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By Mriganabh Choudhury, Sanjoy Bhowmik, Sampat Raj, Vijay Panwar

Tanks play a vital role in Petroleum refineries and Petrochemical complexes by storing Petroleum substances at various stages. The performance of the foundation system of tanks significantly influences their overall performance, which is evaluated during hydro-testing and operational phases. This study focuses on assessing the performance of a large-diameter floating roof tank measuring 92 m in diameter and 20 m in height, which exhibited excessive settlements during hydro-testing due to the presence of organic soil patches. The maximum total settlement observed was 238 mm, surpassing the permissible limit of 150 mm. Additionally, differential settlements at specific locations exceeded the acceptable limit of 1 in 500. A comprehensive performance analysis of the tank's foundation system was conducted, leading to the tank's approval for utilization at 100% capacity. Furthermore, remedial measures were proposed to address the uneven levels at the tank periphery and prevent settlements in the future. This paper highlights the significance of location-specific soil investigation data, critical parameters for tank foundation system selection, detailed performance analysis of tank foundations, and suggested remedial measures for distressed foundations. By addressing these crucial factors, the study enhances the understanding of tank foundation systems, ultimately improving the overall performance and reliability of tanks in Petroleum refineries and Petrochemical complexes. Keywords: Storage tanks, Performance analysis, Hydro-test, settlement, Ground improvement

Oct 7, 2024

By Mark Dowling, Robert Holdway, Bill Baillie

Extending the utility of materials through reuse, repurpose and recycling to minimize waste, pollution, water, and the consumption of finite resources, reduce environmental impacts and cut GHG emissions (CO2) are key tenants of the Circular Economy. John Lawrie Tubulars USA conducted a Life Cycle Assessment to calculate the environmental impacts of the repurposing of John Lawrie Tubulars steel pipe products sourced from pipe mill secondary and oil field surplus stockpiles to compare repurposed steel tubulars to those made from prime (new mill) steel throughout their lifecycle. The analysis includes multiple environmental characterization indicators associated with the material processing, on-site operations, supply chain, distribution, and installation of the pipe for foundations. The benefits of repurposed tubulars are consistently beneficial across all environmental indicators when compared to prime steel tubulars. The life cycle analysis results show that for every tonne of steel tubular repurposed there is a 71% - 80% saving of carbon emissions over the use of a prime steel equivalent from cradle to installation. The methodology used in this study will be described, demonstrating the rigor and 3rd party verification process involved in calculating the CO2 emission savings, one of the first of its kind for secondary steel suppliers in North America. With growing pressure on the construction industry to be more resource efficient, and to lower embodied carbon, material reuse strategies are critical to meet targets. This data can be used to demonstrate, and quantify, the environmental impacts and benefits of repurposed tubulars and supports the efficacy of environmental claims and contribution to a circular economy.

Oct 7, 2024

By Jim Glider, Peter Faust, David Joyner, Michael Muchard

The existing, century-old Portal Bridge over the Hackensack River in New Jersey is a two-track moveable swing span bridge that is nearing the end of its functional life. A new fixed bridge with spans of approximately 400 feet will replace the existing bridge. The new Portal North Bridge will continue service to both Amtrak and NJ Transit rail passengers along the Northeast Corridor to an average of 200,000 passengers per day. Each of the four main span piers will be supported by eight, 8-foot diameter drilled shafts. Malcolm Drilling installed all shafts with permanent steel casing through the Soft Clay and Glacial Till layers with a short embedment into competent bedrock using the Oscillator method. Rock sockets below the casing were drilled with conventional drilling tools. Quality assurance included inspection of the shaft base using a MiniSID shaft inspection, the rock socket side walls using a Down-The-Hole Camera and the verticality using Sonic Caliper. In addition, specifications called for integrity testing using Thermal Integrity Profiling (TIP) and Crosshole Sonic Logging (CSL) on each shaft. Tomography analyses of CSL test data and destructive testing by means of concrete coring had also to be employed on the majority of shafts. This paper will highlight the surprises experienced by the project team when the concrete core specimens were evaluated in relation to the non-destructive testing data.

Oct 7, 2024

By Md Kausar Anik, Ramin Motamed, Peiman Zogh

The earthquakes that occurred in New Zealand and Japan in 2010 and 2011 caused significant damage due to liquefaction. Engineers have adopted various ground improvement techniques to reduce the impact of liquefaction-induced damage, and one of these techniques is installing a sheet pile next to the foundation. However, the optimal depth into a non-liquefiable soil layer for having appropriate fixity of the bottom of the sheet pile remains unclear. To address this issue, a series of moderate-scale 1g shake table tests were conducted to evaluate the effective embedment depth of the sheet pile required to mitigate liquefaction-induced foundation settlement. A 1/5 scaled model consisting of three soil layers with varying densities, namely the crust, liquefiable, and dense layers, was prepared. A shallow foundation was placed over the crust layer and a sheet pile at a horizontal distance of 0.625 times the foundation length from the center of the foundation was inserted into the soil at various embedment depths using the press-in technique. The test results indicated that the foundation settlement could be reduced by 62% and 72% when the sheet pile was embedded to 50% and 100% of the dense layer thickness. It was recommended that the sheet pile be embedded at least 50% of the firm stratum thickness to achieve optimal performance.

Oct 31, 2023

By Joe Welna, Lola Moussey

The Minnesota Department of Transportation (MnDOT) evaluated several concepts to minimize flooding of Trunk Highway 35W (TH35W) near downtown Minneapolis. A deep stormwater storage facility (SSF) was selected for final design. Given the constricted project footprint, open trench excavation construction methods were not feasible, and a top-down construction approach using diaphragm walls (d-walls) was utilized. The SSF is located near the edge of a glacial valley containing glacial and alluvial deposits including cobbles and boulders. Categorizing ground conditions was critical in assessing constructability of the SSF and determining project cost. Multiple phases of geotechnical investigation were conducted including geotechnical borings, geophysical surveys, and pump testing. Obstructions (including cobbles and boulders) were encountered at some of the borings conducted and therefore were anticipated to be encountered during construction. As part of development of a project risk register, it was decided by the Owner that the Contractor should assume no obstructions during d-wall construction, and obstructions encountered during construction would be paid using funds allocated in a project risk pool, which was informed by a Geotechnical Data Report (GDR) and Geotechnical Interpretive Report (GIR). The cells of the structure were successfully completed in 2022 with final completion anticipated for the fall of 2023.

Oct 31, 2023

By Cody Telgheder, Mamoun Laraki

The U.S. Department of Energy (DOE) Hanford Site had a multi-decade career of supporting America’s defense system during World War II and the Cold War. A multi-reactor site, DOE Hanford produced plutonium for atomic weapons and steam for generating electricity. In addition, a network of nuclear facilities was built and used to support the research and development process, like 324 Building contained within the Hanford Site’s 300 Area. In 1989, after closing its doors to plutonium production, the DOE, Environmental Protection Agency (EPA), and Washington State Department of Ecology took on a challenging, legally binding accord to clean up the Hanford Site. As part of the final clean-up project within the 300 Area, CH2M Hill Plateau Remediation Company (CHPRC) contracted Apollo Mechanical Contractors who contracted Nicholson Construction Company (Nicholson) to design and construct an underpinning micropile system to support excavation efforts directly underneath the 324 Building “B-Cell” structure which in turn would facilitate the complete removal of the contaminated soils directly beneath the structure. The work was completed in complex and challenging conditions that required an airtight drilling system, two layers of protective clothing, a hood with a Powered Air Purifying Respirator (PAPR), the use of long reach tools, and continuous radiological monitoring. This paper will address the design, construction, and challenges encountered with underpinning a structure within a highly sensitive Category II nuclear environment.

Oct 31, 2023

By Eric Sturel, Ove Arup, Henry Tayler

One Triton Square was originally a six­storey commercial building with a single level basement located within the Regents Place development near Euston, London. The building was a concrete frame, with steel cores at each corner. The floorplate was approximately 72 x 72 m (236 x 236 ft) with a 36 m (118 ft} wide octagonal central atrium. The original building was well suited for extension due to relatively recent construction standards, high original live load allowances, its large central atrium, generous escape stairs provision and extensive record information. Plant space requirements at basement and rooflevel were maintained. The preferred scheme was the addition of three storeys to the existing six-storey structure and an eight-storey partial infill in the central atrium area, with a further allowance for completely filling in one or two of the lower atrium levels. This allowance was included in the design to offer enhanced flexibility to future tenants. It was clear from an early stage that the foundation load demand would increase to serve the enlarged building area, which increased the existing building floorplate by 70% or 130,000 sq ft (12,100 m2) of commercial space. Maintaining the basement headroom and accessibility for servicing plant would also be important.

Jan 1, 2024

By Joe Heinisch, Trevor Quayle, Brian Huber

Helical piles have often been characterized as handy little tools in the toolbox of solutions for structural support of foundations. They have provided options to construct foundations and anchorage in very challenging locations where more common methods were impractical. The stigma of being efficient for lightly loaded foundations has limited their use as highly loaded deep foundations. This paper will dispel the notion that helical piles are not a deep foundation option for large structures by presenting the case study of a 32-storey building in London, Ontario supported on helical piles. The building was constructed in a downtown location where all the problems associated with deep foundations were present – high water table, vibrations, compressible soil layers, limited access, logistics of soil removal, seismic considerations. These issues all had costs associated with them that helical piles and their installation process would limit or eliminate. This paper will present the detailed solution that helical piles offered the constructor of the new building. The solution included pre-design load testing and analysis of the results. The advantages of using helical piles in this case will also be presented from technical and constructability viewpoints to demonstrate why they should be considered for large structures.

Oct 7, 2024

By Will Frampton, Rachel Salter, Zoe Baldwin, Tim Hampshire

Cementation Skanska were responsible for the design and installation of 200 linear meters of contiguous bored piled retaining wall and approximately 1300 bearing piles for a new commercial arena development in the North of England. Building new retaining walls adjacent to existing infrastructure presents numerous challenges concerning limiting disruption and potential damage to services. The retaining walls formed a partial basement meaning horizontal propping was not practicable. To provide time and cost saving to the project, Cementation Skanska developed a novel, space saving solution to traditional raking temporary propping of the retaining walls. The contiguous wall was propped in the temporary condition by perpendicular secant piled buttresses positioned to avoid the permanent works. The buttresses were constructed from existing ground level simplifying the construction sequence by negating the requirement for additional temporary works associated with conventional propping systems. This paper describes the design and construction of the buttress wall solution, considering retained heights up to 8m, with challenging ground conditions including worked coal seams. The design considered onerous deflection criteria focussing on the services running under the dual carriageway along the East of the site and complex loading conditions from the permanent propping solution resulting in a prop stiffness envelope. The paper will detail the design process for the buttress piles and contiguous piled wall, and the iterative prop stiffness approach utilising Plaxis 2D & Geosolve Wallap. This innovative approach to propping saved the project time and cost by omitting the need for additional temporary works following construction of the wall piles and allowing berms to be removed much earlier. This solution was also considered safer to operatives than raking props. Monitoring was undertaken during the excavation phase of the project and measured deflections were below those predicted during the design process, which could create efficiencies on future projects.

Oct 31, 2023

By Karen Dawson, Qiang Li

Unreinforced displacement augercast piles, or rigid inclusions (RIs), were installed for foundation support of a combined sewer overflow treatment building. The RIs penetrated loose silty sand and soft silt and terminated in medium-dense to dense silty sand, approximately 40 ft below grade. The building houses water-holding basins and level-sensitive weirs and equipment. Strain gage-instrumented static axial load tests and low strain pile integrity tests (PIT) were conducted on the RIs as part of quality control for this technology. Strain gage monitoring continued during the installation of the remaining production RIs, construction of the building, and water preloading of basins and channels within the building. While the composite RI-reinforced ground and load distribution mat system performed as expected for settlement control and was not needed for lateral support, RI fractures as observed by PIT in this project might need to be controlled in other situations. Case history information regarding the subsurface fill and deltaic deposit character, RI installation production rates, RI testing procedures and results, and construction settlement monitoring are presented.

Oct 31, 2023

By Max Ho, Hiu Lee

The Port Lands in Downtown Toronto is a vast waterfront area that has been long remained undeveloped. This is due to the dual challenges of soil contamination resulting from decades of industrial activities and high flooding potential from the nearby Don River. The Port Lands Flood Protection and Enabling Infrastructure Project (PLFP) seeks to unlock the development potential of this strategic downtown land. This initiative also simultaneously mitigating flood risks for the Port Lands and surrounding areas. The project involves the creation of a new river channel through the existing Port Lands to redirect floodwaters into the inner harbor and Lake Ontario. This new river channel excavation is protected by three dam liked plug walls which isolate the lake water from entering the excavation. Given the industrial contamination in the soil, the installation of a permanent cut-off wall along the new river alignment is also imperative to isolate contaminants from migrating into the future river channel. The west plug wall is positioned at the westernmost point of the river channel excavation and directly adjacent to Lake Ontario. The innovative use of a diaphragm wall technique to construct the west plug wall allow the wall to serve as a dock wall, dam, excavation support, cut-off wall, and load-bearing element throughout the different stages of the river excavation. This paper provides a comprehensive overview of the design and installation of the west plug wall. It provides valuable insights into the practical application of diaphragm walls and how it helps deliver this complex urban flood protection and infrastructure projects.

Oct 7, 2024

By Marcel Martineau, Vincent Landry, Simon Didone Arseneau, Ali Fallah Yeznabad, Damien Lamblot, Mathieu Cattone, Habib Akande, Marion Bouet

Vaudreuil-Soulanges Hospital Center in Greater Montreal area is a substantially large construction project with challenging schedule and geological conditions. The foundation consisted of 519 piles with an average overburden of 15 m and 4.5 rock sockets that were constructed in a tight schedule of 9 months. Special Geotechnical considerations were required and adopted for design and construction of this large-scale foundation. In this Design and Build contract, the strong cooperation between the designer and the contractor resulted in a substantial optimization of the quantities through in-situ full-scale vertical static and lateral cyclic pile-load tests, seismic simulations in design of the piles, and orienting the design to fit the planned drilling method. To maintain a challenging schedule in a cost-effective manner, seven drilling rigs fitted with temporary casings were used, operating in two shifts up to seven days a week. For drilling of the piles, cluster drilling was used by contractor due to uncommon abrasiveness and high strength (> 200 MPa) of the encountered sandstone bedrock. To further assist the construction of the piles, a new concrete mix was developed specifically for this project for the purpose of tremie pours. The concrete mix design is based on optimizing its rheology, maintaining its workability up to 6 hours and its durability more than 75 years design life in a particularly aggressive environment in chloride, sulfate, and others aggressive ions. An effective quality control and assurance program made it possible to find optimal solutions during construction.

Oct 7, 2024

By Erich Steinlechner, Freddy Lopez

The Rhine, with its length of approx­imately 1,230 km (764 mi), is the second-longest river in Central and Western Europe and one of the most important navigable waterways in the world. The alpine Rhine (or Alpenrhein) is the section of the river between Reichenau, Switzerland, and the Rhine's confluence with Lake Con­stance on the borders of Germany, Austria and Switzerland. A Swiss­Austrian flood control project known locally as RHESI aims to protect the habitat of about 300,000 people living in the valley along the "international stream" of the alpine Rhine. Along the international stream, the Rhine flows within a central channel toward Lake Constance in a canal-type bed with fortified embankments. In the event of rising water levels, the Rhine floods the foreland, stressing the existing flood embankments (dams). In order to allow even larger amounts of water to flow off safely, more space and new (or rehabilitated) dams are re- quired. With the implementation of the RHESI project, the middle channel of the Rhine will be significantly widened, and the foreland reduced, creating more space for the river. Around 65% of the flood embankments will be rehabili- tated and 25% completely renewed, while 10% of the dams will remain as they are today. These measures will increase the discharge capacity from the current 100-year to a 300-year flood rate. More discharge capacity means better protection against flood events.

Jul 1, 2024

By Blaise Fettig

Santa Cruz Mountains, Ben Lomond, CA Vortex Project Sponsor- Blaise Fettig Vortex PM- Peter Dworetzky Obayashi Corp (Prime Contractor) PM- Kenji Yamauchi ABSTRACT: The City of Santa Cruz Water Department in California replaced the existing Newell Creek Dam inlet/outlet works. The existing inlet/outlet works included a deteriorated 36-inch diameter pipeline under the dam and other components that did not meet current California DSOD dam safety reservoir drawdown requirements. To maintain the reservoir, the City’s engineer designed a new inlet/outlet works that could be constructed under full reservoir conditions, in water up to 115 feet deep. The underwater work began with the dredging of an “amphitheater” on the native 2:1 rock slope. After dredging, three large, critically located benches were excavated into the rock slope with a heavy digging bucket and specialty designed underwater tools. A marine rail was constructed, on which three large concrete donuts were precast and lowered into the water before picking with a crane. These donuts were then installed and grouted in place on the excavated benches. Six foot diameter shafts were drilled through the hole at each inlet foundation donut to the tunnel intersect elevation, and steel casings were installed and grouted into each shaft. Divers installed the three intake structures at design elevations. These 30” intake structures were 30-inch standpipes with 30” diameter hydraulic valves and 48” diameter by 56” tall drum screens. The piping was connected to a 20” diameter air vent line which is designed to prevent vacuum conditions and plumbing to provide a minimum downstream flow. Once the shafts and intakes were in place, a new tunnel was advanced by the general contractor from the downstream right abutment to intercept the shafts. 30” CISS piles were installed to support the 20” vent line from the intake locations to the dam crest. These piles were drilled from barges. Divers then installed Vortex designed articulating pipe supports on the piles, and finally the vent pipe to shore.

Oct 7, 2024

By Jacob Blake, Dan Dwyer, Tulin Fuselier

The recent renovation of Boston City Hall’s Plaza, one of Boston’s premier public meeting spaces, involved heavy construction and grade changes over the country’s two oldest subway tunnels, built in 1898 and 1902. These tunnels presented unique challenges throughout the course of the design and significant logistical issues that had to be carefully managed during the construction process. Despite these challenges, the renovation of the Boston City Hall Plaza has been a major success. This paper aims to explore the successful outcome of the project, highlighting how effective teamwork and collaboration between Owner, Contractor and Engineer played a crucial role in overcoming the challenges faced during the project. The paper also intends to provide insights on how such collaborative efforts can lead to the achievement of a project's goals, despite the hurdles encountered along the way.

Oct 31, 2023

By Glynn Price

Myrtle Creek has been impacted by the subsidence associated with longwall mining at Tahmoor Coking Coal Mine in Picton, NSW.  Specific impacts are fracturing of the rock bed resulting in a reduction in surface flow and pool holding capacity behind the rock bars that are a characteristic of waterways in the southern coalfields. A specific pool, Pool 23, within the impacted Myrtle Creek, was selected for remediation using permeation grouting. First, an investigation was undertaken at Pool 23 to characterise the fracture network and advise on remediation grouting design. The investigation identified the fracture and hydraulic conductivity profiles as well as local hydraulic gradients. Second, a permeation grouting program was implemented which included drilling and permeation grouting completed by Pointe Engineering as per a grout plan and design, using a single part polyurethane grout.  The layout took the form of a grout curtain, perpendicular to the creek and in longitudinal alignment with the rock bar. Permeation grouting as a strategy for remediation of the subsidence impacted water course was demonstrated to have a positive correlation with creek surface flow and pool holding capacity to date.

Oct 7, 2024

By James Walters, Samuel Sideras, Kathryn Petek

The Oregon Department of Transporta­tion {ODOT} is currently performing a seismic retrofit and widening of the Abernethy Bridge as part the 1-205: Stafford Road to OR213 Improvements Project. The Abernethy Bridge, located in Clackamas County, conveys traffic over the Willamette River between the cities of West Linn and Oregon City. The existing bridge structure was completed in 1971 and is approximately 2,700 ft {820 m) in length and consists of 14 piers and two abutments, not including on­and off-ramp structures. At the bridge ocation, the Willamette River is approximately 1,050 ft {320 m) wide. The main channel crossing structure comprises three spans up to 450 ft (137m) long supported on Piers 3 through 6. The west approach structure includes nine continuous spans up to 195 ft {60 m) long and supported on Piers 6 through 14 and Abutment 2. The existing bridge piers are supported on a combination of driven steel H-piles and shallow foundations bearing on basalt bedrock. Construction of the bridge widening and seismic retrofit began in July 2022, which will add one lane in each direction and increase the width of the existing bridge from 100 ft (30 m) to 140 ft {43 m). The seismic retrofit will improve bridge performance to con­temporary seismic design standards and feature a two-level seismic design approach including both operational and life safety design and performance criteria. The foundation design for the project was driven by the highly variable geologic conditions across the project alignment, site constraints and the significant seismic demands. To meet the seismic performance criteria, the foundation solutions for the widening and seismic retrofit included micropiles, ground improvement and drilled shafts up to 12 ft (3.6 m) in diameter. This article describes the foundation design process and methodology and the foundation mitigation solutions developed for the project, as well as discussion of using 12 ft {3.6 m) diameter drilled shafts to mitigate the impacts of deep-seated permanent soil displacements.

Sep 1, 2024

By Md Kausar Anik, Ramin Motamed

The phenomenon of liquefaction-induced ground settlements has been frequently observed in several significant earthquakes, such as the 2010–2011 Canterbury Earthquake Sequence (CES) in New Zealand, the 2011 Tohoku earthquake in Japan, and the more recent 2023 Kahramanmaras Earthquake in Turkey. Various ground improvement methods have been used in engineering practice to lessen the effects of soil liquefaction at shallow depths. Those ground improvement methods signify the outflow of ozone-depleting substances and the release of greenhouse gases, resulting in global warming and consequential environmental changes. Amongst all greenhouse gases, carbon dioxide (CO2) stands as the predominant compound. In our study, we adopted the installation of sheet piles as a measure to mitigate the liquefaction-induced foundation movements. However, the carbon footprint and cost associated with the installation of full-length sheet piles can be reduced by adopting partial floating sheet piles (PFS). Nevertheless, the behavior and characteristics of PFS have not been thoroughly investigated in the existing literature, indicating a research gap in this area. To accomplish these objectives, a 1/5 scaled model, representative of a large-scale shake table test conducted by the University of Nevada, Reno (UNR), is utilized. The scaled model comprises three distinct soil layers with different relative densities: a 50% relative density top crust layer, a 30% relative density middle liquefiable layer, and an 85% relative density bottom dense layer. A shallow foundation is placed atop the crust layer, followed by the insertion of sheet piles (both full-length and PFS) at 0.625 times the foundation width (B) from the center, utilizing the press-in technique. Finally, the scaled models are subjected to harmonic input motions with amplitude and dominant frequency properly scaled based on the large-scale shake table test. The effectiveness of PFS is assessed by comparing reductions in carbon footprint, foundation movements (settlement and tilt), and generated excess pore water pressures with those achieved by full-length sheet piles. In addition, this research also contributes to raising awareness regarding the environmental impact of carbon emissions when selecting mitigation measures.

Oct 7, 2024

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 Michael Arnold, Matteo Bertoni

This paper presents a project which received a DFI Special Recognition Award as a runner-up in the 2023 DFI Outstanding Project Award competition. The East St. Louis levee system is located in St. Clair and Madison Counties, IL, along the left descending bank of the Mississippi River and provides flood protection to approximately 250,000 residents and over $4.5 billion in economic value. The system is aged and requires rehabilitation. The United States Army Corps of Engineers (USACE) devised and designed a cutoff wall to be installed in the Metro East Sanitary District, one of the levees that form the system. The design provided for the installation of an approximately 4,440-foot-long wall, with a minimum 24-inch thickness and a maximum design depth of over 142 feet, through alluvial and outwash soils, and embedded in bedrock. The prescribed “panel method” consisted of overlapping primary and secondary panels, each no longer than 30 feet. The maximum allowed vertical deviation of each panel was 0.5 percent of its full depth. Two sections of single-phase cutoff wall and two sections of seepage barrier using jet grouting were subsequently added to the project, to provide partial closure at two locations where the installation of panels from ground surface to bedrock was not feasible due to the presence of utilities vital for the area. The jet grout columns that comprised the seepage barrier were to be installed at angles varying from 0 to 30 degrees and to depths up to 146 feet. The project included the installation of a minimum 75-foot-long test section and a thorough QC/QA program that provided for the collection and testing of wet grab samples, and the coring of the installed cutoff wall. The paper introduces the project, the geotechnical site conditions and the requirements specified by USACE.  It describes the pursued installation approaches along with the equipment used and focuses on the specific adaption of the methods to site conditions and project requirements.  Selected quality control and verification results obtained from an extensive testing program are presented. The paper also discusses challenges encountered and related lessons learned.

Oct 7, 2024