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By Nathan W. Iverson, David S. Graham, Paul J. Axtell

"The Highway 53 relocation project in Virginia, Minnesota, involves construction of a very tall bridge across a currently inactive iron ore mine pit. The inactive pit is partially flooded and serves as the community’s drinking water source. The 1,132-ft long new bridge is a three-span, plate girder structure. Two intermediate, approximately 200-ft tall piers are located within the pit.The foundations for the two piers consist of groups of 30-in diameter piles which, despite the contradiction in terms, are essentially very large micropiles. Extremely challenging and highly variable subsurface conditions exist at the site, ranging from uncontrolled iron ore mine waste fill to some of the hardest rock on earth that can also be highly fractured and abrasive. Despite the conditions, large diameter (30-in) micropile foundations up to 175 ft deep were successfully installed using down-the-hole hammer methods and full-length permanent casing under an extremely aggressive construction schedule.Full-scale foundation load testing using the Statnamic rapid loading method was also conducted in support of the design and construction but under a separate pre-design phase contract. This paper describes the unique aspects of this foundation project, including design, construction, and load testing of the large micropiles.INTRODUCTION AND BACKGROUNDIn 1960, a segment of Trunk Highway 53 (TH-53) in Virginia, Minnesota, was built on land owned by iron ore mining interests. As part of the roadway easement agreement, Minnesota Department of Transportation (MnDOT) was to be given notice three years prior to termination of the easement. In 2010, MnDOT received notice that the mining interests wished to access the ore. Through negotiations in 2010, MnDOT and the mining interests agreed to a 2017 date for abandoning the existing section of roadway. During this period, MnDOT needed to procure project funding, satisfy environmental permitting requirements, and acquire new right-of-way to permanently reroute TH-53 and keep it open to traffic. This was no easy task due to the existing mine pits surrounding the area.The E-2 alignment option shown in Fig. 1 was ultimately selected for the rerouted highway in 2014. The new highway segment includes a three-span bridge across the currently inactive Rouchleau Mine Pit. The inactive pit is partially flooded and serves as Virginia’s drinking water source. The 1,132- ft long new bridge is a three-span, plate girder bridge. Two intermediate approximately 200-ft tall piers are located within the pit. Fig. 2 is a conceptual rendering of the bridge."

Jan 1, 2017

By Dzianis Proshchanka, Yoshi Izumi, Koji Mitani, Ayuna Kitaura

"A new pile driving and drilling navigation system has been developed. It utilizes the commonly used surveying total station, combined with an innovative reticle. Conventional crosshairs have been replaced by a concentrically circular reticle called Baum. It allows for easily performed measurements of central axes of cylindrical objects such as piles, chimneys, electricity poles, etc. This provides several significant advantages compared to other existing systems. It is cost-effective as only one operator is required to control deviations in positioning and inclination. Furthermore, repetitive reinstallation of the instrument is not required for every pile driven or hole drilled. It is also a safer method, as workers have no need to be near a pile driver or drilling machine to perform the measurements. With Baum Station, necessary measurements can be performed away from the actual work area. Moreover, it is highly accurate with real-time solutions, as three-dimensional orientation information for the pile/drill is obtained simultaneously with the pile being driven or the hole being drilled. This allows for the highest levels of precision-control and correction to minimize eccentricity of the intended center positioning.INTRODUCTIONBackgroundIn foundation construction for structures, pile foundations are widely used for deep bearing strata. There are two patterns to driving piles: vertically or obliquely to the ground. The shapes of the piles are normally cylindrical. Vertical pile foundations are employed as the foundations of many structures due to their high workability. There is a problem however, which is that this method does not bear measurement data as construction accuracy is visually checked. On the other hand, tilted pile foundations are rarely employed because it is too difficult to ensure construction accuracy. In addition, commonly used percussion methods create noise and vibrations when the piles are hit, while there are advantages that thinner piles are available, ensuring earthquake-resistance, as tilted piles curb horizontal displacements of structures, which may be caused by earthquake ground motion. However, current requirements of cost reduction bring professional attention to tilted pile foundations, which can be driven reasonably and economically with much research of tilted piles having been carried out to improve their capacity. Also, a method of screwing piling has been developed, which produces small amounts of noise and vibrations. This method has solved tasks of workability and environmental burdens, and is becoming more and more common. However, there is a necessity to develop a method to accurately measure angles of piles’ axes in order to drive piles into the ground with appropriate angles. It is also expected to find out a way to control construction information, such as correction amount and driving record."

Jan 1, 2017

By Erwin Stötzer, Renato Fiorotto, Wolfgang G. Brunner, Manfred Schöpf

"Deep mixing methods can be used economically for the construction of cut-off or excavation support walls where other systems such as traditional soldier beams and lagging walls would yie ld unsatisfactory performance, where the installation of vibrated or driven sheet piles could cause vibration induced settlements and where concrete diaphragm walls would be time consuming and expensive. The new CSM method can largely replace the more conventional single or multiple auger methods of soil mixing or jet grouting. The cutter tool is similar to a cutter used in diaphragm walls or cut-off walls and is operated with a Kelly mounted on a drill rig. With this system much deeper walls can be installed and even hard soil layers can be penetrated. CONVENTIONAL SOIL MIXINGIn 1962 Norman Liver patented an auger-based soil mixing technique that has become the basis for the world's current technology.The deep mixing method (DMM), as it is known today, is an in situ soil treatment and improvement technology where the soil is blended with binders and/or other materials that are introduced in a slurry or dry form.Typically one or more hollow, rotating mixing shafts tipped with some type of cutting tool are mounted vertically to the mast of a base carrier and are driven into the ground by hydraulic or electrically powered rotary heads. The shafts above the cutting tool may be further equipped with discontinuous auger flights and/or mixing paddles. The binder is injected through the hollow shafts to nozzles located near the cutting tool where it is mixed with the ground to form columns of treated soil.Individual column diameters range from 0,6m to 1,5m and may extend to 40 m in depth. They can be arranged individually or in contiguous or secant patterns to produce a wide range of treated soil structures on both land and marine projects. Typical configurations are: Single elements, rows of overlapping (secant) elements, grids, lattices and blocks (Fig. 1 )."

Jan 1, 2005

By Richard E. Sylwester

Evaluating surface and subsurface conditions for marine foundations (bridges, causeways, terminals, etc.) is often done with a limited amount of data. Subsurface information for these projects is primarily acquired using traditional methods, such as boreholes, test pits or divers, which tend to be expensive and limited in the area of coverage. A number of geophysical methods, including precision bathymetry, sidescan sonar, and seismic reflection or subbottom profiling are extremely cost-effective and obtain significantly more data than can be acquired using traditional intrusive methods. These geophysical methods provide detailed surface images and continuous profiles of the subsurface stratigraphy. This information can be invaluable for selecting the best location for geotechnical boreholes and to map potential geohazards such as submarine slides and filled or open scour holes. Offshore investigations conducted for a proposed highway bridge (Knik Arm Bridge, Cook Inlet, AK), the retrofit of two existing bridge (Antioch and Dumbarton Bridges, CA) and a proposed cruise ship terminal (Ketchikan, AK) used a combination of geophysical methods to map water depth, detect and map debris on the seabed, map the thickness of unconsolidated sediment, determine the depth to bedrock and identify potential geohazards such as scour holes. The results of the geophysical investigations will be used to select locations for obtaining geotechnical borings, to extrapolate geologic information between existing or proposed boreholes, evaluate the potential depth of scour and design a pile support pier. Geotechnical engineers, offshore contractors and bridge designers are realizing the importance of the early use of offshore geophysics for (i) site characterization, (ii) to reduce the uncertainty of geotechnical conditions thus avoiding designs that may be overly conservative and thus more expensive and (iii) to assist in selecting locations for geotechnical borings.

Jan 1, 2013

By Pancho J. Garza, Keith H. Dahlen, Chris A. Labye

"Design for reconstruction of the East Flagstaff traffic interchange project located in Flagstaff, Arizona posed particular challenges. The proposed design included construction of a nearly 50-foot tall mechanically stabilized earth (MSE) wall given rightof- way constraints and soft subgrade soils. The tight right-of-way, approximately 15 feet in certain locations, adjacent to existing structures limited the number of viable remedial alternatives to provide grade separation at the proposed bridge abutment without significant settlement. Preliminary analyses indicated the existing subgrade soils - consisting primarily of relatively soft silts and clays with decomposed pumice - would settle approximately 12 to 14 inches resulting in unacceptable wall deformation. Stone columns placed via vibratory methods (vibro-replacement) consisting of circular excavations which penetrate to firm bearing soils and which are filled with crushed stone were selected to densify the existing subgrade soils. The implemented mitigation measures helped limit settlement to less than one inch and allow for successful construction of the project. The project history - including site constraints, subsurface conditions, evaluation of remedial alternatives, stone columns methodology, and effectiveness of ground improvements - will be discussed.IntroductionThis paper describes the subsurface investigation performed for the reconstruction of the Business Route 40 (B-40) (Country Club Drive) and United States (US) 89 Traffic Interchange (TI) located within the city limits of Flagstaff, Arizona. This project is currently referred to as the East Flagstaff TI. The Project Site Vicinity Map is shown below.The former B-40/US 89 TI was considered ineffective in handling the current and projected volumes of traffic which transition from northbound (NB) B-40 to US 89 (both directions), as well as from southbound (SB) US 89 to SB B-40. The intent of the project was to reconstruct the TI to better accommodate projected traffic volumes. The project eliminated the existing ramps from both NB B-40 to SB and NB US 89. The new interchange includes a Tee intersection from B-40 to US 89. In order to accommodate this alignment, the profile of US 89 was raised several feet (on nearly the same as existing horizontal alignment) to match the elevated profile of B-40. B-40 was shifted just west of its current alignment to accommodate construction of a new, wider bridge structure which spans over Industrial Drive, the Burlington Northern Santa Fe (BNSF) railway, and old Route 66. South of the new bridge, B-40 transitioned back to the existing alignment just north of the I-40/B-40 TI. Within the project limits, both US 89 and B-40 were widened to three travel lanes in each direction."

Jan 1, 2015

By Nick Hytiris, Mohammed Al Maadheedi, Slobodan B. Mickovski

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Mohammed Al Maadheedi

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Song-yu Liu, Chao Yan, Yong-feng Deng

"In order to investigate the stability of embankment on soft subgrade improved by T-shaped deep mixed column composite foundation, the internal forces and failure modes of columns were analyzed on the shape of critical slip surface and the displacement fields of composite foundation through strength reduction method of three dimensional numerical simulation. Then comparison between T-shaped and conventional deep mixed column composite foundation were conducted. The simulation results indicate that the stability analysis was overestimated by limit equilibrium methods. Piles within the slope shoulder provide great resistance slide effect through the vertical bearing capacity, while the piles nearby slope shoulder and outside slope shoulder providing great moment to resistant slip. The embankment stability of T-shaped deep mixed column composite foundation is higher than that of conventional deep mixed column composite foundation while cost less cement and construction time.INTRODUCTIONThe soft soil has many unfavorable project properties such as high compressibility, low strength, and high water component. Embankment built on the soft soil will face subsidence, horizontal displacement and stability problems. Cement-soil deep mixed column composite foundation is more commonly used as a method for construction of embankment on soft ground [1-2]. For the existing problems of China's current cement-soil pile (wet jet mixing pile), including strength uneven, effective treatment with shallow depth and high cost, a new technique, T-shaped bidirectional deep mixed column, is introduced [3]. An automatic expanding mixing blade was developed by Liu et al. shown in Figure. 1, to install TDM columns [4].T-shaped deep mixed (TDM) column combines bi-directional deep mixing technique and T-shaped deep mixing technique: ?Using concentric biaxial drill pipe, opposite rotational direction of the blade on the inner drill pipe and the outer drill pipe. By squeezing action of the blade on the outer drill pipe, forward and reverse rotation of the blades bidirectional mixing at the same time, blocking the way to take the grout, the uniformity of cement mixing is improved. ?Scalable stirring blades, which can be stretched for two different radius at any depth below ground, expand cross-section of the upper pile (enlarged head), forming expanding cross-section within the upper part of a certain depth which is similar to the shape of nail. As a new composite foundation, T-shaped mixing pile composite foundation is widely applied. However, studies on the stability of T-shaped column treated soft subgrade are rare in the research. So the stability study on T-shaped column composite foundation under embankment for guiding the design and construction has important significance."

Jan 1, 2015

By David W. Martel, Tom George

"As part of the regional water authority review and upgrade of local dams a 35m x 5m x 3m wet soil mixed block was required for stabilisation of a dam wall toe in remote Victoria, Australia. Remote access, extremely poor roads and high mobilisation costs made more traditional CSM and deep mixing methods cost prohibitive. The dam required a redesign to raise the wall by 2.0m to increase water storage. Additionally, the dam required additional stabilisation to reduce the risk of liquefaction during an earthquake event. Soil testing indicated loose, cohesionless, high permeability soils to a depth of 3.0 to 3.5m across the toe of the wall. This resulted in high dam seepage through the toe of dam wall potentially causing the factor of safety during a seismic event to decrease to a dangerous level. A number of laboratory trials were completed to determine the mix ratio of cement required to improve the strength of the saturated, liquefiable soil.Wagstaff Piling was responsible for achieving the required soil/cement strength and mix depth on site. As the ground conditions were too soft for conventional soil mixing equipment, an excavator mounted Mitsui road header was modified to fit a 20 tonne excavator. A purpose built remote batching plant was set up on more stable ground approximately 200m from the wall and utilised for preparation of cement and water slurry for supply to the machine. As the ground was too soft to support the excavator, the progressively improved ground was used as the working platform. Both wet grab sampling and in situ testing was undertaken to determine the UCS of the improved soil. These results indicated several variations in the results due to size effects.1 INTRODUCTIONA small town in remote Victoria relies totally on its water supply from a small dam. The dam wall required stabilisation works by ground improvement as studies completed on the dam classified it as a high risk of failure under an earthquake event. In addition, the earth fill dam had high levels of seepage and poor control measures, requiring the dam to be upgraded to comply with all regulations.The relevant water authority engaged a contractor under a design and construct contract to complete the works. Wagstaff Piling was engaged as the Subcontractor to provide design and construction advice including the contract for the ground improvement works. Initial discussions involved CSM walls, cut-off walls and mass soil mixing solutions. However, due to the access restrictions for piling equipment, mass soiling mixing was the chosen method of ground improvement."

Jan 1, 2015

By John L. Walkinshaw

It is obviously not possible in the time given me today to review in great detail all the research of the past 20 years that the (FHWA) has sponsored or participated in. In this presentation I will highlight some of the principal programs that I am familiar with. This handout lists practically all the reports prepared for the FHWA involving deep foundations and some related work involving the same structural elements (piles, shafts, ground anchors).

Jan 1, 1993

By Chris Leach, Lucie Spencer

This case study describes the geotechnical aspects of the basement construction for a multi-storey, residential and hotel complex located in the newly developed Elizabeth Quay precinct in Perth, Western Australia. The development included a three-level basement for car parking covering the full site area which was constructed using the top-down construction sequence. Soil conditions generally comprised 2m of fill overlying medium to dense clayey sands that in turn were generally overlying a very stiff clay stratum at approximately 13m depth. Bedrock level was generally encountered at approximately 22m to 35m below ground level. The ground water table was at a depth of approximately 1m below the existing ground surface level. A site boundary basement wall was constructed using a diaphragm wall retention system. The majority of the vertical loads from the building were transferred to the Kings Park Formation (KPF) bedrock through the use of foundation piles constructed by the CFA method. The CFA piles were installed from existing ground level, resulting in approximately 9m sacrificial concrete length from pile platform level to basement 3 (B3) level. The permanent column loads are such that a single CFA pile was not structurally adequate. To allow a full CFA foundation system to be adopted, an innovative design and construction approach was developed for these heavily loaded columns. This paper discusses the site technical details and the design and construction aspects required to meet the challenges offered by this project.

Nov 1, 2022

By Jeffrey M. Taylor, Arturo Ressi di Cervia

"Construction of the drilled shafts for the Brightman Street Bridge Replacement Project were not only challenging due to working over the water but were also challenged by changed soil conditions, concurrent work being performed by an adjacent contractor on the same project, environmental restrictions and severe winter conditions. A total of 36 x 8 foot (2.44m) diameter drilled shafts with 7.5 foot (2.31m) rock sockets were installed for the East and West bascule piers. This project also included Osterberg Cell load testing on two production drilled shafts at both the East and West bascule piers. The results from the load test program were used to fine tune the design of the drilled shaft rock sockets. From a constructability standpoint the reverse circulation drilling method with a pile top drill rig proved to be an excellent choice for drilling the overburden and rock sockets of the large diameter deep drilled shafts. INTRODUCTIONThe replacement Brightman Street Bridge spans the Taunton River between Fall River and Somerset in Massachusetts.The new crossing is located approximately 1500 feet (450m) upstream from the existing Brightman Street Bridge, which was built in 1908. The new mainline bridge includes nine spans totaling 1725 feet (525m). A bascule type moveable span will be located in the middle of the Taunton River and provide a 200 foot (61m) open channel centered about the 400 foot (122m) navigational channel. The bascule span, which has a span length of 409 feet (124.7m), will be a trunnion-type four leaf structure with a solid deck. A site plan is shown in Figure 1 Contract 3, which includes construction of the foundations for the East and West bascule piers, was bid on December 19, 2000 and was awarded to Modern Continental Construction Company (MCC) on January 24, 2001. MCC in turn awarded the subcontract for the installation of the drilled shafts to TREVIICOS Corporation, which started mobilizing in June of 2001.The scope of work for the drilled shafts of Contract 3 consisted in installing 18 drilled shafts in three rows on each side of the river to support the bascule piers located in the middle of the Taunton River.The foundation plan for the bascule span is shown in Figure 2."

Jan 1, 2004

By Tanaya Deb, Sujit Kumar Pal

"Experimental investigations are carried out on failure pattern around 2D models of belled anchor piles in dry sand bed of density 15.60 kN/m3 under uplift. The models are having thickness ratio (Ts/Tb) = 0.28, 0.32, 0.38 and 0.46 and total 12 numbers tests are performed on models possessing 45° bell angle and shaft thickness 26 mm. The foundation bed is prepared with alternate dyed and non-dyed sand layers and continued upto reaching embedment ratio of 3, 4 and 5 for each width ratio. The failure points are presented with respect to meridian section of anchor in X-Y coordinate system and the equations formed are of polynomial of degree 3; and R2 values are near about 1. The developed wedge is implemented as three-dimensional axisymmetrical failure surface around similar 3D models. In the horizontal slice method vertical limit equilibrium is used for calculating weight of wedge and mobilized shear (as per Chattopadhyay and Pise, 1986) on the slip surface of each element. The summation of all elementary forces demonstrates gross uplift capacity. The initial and final failure angles are detected and parametric study is conducted on failure pattern as well as predicted net ultimate uplift capacity. Almost all the analytical data are within ± 10% variations with respect to the experimental results of uplift capacity which shows better correlations. INTRODUCTION Belled or enlarged base anchor piles are attractive and economic alternative to the geotechnical engineers for compressive load bearing capacity as well as tension anchorage. These types of anchors may be useful for foundations erected below ground water table. In light weight structures like radar tower, television tower, power pole and outdoor sign pools imbalance horizontal forces due to wind loads, are more than of those self-weight of those structures. Due to chronic tensile loads most possibly from wind loads and associated imbalanced cable tension, the legs of power transmission tower should be properly designed to be safe against resultant pull-out forces. In belled anchor pile, uplift is influenced by embedment ratio, diameter ratio; so, contributions of these parameters on failure surface influence uplift capacity. Balla (1961) first introduced non-linear failure surface in the pattern of circular arc based on Kotter’s equation (1903) and soil friction was assumed to act on slip surface. The predictive mathematical models established by Matsuo (1967), Rao and Kumar (1987), Chattopadhyay and Pise (1986), Saeedy (1987) and Ghaly and Hanna (1994); it was reported that net ultimate uplift capacity was combination of bulk weight of failure wedge and shear resistance along slip surface acting in opposite direction of wedge movement. From the literatures available till date, it reveals that the contribution of mobilised shear and weight of breakout wedge separately, demanding for more clarification depending on the on parameters like embedment ratio, diameter ratio."

Jan 1, 2015

By Steven R. Ahlfield, Ali Ghandeharioon

A wastewater treatment plant commissioned in 1978 is undergoing a major expansion. Planning various phases of the 8-hectare expansion at this site requires an understanding of the site response during and after construction, and the potential impact on adjacent properties and infrastructure. The expansion project requires nominally 5 m of site grading fill for flood protection. The site is underlain by loose to compact fine sand over firm to very stiff clay stratum that extends to great depths. Ground improvement is required to mitigate the liquefaction hazard in the fine sand stratum, and preloading is proposed to reduce post- construction settlements in the deep clay. Site development and foundation systems for the plant expansion project were evaluated by conducting settlement analyses which accounted for the historic and future site loading and 3-D modeling of soil layers with interpolation between borehole and cone penetration test (CPT) locations. The numerical model was calibrated to match short-term and long-term settlements measured at the plant site. The analyses were carried out to assess the effects of past loading, proposed preload and surcharge heights, lateral extents and durations as well as vibro-replacement ground improvement on post-construction settlements. Two design options were considered for the preload footprint across the site and foundation system for proposed facilities. It is shown that limiting the preload extent and founding some of the proposed structures on deep friction piles reduce the predicted settlements of adjacent infrastructure and result in reasonable performance for the proposed facilities. INTRODUCTION A wastewater treatment plant commissioned in 1978 will be replaced with a new plant on an undeveloped portion of the site to provide wastewater treatment for an expanded service area. The existing facilities must remain in operation until completion of the new plant. The site grade will be raised nominally 5 m for flood protection. The large areal extent of the site grading fill and plant structures will cause stress changes extending to great depths in the underlying soils and result in settlement of the existing and new structures. Historic settlement of the existing facilities has been tolerable for plant operations, but no settlement performance data was recorded during site development and post-construction from 1978 to 2007. Development of the 8-hectare expansion at this site is planned in three phases to reduce the overall construction schedule. Planning for each phase requires evaluating the effects of various site development activities from start to completion of expansion and during the design life (i.e. post-construction period), and the potential impact on existing wastewater treatment facilities and adjacent properties and infrastructure including an adjacent viaduct structure. Figure 1 presents the site plan and three distinct site development phases considered for the plant expansion.

Jan 1, 2019

By Karsten Beckhaus

Barrier walls in levees and dams are designed and constructed for new structures and for rehabilitation or upgrade of existing structures to control seepage. Construction methods applied are often deep soil mixing with a cementitious slurry or excavating a trench and refilling it with a plastic concrete. This paper explains the technical background of jointless cementitious barrier walls inevitably developing thermal tensile stresses and how these stresses can be controlled. The theoretical background of thermal stresses is explained based on experimental and numerical studies of essential factors. Although a low cracking risk is generally inherent, risk mitigation measures should be taken to thermal cracking and to ensure the permanent function of such walls as a low-permeability and high-deformability barriers.

Sep 8, 2021

By Dino Kartofilis, Rick Deschamps, Giovanni (John) Bonita

"Anew condominium complex in Arlington, Va., presented some formidable constraints. One was the requirement for a permanent retaining wall to support a 48.5-ft (15-m) cut and an existing 16- story building on top of the slope. Another was the adjacent property owners’ refusal to allow tieback anchors to encroach on their property. The General Contractor (GC) proposed an innovative design incorporating vertical concrete load-bearing elements (LBEs) supported by post-tensioned tiedowns. The owner accepted and the project was successfully completed in 2007.The original designer had proposed a system that included a temporary, raked soldier pile and lagging wall and a permanent cantilever retaining wall with a large piled footing. The system was potentially costly and its constructability questionable.The GC then asked for a design-build alternative to reduce costs and enhance the schedule. The first idea was a diaphragm wall with vertically anchored T-sections. However, configuring a crane to excavate perpendicular sections using grab equipment seemed impossible. There were also utilities approximately 25 ft (9 m) from the existing building, two tiered retaining walls down the slope and a large swimming pool at the base. However, the GC was committed to providing a stable bench 20 ft (6 m) wide along the wall alignment to support the crane.The design evolved to single bite panels using diaphragm wall technology, commonly called LBEs, or barrettes, when they carry vertical loads. For this project, 44 LBEs were horizontally spaced at 9 ft (2.75 m) on center, oriented perpendicular to the wall, extending into bedrock and anchored vertically on the upslope side to resist overturning moments. They were essentially large soldier piles that provided both temporary and permanent support of excavation.An unusual formal agreement was established with the GC to complete the work based on pricing, and prior to completion of final design. This arrangement allowed for an exchange of ideas that increased project efficiencies and lowered costs — without the fear that design concepts would be “shopped” to competitors."

Jan 1, 2009

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Oct 1, 2021

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Sep 8, 2021

By James F. Davis, Matthew A. Conte, Robert F. Tonning

This is a paper demonstrating the steps taken to combine multiple types of piles for a single site to maximize the benefits and characteristics of each method. We intend to discuss the use of grouted displacement piles in lieu of traditional pile types that were specified on an individual project. We will show how implementing this alternate pile type can both supplement and replace the originally specified pile to increase efficiency and lower costs. We will demonstrate a reduction in spoils, vibration, crew hours, and equipment size while employing methods to overcome unforeseen ground conditions.

By Manuel M. Reyes, Thuraisamy Thavaraj, Alex Sy

"The new east span of the San Francisco-Oakland Bridge features a single tower self-anchored suspension (SAS) bridge. During construction of the SAS bridge, a temporary bridge was used to support the box girders until erection of suspension cables was completed. The transfer of deck load from the temporary bridge to the suspension cables was achieved in November 2012 and the SAS bridge has become the largest of its kind in the world. The new bridge will be in service in Fall 2013.Large diameter driven steel pipe piles were used for the temporary bridge foundations at Towers D, F and G located in San Francisco Bay. At Tower D, the large diameter steel pipe piles were driven through thin overburden into bedrock using a large Menck MHU500T hammer with a rated energy of 550 kJ. As there was no precedence in driving open-ended pipe piles into the Franciscan Formation bedrock, challenges were faced with uncertainties in drivability, driving stresses, pile embedment in bedrock and pile capacity. These uncertainties were addressed by incorporating additional measures into the pile design, and by the use of dynamic pile monitoring during initial driving and re-strike. Pile relaxation was observed during pile installation.At Towers F and G, setup effect was a key issue for the piles driven into the deep soft marine sediments. Drivability analyses were conducted to predict pile run, driving stresses, selection of hammer and refusal criteria. The piles were dynamically monitored during driving to estimate pile capacities. Due to the set-up effect in the Bay Mud, the piles gained up to 3.3 times the initial capacity during the re-strike and were in excess of the design capacity.This paper presents details of the design, construction, testing and performance of the driven pipe piles at temporary Towers D, F and G. Settlement data of the temporary tower foundations while in service confirmed the satisfactory performance of the pile foundations.INTRODUCTIONThe new east span of the San Francisco-Oakland Bay Bridge features a single tower self-anchored suspension (SAS) bridge, the largest of its kind in the world. The new east span replaces the existing double-deck steel bridge built in the mid-thirties. A span of the existing bridge had collapsed during the 1989 Loma Prieta earthquake but was repaired. Construction of the new east span commenced in 2008 and is expected to be completed for the Labour Day opening in 2013. Figure 1 shows a schematic (looking north) of the new bridge with its 160 m high main tower T1 in the middle, and Piers W2 and E2 at the west and east ends, respectively. The west and east spans of the SAS bridge are 180 m and 385 m, respectively.During construction of the SAS bridge, a temporary bridge, complete with towers and trusses, was used to support the box girders of the new permanent bridge until the loads from the box girders were transferred through suspension cables to the permanent bridge. The transfer of deck load from the temporary bridge to the main cable was completed in November 2012."

Jan 1, 2015