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By Grace Keller, Jay Jackson, Patrick Allen, Scott Lakes

Dam construction and remediation projects generate vast quantities of data. All information must be meticulously tracked, analyzed, catalogued, and submitted to the proper stakeholders to ensure safe construction, compliance with design intent, and efficient execution of the work. Traditional data collection involves hundreds or even thousands of hand-written records and checklists, which must be deciphered and manually digitized to verify work outcomes. This process is time-consuming and leaves much room for error. To maximize quality and efficiency while minimizing errors, we deployed a robust Data Management Program. By utilizing digital tools and cloud-based automation, we optimized the Quality Assurance program on the Gross Reservoir Expansion (GRE) Project. The GRE project is a large-scale dam raise located near Denver, Colorado, designed to increase the capacity of Gross Reservoir by raising the existing dam 131 ft using Roller Compacted Concrete (RCC). Given the complex nature of the project, extensive data management and post-processing were required to ensure quality construction. We eliminated the need for paper records by implementing source-to-source data collection. Contractor data was exported in raw form and automatically collected via cloud-based automation. We also built customized mobile applications for inspections, which sends checklist results directly to a cloud database. Data visualization occurs in real-time, and interactive dashboards track status and automatically reflect the updated database, allowing stakeholders to interact with the data to gain insights. Document generation and distribution were also automated, streamlining reporting and filing processes and directly impacting regulatory site audits. This paper will expand on these tools and solutions to provide greater insight on their purpose, use, and execution and illustrate the benefits of an efficient data management program on large-scale dam projects.

Oct 7, 2024

By Katerina Ziotopoulou, Martin Yossifov, Jim Gingery, Katherine Cheng

Soil mixing is an in-situ soil treatment method that consists of mixing cementitious binders with in-situ soil to create soilcrete. The success of this treatment often relies on the value of the Unconfined Compressive Strength (UCS) of the soilcrete after a given curing time. Estimating the UCS can be challenging because numerous factors influence the results, including soil type, soil moisture content, binder content, soil chemistry, soil heterogeneity, and mixing means and methods. In current North American design-build practice, pre-construction design UCS values are typically estimated qualitatively based on a contractor’s experience. Existing correlations may not be suitable for current applications because of recent advances in deep mixing equipment and methodologies. There is a need for more rational and quantitative estimates of UCS for use in pre-construction design analyses.  This paper will explore the intersection of Machine Learning (ML) with geotechnical engineering and soilcrete applications. A database of soilcrete UCS and site/soil/means/methods metadata is compiled from recent Keller projects and leveraged to explore UCS prediction with advanced ML regression techniques. From this ML exploration, a blueprint of how to scaffold, feature engineer, and prepare soilcrete data for various ML techniques will be created. However, many ML models sacrifice explainability for higher accuracies. To achieve insights from ML models, Explainable ML will be applied to the ML models to explain variable importances. Explainable ML can reveal complex patterns and interactions in the model variables, along with the relative importance of each variable’s contributions to the final UCS value. The insights received from the Explainable ML model can then be further pursued in traditional geotechnical research approaches to expand soil mixing knowledge.

Oct 7, 2024

By Thomas Fiala, Derrick Speakman

Green Infrastructure Partners (GIP) is an experienced specialty contractor who installs deep foundation and excavation shoring.  The last 50 plus years has given us a unique perspective by witnessing firsthand the evolution of deep foundation and shoring works across Canada, but specifically in the province of Ontario and the city of Toronto. Toronto is Canada’s largest city, with the population doubling over the past forty years. The volume and complexity of construction projects has kept pace with this rapid urban growth. In this paper, we explore the massive increases in construction complexity by delving into the past half-century of archives of a Toronto deep foundations contractor. Fifty years ago, two to three levels of underground parking with driven pile foundations was considered a complex project. Today, Toronto sees the construction of basements eight parking levels deep, secant pile headwalls upwards of 60 m (200 feet) deep, and drilled shafts to even greater depths. Projects sites in Toronto have also increased in complexity over the years, with more projects of greater depth being built on less desirable sites such as in the infilled Lake Ontario waterfront neighbourhood. As construction complexity has increased, equipment and monitoring technology has also improved over the years as tighter movement limitations on construction have become the norm, especially in infrastructure projects. We will explore the local philosophy of shoring construction, including how it has evolved over the years to suit the continuously more complex projects. An emphasis will be placed on deep secant walls which have served as cutoff walls up to 60m deep and excavation support over 30m (100 feet) deep. We will use several historical and modern case study examples to illustrate this chronicle as Toronto contractors evolved over the years to be leaders in installing these deep foundations and excavation shoring for these unceasingly more complicated and risky projects. 

Oct 7, 2024

By Daniel Renosto, Crysthian Azevedo

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

Oct 7, 2024

By Takefumi Takuma, Tsunenobu Nozaki

Light rail transit (LRT) systems have been built in cities all over the world in order to cope with increasing population and heavy car traffic in their downtown cores and surrounding areas. Light rail tracks are often sharing the roadways with automobile traffic while some of them are on the dedicated trackage for safer and faster transit. For example, the twin cities of Minneapolis and St. Paul in the state of Minnesota in the U.S. have their Blue and Green LRT lines in operation with the latter line being extended by 23km to a southwestern suburb of Minneapolis. The mostly dedicated extension alignment includes an 875m long cut-and-cover tunnel because the alignment there is just next to a high-rise condominium complex, a cluster of townhouse buildings, and a parallel running railroad track. Sheet pile walls were selected as part of the earth retaining structures needed for this section of the extension project. The distance between the buildings and the sheet pile alignment is a mere 3m at their closest point. In order to minimize negative impacts to these existing structures from sheet pile installation, press-in piling was utilized. The soil conditions were alternating sand and silt layers with the SPT value varying between 23 and above 50, which necessitated the use of auger attachments. It took two press-in piling machines 14 months to install approximately 2,500 pairs of Z-shaped sheet piles with their lengths between 7.6m and 19.8m. After the sheet pile wall installation, excavation between the walls, installation of internal bracing, and construction of a concrete tunnel box followed.   

Oct 7, 2024

By Spencer Ness, Yazen Khasawneh

Onshore wind turbines are complex and dynamic systems, undergoing variable environmental and mechanical loads. These dynamic loads are transferred through the turbine components and tower to the foundation system and, subsequently, the adjacent soil. As the size of onshore wind turbines continues to grow, intermediate-type foundations are being developed and implemented to better leverage the strength of the adjacent soils while avoiding some of the drawbacks of deep foundations. However, these foundations can be relatively sensitive to ground conditions. When considering a wind energy site that may consist of dozens of wind turbines across thousands of acres, it can be difficult to determine a design stratigraphy that is reflective of the entire site and takes conservative approaches to all potential failure modes and design checks. As intermediate foundations are inherently a soil-structure interaction problem, computer-aided numerical methods are often necessary. To highlight this condition a typical intermediate foundation with tower and turbine is assessed under eighteen different soil profiles within a finite element software and performance is compared.

Oct 7, 2024

By Keith Herman, Lisa Papandrea

While New York City is known for its bedrock and being home to one of the greatest concentrations of tall buildings in the world, its soil conditions are quite variable and can be very challenging in some locations. One such neighborhood is Manhattan’s Upper East Side, particularly near East 96th Street. Historic maps show that the area was once a wetlands network of marshes and creeks. Construction projects in this area have often led to settlement of existing structures, many of which are old, low rise residential buildings supported on shallow foundations bearing on uncontrolled fill.   This case study presents the design, testing, quality control and construction of rotary-driven pipe piles for support of an 8-story medical research facility on the Upper East Side. Three hundred twenty (320) 12.75-inch diameter, rotary driven pipe piles were installed 120 feet deep. The subsurface stratigraphy consists of uncontrolled fill, organic silts, and peat over stiff, saturated, varved silts and clays. Groundwater is approximately 7 feet below grade.  The rotary-driven pipe pile does not fit neatly into any of the pile types prescribed in the NYC Building Code. Challenges were encountered developing installation criteria and a quality control program for code compliance. A “re-torque” program measuring resistance to torque and crowd-force during installation was used to verify production pile capacity and to estimate soil setup, similar to conventional driven pile restrikes.  Design methodology, torque and crowd-force measurements, load test results, and installation observations are presented. The project benefited from coordination and collaboration between the designer, contractor and special inspector during the test program and development of the final installation criteria. The rotary-driven pipe pile provides a novel “no spoils” alternative for installing deep foundations adjacent to sensitive structures. Lessons learned and potential future developments are discussed. 

Oct 7, 2024

By Andrew Lees, Chris Iereidis, Mark Wayne

The design of working platforms typically involves the calculation of a two-layer bearing capacity to ensure that tracked piling plant can operate with an adequate safety margin against rig toppling due to ground failure. A number of guidance documents on the design and management of working platforms have been published in recent years, as summarised in this article. None of these provide definitive guidance regarding design for very soft subgrade soils or on platform edge stability. Among the calculation methods available for working platform punching shear capacity, the T-value method is a practical but accurate method that has been used in working platform design for over four years. A correction to the T value is proposed for very low subgrade shear strengths to take into account the greater sensitivity to subgrade shear strength and the difficulty of constructing and compacting an aggregate over such soft ground. Furthermore, a simple equation was derived by finite element analysis (FEA) parametric study to calculate a safe edge distance for working platform operation taking into account the width and aspect ratio of loaded areas, platform thickness and subgrade soil strength. These findings are being applied in the design of working platforms to include very soft subgrade soils and to help avoid rig toppling near platform edges.

Oct 7, 2024

By Seth Hamblin, Bill Oder, Les Chernauskas

Thermal Integrity Profiling is a non-destructive test method used on cast-in-place concrete deep foundation elements such as drilled shafts.  The method has progress steadily over the last 15 years with improvements to the equipment, data acquisition and analysis of the data. Current analysis of TIP data incorporates temperature vs depth and temperature vs. time. The current acceptance criteria for TIP includes using reductions in effective shaft radius and concrete cover (Piscsalko, et al. 2016).   However, these criteria are heavily based on knowledge of concrete volume and can be significantly affected by the lack of good concrete volume data.  An additional criterion using temperature is proposed for potential use in the industry, which can supplement the existing effective radius/cover criteria and will be less dependent on volume knowledge. However, the relationship between temperature reductions and defect size and position are not well known for various reasons.  The major reasons for this include; not a lot of studies/data available, variations in mix designs, variations in shaft sizes, and variation in defect types. Research was recently performed by the Authors on three drilled shafts with manufactured defects under grants from DFI and ADSC.  The study included running theoretical simulations to predict the sensitivity of temperature reductions to the defect size and location. Data was collected and the temperature with depth was compiled for various defects. The results show a promising relationship between temperature reduction and defect cross sectional area.  When considering local temperatures and average temperature changes, the criteria can consider location and size.   When including data from other recent research studies for similar size shafts and defects, we found the relationship to be consistent with our data.  The findings of this research provided a better understanding of the relationship between temperature reductions and defect size and location and provide the basis of the proposed temperature criteria.  

Oct 7, 2024

By Tony Sangiuliano, Jason Weck, Ryan Regier, Alper Turan

Cast-in-place concrete piles socketed in rock are a commonly used foundation solution in the province of Ontario. Although cast-in-place concrete piles are common, limited pile load testing has been undertaken on these foundations to confirm shaft friction (side shear) and end bearing parameters. Particularly, the large diameter piles bearing on rock makes conventional pile loads tests impractical and costly due to large capacities that need to be mobilized during testing. Performance of piles loads test come with the advantage of confirming the assumed geotechnical design parameters and permitting the use the larger strength reduction factor as per LRFD design. This paper presents the preparation, execution, and result interpretation of a pile load test carried out on two Cast-in-place concrete piles with diameters of 1.5m and 1.8m for Garden City Skyway Project in the City of St Catherines Ontario, Canada. The 1.5m and 1.8m diameter test piles were socketed 4m and 6m into shale bedrock. Osterberg cells were used in both load tests to provide end bearing and shaft friction parameters for the shale bedrock as well as overlying layers of till and soft clay. The results of the load test provided valuable insight into the load settlement performance exhibited by these piles. The results are also compared with the analytical estimates of the pile capacities presented in geotechnical report as well as the results of a number of other analytical socket design approaches.

Oct 7, 2024

By Rajni Saggu

This study presents the cyclic load-displacement response of thermal piles in a pile group consisting of thermal and mechanical piles. To investigate the effect of different (i) layouts of thermal piles and mechanical piles, (ii) pile spacing, and (iii) soil type on the pile displacements and axial stresses, numerical analyses were performed over 50 cycles of thermal loading and unloading of the thermal piles. The analysis outcomes show that the thermal changes in the load-displacement characteristics of the piles become complex during cyclic thermal loading and unloading of the thermal piles. The mechanical piles also exhibit uplift after thermal loading of the thermal piles, and significant differential displacements occur at the pile cap, head and base for all the piles. Higher pile spacing imposes a positive effect in terms of lower thermo-mechanical stresses in the piles compared to the case of closely spaced piles. Axial stresses in each pile are notably non-uniform after the thermal loading cycles applied on the thermal piles. Cyclic alterations in the load-displacement of thermal piles also impose alterations in load-displacement of the mechanical piles. Further, the layout of thermal piles, pile spacing, and soil type control the long-term cyclic thermo-mechanical response of the pile group.

Oct 7, 2024

By Seth Robertson, Alex Ciccone, Lawrence Johnsen, James Davis

The most sustainable foundation is the one that is already in place. That doesn’t mean it is the easiest to RE-use. This was realized when replacing a multi‑story hospital parking garage in Hartford, Connecticut. The previous garage was constructed in the 1980s and was supported on grade beams with 3.0‑ and 4.5‑foot‑diameter drilled shafts that extended through 100+ feet of problematic soft Connecticut Valley varved clay, glacial till, and end‑bearing in or on arkose bedrock. The proposed garage consisted of relatively high loading demands, was susceptible to excessive settlements, and was also located adjacent to an active hospital with sensitivity to vibrations, thereby limiting many foundation design options. An innovative solution was proposed to re-use many of the existing drilled shafts, supplemented with a combination of micropiles and composite piles. Composite piles were comprised of 3.0‑foot‑diameter drilled shafts with a central, 11.75‑inch‑diameter micropile to transfer structural loads to bedrock. Installation information on the existing drilled shafts was heavily limited. Dynamic load tests were therefore performed on 12 existing shafts spread across the garage footprint, confirming geotechnical resistances up to 4,500 kips and significantly improving quality assurance of the existing foundation construction. Additionally, two micropile load tests were performed in tension to 900 kips, confirming design loads could be resisted by the bond strength in rock. The foundation re‑use methodology saved over 3 million dollars in installation costs, weeks of construction schedule, and resulted in a significant carbon reduction compared to conventional, and inherently more substantial, foundation replacement strategies. Critical aspects of the foundation re‑use design strategy and limitations of alternatives will be discussed. Implementation of innovative load testing techniques are addressed, focusing on optimizing quality assurance for utilizing existing deep foundations in modern construction. Lessons learned and recommendations for future practice are presented.

Oct 7, 2024

By Eric Brichler

Shaft Construction Using Diaphragm and Cement Bentonite Walls at Shoreline Storage Tunnel Eric Brichler, Senior Estimator, Major Projects eric.brichler@nicholsonconstruction.com Nicholson Construction Company, Denver, Colorado The Shoreline Storage Tunnel (SST) Project in Cleveland, Ohio is part of EPA-mandated Project Clean Lake, Northeast Ohio Regional Sewer District’s program designed to reduce pollution in Lake Erie by 4 billion gallons per year over the next 25 years.  The $3-billion program includes construction of large ‑diameter storage/conveyance tunnels, shafts at key combined sewer overflow (CSO) pick-up points, underground pump stations, improvements to wastewater treatment plant capacity and treatment, and expansion of green infrastructure.  When completed, SST will comprise over 2.5 miles of 23-ft-diameter tunnel installed 87 to 135 ft below ground.  The storage tunnel will manage higher flow volumes and keep stormwater out of the combined sewer system to reduce overflow occurrences.  As part of the project, three deep shafts (SST-1, SST-2, and SST-3) were constructed to provide access to the tunnel, launch and retrieve the tunnel boring machine, and provide ventilation.  Several additional structures will serve as diversion structures, drop manholes, gate structures or gate control structures.  A short connection tunnel will connect the SST to the Dugway Storage Tunnel, which was completed earlier in the Project Clean Lake program. The shaft support of excavation system was designed using diaphragm wall methods.  This innovative solution provided watertight, continuous shafts keyed into rock that significantly reduces risks as compared to traditional secant piles combined with a rib and liner plate system.  Unreinforced concrete diaphragm walls were constructed using mechanical clamshells for shafts SST-2 and SST-3, and clamshell equipment and a hydromill were used for SST-1.  All the SST shafts were lined with reinforced cast-in-place concrete and include baffle drop structures. Outside of the SST-1 and SST-3 shafts, several ground improvement blocks were installed using overlapping cement bentonite panels. These ground improvement zones were created to provide increased strength and water cutoff in the soil at locations where the TBM broke into and out of the shafts. A gate structure attached to both the SST-2 and SST-3 diaphragm wall shafts was supported by a soldier pile reinforced cement bentonite wall.  The design of the gate structure SOE was handled collaboratively with the owner and their engineer, McMillen Jacobs Associates.  The team worked together to resolve challenges surrounding tying in the originally designed bracing scheme to the new SOE method and methods for exposing and supporting a 100-year-old existing brick sewer, as well as excavating through an abandoned brick sewer. This case study will present the design for the shafts and gate structures, the diaphragm wall construction methods, the unique challenges overcome for each shaft, and the benefits of the final solution to the overall project.

Oct 7, 2024

By Eric Lindquist, Scott Chambers, Rob Jameson

The Salt Lake Temple is undergoing its most significant renovation since its dedication in 1893. The renovation includes a seismic retrofit of the historic stone structure’s foundations using base isolation. This paper focuses on the temporary underpinning of the 16 to 35 feet thick unreinforced masonry perimeter walls of this massive structure. Conventional needle beam or direct structural underpinning approaches to support the Temple in place during base isolator installation were precluded by its immense weight and extremely thick walls. The design-build team instead developed a unique temporary support of excavation (SOE) program to allow the 19-foot-deep excavations for the new base isolator foundations. The SOE scheme allowed the massive structure to be supported on confined soil “columns” located directly below the masonry wall footings while excavation to construct the new foundations was advanced concurrently along the Temple’s outer perimeter and inside the building. Shoring system stiffness was critical to mitigate settlement risk for this historic building and construction methods were selected to minimize detrimental installation effects.    The structural engineer’s permanent design required sequentially jacked steel pipes immediately below the walls, which were filled with post-tensioned reinforced concrete to create transfer beams. After completion of the foundation excavation, two new grade beams separated vertically by base isolators were constructed along both the interior and exterior sides of the perimeter walls. The concrete filled steel pipe transfer beams were structurally connected into the upper grade beams above the isolators. After load transfer is completed, the soil directly below the walls will be excavated to allow free movement of the structure and grade beams above the base isolators in the event of a future earthquake. The historic temple SOE and underpinning system employed multiple construction methods, including micropiles, secant piles, tieback anchors, tensioned tie-rods, temporary attachments to the jacked permanent steel pipes, hand-dug underpinning piers, permeation grouting and steel structural headers supporting interior walls. Design and construction of the historic retrofit SOE system is detailed in this paper.

Oct 7, 2024

By Samar Saad, Mazen Adib, Farid Motamed, Medji Sama

Abstract Deep foundations were necessary to support bridges, retaining walls, and other structures at the I405 Improvement Project in Orange County, California. The ground properties and stratigraphy were primarily investigated using cone penetration tests (CPTs), with confirmatory boreholes and laboratory tests. A CPT-based design calculation method, the LCPC-CPT by Bustamante and Gianeselli, was followed to predict the axial geotechnical resistance. To justify a resistance factor of 0.7, extensive Pile Driving Analyzer (PDA) measurements were performed to allow calculation of the driving resistance using Case Pile Wave Analysis Program (CAPWAP). The piles included open ended 24-inch diameter steel pipe piles, 14, 16, and 18 inch H Piles, and 14-inch square Precast Prestressed Concrete Piles. The paper presents the subsurface conditions and ground properties from the CPTs and the predicted versus CAPWAP axial capacities for the various types of piles. The paper will also present challenges encountered and opportunities from lessons learned. It was observed that, in general, the CAPWAP axial capacities were in acceptable agreement with the LCPC-CPT predictions, although capacity incorporating full setup was not measured on all piles. Also, the correlations between LPCP-CPT predictions versus CAPWAP axial capacities depended on the type of pile.

Oct 7, 2024

By Jarod McBride, Mike Johnston

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

Oct 7, 2024

By Omar Conte, Roger Archabal

In recent years, numerous developers have invested in former deep quarry lake sites, particularly to develop massive new logistics and residential projects in South Florida. Due to the flat geology encountered, necessary construction materials (structural fill, sand, concrete aggregate, etc.) have been quarried from the upper limestone and sand layers encountered in the region. Considering the shallow groundwater, these quarry excavations have created numerous large bodies of water (“lakes”) over the decades. Restoration of these massive lake areas which are now dispersed throughout prime real estate is ideal for development. There is a strong incentive to restore these large lake areas due to the lack of available large tracts of land near Miami or Ft. Lauderdale. The redevelopment of these large and deep-water bodies has important geotechnical challenges that need to be addressed before finalizing the infrastructure and foundation design/construction. This paper will go over the investigation techniques utilized, the geotechnical evaluation, analysis, and soil improvement recommendations to allow for safe bearing support and to overcome the uncertainties associated with settlement potential.  Several geotechnical aspects need to be considered to effectively perform mass lake backfill. These include: 1) the pre-backfill site investigation, 2) understanding the lake bottom conditions and soil layering below the bottom, 3) backfill material selection and backfill methodology, 4) quality control/quality assurance during lake backfilling, 5) post-fill ground improvement (preloading, dynamic compaction, vibro-compaction) and foundation construction are some of the key aspects for these types of projects. The geotechnical findings and lessons learned from several massive lake backfill projects will be discussed in the paper. This includes sites with measured lake bottom sediment layers of up to 15 to 20 feet thick, resulting in consolidation settlement of nearly 3 feet during ground improvement/preload settlement monitoring. The paper will present some innovative exploration and laboratory techniques to obtain important geotechnical data to cost-effectively develop these massive areas.

Oct 7, 2024

By Kevin Baumgartner, Howard Perko

Common technologies for temporary and permanent support of excavations (SOE) include soldier piles and lagging, secant/tangent piles, slurry walls, and tie-back walls. This paper discusses an innovative technology consisting of helical soil nails with high tensile wire mesh facing.  This novel technology has been used on a number of SOE projects in recent years saving both time and money as well as providing a number of other benefits.  Case histories including Denver Bronco’s training facility, Pulliam Theater, a bridge abutment, and a train platform are presented.  This SOE technology is highly sustainable as both the mesh and soil nails can be removed and re-used, if desired.  The system avoids the need for concrete or grout, so it eliminates curing times and problems associated with field quality assurance and inclement weather placement.  Helical soil nails consist of central pipe or solid steel shafts with small diameter helices spaced over the entire length.  The length of the nails is typically on the order of the height of the excavation.  The nails are spaced relatively close together in rows to reinforce the earth.  The face of the excavation is held back using high tensile strength steel wire mesh over geo-fabric.  The mesh is stretched between the helical soil nails and fastened down using spike plates on the helical nail caps.  Both hand calculation and computer methods for design of this concrete-less alternative to the traditional SOE will be covered. The SNAP 2.0 computer program is used to determine factors of safety with regards to overturning, sliding, and bearing, among other checks.  Through practical applications and real-world calculations, this paper educates the reader on the proper design and application of the helical soil nail and high tensile mesh SOE system.  AutoCAD details and example plans are provided.

Oct 7, 2024

By Kenichi Soga, Andrew Yeskoo

Distributed Fiber Optic Sensing (DFOS) allows the user to measure continuous strain and temperature profiles along an installed fiber optic cable. The technology has successfully been deployed for a range of geotechnical and geostructural applications, including monitoring of deep foundations This paper presents the results of a fiber optic sensing installation for the measurement of strain in a cast-in-drilled-hole (CIDH) foundation element during a top-down load test. DFOS is particularly suited to strain measurements during pile load testing as it can generate continuous strain profiles along the length of the pile, removing the need for interpolation between point-based strain gauges. The hypothesis is that continuous strain profiles allow insight and understanding of the true, non-idealized pile behavior during loading. A field trial was performed north of Sacramento, California, where a series of load tests were performed on sacrificial piles instrumented with fiber optic strain and temperature sensing cables. The fiber optic instrumentation design consisted of 4 vertical strain cables, as opposed to the more common 1 or 2 cables, allowing for the identification and analysis of non-uniform strain distribution across the pile at single depths. This non-uniform distribution has often been ignored through averaging or discarded as erroneous data, missing potentially real behavior within the pile. The fiber optic data was used to evaluate an independently identified outlier strain gauge reading and confirm the reading as valid, as well as identify bending behavior within the pile which contributed to non-uniform strain measurements across the pile. This research demonstrates the value of the use of DFOS for pile strain measurements and the benefit that it offers over point-based measurements and the interpolation that it necessitates between discrete readings.

Oct 7, 2024

By Guoming Lin, Yan Jiang

The Hutchinson Island ferry landing, a vital transportation hub located between the Savannah Convention Center and Westin Hotel, faced a critical infrastructure challenge on June 18, 2022, when the sheet pile bulkhead along the Savannah River experienced movement, resulting in a substantial crack in the brick-paved plaza.  Immediate monitoring efforts commenced within two hours of the bulkhead disturbance, revealing progressive movements over the subsequent two weeks, leading to approximately ten feet of deflection and six feet of settlement behind the bulkhead.  Subsequent repair work involved the extraction of 65-ft-long steel sheet piles. This investigation embarked on a meticulous review of the original design and construction procedures, followed by a comprehensive subsurface exploration program.  The steel sheet piles were originally supported by drilled helical anchors, and the failure mode and pattern were closely scrutinized.  Analysis of the pulled-out sheet piles revealed consistent shape and yield points.  Computer modeling was conducted to replicate the actual deflection profile and yield point as verification of the soil parameters and design models. This paper presents the investigative findings, including an analysis of subsurface conditions and the most probable causes for the bulkhead failure.  The results of the investigation have been instrumental in formulating design recommendations for the repair of the bulkhead system.  By shedding light on the root causes of the failure, this research contributes valuable insights to the soil-structure interaction in the steel sheet pile design. Top of Form

Oct 7, 2024