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By Shaun Wulff, Kam Weng Ng, Nafis Bin Masud, Opeyemi Oluwatuyi

Pile foundations are often driven in intermediate geomaterials (IGMs) to attain higher resistances in order to meet the increasing load demand, satisfy Load and Resistance Factor Design (LRFD) specifications, improve design efficiency, and reduce construction challenges. IGMs are transitional geomaterials that possess a high natural variability. However, these geomaterials are not well defined and characterized in the design and construction of driven piles. This paper presents the recent development using over 150 load test data on steel piles to comprehensively address current challenges with pile foundations in IGMs. A methodology is presented to classify soft rocks and soil-based IGMs to reduce pile design and construction uncertainties. New static analysis methods are developed and validated to improve the estimation of shaft resistance and end bearing of piles in IGMs. New procedures to model pile driving in IGMs using the wave equation analysis program (WEAP) are proposed to improve the construction control efficiency. LRFD resistance factors are calibrated using probability-based methods to achieve a target design reliability. Finally, extensions to include inherent variability and geological uncertainties of IGMs using geostatistics are suggested to develop a geotechnical investigation plan and improve pile design reliability.

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

By Jordan Romero, Jimmy Nettles, Daniel Sprunk

The Venture Global Plaquemines LNG Project in Port Sulphur, Louisiana, stands as a great achievement in the world of liquefied natural gas (LNG) infrastructure. Encompassing a 632 acre (255 ha) site, 20 miles (32 km) south of New Orleans along the Mississippi River, it's designed to be one of the largest LNG export facilities in the U.S., with the capacity to handle up to 20 million metric tons (22 T) of LNG per year. The project's scope includes multiple LNG trains, storage tanks and large marine terminal infrastructure. The construction involves significant civil works, including deep foundation and flood protection systems. Given the scale and complexity of the project, the construction process is highly intricate, involving a multitude of deep foundation disciplines and coordination among various contractors and stakeholders. Cajun Industries was tasked with several critical components of the piling and civil construction phase, including the development of hurricane protection systems and the execution of extensive deep foundation scopes through the life cycle of the project. This involvement in the project began with a small-scale precast concrete test pile program using just one pile driving rig in 2020. By May 2024, operations had expanded significantly, with a peak workforce of 200 employees, 30 piling rigs and 15 different piling scopes. These scopes included a design-build flood protection system for the project's laydown yard and construction support facilities, single-piece pipe piles up to 145 ft (44 m) long, precast concrete piles up to 120 ft (37 m) long, 41 cofferdams with sheet piles up to 80 ft (24 m) Jong, as well as 140 ft (43 m) long H-piles. The scope also encompassed a comprehensive test pile program featuring more than 150 load tests. Over the course of the project, the team executed more than 575,000 safe man-hours, installing 18,300 piles of various types and sizes. These efforts equated to the installation of more than 1,965,9001ft (600,000 m) of piling or 372 mi (600 km), weighing a staggering 312 million lb (142 million kg). For perspective, one could travel three round trips to outer space when comparing the linear footage of piling.

Sep 1, 2024

By George Onorato, Giovanni Bonita

Deep soil mixing (DSM) has become a widely used ground improvement technique globally, producing soil-cementitious materials for various complex civil and environmental applications. In the field, the soil-cement materials form under confining stress conditions, which are often overlooked, as most wet grab specimens are cured and tested under ambient atmospheric conditions. This oversight has led to an underestimation of the engineering and mechanical properties of the soil-cement mixed material. With support from the DFI Technical Committee Project Fund, the authors initiated a multi-phased comprehensive research study in collaboration with industry experts to gain a fundamental understanding of these effects. This study investigates the curing conditions to which in-situ materials are exposed and how these conditions influence the strength of deep mixed materials. The findings reveal that the curing conditions for in-situ materials, including applied stresses and temperatures, significantly differ from those under which typical quality control specimens are cured. Neglecting these conditions can lead to a substantial underestimation of in-situ material strength. The data compiled for this study encompass strength and temperature data obtained from specially designed laboratory bench tests, field-conducted modified oedometer tests, in-situ instrumentation tests within deep mixed columns, and a review of independent coring data from deep mixed projects across North America. Analysis of these collective studies reveals a correlation between curing stress and unconfined compressive strength (UCS). The rate of strength gains follows a linear pattern and is influenced by the soil type being treated. Fine-grain soils, in particular, exhibit a higher rate of strength gain when subjected to in-situ curing stress (with depth) compared to granular soils. The paper delves into fundamental processes such as drainage, consolidation, and interparticle behaviors of deep mixed materials from their fresh state until the treated column has cured. It also presents empirical and analytical methods to correct in-situ strength measurements to account for the effects of curing stresses.

Oct 7, 2024

By Tina Hastings, Karen Dawson, Ryan Dunne, Patricia Bennett

The Georgetown Wet Weather Treatment Station is located in Seattle and will treat up to 70 million gal {265 L) per day of combined sewage that would have otherwise discharged directly to the Lower Duwamish Waterway without treatment during storms. The facilities also include conveyance of raw combined sewage from existing large­diameter pipes to the treatment station and of treated effluent from the treatment station to the new outfall structure located in the Lower Duwamish Waterway. The most geotechnically significant structures at the treatment station are a large process building (approximately 220 x 110 ft [67 x 34 ml) that houses mostly above-grade ballasted sedimentation, solids storage and ultra-violet disinfection, and a below-grade, nominal 100 ft (30 m) diameter influent pumping station/equalization basin (IPS/EQ) constructed within a 92 ft (28 m) deep secant pile ring. The station also includes additional support buildings, vaults, above-grade rainwater harvesting cisterns and large-diameter pipelines. This article specifically outlines key geotechnical decisions for design and construction of the process building and IPS/EQ at the treatment plant site and presents case history information from construction of the IPS/EQ. The key geotechnical challenges faced during design included: A site with more than 120 years of industrial use, occupied by operating businesses; this resulted in limited access for subsurface explorations, soil and groundwater contam­ination, potential obstructions/undocumented utilities, restrictions on hauling and street closures, and existing structures within feet of the property lines. Compressible soils also subject to seismic liquefaction. Tight grade tolerances for weirs, large pipe connections and some equipment that reduced the amount of allowable settlement. A schedule with immovable milestones dictated by consent decree. A companion paper titled "Instrumented Load Testing and Construction Monitoring of Rigid Inclusions in Seattle" was presented at the DFI 48th Annual Conference on Deep Founda­tions and delves into the technical details of the unreinforced rigid inclusion ground improvement system that supports the process building.

Mar 1, 2024

By Aaron Gallant

Civil engineering and construction companies are increasingly aware of the environmental impact and associated greenhouse gas (GHG) emissions linked to their daily operations and design decisions. Many have already taken significant steps to track and report emissions to better understand their impact on the global carbon footprint. Most generally align accounting practices with the Greenhouse Gas Protocol {GHG Protocol), which has become the most widely adopted international framework to measure and report GHG emissions. The GHG Protocol was developed by the World Resources Institute and the World Business Council for Sustainable Development and categorizes emissions into three scopes. Scope 1 constitutes direct emissions caused by operating equipment and resources it controls and owns (e.g., fossil fuels to run machinery, vehicles, etc.). Scope 2 incorporates indirect emissions linked to purchased electricity, heat, or energy owned or operated by a third party, but influenced by the individual entity's usage. Scope 3 encompasses all other indirect emis­sions associated with entity operations. In other words, Scope 3 attempts to put a spotlight on the indirect emissions within an entity's entire value chain that allow the entity to operate and provide a service.

Nov 1, 2024

By Andreas Stimpfle-Ziegeler, Harald Heinzelmann, Karsten Beckhaus, Rabea Barhum, Askin Onur

In October 2023 Bauer has completed the execution of deep foundations for the Saint-Brieuc offshore wind farm 16 km off coast north of France. Once operational, the 496MW wind farm will generate enough clean energy for 835,000 inhabitants. Ailes Marines, owned by Iberdrola, contracted Van Oord who deployed Bauer. In total, 190 shafts have been drilled and the same number of pin piles were grouted to support 62 wind turbines, based on triple jackets, and an offshore substation, based on a four-pile jacket. Bauer did the works from Van Oord’s offshore installation vessel called “Aeolus”. The Atlantic environmental conditions in combination with the extremely hard and rocky seabed and high requirements to geometrical tolerances and other key quality indicators challenged the contractor’s expertise and equipment in several ways. The paper shall illustrate the planning, execution and particular solutions to meet the client’s demands to their full satisfaction. First of all, an innovative drilling method was used to install the foundations for which project-specific “dive drills” were engineered and constructed by Bauer. Secondly, the underwater survey tasks needed smart solutions and skilled personnel to prove the accurate final position of the pin piles. The survey must ensure the precise position of the newly designed drilling template, which functioned as a positioning and casing drilling tool, but also the subsequent placement of the pin piles.   Last but not least, the pin piles inserted into the shafts needed a fixed and force-locked connection with the ground. Great efforts were done to get to the necessary fresh and hardened properties of the cementitious grout itself, and to control the complete filling and necessary integrity of the structural sleeve grouting. All above three aspects, the dive-drill method, the underwater survey and the sleeve grouting will be explained in detail and challenges experienced offshore will be showcased. Eventually, a full set of individual expert features for drilling, monitoring and grouting techniques have been developed towards an optimized installation system of which parts have been already introduced into other fields of geotechnical works. Accepting challenges based on passion for progress for this outstanding project has brought innovative techniques and features into the deep foundations industry with great potential for adaptions in other fields of geotechnical works.

Oct 7, 2024

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 Joshua Zimmermann

For years, a subdivision in Glenrock, Wyoming, suffered from various odd damages, including the sudden appearance of artificial springs, flooded basements/crawlspaces, and shifting foundations. The source of this damage was the underlying Glenrock No. 1 and No. 2 Mines, where years of collected groundwater had resulted in high-pressure artesian conditions within the mined interval. The high groundwater pressures within the mine eventually hydraulically fractured the overlying rock, resulting in the communication of the shallow groundwater table with the deep aquifer within the mine interval, damaging the homes in the overlying community. Additional damages, such as subsidence, also impacted various homes in the area. To address these conditions, there was a question as to whether or not void fill grouting would be feasible for mitigation in an area known to exhibit high artesian head pressures. A pilot program was initiated to determine the feasibility of this method and create the methodology/design approach to alleviate any potential risks from the mitigation program to the surrounding densely populated overlying sub-division. These potential risks associated with the injection and pressurizing high mobility grout included displacement of groundwater into building foundations, inducing the structural collapse of the mine, infrastructure sub-grade failure through over-saturation, environmental considerations, and ground surface movement. After extensive analysis of this pilot study, a specially designed mitigation program was established for mitigating the mine subjacent to a sub-development and took place during the Summer of 2021 using an extensive groundwater monitoring network, specially designed discharge wells, and remote sensing technologies to mitigate the area with no damage reported to the overlying community.

Oct 7, 2024

By Dov Leshchinsky

Mechanically stabilized earth (MSE) walls are composed of three main elements: soil, reinforcement and a facing. If any of these elements are not functioning, its internal performance would be unacceptable. In extreme cases, it will result in a collapse. How­ever, if material characterization, design and construction are properly done, MSE walls will exhibit excellent long-term performance while being economical. In fact, when using multiple reinforce­ments, redundancy is rendered, i.e., 'overstressing' loads can be alleviated by shedding it to understressed layers. Common design of MSE walls with respect to reinforcement and facing is generally conservative. However, soil is often poorly characterized. The result is either an overly conservative structure or worse, unacceptable structural per­formance. Underestimation of backfill strength is typical as often default shear strength is used. For example, the American Association of State Highway and Transportation Officials (AASHTO) specifies select reinforced soil, sug­gesting a default friction angle of q>=34° with an upper limit of 40°. For the select backfill specified in AASHTO, this angle is likely to be 45-55° implying that the actual strength of the compacted backfill could be as much as 50% larger. However, if in construction the rein­forced soil is poorly compacted or drained, conservatism due to underes­timated soil strength may vanish, potentially leading to poor wall per­formance. This is not different from other geotechnical structures. The objective of this article is to report failures of two dissimilar walls, ending with costly remediations that changed the characteristics of original MSE structures. The cases reported are not unusual and reflect similar prob­lems in other MSE wall failures the author has investigated. The reported cases are based on forensic studies and, in a general sense, are structured as such: A known outcome, e.g., excessive settlement or collapse. An investigation process to separate the chaff from the wheat, i.e., distin­guish between the "noise" typically promoted by lawyers who are ad­vocating for a client.

Jul 1, 2024

By April Fontaine

Climate change is occurring, and owners/agencies are seeing the impact of warming temperatures and extreme weather on landslides and other geohazards across the globe. Asset management is becoming more important and more challenging with the rapidly changing environment.  State and Federal agencies need to collaborate and partner on new ways to address these challenges; design of one-size-fits-all engineering solutions won’t work effectively anymore.  Alaska is an obvious nexus of these issues as the state is experiencing observable and measurable impacts from climate change in real time.  Landslides and climate (as well as resilience) are significant administration priorities, and there is benefit in understanding how other agencies are approaching today’s challenges.  These topics were explored at a peer exchange meeting in Alaska in 2023.  Key takeaway from that exchange include: the need to understand the inventory of hazards; the context of each agency, which provides key differences in strategy, policies, and priorities; the constraints that will drive risk reduction versus risk mitigation; the need to evaluate the entire system and not look at each individual hazard; and the criticality of relationships across organizational boundaries – no one agency can solve these challenges on their own.  Strategies used by various agencies in Alaska can inform practices in other regional settings with their own distinct climate and extreme event challenges and project characteristics.

Oct 7, 2024

By Albert Allaart, Rodriaan Spruit, Hans Pacejka, Suzanne J. M. van Eekelen

The Sint Sebastiaansbrug (Saint Sebas­tian Bridge) in Delft, the Netherlands, was built in 1964. The bridge crosses the Delftse Schie, or waterway, with a fixed span of 12 m (39 ft} and a movable span of 12 m (39 ft). In the middle of the waterway, both the fixed and movable bridge decks rest on a pier. The vertical clearance of the fixed part is 4.5 m (15 ft}. On both banks there is an ap­proximately 80 m (262 ft) long access ramp, consisting of a concrete con­struction on piles. Each section of the access ramp has a span between supporting structures of approximately 10 m(33 ft}. During the preparations for con­verting the bridge to accommodate a tram in 2006, a thorough inspection of the bridge was executed. The inspection conclusions were very unfavourable. Several supporting structures had settled considerably, causing structural damage to the upper structure. Adding bearing capacity to the failed foundation, repairing the struc­tural damage and accommodating the tram on a wider bridge was studied in 2010 and was found unfeasible and the uncertainty profile associated with this solution was also considered to be too high.

Mar 1, 2024

By Nick Benedetto, Sonia Sorabella Swift, Taylor Towle, Seth Pearlman, Andy Sullivan

The Route 1&9T/New Road project is a three-part program to relieve the notoriously congested Route 1&9 (Tonelle Avenue) in the heart of the industrial sector of Jersey City, New Jersey. Contract 1 consisted of con­structing a new road over a 1 mi (1.6 km) Long stretch of unimproved land serving as part of the parking lot to a large postal facility. To get to grade, modular gravity retaining walls were specified on either side of the 54 ft (16.5 m) wide roadway corridor. While the proposed wall heights ranged from only 2-8 ft (0.6-2.4 m), the soils present on-site were not even suitable for a shallow embankment. The underlying soils were mixed fills and organic peat, underlain by soft clay and silt to depths ofupto 75 ft (23 m). The proposed solution presented in the project plans certainly would have worked on paper; however, Menard, having had poor experiences with rigid inclusion installation and load transfer platform (LTP) compaction at or just above the groundwater table, recog­nized the potential difficulties, delays and rework that would likely be required during construction of what was shown on the contract plans. As such, it proposed a value-engineered solution that resulted in a vast improve­ment in the constructability, perfor­mance and overall cost of the system. However, the benefits of this solution were not appreciated by the owner and the solution was met with high levels of scrutiny, perhaps because it differed from what was shown on the contract plans. The level of testing required of the solution was far greater than what was required of the design shown on the contract plans. Such rigorous and unwarranted confirmation of a value­engineered solution consumed time, money and resources that could be better used elsewhere. Instead, these designs should be compared to the design in the original contract plans based on technical merit and expected long-term behavior. This article walks through the design and construction process for the value-engineered solu­tion and highlights the many challenges experienced by the contractor to get final approval of the work perormed. Though the COVID-19 Pandemic was an unanticipated complication, the per­ceived distrust of the contractor's proposals and work was a barrier to progress that the authors hope will not exist in the future.

Feb 1, 2024

By Muhammad Naeem, Allison Digregorio, Sam Yao, Joshua Core

Located at the Eastern shoreline of the San Francisco Peninsula, the Potrero Power Station Project is transforming a 29-acre industrial site into a mixed-use redevelopment with 7 acres of new waterfront public spaces. The primary goals of the infrastructure renovations are to protect the new waterfront developments against sea level rise (SLR) and to mitigate the risk of seismic instability of the shoreline. As a result, the site was generally raised by approximately 8 ft. Various design solutions were developed and implemented to address differing field conditions throughout the site. Deep soil mixing (DSM) buttresses were used to combat seismically induced slope instability throughout the entire shoreline. New pile-supported wharves were designed using an innovative engineering solution to resist kinematic seismic loading in the offshore slope. Several types of retaining walls and a grouted tieback system were selected along the shoreline to facilitate numerous waterfront recreational experiences for the public. Collectively, these structures and ground improvements have minimized adverse impacts of SLR and ensured seismic stability of the shoreline. This paper presents a successful project that demonstrates the benefits of tailoring design solutions to unique field conditions to enhance the resilience of the San Francisco waterfront development.

Oct 7, 2024

By Jesus Gomez, Carlos Englert, Amanda Mallon, Mary Nodine

Rigid inclusions are a ground improvement technique that provides soil reinforcement and settlement mitigation using drilled displacement elements. Rigid inclusion installation typically uses a Monitoring While Drilling (MWD) electronic logging system that captures data such as torque, downward thrust, rotary speed and grout take with depth and time. Installation of each rigid inclusion can be considered data from a large-scale in-situ test consisting of penetration of a rotating probe into the ground. Automatically generated graphic logs are typically reviewed visually by members of a project team for quality control during and after installation. This workflow underutilizes the valuable data provided by these MWD systems. This paper discusses the use of MWD installation data integrated with cone penetration test (CPT) data and static load test results to develop a streamlined and robust quality control workflow for rigid inclusions. A compound parameter designated the Penetration Resistance Index (PRI) is computed using soil-tool interface mechanics principles for each production element. The PRI, when plotted with depth, can be correlated with CPT data so that changes in soil profile can be detected as production elements are installed across the site. When the PRI is integrated over element length below the neutral plane, the resulting Integrated Resistance Index (IRI) value can be compared with the IRI of load test elements to rapidly assess element suitability. Use of the PRI and the IRI can help improve quality and efficiency of Rigid Inclusions systems by detecting potential areas where geotechnical conditions are sufficiently different or have improved significantly as production installation progresses. This information allows designers to determine whether optimization of the intended element lengths is possible or where a more intense treatment may be necessary. This quality control workflow can be performed in near-real time.

Oct 7, 2024