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By Brian Isherwood, Tara Brown, Paul Kreycir, Jenny Earle

"The Shangri-La hotel and luxury condominium tower, recently opened on University Avenue in downtown Toronto, required eight levels of underground structure, four extending into the shale bedrock.Isherwood Geostructural Engineers was retained in 2007 by Anchor Shoring Limited to provide an alternative design-build solution to better address serious foundation risks. The site, bounded on three sides by City streets, abuts an existing 1957 14-storey building with five underground levels to the north. Sitting on the rock surface along the east perimeter under University Avenue runs the existing Toronto Transit Commission’s University Subway Line built by cut-and-cover in the 1950’s and which was believed to lie very near the property boundary at the southeast corner of the site.The bedrock under Toronto is known to contain very high locked-in horizontal stresses, much higher than can be resisted by shoring techniques, which result in inevitable wall movement when excavating deep into the rock. The strategy adopted to control the risk to the Subway, adjacent building, and major utilities is described in the paper, along with the comprehensive monitoring of movements, and their comparison to predictions.The ProjectThe 66-storey Shangri-La hotel and luxury condominium tower, recently constructed on University Avenue in downtown Toronto, houses 222 hotel rooms in floors 1-17; 287 residences on floors 18-49; and private estates including two 2-storey penthouses on floors 50-66. These comprise 873,000 square feet of development. Eight levels of underground basement are required to provide parking and other amenities, the lower four extending into the shale bedrock."

Jan 1, 2015

By Richard D. Luark, Fernanda S. Madrona

Designing temporary retaining systems that allow for deeper excavation amid the existing urban infrastructure has become a challenge. A 60-foot-deep excavation in downtown Seattle was required to construct five levels of below grade parking for a 35-story high-rise building, Tower 12, next to an existing 20-story tower with three levels of below grade parking, separated from the project by an 18-foot wide alley. The solution was to combine two temporary excavation support systems, soil nailing and anchored soldier piles, to work within the site constraints. Densely-arranged, short-length soil nails were used to support the upper 30 feet of the excavation, while the lower 30 feet of the excavation was supported with soldier piles combined with steeply-inclined, high-capacity ground anchors, which extended below the adjacent building foundations. The combined temporary support system eliminated the need for internal bracing, reducing construction cost and schedule. The performance of the combined soil nail and soldier pile system was monitored with an inclinometer and optical survey monitoring, which demonstrated the performance of the combined temporary support system. This paper provides a discussion of the advantages of combining different excavation systems and an analysis of movement monitoring data collected. SITE CONDITIONS AND PROJECT INFORMATION Tower 12 consists of a 0.45-acre development with 36-stories of mixed, residential and commercial use with four levels of below grade parking. The project site is bounded by the Cristalla Condominium to the north, Virginia street to the south, 2nd Avenue to the East, and an 18-foot wide private alley to the west. The One Pacific Tower Condominium, which has three levels of below grade parking, was located to the west across the alley. A site layout plan is presented as Figure 1. As shown in Figure 1, the construction of the west wall required a maximum 51-foot-deep excavation, from elevation (EL) 162 feet to EL 111 feet. Adjacent to the west wall, the existing alley grade varies from elevation 154 to 161 feet, leaving a narrow block of soil 18 feet wide and up to 42 feet high to be shored along the alley in order to reach the One Pacific Tower bottom of mat foundation at EL of about 120 feet. In addition to the existing One Pacific Tower Basement wall, site constraints included existing utilities along the alley such as an existing 4.5-feet wide by 7-feet high vault, with bottom at approximate EL 146 located 10 feet from the back face of the proposed Tower 12 basement wall.

Jan 1, 2019

By Mihir B. Roy

"Coal transported by rail for Thermal Power Plant in Haldia, West Bengal, India, was to be received and stored in Coal Complex comprising of Wagon Tippler, Track Hopper, Junction Houses and network of horizontal and inclined tunnels. The site was very soft with high ground water level. Deep excavation and dewatering posed great difficulty. Original plan was to drive about 1000 m of steel sheet pile and well sinking which had major impact on cost and time. High ground water was identified as the main problem. Controlling water level and maintaining it would allow open excavation over major areas. Scheme for lowering aquifer with one and two-stage well-point dewatering system was developed following basic principles of groundwater and seepage. Arrangements of wells, installation and pumping were worked out in detail. Water levels could be lowered below bottom levels of excavation. Design of sheet pile was modified under lowered ground water condition. Overall length and depth of sheet pile were reduced drastically. Open excavation was possible in segments over major areas. The scheme was highly successful in smooth and fast progress of underground works. The works were completed safely months ahead of schedule time and with significant saving in cost.INTRODUCTIONThe Coal Receiving Complex of thermal power plant comprised of 250 m long 8 m deep Track Hopper (TH), 12 m deep Wagon Tippler (WT) with provision for addition of another Wagon Tippler. Track center lines of TH and WT were very close. Coal unloading facilities were connected with a network of underground tunnels and Transfer Points (TP) upto Pent House (PH). The facilities were optimized in a compact layout within about 400 m x 120 m area. Initially excavation for TH was started adopting side slope of (1 V : 1.5 H) with 2 m wide berm and dewatering by in-pit sump and pump. When depth of excavation reached about 5-6 m, failure occurred over a long stretch as shown in Figs. 1a - 1b photos. Further work was stopped to develop scheme for carrying out deep excavation and civil works safely."

Jan 1, 2015

By B. H. Moore

Foundation and excavation problems associated with lock construction projects vary widely. Each lock requires a different foundation to respond to a unique geologic setting. The range of heights and founding materials are illustrated thru description of selected structures encountered in the United States. Examples range from 113-ft high John Day Lock on the Columbia River founded on basalt rock to the 17-ft high Lock No. 5 on the Arkansas River floated on a clay foundation. A description of the basic elements of design and construction is presented. Several case histories involving lock design and construction are assessed to aid in recognition of potential problem areas on forthcoming construction. In the past decade there have been many improvements in construction materials and techniques. The application of these new approaches to lock construction is discussed.

Jan 1, 2010

By J. J. Hussey

"Abstract-The ""Brunswick Horizon"" an informally named ore-bearing unit near the top of the Nepisiguit Falls Formation in the Ordovician Tetagouche Group, hosts the Brunswick No. 6 and No. 12 base-metal mines, as well as the former Austin Brook iron mine, in northern New Brunswick. Detailed structural analysis of the No. 6 and No.12 mines led to the prediction that a massive­ sulfide deposit may have been repeated by F1 folding along the Brunswick Horizon. A subsequent drilling program discovered the new massive-sulfide North End Zone at a vertical depth of 1100 m, 1 km north of the No. 12 underground workings. By the end of 1990, Zn-Pb-rich massive sulfides had been delineated over a strike length of 200 m and a down-dip extent of 170 m. Rock units intersected in the North End Zone are generally thinner and vary somewhat from those at the Brunswick No. 12 mine. Thinning of the hanging wall rocks may be primary, may result from attenuation along F2 folds, or may represent truncation by a thrust fault. The newly discovered sulfide zone indicates that significant potential exists for the discovery of other deposits at previously unexplored depths.SOMMAIRE-Dans le nord-est du Nouveau-Brunswick ""l'horizon Brunswick"" est le nom usuel de la zone qui contient les mines de métaux de base Brunswick No. 6 et No. 12, ainsi que l'ancienne mine de fer Austin Brook, toutes situées sur le dessus de la Formation ""Nepisiguit Falls"" dans le Groupe Tetagouche d'âge Ordovicien. Une analyse détaillée de la structure des mines No. 6 et No. 12 à permis a van Staal de prédire qu'un gîte de sulfures massifs pourrait se répéter dû à une déformation F1, au nord de Brunswick No. 12. Suite à un programme de forage, la nouvelle zone de sulfures massifs appelée le ""North End Zone"", profonde de 1100 rn, et à une distance d'un km au nord des chantiers souterrains, fut découverte vers la fin de l'année 1990, les sulfures massifs riches en Zn-Pb ont été délimités sur une longueur de 200 rn et une hauteur de 170 rn le long du pendage. Les unités de roches intersectées dans le ""North End Zone"" sont généralement plus minces et sont quelque peu différentes de celles de la mine Brunswick No. 12. L'amin­ cissement des roches pourrait être primaire ou être le résultat de l'atténuation le long des plis F2, ou soit tronqué par une faille. La nouvelle découverte d'une zone de sulfures indique un potentiel énorme pour la découverte d'autres g ""tes à ces profondeurs inexplorées."

Jan 1, 1992

By Zharinov SE

Geonechanical modelling of island arc sys- tems and their analogs is investigated. Slow seismotectonic movements along the inclined deep fault zone under the compressive horizontal stress conditions are proposed to be the princi- pal mechanism controlling the structures and processes in the active continental margins. A model of shearing surface crack in an elastic half-plane is used for simulation. The main ele- ment of the model is viscous interaction bet- ween the crack sides, the viscosity varying with depth. To describe the stress-strain state of the medium an integro-differential singular equation is derived and solved numerically. The results of simulation are in good agreement with geological and geophysical data on the ac- tive continental margins.

Jan 1, 1987

By Ezra Ballinger, Matthew R. Glisson

Located in downtown Fargo, North Dakota, the Block 9 Redevelopment project site contains highly- compressible soils in the upper 100 feet with groundwater about 10 to 15 feet below the existing ground surface. The owner prohibited using driven piles to avoid disturbing neighbors of the project and historically, drilled shafts are used in Fargo as a reduced noise and vibration alternative to driven piles. However, developments over the last 20 to 30 years in drilling equipment, load testing and integrity testing resulted in the project team identifying augered cast-in-place piles as a suitable alternative for this project. To reduce the risks associated with using a relatively unproven foundation system in the area, the project team used the design-build delivery method for foundation design and construction. The team also specified compression load testing and higher-than-normal integrity testing. A successful bi-directional load test validated the design parameters for the augered cast-in-place pile while thermal integrity profiling gave the team confidence that these piles would perform similarly to the test pile. PROJECT DESCRIPTION The Block 9 Redevelopment project goal was to turn an existing, at-grade parking lot in downtown Fargo, North Dakota into a public outdoor plaza, a mixed-use building and a parking ramp. The project provides new offices, retail spaces, a hotel, a restaurant and private apartments. Situated in the southeast quadrant at the intersection of Broadway and 3rd Avenue North, the project site wraps around a bank building that was to remain. According to aerial photographs, the eastern portion of the site contained a public parking ramp that was constructed between 1952 and 1976, and subsequently demolished between 2009 and 2010. The western portion of the site had some combination of buildings and surface parking visible in aerial photographs taken between 1952 and 1979. Since 1984, aerial photographs show the western portion of the site being entirely surface parking. The redevelopment included the construction of three structures: the Tower, the Podium and the Parking Ramp, as shown in Fig. 1. With plan dimensions of roughly 100 feet by 100 feet, the Tower has 1 level of below-grade parking and 19 above-grade levels rising to a height of about 230 feet above grade. The Tower contains eight levels of commercial office space, four levels of hotel, six levels of residences and a mechanical level. This configuration resulted in column service loads ranging between 435 and 2,685 kips. The Tower core area has a total service load of about 30,000 kips.

Jan 1, 2019

By David C. Lager

While not a new construction technique "top/down" construction is seeing increased use in high rise building construction. Using diaphragm wall, drilled shaft and mining construction techniques, top/down construction enables construction of both the below grade basements and high rise structure simultaneously. To date the top/down method has been used on at least four major building projects in the United States. This paper will review the economic, engineering, construction and schedule issues associated with top/down technology on two projects -Olympia Centre, Chicago, and One Westwood, Los Angeles. Top/Down construction is currently under consideration on several additional projects in the United States.

Jan 1, 1987

By Zia Zafir

Design of the deep foundations for the loads imposed by lateral spread include the estimate of the pressure applied by the liquefied material as well as amount of anticipated displacement. In the absence of a non-liquefiable cover over a liquefiable layer, it is possible to design the foundation system just for the additional pressure applied by the flow slides. On the other hand, if a non-liquefiable layer exists above the liquefied zone, the foundation should be designed for anticipated movements. To completely account for liquefaction and/or lateral spread and their interaction with the deep foundation system, a coupled soil-structure interaction (SSI) analysis should be performed. However, a complete SSI analysis may not be feasible for most of the projects. This paper will present recent advances in analysis techniques and simplified methods to design deep foundations for liquefaction and lateral spreading. In addition, a case history of the Rancho California Bridge in southern California located within 1 km of the active Elsinore fault will be presented. One of the bridge abutments is underlain by potentially liquefiable layers. The pressure applied by the liquefiable layer was estimated to be greater than the shear capacity of the 36-inch CIDH piles designed for the abutment. However, with limited ground improvement and more careful analyses incorporating structural effects of CIDH piles, resulting design and construction resulted in a factor of safety greater than 1 against slope failure. The recommended approach was generally consistent with the recently published, and AASHTO sponsored, NCHRP 12-49 project regarding seismic design guidelines for new bridges and the effects of seismic displacements against bridge foundations.

Jan 1, 2006

By Satyajit A. Vaidya

This paper presents a case-study in the design and construction of deep foundation element supported mats for two residential towers on an18,000-square-foot site in Brooklyn, New York. Based on site sub-surface conditions, conventional mat foundations bearing on medium dense sand, having an allowable bearing capacity of 3 tsf, were originally anticipated for the 16 and 25-story towers. However, when the tower shear walls were relocated to the edges of the mat foundations due to architectural revisions, the significantly increased mat edge contact stresses applied to the soil subgrade resulted in calculated settlements of a magnitude that would adversely impact the proposed structures and the neighboring/bordering lot-line building and rail transit subway structures. To address this issue, deep foundation element supported mats were designed for the towers. The design was performed as an iterative process involving structural SAFE and geotechnical Plaxis finite element computer analysis to develop a coordinated geo-structural model of the foundation system. Initial presumptive design values of 45 pci and 445 kips/inch were used for the modulus of subgrade reaction and minimum deep foundation element stiffness, respectively. The designed foundation system consisted of 40 and 60-inch-thick mat foundations for the 16 and 25 story towers, respectively. Initially, the deep foundation elements were designed as 50-foot-long, 14-inch-diameter elements installed to sustain a maximum individual compressive load of 250 tons. The final deep foundation element design was subsequently refined to consist of a 48-foot-long, drilled and grouted IBO Titan 103/51 element designed to sustain a maximum load of 167 tons. Subsequent field load tests on the deep foundation elements confirmed element stiffness ranging from 1,040 to 1,530 kips/inch, with measured mobilized side shear of about 29 psi. The mat foundation reinforcement was adjusted for the pile stiffness values determined in the field load tests, and the deep foundation supported mats were constructed. The two towers were subsequently constructed, and have performed successfully.

Jan 1, 2010

By Josef K. Alter

Long-term performance and behavior of post-tensioned ground anchors subjected to axial cyclic loading constitutes an important aspect of the stability, reliability and overall performance of wind turbine deep foundations. Axial cyclic loading of post-tensioned (PT) ground anchors in soils has not been thoroughly investigated as evidenced by the research conducted for this topic. This paper evaluates research test data, available literature, and industry expert opinion on the current status and problems of deep foundation post-tensioned ground anchor (PTGA) technology, as applicable to the wind energy industry. It also introduces a proposed design solution that addresses the problems of construction cost and long-term performance of wind turbine deep foundations in soils subjected to dynamic cyclic axial loading. Deep foundations using ground anchors for wind turbines have only recently gained attention as a possible viable alternative to the mass spread footings currently in use. One of the primary problems with general acceptance of current PTGA designs is the need for long-term anchor maintenance. The research that was conducted for this study indicates that current literature only partially addresses the many factors influencing load capacity and pullout performance of ground anchors. The lack of information indicates the deep foundation industry has fallen behind in designing and implementing new technology to improve safety and performance, ensure sustainability, reduce costs, and address environmental responsibility. This paper describes the significance of this problem as it applies to the wind energy market, and proposes a new technology solution. The research, expert opinion, and analysis presented by the author is used to support the premise that ground anchor construction cost and long-term maintenance can be reduced with PTGA systems using the Con-Tech Systems (CTS) patent-pending Groutable Void Form (GVF) technology.

Jan 1, 2010

By Douglas C. Brunot

Mabey Inc. is providing for the shoring design for the Naples bay Center project, located in Naples, FL. The excavation is approximately 374' long by 164' wide and is 27'-8" deep at the shoring line with a groundwater level six feet below present grade. The project Excavation is for a multi-use facility for residential and retail with underground parking. The shoring design will be incorporated into the foundation walls for the building. Mabey is using its pre-engineered Super Powerbrace Plus (SPP) wales and Mega Struts to support the excavation in two phases. The system design and the design of all the pre-engineered components are by Mabey. The foundation is supported on drilled shafts arranged with the building column grid. The excavation will be completed in two phases to allow for equipment mobilization and operation on a site with limited access. The construction sequence will begin with placement of the drilled shafts. The drilled shafts will also serve as the building columns. After the drilled shafts have cured, 630 AZ24-700 x 45 ft. long sheet piles will be installed. The sheets will be arranged in two phases, divided by a center row of piles. Since de-watering in south Florida is very expensive and often downright impossible prior to placing the seal slab, all the initial foundation and excavation bracing work will be completed with groundwater in situ. The entire excavation will be excavated to 5 ft. below ground surface to allow for the installation of the wale support brackets at 12 ft. on center, welded to the sheet piles. After the support brackets are installed, the SPP hydraulic wales and the Mega Strut hydraulic braces may be installed for both phases. Once the frames and struts are in place, Phase 1 excavation is completed, followed by Phase 2 excavation. The 4-ft. thick seal slab is then placed and cured in the wet. De-watering is now possible with the seal slab in place. Once the excavation is de-watered the leveling slab is placed and cured. The center row of sheet piles is then cut off at the top of leveling slab. With the leveling slab cured, the sheet piles have enough strength to support the excavation without the frames and struts near the ground surface. The permanent sheet piles are then seal welded for water proofing and the foundation walls are cast with the sheet piles. The design is modelled in 3D using REVIT to ensure accuracy of the design. The earth pressures are developed using Coulomb theory as there is a top frame and the frame and sheet pile are flexible and move to develop an active pressure wedge. Earth pressure uniform loads and loads from predicted surcharge are modeled in STAAD to determine load effects on the SPP frames and Mega Struts. Coulomb theory and Mabey’s structural model will be tested through monitoring with Mabey’s LIVEPin system. LIVEPin will be placed in struts for each phase of construction. The LIVEPin results will be calibrated with the structural model to determine actual frames forces and will also determine the actual earth pressures applied to the system from surrounding soil. Mabey has used the LIVEPin system in similar applications and this has helped us determine modelling accuracy.

Jan 1, 2018

By Peter Florian

At 5:50 am on October 1, 1992, the new $800 million Pittsburgh International Airport Midfield Terminal opened its gates to the world after five years of construction and more than 24 years of planning. Despite numerous design changes, this massive project was completed on time and substantially within budget. The importance of this airport to Allegheny County and the Pittsburgh region was recognized 24 years earlier by Allegheny County Commissioners Tom Foerster and the late Leonard Staisey. Staisey and Foerster established a program to acquire land for the "Airport of the Future".

Jan 1, 1993

By Satyajit Vaidya, Rudolph Frizzi, Quadri Owokoniran

"This paper presents a case history in the design and construction of high-capacity drilled shafts for the iconic New York Wheel presently being constructed along the St. George area waterfront in northern Staten Island, New York. Although the site is located in an area that offers views of the Statue of Liberty, the Manhattan skyline, and New York Harbor, the variable and challenging subsurface conditions at the site and the structural loading requirements for Wheel erection and service conditions presented geotechnical design and construction challenges. The paper focuses on site and subsurface conditions, drilled shaft design and construction details, results of Osterberg-cell and lateral load testing, and load test data analysis and evaluation.PROJECT DESCRIPTIONThe proposed 630-foot (190 m) -tall New York Wheel (the Wheel) is projected to be one of the tallest observation wheels in the world. Upon completion, the Wheel will be capable of carrying over 1,400 passengers in its 36 capsules. The Wheel site is located along New York Harbor offering views of the Statue of Liberty, the Manhattan skyline, and the New York Harbor; see Fig. 1. The Wheel structure is sited along the waterfront, and served by a 3-story terminal located south of the Wheel in the eastern portion of the site and having a footprint area of about 34,250 sq-ft (3,180 sq-m). A 4-story parking Garage, with a footprint of about 112,840 sq-ft (10,480 sqm), is to be constructed south of the Wheel in the central and western portions of the site.SITE AND SUBSURFACE CONDITIONSThe site’s close proximity to the New York Harbor presented geotechnical challenges because the site is located in an area that was once beyond the historic shoreline of Staten Island. The site is an about 350,000-sq-ft (32,500-sq-m) parcel generally bounded by the Richmond County Bank Ballpark to the southeast, the 9-11 Memorial to the east, Bank Street to the north and northeast, and Richmond Terrace and an associated retaining wall to the southwest and south. A 50-ft (15-m) -wide New York City Transit Easement, with an active on-grade service area and tracks, is located in the southern portion of the site. See Fig. 2 for site location and approximate location of the Wheel foundation footprint."

Jan 1, 2016

By David C. Kraft

Atlas Systems, Inc. (ASI) resistance type piers were used to underpin a 100 year old historic structure at Fort Monroe, Virginia. This 3-story structure with basement was underpinned with 155 steel tubular push piers (4" OD) that were hydraulically installed to depths ranging between 90 and 110 ft. and to installing forces in excess of 60,000 lb. Project requirements included lowering the basement floor by 1-1/2 ft. and constructing new footings and adding stem walls to connect to the existing masonry walls. Additionally, the underpinning piers were temporary which required the development of a decoupling system to permit the transfer of the building loads from the underpinning piers to the new footings. The structural loads at the foundation level required a c. to c. pier spacing of 3.75 ft. in order to meet project requirements of a minimum Factor of Safety of 3.0 on the pier load capacity. Project requirements included a load test on the selected underpinning pier (ASI - AP2 4000.219) in order to establish installation depths for seating the piers to 60,000 lb. The project was successful in supporting the full load of the structure during the construction phase. Considerable savings in time and cost were achieved as well as avoiding any vibrations or noise during installation of the piers.

Jan 1, 2002

By S. R. Nandargikar

Construction of open foundations for the Second Thane Creek Bridge was indeed a challenging task. Some major problems were encountered during the construction of foundations for pier No. P22 (S/N), P.6(S) and P.12(S) of this bridge. This paper describes these problems briefly and also highlights how they were solved.

Jan 1, 1996

By Peter A. Thompson, Richard E. Prust

"The Bangkok Mass Rapid Transit (MRT} Chaleom Ratchamongkhon Line project is the first underground subway to be completed in Thailand. It consists of 22 km (14 miles) of twin-bored tunnels and 18 cut and cover stations constructed within the deltaic deposits that underlie the city. This paper describes the ground conditions, site investigation, including the use of the self-boring pressuremeter and the associated design issues for the construction of deep foundations. The paper also describes a selection of the various deep foundation solutions that were adopted to address particular constraints of the project and the ground conditions, including slurry walls for the cut and cover stations and foundations used for the underpinning of existing structures.INTRODUCTIONThe MRT Chaloem Ratchamongkhon Line Mass Transit Underground Railway comprises approximately 22 km (14 miles) of tunnels and 18 stations. The route is shown in Figure 1.The project was divided into two design and build contracts. The northern section was awarded to the ION joint venture, composed of Italian-Thai Development PLC, Obayashi Corporation and Nishimatsu Construction Co Ltd. Arup were contracted by ION for the design of the northern section. The section comprises 11 km (7 miles) of twin-bored tunnels, nine cut and cover station tunnels constructed within perimeter slurry walls using top down construction methods, and two cut and cover tunnel structures.The majority of the route of the northern contract follows existing highway Rights of Way. This results in the tunnel alignment passing through the foundations of existing highway bridge structures for which a variety of deep foundation solutions were adopted to underpin these structures.An 8-story park and ride building in the Lat Phrao area was also constructed using deep foundations."

Jan 1, 2005

By Martin B. Hudson, Kenneth S. Hudson, Gwendolyn Arreguin

A twin high-rise project site in Century City posed several foundation engineering challenges for the design team. One portion of the twin high-rise project site was required to utilize top-down construction in order to allow a driveway to remain open during construction of the project’s 40-foot deep excavation. The challenge was compounded by the need to utilize a mat foundation to support the high-rise construction and yet have temporary drilled shafts through the mat foundation area that would not create excessive differential settlement. This was accomplished by constructing a deck supported by eight drilled end- bearing drilled shafts with Osterberg load cells and five 7-foot-diameter end-bearing drilled shafts. The Osterberg load cells served to verify the capacity of each of the drilled shafts and preload the soils at the drilled shaft tips. The 7-foot-diameter shafts were constructed with bond breakers to prevent skin friction but instead mobilize end bearing (for settlement compatibility with the surrounding mat foundation). After the drilled shafts were placed, then top-down construction began beneath the driveway, leaving the driveway supported on the drilled shafts. Construction challenges included drilling of the shafts through previously abandoned tieback anchors from an adjacent parking structure basement, as well as cemented layers within the rock materials. The paper describes the use of the various analytical methods used to calculate capacities and check settlement compatibility, the construction and testing methods utilized, and the construction challenges encountered. INTRODUCTION Wood Environment and Infrastructure Solutions, Inc. (hereafter referred to as Wood) performed a geotechnical investigation for the New Century Plaza currently being constructed in the Century City District of Los Angeles, California. The New Century Plaza project consists of the construction of two new towers (designated as North and South Buildings) and the rehabilitation of the existing Hyatt Regency Century Plaza Hotel. The existing hotel tower is 15 stories in height above the existing grade and is underlain by four subterranean basement parking levels. The new North and South Buildings will stand approximately 46 stories in height above the existing grade to accommodate residential use. The new towers are planned west of the existing hotel. The site was previously occupied by the existing hotel subterranean parking structure and overlying podium structure, and a loading dock in the southwest portion of the site. The former western portion of the podium and subterranean parking structure west of the existing hotel building western edge were demolished to allow for new subterranean levels, a new podium structure, and the new towers. The lowest floor of the proposed subterranean level required excavation on the order of 35 to 80 feet.

Jan 1, 2019

By Martin Pratt

This paper is an overview of deep foundation engineering in Hong Kong past, present and future. The enormity of the subject compared with the space available makes brevity inevitable. Issues of construction and design are covered and some examples of recent challenging projects are given. The content is aimed at those with an interest in foundations generally, but with limited knowledge of the Hong Kong scene. Reference is made to informative publications for further reading on specific topics.

Jan 1, 2000

By James L. Vinson

Wilbur Smith Associates (WSA) has provided planning, engineering and construction oversight assistance to the Tennessee Department of Transportation (TDOT) for three construction projects intended to widen and improve segments of I-40 and associated interchanges in Knoxville, Tennessee. The projects are within the karst terrain of the Valley and Ridge Province. Subsurface conditions are characterized by an irregular rock surface coupled with differential weathering. Because of the projects? impact to local and interstate motorists, consideration was given to innovative planning, materials and construction practices that could accelerate construction. Two innovative deep foundation measures included rock-socketed pipe piles, which act as both foundations and substructure elements for a bridge?s interior bents, and the first widespread use of rock-socketed drilled shafts as bridge foundations on a TDOT project. The pipe piles were used at a site with significant cavities within the limestone bedrock. This resulted in design verification and constructability difficulties that required delays, but measures were ultimately employed to produce a sound foundation system. Over 110 drilled shafts have been constructed at sites with generally low solution activity. Relative to H-pile footings, which were included as an alternate foundation, they have apparently allowed accelerated construction at a competitive cost.

Jan 1, 2006