Search Documents

By Brendan Stepek, Mike Senior, Gary Brill

Norfolk Southern Railway (NS) has mainline rail passing through the foothills of the Blueridge Mountains of Central Virginia. The project site is a 70-foot-high cross valley embankment fill in close proximity to an adjacent stream. The embankment has a history of instability dating back to the 1960’s with both significant track and slope movement and numerous attempted repairs. NS elected to have a comprehensive geotechnical study of the embankment performed, install slope inclinometers to identify sliding planes, and ultimately stabilize the slope. The slope stabilization system included a two-tiered system. The primary and lower slope support consisted of a concrete cap beam with post-tensioned tieback anchors and compression micropiles socketed into sandstone. The secondary and upper slope system consisted of a concrete cap supported by an A-frame layout of tension and compression micropiles in soil. All elements of the stabilization system were designed to allow for construction while the track remained in service without impacting rail operations. This paper will discuss the geotechnical conditions of the site including brief overview of past stabilization attempts, the design of the slope stabilization elements, and a successful construction summary given limited access and close proximity to active rails.

Oct 31, 2023

By John Bryant

As engineers, we must understand all possible failure modes and design structures to avoid or safely accommodate them. For the safety of our communities, we must remember that quality foundation engineering is imperative. These case studies provide insight into the awareness we must have and the adjustments we must make to avoid catastrophic, dangerous, and costly failures.

Oct 31, 2023

By Martin Hudson, Lisheng Shao, Navid Plaseied, Adam Richardson

At a project site in San Diego, California, the hazards of liquefaction and seismically-induced settlement were present, in conjunction with relatively compressible soils that would require a low bearing value for use of spread footings. In addition, the site had variable conditions such that a portion of the site did not exhibit such hazards. Therefore, vibro-replacement stone column ground improvement was chosen to be performed such that the multiple hazards would be mitigated, allowing for use of spread footing foundations for a new building throughout the site. The post-improvement seismic performance of the soils beneath footings was calculated and served as the basis for seismic design for the vibro-stone columns. The post-improvement static performance of the soils beneath footings was evaluated using a modulus test in the field. The results of the modulus test confirmed the design assumptions regarding static settlement. The construction techniques are discussed herein, as are the testing and calculations used to justify the mitigated hazards and compliance with the design criteria.

Oct 31, 2023

By Ramin Motamed, Fahim Bhuiyan

Damage dealt with by some recent major earthquakes has raised concerns among the geotechnical engineering community to delve more into the area of soil liquefaction. As part of research funded by Pacific Earthquake Engineering Research (PEER), a large-scale shake table test on a laminar soil box was carried out at the University of California, San Diego, to investigate the effect of liquefaction-induced ground motion on a shallow foundation. In this study, a 2D numerical finite difference simulation of the baseline test was conducted in FLAC using the PM4Sand plasticity model. Some general behavior of sand layers during liquefaction including generation of excess pore water pressure, development of shear and volumetric strain, and their relative contribution to the total settlement were investigated. The model predicted the average final foundation and free-field settlements to be 21.94 cm (measured value 26.05 cm) and 12.36 cm in heave (measured heave value 1.57 cm) respectively. The shear strain appeared to govern the total settlement during seismic excitation compared to volumetric strain, during strong ground motion, while the latter became more apparent after the ground motion had subsided.

Oct 31, 2023

By Greg Stokkermans, Jim Hansen, Mary Kate Dempsey, Mark Reinders

The City of Toronto is reshaping and revitalizing its waterfront in the largest ongoing urban redevelopment project in North America. The redevelopment includes naturalizing the mouth of the Don River, which has become a source of flooding as the city has been built around it. Constructing a new river valley to alleviate this bottleneck involves multi-staged excavations up to 7 meters below Lake Ontario in permeable alluvial sands. In order to place a protective environmental barrier, these excavations need to be dewatered and require cantilevered earth retention over 6 meters high. This paper highlights the rapid design and construction of a 1.1-kilometer-long, up to 45-meter-deep secant pile cutoff wall that was constructed to support the first phase of excavation and dewatering of the new river valley. The paper discusses the geotechnical investigation and seepage analysis, selection of wall type, verticality criteria requirements, and construction challenges associated with the deep secant pile cutoff wall. Data collected during construction confirmed that the cutoff wall met critical design objectives and allowed for successful construction of the new river valley.

Oct 31, 2023

By Casey D. Shanahan, Dustin Walkenhorst

The Howard Frankland Bridge megaproject consists of a new, 3.2-mile (5.1 km) bridge extending I-275 across Tampa Bay. Two steel sheet pile and combi-wall bulkheads with a total wall length of over 11,000 ft (3350 m) were required to create the land for the new roadway and bridge approaches. A total of 1,287 permanent grouted soil anchors supports the bulkheads, which in some areas retain a 20-ft (6.1 m) tall MSE embankment. Anchors with lengths up to 200 ft (60.1 m) were installed, and project design loads necessitated anchors that varied from 3-strand to 8-strand. The soil conditions at the site were typically loose to dense sands underlain by a thin layer of clay over karstic limestone of variable hardness. Given the magnitude of the design loads, the larger anchors were designed to bond into limestone. Limestone variability along the bulkheads was observed. In some extreme cases, the top of the limestone elevation varied by nearly 100 ft (30.5 m), which created challenges for designing the length for anchors that were required to bond into limestone. Given the proximity to Tampa Bay, most of the work was performed from a barge. Waler systems were installed on the waterside of the sheet piles, so installation and welding work was limited to lower tide stages. The geotechnical contractor designed and installed the anchor and walers systems to fit within the proposed concrete cap. The objective of this paper is to discuss the significant design and installation challenges of the anchor and waler system for this high-profile project.

Oct 31, 2023

By Brian Wilson, Franz-Werner Gerressen, Johannes Reinisch

Specifications for traditional auger mixing methods have made use of the Blade Rotation Number (BRN) to establish acceptable levels of mixing. Cutter Soil Mixing (CSM) has no such established parameter. Previous research has proposed the adoption of an Energetic Mixing Index for CSM and has attempted to establish a basis for this utilizing results from a limited number of panels. This paper reviews the basis of this previous proposal and assesses the applicability of the proposed index utilizing a review of production data from a number of sites in proximity to Vancouver, British Columbia, Canada. Based on the outcome of the review, the paper proposes adoption of a new index for initial field quality control of CSM operations.

Oct 31, 2023

By Kamil Nuzha, Jianchao Li, Bashar S. Qubain

A 52-story high rise building in Philadelphia is constructed adjacent to a 3-story historic structure, supported on a rubble foundation at a depth of 2.4 m (8 ft) below grade. The high rise is supported on a mat foundation at a depth 36 ft below grade with an average service contact pressure of 670 kPa (14 ksf). Evidently, the existing foundation requires underpinning but extra care is necessary to safeguard the historic building. A detailed finite element analysis showed that the mat foundation would settle about 38 mm (1.5 in). Although such settlement would be acceptable for the high rise it would cause intolerable distress to the historic building by dragging down its underpinning. To minimize the settlement impact, an innovative micropile solution was implemented to safely transfer the underpinning load into the underlying mica schist bedrock and prevent the existing building from being overstressed by the mat foundation. The specifics of the micropile pile design and associated details are presented herein. The new building was completed almost two years ago and the adjacent historic building has been functioning well without any signs of distress.

Oct 31, 2023

By Mirza Shafiq Ibrahim, Martin Hudson, Rishabh Singhvi, Saiful Islam

The Landmark Apartment building is a 34-story high-rise constructed in West Los Angeles. The high-rise was constructed within a portion of the footprint of an existing parking structure with four subterranean levels. The foundations of the new high-rise were cast-in-place drilled hole (CIDH) piles in order to limit settlement of the new construction relative to the existing parking structure spread footing foundations. In order to construct within the parking structure, a gloryhole had to be cut in the parking structure at the location of the new high-rise footprint, necessitating temporary bracing of the parking structure basement walls. The temporary bracing had to be accomplished using both tie-back anchors and internal bracing (rakers) in order to provide lateral restraint for the basement wall. The internal bracing required its own set of foundations, including micropiles and tie-back anchors to laterally restrain the micropile caps. The foundation system for the new high-rise had to be split into two major pile caps on either side of the temporary micropile cap foundation for the bracing system, with the temporary micropile cap tie-back anchors threading between the permanent structure drilled shafts. In addition, groundwater was located just beneath the bottom-most slab of the parking structure, requiring dewatering of pile cap excavations. With high groundwater conditions, drilling mud was required to install the CIDH piles. These design challenges were accomplished successfully and meeting the requirements for foundation performance and seismic performance of the structure. The multiple challenges of temporary works also required careful coordination of dewatering, shoring installation, and foundation installation among the various disciplines.

Oct 31, 2023

By John Roxas, Rodrigo Fragachan, Alex Gossen, Jakub Szary

The Gilmore Place development is mixed-use transit-oriented development in Burnaby, British Columbia, Canada. The development replaces the underutilized space surrounding the existing Gilmore SkyTrain Station and overhead SkyTrain guideway that bisects the site with three support piers fully contained within the building footprint. The site includes six combined office and residential towers, including the tallest tower in British Columbia when constructed at 64 stories. Below grade development includes a phased temporary support of excavation. The first phase involves the excavation of a 14,200m2 pit up to depths of 30.5m below street grades removing about 42,475m3 of soil. Support of excavation included 1,229 secant piles and 2,689 strand anchors of high-capacity, achieving working loads of up to 1800kN. Each of the three SkyTrain piers are supported by a single 3.0m diameter caisson. To facilitate excavation below each caisson supported pier and encapsulate them by the base building structure, temporary support measures were developed. Bracing included sets of 22.0m long inclined 610mm diameter x19mm thick steel pipe raker braces connected at the base of each pier and three rows of jackable frames connected to the piers and temporary shoring walls. This shoring system is one of the most challenging shoring systems in Metro Vancouver as the original SkyTrain pier foundations had to be exposed. Secant piles were installed down to bedrock around the existing caissons utilizing a custom low headroom drill rig. A robust automated instrumentation program was established to monitor movements of the shoring wall and SkyTrain infrastructure in real time, and to provide immediate alerts to the design and construction team should movements exceed predetermined thresholds established by the design team. The monitoring program indicated movements of the guideway, station, and supporting piers were below the maximum tolerances during the excavation phase of construction and enabled the continued use of the transportation system without disruption or jeopardizing public safety.

Oct 31, 2023

By Seth Knihtila, Bryce Niekamp, Adam Running

The current home of the Seattle Kraken NHL team is the Climate Pledge Arena in Seattle, Washington. The renovation of the existing 1962 World’s Fair Pavilion transformed the aging and outdated facility into a modern 900,000 square ft., 17,000 seat arena with all modern amenities. Although the existing arena already extended below grade, it included minimal event and amenities space, and did not meet the current needs for a sports and entertainment venue. In order to transform the arena, the site was further excavated to about 60 ft. (18.3 m.) below grade in order to provide additional space and access. The challenge: the existing roof was to remain in place with the majority of the expansion occurring below grade. The existing roof was underpinned on a series of 67 drilled shafts installed with low headroom equipment. In addition, support of the new arena structure required deep foundation support consisting of 117 drilled shafts of varying diameter and depth within the excavation. The primary support of excavation system or shoring system selected was permanent soldier piles and lagging with permanent tiebacks. This installation of the shoring system and excavation had to be completed with the iconic concrete roof, weighing in at 22,000 tons, suspended in place on temporary steel support framing and drilled shafts. The support of excavation system consisted of four elements: the primary perimeter excavation, snorkels, pylon shoring, and the south buttress shoring and support, each of which had their own unique design and construction challenges. In the end, the construction team installed approximately 178,000 square feet of permanent shoring, including 500 soldier piles and 130,000 linear ft. of tiebacks. The performance of the drilled shaft installation was monitored by CSL testing. The performance of the shoring system was monitored by geotechnical instrumentation and performed as predicted in our analysis.

Oct 31, 2023

By Tae H. Lee, Tae-gyun Jung, Sangchul Bang, Guen-woo Park, Sungmin Kim

ADVACT Co., Ltd. of Korea designed, fabricated, and installed a meteorological tower on behalf of Korea South-East Power Co. Ltd. near Yeosu, Korea, in April, 2021. This tower was of its first kind in Korea, where the tower would gather meteorological data for a period of 19 months and then be retrieved, moved and installed at a new location for same data gathering purposes. The meteorological tower’s foundation utilized three-leg suction piles that are 28 m long and 4.12 MN in weight. The super-structure is 69 m high and 6.19 MN in weight with concrete fill. Both suction piles and the super-structure were fabricated and assembled on land and then transported as a single unit to the first site. All-in-one suction installation of the entire unit was completed in approximately 14 h. In November, 2022, the entire tower was retrieved, inspected, transported to the second site, and then installed successfully. This paper describes brief details of the design, construction, and installation of the tower supported on three-leg suction pile foundation. The design of the suction piles considered the conditions of both sites to ensure the stability of the tower when operational at both sites.

Oct 31, 2023

By Peter Sudkamp, Ariel Sarno, Andrew J. King

The design and installation of elliptical shafts for the City of Baltimore, Maryland DPW Contract SC-940, “Hydraulic Improvements to the High-Level Sewer Shed Collection System” (SC-940) will be discussed as a case study for elliptical shafts as an alternative to standard circular, rectangular, or square shafts. The project involved construction of 21 shafts varying from 6 meters (m) to 12 m (20 feet (ft) to 40 ft) in depth. Eighteen (18) of 21 shafts were constructed utilizing liner plate and ring beams including 15 elliptical shafts. Construction challenges included site condition difficulties, namely grouting of boulder cavities, keeping the correct orientation of the slender shaft elements, and minimizing impacts to the construction schedule from the added time necessary to stagger the liner plates, ring beams, and blocking. However, utilizing an elliptical shaft design allowed for property features to remain accessible, management of conflicting utilities within the excavation footprint, and reduced shoring and disposal cost. Ultimately, the decision to utilize elliptical shafts provided a cost saving over traditional shoring options.

Oct 31, 2023

By Paul Creswell, Hannah Davies

London City Airport’s only runway perches on a narrow finger of land close to the old city of London. Formally the central quay of the Royal Docks, the runway is encircled by redundant deep-water berths that were heavily bombed during World War II before its conversion to an airport in the late 1980’s. The owners’ need to increase capacity drove the addition of a parallel taxiway to the runway formed of a 20acre reinforced concrete deck supported by piles over the dock. This paper presents a number of the challenges experienced during the installation of over 1000 piles into the existing dock using cased rotary bored techniques under polymer support fluid for the expansion of the airport. The complex nature of London geology, including features which have not been seen in this detail before, across a site that extended over 1000m in length, required significant time and resources to determine the contributing factors to a number of piles collapses. The most significant causes were locally instability in the Thanet Sand Formation due to faulting and loss of dilatancy associated with post deposition shearing as well as a disturbed ground and groundwater regime due to puncturing of the puddle clay dock liner during UXO clearances. This paper will discuss these challenges encountered and how they were overcome.

Oct 31, 2023

By Joe Smith, Roberto Rodriguez, Francisco Ciruela-Ochoa

Drilled-In Displacement Piles (DDPs) present some advantages over other deep foundation solutions making them suitable for challenging conditions encountered at John F. Kennedy (JFK) International Airport Headhouse Expansion Project. For one, elevated railway tracks required the installation to occur with as little as 12 ft of clearance. Secondly, their ease of installation and overall material requirements deemed them more efficient than traditional micropiles from a schedule and cost point of view. Lastly, the low vibrations induced by DDPs to the surrounding sensitive structures were crucial for an operational airport. All combined contributed to the final decision of recommending this foundation system for the Project. This paper documents the use of DDPs for the Project and documents the design and specification process along with load testing program results and observations made during the construction of production elements from a case history perspective.

Oct 31, 2023

By Takefumi Takuma, Masashi Nagano, Yuichi Matsuoka

Pressed-in sheet pile bulkheads were built as part of an environmental cleanup known as the Gowanus Canal Environmental Remediation Project in Brooklyn, New York. These pressed-in piles minimized the potential settlement and displacement along the existing canal frontage and nearby buildings. The sheet piles were fully interlocked to be impervious, which was verified with non-declutching sensors. The soil conditions consisted of a top layer of contaminated soft sediment with debris and underlying sand and gravel layers with equivalent N-values ranging from 20 to 100. Coated Z-shaped sheet piles in lengths of up to 70 feet were installed.

Oct 31, 2023

By Meeok Kim, Thornton Tomasetti, Seth Knihtila, Michael Oakland, Shawn Leary

The transformation of Seattle's historic KeyArena into the state-of-the-art Climate Pledge Arena, home to the NHL's Seattle Kraken, was no small feat. The $930-million renovation and expansion required the near-total demolition of the old structure and construction of an 800,000 sqf (74,000 m2), below grade venue while keeping its landmarked façade and roof intact. To do that, the project team had to come up with solutions for excavating 680,000 cu yd (520,000 m3) of soil to make way for the new 17,000-seat arena while working around the massive temporary shoring supporting the 44 million lb (20 million kg) roof all in time for the NHL's 2021-22 season.

Sep 1, 2023

By Joe Harris

Large structures, such as a multistory office building or a large storage tank, are constructed the most economical way possible, which may involve a shallow foundation system placed on native soil or compacted fill material. Over the life of the structure, the foundation system may not perform as originally anticipated, leading to differential settlement. Minor differ- ential settlement is expected; however, settlement that exceeds allotted tolerance can render the structure inoperable. Compaction grouting is a well-known and accepted ground improvement technique that can be used to not only stabilize but relevel multistory buildings and large dia- meter storage tanks. Two projects, each with differing types of structures, were successfully remediated utilizing com- paction grouting as the primary method to remedy settlement.

Sep 1, 2023

By Derrick Dasenbrock

Two DFI committees independently organized two complimentary panel sessions for the recent American Society of Civil Engineers' (ASCE) Geo- Risk 2023 "Advances in Theory and Innovation in Practice" Conference in Arlington, Virginia, July 23-26. The Geo- Institute (GI) specialty conference welcomed more than 200 professionals and students interested in risk from around the world to the Washington, D.C., area for three full days of plenary keynote lectures, papers and no-paper sessions. The GI Risk Assessment and Management Technical Committee organized the event, which is the third in a series planned on a 6-year cycle. The previous two events were in 2011 in Atlanta and 2017 in Denver.

Sep 1, 2023

By Osvaldo Valdez, Matteo Bertoni, Aem Ragy

The East St. Louis Deep Cutoff Wall project is located in the area of East St. Louis, Illinois, across the Mississippi River from the city of St. Louis, Missouri, along the left descending bank of the river. The project is a fundamental part of the U.S. Army Corps of Engineers' (USACE) effort to rehabilitate and secure the aging East St. Louis levee system that provides flood protection to approxi- mately 250,000 residents and more than $4.5 billion in economic value. The project was devised and de- signed by USACE as a cutoff wall to be installed in the Metro East Sanitary District levee segment, one of the levee segments that form the East St. Louis system. The contract for the construc- tion of the cutoff wall was awarded in November 2019 to Bauer Foundation, the American subsidiary of the Bauer Group.

Sep 1, 2023