Salvatore Miranda

The paper describes an innovative geotechnical engineering solution that has been provided within the scope of the Galataport Project, in Istanbul, Turkey. Among all interesting geotechnical works included in the Project, this paper presents the design principle, adopted technologies and performance controls related to the Multi- Purpose Bottom Plug (MPBP). This original geotechnical engineering solution has been employed for the deep basement excavation in Karaköy and consists of a combination of seepage control, ground improvement, and load bearing elements, which have been executed with double-fluid jet grouting, pseudo-elliptical jet grouting and permanent micropiles, respectively. The paper highlights the importance of employing cutting-edge technologies within the foundation engineering field and state-of-the-art electronic control devices, in parallel with the essential human expertise, in order to obtain the desired results in this high-profile Project.

Nov 1, 2022

By Matthew Runion, Christopher Lawler

The Aeolus – Jim Bridger Transmission Line Project is located in southern Wyoming, home to some of the largest coal seams in the world. Coal seams present unique challenges to underground construction, as they are at high risk of coal-seam fires and do not provide a reliable bearing stratum. Accurate identification of these hazards was essential for reliable design and successful construction of foundations on this project; however, environmental restrictions and other protections created short time frames to access several sites. Coupled with a firm construction deadline, this meant that a comprehensive geotechnical investigation prior to construction would not be possible. This paper presents the project as a case study, and details how an Engineer-Procure-Construct (EPC) contracting format supported by a comprehensive Quality Assurance (QA) program provided a solution to the defined challenges. It describes the initial design process using incomplete geotechnical data and explains how the developed QA program verified design assumptions and reduced geotechnical risk through early identification of geologic conditions during construction. Specific examples will be given, and industry implications will be discussed.

By W. L. Chong, Y. Zou

There are many types of Earth Retention Systems (ERS) available in the market where more than one method can be a feasible solution for a project. This paper examines the design and construct process of a project in Dee Why, NSW using a hybrid ERS comprising contiguous piles with jet grout infill. The development comprises a deep basement and mixed-use urban superstructure. The site is located in an area of variable ground conditions, high ground water table and in proximity to existing buildings with multi-level basements. This paper details a comprehensive assessment of the geological conditions and strategies adopted to better understand the effectiveness of the proposed product and to minimise the associated risks of the proposed solution. This involved conducting additional geotechnical investigation, extensive numerical modelling and in-situ monitoring of the movements and the performance of the walls. A monitoring regime consisting of inclinometers, survey points on capping beam and prisms on the neighbouring buildings and roads surrounding shoring wall was implemented. The monitoring results were back-analysed using computer software WALLAP, Plaxis–2D and Plaxis–3D for the post-construction examinations. This paper details the effectiveness and advantages of a hybrid ERS using contiguous piles with jet grout infill.

Nov 1, 2022

By Brandon Smith, William Bohlen

Riverbank erosion along the Brazos River has modified the structural support conditions for an existing bridge structure in Southeast Texas. The 8-span, 1,200-foot long bridge was completed in 1992 along Highway 99, a key corridor for the Houston area. Foundation support conditions have been altered due to natural, ongoing river morphology for three bents on the affected riverbank. Recent events include three storms within a three-year period that each exceeded the 500-year return probability. This resulted in accelerated erosion along the northern riverbank. Over forty vertical feet of soil has been removed in some locations. Drilled shaft foundations are now functioning as columns. This review considers the behavior of columns and deep foundation elements due to the modified support conditions. The review ultimately presents a rational methodology for the review of the present and anticipated future bridge configuration with respect to current strength, service, and extreme event limits, with corresponding safety factors for the design. Introduction and Background The Fort Bend Grand Parkway Toll Road Authority (Owner) oversees the State Highway 99 Judge Jodie Stavinoha Bridge over the Brazos River. The 8-span, 1,200-foot long bridge was originally designed with four southern approach spans of 115 feet; a three-span continuous river crossing with span lengths of 195 feet-235 feet-195 feet; and a single northern approach span of 115 feet. Figure 1 provides an overview of the northern portion of the bridge. Table 1 provides a summary of the original bridge substructure configuration. When the bridge was completed, the centerline of the Brazos River was located at midpsan of the main span and the northern high bank was originally located at Bent 7. Erosion process has forced the northern high bank to Abutment 9 (also called Bent 9), and the river centerline during normal flow conditions is located south of Bent 8. The overall estimated river excursion at present day is approximately 270 feet to the north from its original location. An erosion wall that was installed in 2017 limits further erosion of the north river bank within the 300-foot width of the roadway corridor right-of-way. This study was developed to better understand the existing conditions, and to forecast the need, nature, and criteria for potential future improvements.

Jan 1, 2019

By Kevin P. Gleckler, Steven C. Highfill

"Escalators to access platforms for the Second Avenue Subway Station at 72nd Street in Manhattan are to be installed in the basement of an existing 19-Story residential building. The escalators, which extend below the existing building foundations, require excavation of an inclined rock cavern up to 80-feet deep. Underpinning of columns within the 19-story building as well as a stone masonry party wall and columns for an adjacent 5-story building was completed prior to excavation of the rock cavern to ensure structural stability.This paper will discuss the analysis and design of the underpinning system, the installation and load transfer procedures and the cavern excavation immediately below. The underpinning system was subject to very strict deformation limits and to electronic monitoring prior to and throughout the load transfer and construction process. Key details such as the load transfer mechanism between the reinforced concrete column and the temporary structural steel underpinning frame will be discussed. The challenging rock excavation process will be described which utilized conventional equipment and pattern drilling with Damite rock splitting mortar.INTRODUCTIONPhase 1 of the Second Avenue Subway is being built by MTA Capital Construction (MTACC) to improve subway service on the east side of Manhattan. Entrance 1 for the 72nd Street Station of the Second Avenue Subway is located on the east side of 2nd Avenue at the corner of E 69th Street in New York City. Access to the station mezzanine, approximately 80-feet below grade, is designed to be routed through the basement of an existing 19-story residential building. From the sidewalk, stairs and escalators within the width of sidewalk connect the riding public to a basement level mezzanine, which turns into the building at roughly 16 feet below grade (Fig. 1). Riders then connect to three long escalators to arrive at the station mezzanine. The escalators are to be installed within an inclined and arched cast-in-place (CIP) concrete lined rock cavern (Fig. 2). Construction of both the entrance into the basement and the escalator cavern require the transfer of columns within the 19-story building. Excavation of the escalator cavern also impacts the foundation support for columns and a load bearing party wall for the 5-story residential building immediately to the north. Two stages of load transfer were used at each location. The Stage 1 transfer used a temporary underpinning system to unload the current structure which allowed for construction of the permanent transfer girders. Stage 2 transferred the load from the temporary system to the permanent transfer girders."

Jan 1, 2016