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By Yuexin Han, Wenbo Li, Xinran Zhu, Pengchao Li

A multi-stage fluidization magnetization roasting is a promising method to treat limonite ore. The dehydroxylation of limonite ore is a key reaction in the pre-heating stage. In this study, the dehydroxylation mechanism of limonite was studied in a laboratory fluidization roasting reactor. The samples were characterized using in situ X-ray diffraction, Fourier transform infrared spectroscopy, and simultaneous thermogravimetry and differential scanning calorimetry analysis. The phase transformation and kinetics analysis were studied. Results indicated that the dehydroxylation occurred at the temperature of 250–350 °C with the vanish of hydroxyl functional groups (-OH). The dehydroxylation kinetics followed the 2-D diffusion (Jander) reaction model G(α) = [1 − (1 − α)1/2]2, and the calculated activation energy was 113.43 kJ·mol−1. This study is conducive to exploiting limonite ore resources using magnetization roasting technology.

Nov 2, 2023

By Ronald C. W. Webber‑Youngman, Philani Larrance Ngwenyama

Entrapments are a huge risk in underground mines. This happens when miners (or any other persons who have entered underground) survive the initial event of an accident, become trapped or lost in unknown and life-threatening locations after evacuation, and remain unaccounted for. At this point, every second counts, and emergency response is highly desired for any chances of saving survivors. The survival chances of the missing persons depend on how quickly they can be located. Rescue teams are often deployed to search for the missing persons underground. However, the rescue teams are forced to search in random and presumed areas of the mine. This is due to the unavailability of information pertaining to the whereabouts of the missing persons. Not only the provision of accurate locations, but various other types of information such as post-accident two-way communication can enhance the survival chances of the missing persons. This information can be provided by a fit-for-purpose missing person locator system. A wide variety of missing person locator systems are already commercially available, some are in testing phases and others in prototype and development phases. This includes tracking, tracing, location detectors and post-accident two-way communication systems. These systems have unique functionalities, capabilities and limitations; making it difficult for mines to select the most effective, applicable and suitable system specific to their mine. In this study, the user requirements for a fit-for-purpose missing person locator system were developed. The purpose of the user requirements was to provide a guideline to facilitate the system selection process. The user requirements can also be used as a tool to measure and evaluate the performance of the selected missing person locator system. The user requirements were also used to predict the success of the selected system under different missing person incident scenarios. The development of the user requirements showed a potential for many other benefits for missing person locator systems.

Nov 2, 2023

By Feida Wu, Yuhang Liu, Huimin Gao, Yuhan Song, Zhi Liu, Zijie Ren

In the process of quartz purification by calcination water quenching, the different expansion rates of gangue minerals and quartz were used to produce cracks or remove fluid inclusions, which is conducive to subsequent purification. However, the role and mechanism of calcination-water quenching are still lacking in research. In this paper, the position of calcinationwater quenching in gangue quartz purification process was adjusted and the removal effect of calcination-water quenching process at different nodes in the process was explored. The results show that the purification effects of grinding-calcinationwater quenching-classification-acid leaching process and grinding-classification-acid leaching-calcination-water quenching process were relatively good. The main reason is that calcined water quenching can make quartz produce cracks, which are more rough. At the same time, calcined water quenching is located after grinding, which has a larger specific surface area, pore volume and pore diameter, and has a strong adsorption capacity for acid solutions.

Nov 2, 2023

By Mustafa Fener, Masoud Rostami, Sair Kahraman, Behnaz Dibavar

The paper introduces a new rock mass cuttability classification (RMCC) system for roadheaders used in coal mines. It includes performance prediction models for both axial and transverse roadheaders, based on six parameters: uniaxial compressive strength, Cerchar abrasivity index, volumetric joint count, strike and dip of joints, joint aperture, and groundwater condition. The study validates the RMCC system through field and laboratory measurements, showing high correlation coefficients between net cutting rates and RMCC indices.

Nov 1, 2023

By Erik Sundström, Magnus Nygren

The study explores the influence and consequences of safety initiatives on the development of safety cultures in the Swedish mining industry. It involves interviews with experts from four mining organizations, highlighting themes such as organizational structures, safety leadership, feedback, and communication.

Nov 1, 2023

By Gregory M. Rumbaugh, Todd R. Kostecki, Christopher Mark

The paper examines five massive pillar collapses in underground stone mines in the eastern United States from 2015 to 2021. These collapses caused significant airblasts, surface subsidence, and damage to mine infrastructure. The study identifies factors contributing to pillar collapses, such as slender pillars with width-to-height ratios of 0.8 or less, and proposes a framework for evaluating and mitigating collapse risks.

Nov 1, 2023

By A. Dell’Era, E. Ciro, C. Lupi

The paper explores the recovery of indium via electrowinning from sulfate baths, focusing on the impact of different cathodic supports (AISI 316L and nickel) on process parameters such as electrolyte composition, current density, and temperature. The study compares productivity, morphology, and structure of indium deposits on both cathodes, finding that nickel cathodes generally yield better results.

Nov 1, 2023

By Turan Uysal, Ramazan Aydogmus, MURAT ERDEMOGLU

The paper investigates the effects of calcination for thermal activation and intensive milling for mechanical activation on aluminum recovery by acid leaching of pyrophyllite ore enriched via attrition scrubbing and froth flotation. The study compares these methods in terms of energy consumption and aluminum recovery, concluding that mechanical activation is more economical and environmentally friendly.

Nov 1, 2023

By Arash Khosravifar

One of our research thrusts at Portland State University (PSU) centers on developing design guidelines for pile foundations in liquefiable, laterally spreading grounds. This research has been primarily sponsored by the DFI Committee Project Fund (CPF) program through four awards, totaling nearly $240,000 in financial support. DFI contributed half of this financial support, while the other half was contributed in-kind by PSU and DFI Project Advisory Board members. Leveraging the CPF funds, we secured an additional $550,000 in financial support from the National Science. Foundation (NSF), which has enabled our research group to continue exploring this topic and contributing to the broader engineering community's understanding of the behavior of pile foundations in liquefiable soils. The CPF funds have fostered collaborations with practitioners and researchers beyond PSU. Notable examples include collaborative research involving data from five large-scale centrifuge tests on pile-supported wharves by Steve Dickenson, Ph.D., New Albion Geotechnical; Nason McCullough, Ph.D., Jacobs Engineering and Scott Schlechter, Geotechnical Resources, as well as 1-g shake table tests of bridge pile shafts conducted by Professors Ahmed Elgamal, Ph.D., and Ahmed Ebeido, Ph.D., of the University of California, San Diego. In addition to these collaborations, our research has benefited from industry-university partnerships formed through the involvement of DFI Project Advisory Board members. Their support and feedback ensure that our research products are practical and imple- mentable in real-world projects. The impact of the CPF funds extends to supporting graduate students' theses, which were the basis for 17 technical publications. Some of these publications are expected to have a significant impact on the industry. For instance, our 2018 DFI Journal paper, co-authored by former master's student Jonathan Nasr, cur- rently with the Army Corps of Engineers, has been cited in the 2022 British Columbia Supplement to Canadian Highway Bridge Design Code S6:19. A noteworthy product of our study is a step-by-step design procedure for pile- supported wharf structures subjected to the combined effects of lateral spreading and inertial loads, outlined in a 2022 American Society of Civil Engineers' (ASCE) Journal of Geotechnical and Geo- environmental Engineering paper co- authored by former doctoral student Milad Souri, Ph.D., PE, Geotechnical Resources.

Nov 1, 2023

By Ramin Motamed, Reza Mohammadi, Zahra Faeli

Finite element methods can be used to analyze the dynamic responses of soil-foundation-structural systems during earthquakes. Therefore, the validation of finite element models with actual seismic recordings is required to benefit from their use in foundation seismic design. In this paper, the acceleration records from the Hayward-I580/238 bridge in California will be studied. At the HaywardI580/238 bridge, three-component accelerometer recordings from two geotechnical downhole arrays at the surface and depths down to 90 meters were used. Furthermore, from 2011 through 2022, 15 earthquakes were recorded at these downhole arrays ranging from Mw 3.4 to Mw 6. However, this paper focuses on the earthquake events within the range of Mw 3.4 to Mw 4.4. Therefore, this study is limited to earthquakes up to Mw 4.4. In the first part of this study, a free-field model of the Hayward-I580/238 bridge site is built using the OpenSees software. Then, in the second part, a drilled shaft of the HaywardI580/238 bridge is modeled. A comparison of the dynamic responses generated by OpenSees with the recorded data from the geotechnical downhole arrays will be used to validate the free-field model, and the acceleration responses from the free-field model will be applied to the drilled shaft. Then, the behavior of the drilled shaft under the applied seismic forces in terms of different calculated parameters (e.g., displacements, reaction forces, etc.) will be investigated. As a result of this study, despite the absence of actual acceleration recordings, obtaining the responses of the soil layers in various depths is possible using a numerical modeling method. In conclusion, not only OpenSees provides a tool for monitoring drilled shaft behavior during seismic events, it provides a robust tool for future drilled-shafts seismic designs.

Oct 31, 2023

By Taylor Stevenson, Takefumi Takuma, Andrew Rose, Chris DellAringa

The city of Huntington Beach is a coastal community along the Pacific Ocean in Southern California with a series of intracoastal flood channels that run through densely populated residential areas. The Huntington Beach Channel and Talbert Channel Sheet Pile Repair Project was designed to improve flood protection for surrounding Huntington Beach communities. The project consisted of installing over 16,000 linear feet of new steel sheet piles adjacent to existing steel sheet piles that line the sides of both flood control channels. This paper studies the unique project dynamics and constraints, and highlights the capabilities of the press-in piling method for sheet pile installation.

Oct 31, 2023

By Vijaya Rao Parigela, Jason Redgers

A 6m height approach ramp was proposed connecting the new railway line at ground level with the existing, elevated line and facilitating an intersection. The ramp mainly consists of a reinforced concrete box section with rising top elevation following the gradient of about 6 degrees for a total length of 120m. Based on the provided SLS loads, resistance was required for 75 kPa to 280 kPa loading pressures. Soil stabilization using Deep Soil Mixing, DSM technique was chosen as alternative to CFA piled foundations by the client to limit settlements. Generally, soil conditions consisted of a made ground layer comprising of granular and cohesive deposits underlain by boulder clay and the Pennine middle coal measures. The specifications for treatment were based on the Federal Highway Administration Design Manual: Deep Mixing for Embankment and Foundation Support and required improving the strength of the made ground below the reinforced concrete elements to an acceptable stiffness such that the structural and track bed movements are acceptably small, and future settlement is mitigated to less than 20 mm, with a maximum of 10mm occurring following the track installation. Verification testing to prove that design requirements have been achieved included coring and testing of samples, as well as zone load pressure test. As such the design necessitated a grid of 2.0m diameter DSM columns with target UCS strength of 0.75 MPa. A load transfer platform (LTP) of 0.5m thickness enclosing 2 layers of geogrid was provided on the top of the treated ground to enhance and ensure uniform transfer of the loads.

Oct 31, 2023

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 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 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 Brendan Stepek, Mike Senior, Gary Brill

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

Oct 31, 2023

By John Bryant

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

Oct 31, 2023