Search Documents

By Md. Nafiul Haque, Murad Y. Abu-Farsakh, Chris Nickel

"This paper presents the results from a pile load testing program for a bridge construction project in Louisiana. The testing includes two 54-inch open-ended spun cast concrete cylinder piles (OECP), one 30-inch open-ended steel pile (OESP), and two (30-inch and 16-inch) square prestressed concrete (PSC) piles driven at two locations with very similar soil conditions. All the test piles were instrumented with vibrating wire strain gauges to measure the load distribution along the length of the test piles and the skin friction and the end bearing were derived from strain gauge measurements. High strain dynamic load tests (HSDLT) were performed on all test piles at different times after pile installations to quantify the amount of setup with time. Static load tests were also performed on the PSC and open-ended steel piles. Due to expected large pile capacities, the statnamic test method was used on the two open-ended cylinder piles. The pile capacities of these piles were evaluated using various CPT methods (such as Schmertmann, De Ruiter and Beringen, LCPC, COFS methods). The result showed that all the methods can estimate the skin friction with good accuracy; but not the end-bearing capacity. Setup was observed for all the piles, which was mainly attributed to increase in skin frictions. The setup rate parameters “A” [The “A” parameter is defined as the rate of increase of pile capacity ratio (Rt/Rto) per log cycle of elapsed time] were back-calculated for all the test piles and the values were between 0.31 and 0.41.INTRODUCTIONDue to greater efficiency (capacity to weight ratio) of the pipe piles, open-ended piles are a viable option to solid piles. However, the behavior of open-ended piles is more complicated compared to the close-ended piles owing to possible formation of “soil plug” inside the open-ended pile. Many researchers have analyzed the behavior of both types of piles for different purposes; however, very few studies in the literature offer the side-by-side comparison of the close-ended and open-ended piles."

Jan 1, 2017

By Paul Thurlow, Richard K. Lipscombe

The measurement of deflection of designed diaphragm walls is critical for near real time information to assess wall and soil behaviour as the internal area is excavated in a controlled manner. Data enables the site team and designers to check performance of the design, which is linked to safeguarding the site and the external stakeholders.This paper documents the use of Shape Accel Arrays at the Tottenham Court Road Western Ticket Hall during excavation and propping within the diaphragm wall for the Crossrail project. It shows how the data obtained was used within the site settlement management plan to assist in the control of the works and the information used for Value Engineering purposes that benefitted the project.The use of Shape Accel Arrays for measuring the deflection of retaining walls is not commonplace in the UK construction industry, with the Tottenham Court Road Western Ticket Hall being one of the first times they have been used in such a way. A detailed analysis of the data obtained from the instruments has been undertaken, and compared to the results obtained from the manual inclinometers that were read next to the SAAs. The advantages of the relatively new SAAs have been discussed, as well as other applications of the instrument.

Jan 1, 2017

By Christopher Mark

Coal bursts are typically associated with highly stressed coal. Most bursts occur during retreat mining (longwall mining or pillar recovery) in highly stressed locations like the tailgate corner of the longwall panel. Others are associated with multiple seam interactions. However, a small but significant percentage of coal bursts have occurred during development or in outby locations unaffected by active mining. Most development bursts have been relatively small, but some have been highly destructive. No theory of coal bursts can be complete if it does not account for this type of event. This paper focusses on the development mining coal burst experience in the US, putting it into the context of the entire US coal burst database. The first documented development coal burst occurred almost exactly 100 years ago during slope drivage at the Sunnyside Mine in Utah. Sunnyside subsequently had a long history of bursts, mainly during retreat mining but also during development. Several Colorado mines have also experienced multiple development bursts. Some, but by no means all, of the development bursts in these western US coalfields have been associated with faults. In the Central Appalachian coalfields, most development bursts have occurred in multiple seam situations. In some of these cases, however, there was no retreat mining in either seam. The paper closes with some lessons from this history, with implications for preventing such events in the future.

Jan 1, 2017

By Justin Simmons, Michael Arnold, Bob Faulhaber

"In order to remodel an existing beach resort on the Gulf of Mexico, an existing three story structure, founded on stepped tapered piles, was to be replaced by a ten-story building with service rooms on a daylight basement level, conference rooms on the next levels and up-scale hotel rooms on the upper levels. The new building was founded on augered-cast-in-place (ACIP) piles. The pile caps and the basement required excavations between nine and fifteen feet (three to five meters) below ground surface.BAUER Foundations Corp. (BFC) successfully used Cutter Soil Mixing (CSM) to install the support of excavation walls. This technique allowed for the adjustment of the wall alignment during execution in order to avoid existing and new piles and other underground obstructions. Nearly 1600 – 16-inch (400 mm diameter) ACIP piles were installed to an average depth of 71.5 feet (22m) below ground surface (BGS) by BFC to support the new hotel structure. Initial grout overages in piles were excessively high and ground stability issues were encountered in some pile locations. By identifying specific areas of concern BFC was able to modify the approach to ACIP installation, effectively mitigating the ongoing risks and successfully completed the project.PROJECTMarriott Hotels began the $300 million renovation and upgrade of their Marco Island Marriott Beach Club Hotel in Marco Island, FL to JW Marriott status in May 2015. The renovation included the demolition of a portion of their existing hotel tower, and the construction of a new 10-story hotel tower consisting of 94 new guest rooms and a 10,000 SF (900 m2) ballroom, among other amenities. As is typical with hotel construction, time was of the essence. The schedule was the driving factor of this project as the owner had already booked events in their new ballroom starting in January of 2017.BFC provided the client with a deep foundation package that included the installation of 1562 Augered Cast-In-Place (ACIP) piles supporting the new tower, and the design and construction of approximately 36,500 SF (3,400 m2) of soil-mixed retaining wall for support of excavation (SoE)."

Jan 1, 2017

By Joel B. Dellaria, Justin R. Lewis

"No. 9 Walton is a new high-rise condominium building located in the Gold Coast area of Chicago. The adjacent building, Walton on the Park, featured 4 levels of below grade parking and utilized a secant pile wall with integral drilled shafts to support the exterior columns. The earth retention system (ERS) for No. 9 Walton also employed a secant pile wall in combination with drilled shafts. The excavation into the soft Chicago clays varied in depth from 9.75 m to 12.5 m (32 feet to 41 feet) below grade. The temporary excavation support used internal braces from the new secant piles to the existing foundation system of Walton on the Park to provide earth retention. Engineering teams for both projects worked together to design the bracing scheme and connections to ensure that the new excavation and internal bracing would not overstress any elements of the existing structure. Further complicating the project, immediately to the west of the project was a historic church founded on shallow spread footings which required underpinning to minimize movements.The project involved three different building owners, small values for acceptable wall movement, an extensive monitoring program and the challenges of merging two earth retention systems. The subsurface conditions at the site, the adjacent structures, the excavation, and the performance are described. A summary of the design methods and the expected movements of the ERS are discussed, and the performance monitoring system is described. Overall, the ERS performed better than expected with less than 1 inch of measured lateral wall movement during and after the excavation was completed. Measured performance of the ERS is compared to the predicted performance and to the performance requirements for the project.INTRODUCTIONNo. 9 Walton is a new high-rise condominium building in Chicago located in the Gold Coast. The building has 3 levels of below grade parking and 36 levels of living space above grade. Developers originally slated the project to be Phase 2 of the Walton on the Park development built in the mid 2000’s, using portions of the existing foundation system for development of the new structure. However, the housing market crash in 2007 prompted cancellation of Phase 2 of the Walton on the Park development. The property sat undeveloped until 2015 when design and construction for No. 9 Walton began under a new development and design team. The project team completed foundation excavation and below grade structures in 2016 with the first units of the building turned over to new homeowners in 2017.The structural design for No. 9 Walton consisted of reinforced concrete columns and slabs, supported laterally by a heavily reinforced concrete central core. Drilled shafts to rock supported the interior columns and core with the exterior columns and foundations integrally included in the earth retention system. The structure had a below-grade footprint of approximately 1,490 m2 (16,000 ft2). The general excavation extended 9.75 m to 12.5 m (32 feet to 41 feet) below street level with the deepest portions at the central building core mat foundation."

Jan 1, 2017

By Tony Amis, Marco Barla, Alice Di Donna

"Energy geostructures are becoming an increasingly popular solution around the world for Developers looking to reduce CO2 and system running costs. Energy geostructures are geotechnical structures that provide both the important role of structural stability while also acting as a heat exchanger with the ground, enabling the supported buildings and or infrastructure to be heated and cooled using the principle of low enthalpy geothermal systems. The main advantage of this innovative technology with respect to standard geothermal plant is the reduction of the initial installation costs and construction schedule benefits, compared to installing conventional geothermal solutions, largely due to the additional use of structures which would be constructed in any case. However, it is important with respect to energy geostructures that additional aspects need careful consideration. For this very reason, several research studies have been carried out over the last decade on this subject and a number of real case studies have been monitored and analysed. The key difference with respect to conventional shallow geothermal systems are mainly related to the geometry, which is imposed by the geotechnical project, and the need to ensure that the primary structural role is always guaranteed. Special boundary conditions, the reduced depth, the influence of atmospheric external temperature can also play an important role for energy geostructures. They can affect, both energy efficiency and, the geotechnical behaviour because of the possible thermal induced mechanical effects. This paper presents a picture of the current situation regarding energy geostructures and their peculiar features, and collects available data to provide a reference framework. Data has been collected from literature and personal communications and then processed to provide easy-to-read charts useful for practical consultation at a glance. This paper provides, an indication of the distribution of such systems worldwide, their spread in time, and a global view of their actual efficiency from the structural, energy, economic and environmental point of view.1. IntroductionEnergy geostructures are becoming an increasingly popular consideration around the world. Energy geostructures are geotechnical structures with a dual role of providing structural stability and the ability to exchange heat with the ground, to provide low carbon heat and coolth to supporting and or adjacent buildings and infrastructure, using the principle of low enthalpy geothermal systems (Barla and Di Donna, 2016; Laloui and Di Donna, 2013). A closed circuit of high density polyethylene (HDPE) pipes is embedded in the concrete, and a heat carrier fluid circulates through them exchanging heat with the ground. The HDPE pipework circuit inside the geostructure is linked to one of the above buildings or infrastructure through a heat pump, which adapts the temperature of the circulating fluid to the heating (winter mode) and cooling (summer mode) needs. In this way, heat can be injected into the ground during summer and extracted from it during winter. In principle, all structures in contact with the ground can be used as energy geostructures. The first examples of energy geostructures date back to the eighties in Austria and were mainly piles and shallow foundations. A decade later, Henderson et al. (1999) reported on what would appear to be the first successful use of geothermal energy piles in the US, with loops incorporated into the foundation for a hotel in Geneva, New York. As was their use in this New York case history, the typical geothermal energy pile application is used in conjunction with additional closed loop boreholes to provide the required energy capacity for a structure. Interestingly the report concludes that the geothermal energy piles had a better heat transfer performance than the borehole field. The first energy walls appeared slightly later, while still today only a few experimental cas"

Jan 1, 2017

By Gerald Verbeek, Erick Baziw

"Downhole Seismic Testing (DST) is an important geotechnical testing technique for site characterization as it provides low strain (<10-5) in-situ interval compression (Vp) and shear (Vs) wave velocity estimates. These velocities are determined by obtaining relative arrival times of source waves as they travel through the stratigraphy and are recorded by one or more vertically offset seismic sensors. A challenging aspect of this process is to characterize the seismic data sets to determine the analysis method that will result in the most accurate interval velocity values. This paper introduces an assessment technique which utilizes linearity estimates (i.e., hodograms fitting straight lines) from the polarization analysis in conjunction with crosscorrelation coefficient calculations of the full waveforms as well as the deviation of the source wave frequency spectrum from a desirable bell-shaped curve. The paper will provide an overview of the technique and include some examples of actual data sets where the technique was applied to analyze those data sets.1. INTRODUCTIONIn general terms, Downhole Seismic Testing (DST) such as Seismic Cone Penetration Testing (SCPT) is a geotechnical technique for measuring in-situ shear and compression wave velocities (VS and VP respectively). The main goal in DST is to obtain arrival times as the source wave travels through the soil profile of interest, and from these arrival times the velocities are then calculated. Figure 1 shows a schematic of the typical DST configuration: a seismic source is used to generate a seismic wave train at the ground surface. One or more downhole seismic receivers are used to record the seismic wave train at predefined depth increments. The downhole receiver(s) may be positioned at selected test depths in a borehole or advanced as part of an instrumentation package as in the case of SCPT. When triggered by the seismic source a data recording system records the response of the downhole receiver(s)."

Jan 1, 2017

By Shawna Munn, Nadir Ansari, Allison Bennett

"This paper outlines how specification driven design has made Toronto Area transit infrastructure projects more expensive than similar private projects, and provides a case study of the results of an excavation at Launch Shaft 1 (LS1) for the Eglinton Crosstown Light Rail Transit project in Toronto, Ontario. The paper will describe the impact specification driven design parameters can have on design economy, constructability, and schedule and will suggest an alternative approach utilizing the Observational Method. As a result of the initial specification based design, Isherwood was retained by both the General Contractor and the Specialty Excavation Shoring Contractor to provide value engineering leveraging the Observational Method to improve constructability and construction schedule. By using well known, accepted design methods coupled with local experience in lieu of the specified design pressures and parameters, the redesigned bracing scheme reduced construction cost and schedule. This excavation case history can be a lesson learned for future transit projects.The City of Toronto has been developing its transportation network since the mid 1800’s. “Canada’s First Subway” along Yonge Street opened in March 1954 (TTC 1954), with a few additions to the subway network through to the 1980’s. The following two decades marked a long period of slow development due to recessions, budget cuts, and politics along with several cancelled projects. To fill the gap left by years of underfunding, several new transit projects are now under construction in the city as a part of Metrolinx’s $50B, 25 year, “The Big Move” initiative (Metrolinx 2013). The work on these types of infrastructure projects is highlighting a different and developing challenge within the tendering and design specification structure we will call Prescriptive Specification Design (PSD).PSD is a method used within contract specifications to control design risk on a project by applying conservative design methods, factors of safety, or other parameters to make a “fool proof” design. It is akin to requesting a colouring by numbers approach from a painter. There are inherent risks of using this method of tendering a project including increased project costs, longer construction schedules, and decrease of overall project economy. In PSD, the Owner “owns” all of the design risk on a project, including any additional costs due to changed site conditions. However, the Contractor commonly “owns” the risk of any deviations from the design specification they pursue, therefore making any improvements to the design, cost, or schedule less desirable from the Contractor’s point of view. The impact of this type of strict specified approach to design has been seen in transit infrastructure projects in the Toronto area. Figure 1 outlines the range of specified AEPD design pressures as a function of excavation height (H) specified for use in Toronto underground transit projects since the 1970’s to present day. A clear trend can be seen with respect to increased design pressures specified. The ranges shown for each project are intended to account for the potential differences in soil conditions for the highly overconsolidated glaciated soils in the Toronto area. The graph also highlights the typical range, in blue, for the industry practice in Toronto for comparison."

Jan 1, 2017

By Neil T. Russo, Peter M. Kandaris, Jogi S. Gadok

"Assessment of subsurface data for foundation design in support of long high voltage electric transmission lines is best accomplished using a probabilistic strategy since only a small portion of structure locations are typically sampled. Probabilistic approaches provide a tool to evaluate site uncertainty in a systematic and rational manner. This paper provides a case history of a risk-based design approach for a recently completed 191-mile long 69/161/345kV steel monopole transmission line traversing Central Iowa. The project owner made available limited subsurface information at project initiation, requiring the design team to obtain additional data within a constrained budget for 1067 large diameter, laterally-loaded deep drilled shaft reinforced concrete piers. The team commissioned a geologic desktop study to reduce uncertainty in subsurface evaluations and aid in selecting additional sample sites. In total, investigation programs tested approximately 15 percent of structure sites. The paper details the probabilistic approach used to estimate foundation geotechnical design parameters, with information from the various studies categorizing strata both laterally and with depth. Low-bound parameters were estimated via a statistical approach at a predetermined reliability level. Significant savings resulted from this approach when compared to conservative deterministic processes. Project QA/QC logged subsurface soil conditions during foundation excavation, then compared as-found conditions to the conditions assumed for design. The team redesigned foundations if either a non-conservative variance in soil conditions was observed or if bedrock elevation differed significantly from design assumptions. As a result, only 22 out of 1067 foundations required modification during construction (2% variance from initial design) with negligible impact on the construction budget and schedule.INTRODUCTIONFoundation design for long high voltage transmission lines presents a unique challenge in that the assessment of subsurface conditions typically requires substantial data that may or may not be obtainable. Investigations are usually performed well in advance of construction, often with limited access to structure sites and typically in remote areas. Probability and risk-based investigation and design strategies offer an opportunity to systematically estimate subsurface profiles and geotechnical design properties with limited data. Risk can be further reduced with dedicated field inspection of foundation construction along with good field and design team communication during construction. This paper presents a case history of probabilistic methods used for the investigation and design of electric transmission line foundations."

Jan 1, 2017

By Alexander Filotti, Richard Kalson

"1. INTRODUCTION- WHAT IS P3 OR PPP ?The Public Private Partnership (PPP or 3P) is a project delivery scheme based on the government providing land and/or a concession agreement, and on a private entity providing the design, construction, financing, operation and maintenance of the project for an extensive duration of time (up to thirty years). At the end of the operation-maintenance period, the project is turned over to the public entity, which fully owns the project at all times. While there are many PPP delivery schemes used around the world, for the present paper, we are going to analyze the impact of the Design-Build-Finance-Operate-Maintain (DBFOM) scheme on the deep foundation specialty subcontractor. There are couple of reasons that the PPP delivery system started to be used and implemented not only by developed nations (e.g. United Kingdom, USA etc.), but also by the International Development Bank for delivering major infrastructure projects in developing nations. From the point of view of government agencies, some of the reasons to use PPP are the following:??The primary use of private capital in an era where borrowing and/or supplemental taxation represents too much of a political risk. Budget deficits and taxation limits are extremely hot topics in every election (national or local) and the level of education of the electorate in this area is making it more and more difficult for politicians to use borrowed funds and additional taxation finance sources for public projects. At the same time, we see an increase in the social expenditures of the government in parallel with a needed increase in expenditures on infrastructure due to aging and neglect.??Bundling the construction risks with the operational and maintenance risks naturally pushes the private entity to increase the level of innovation and communications in the primary phase ( the construction phase) in order to develop future process based upon the innovation and communications utilized in the operation and maintenance phase of the project. This is true if contractual incentives are properly structured because “all revolves around incentives. In a world of ‘incomplete’ contracts, where it is difficult to foresee and contract about uncertain future events, it is important to get the incentive structure right” (Grimsey and Lewis, 2004).??The transfer of very expensive risks such as differing site conditions, schedule, design, construction, maintenance and operation costs from the public authority to the private entity.??The timespan of development and construction of a PPP project is usually shorter than the traditional procurement process (e.g. “ the I-595 P3 provided capacity improvements fifteen years sooner than a conventional plan would have offered. In Maryland, an innovative expansion of the Seagirt Marine Terminal in the Port of Baltimore was completed two years ahead of schedule due to the P3 model. As a result, the Port of Baltimore is only the second port on the US East Coast to have unrestricted access to both a fully functioning 50-foot channel and 50-foot berth.”)"

Jan 1, 2017

By Chris Normand, Paul Volpe, Eric Wey, Howard Perko, Burt Ogilvie, Patrick Murray

"A refinery expansion project for Marathon Petroleum Company in Southern Louisiana required existing medium to large pipe racks to be expanded for additional capacity. Foundation modifications were necessary in order to add levels to the existing pipe racks. New piles were added and existing pile cap foundations were expanded. Several different pile types were considered. Custom designed large diameter helical piles were chosen, because they can be installed quickly with low overhead restrictions, produce minimal soil spoils, and are cost effective. The load capacity required for piles was higher than typical, off-the-shelf helical piles. In particular, the lateral load capacity demand was high due to wind loads of a hurricane prone region. Methods used to design and size helical piles are summarized including capacity to torque ratio estimation for composite helical piles. Pile load testing was performed in order to confirm design capacities of the helical piles under axial and lateral loading. Measured axial and lateral deflections compared well with predicted values. This case history evaluates the effectiveness of modern helical pile design methods within the context of a real and practical example.INTRODUCTIONAs the capacity of modern installation equipment increases, large-diameter helical piles are being used to support higher loads in more diverse applications. Currently, large-diameter high-capacity helical piles are used for electrical power transmission, power generation, high-rise buildings, bridges, and industrial applications. This case study regards a 2.5-mile pipe rack modification project within an existing refinery. One of the many challenges for engineering and construction of refinery revamp projects is determining how to effectively expand the capacity of existing foundations for additional equipment, piping, and other facilities. Custom designed large-diameter helical piles provided an effective solution to the challenges faced when expanding the capacity of existing pipe racks."

Jan 1, 2017

By X. Zhu, Chen. L., R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study is to develop a suitable flow sheet to extract rare earth elements (REEs) from coal ash. A total of 14 coal samples of different ranks were examined for REE concentration, and an anthracite coal sample with the highest REE concentration of more than 700 ppm in the coal ash was selected for REE extraction tests. This paper reports on the results of the experimental program completed in the first part of the study, which included hightemperature leaching with nitric acid followed by solvent extraction tests using various organic extractants, namely, tributyl phosphate, Cyanex 572, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and their combinations. A 4×2×2 experimental design was used to conduct a total of 32 high-temperature leaching tests by varying acid molarity at four levels, solids content at two levels and leaching time at two levels. The highest recovery rates of 90 percent for light rare earth elements (LREEs) and 94 percent for heavy rare earth elements (HREEs) were obtained from the optimum leaching test conditions while maintaining impurity recovery to the leachate at less than 40 percent. D2EHPA was found to be the best extractant in this solvent extraction test series, providing an REE recovery rate of nearly 99 percent.IntroductionGlobal demand for rare earth elements (REEs) and other strategic metals is increasing rapidly due to their use in a variety of advanced technological applications, with more than 100 kt of rare earth oxides used worldwide on an annual basis. The United States has less than 10 percent of the world reserves of REE mineral deposits, and in 2013 imported more than 60 percent of its rare earth oxides from other countries, mainly China (United States Geological Survey, 2017). China’s institution of export quotas has significantly reduced supply to the United States, raising the urgency of finding new ways of producing REEs and/ or substitutes. Coal combustion byproducts, which are usually discarded as waste materials, are known to contain REEs in low concentrations that could be extracted with a suitable process flow sheet. This may be a worthwhile route to pursue, considering the short supply of rare earth minerals and the abundance of coal ash in thousands of ash ponds in the United States. More than 110 Mt of coal combustion byproducts are produced annually in the process of satisfying the country’s need for electricity (American Coal Ash Association, 2016), and less than 50 percent of these byproducts are being successfully used in various applications, with the remainder dumped as waste materials in landfills and ash ponds."

Jan 1, 2017

By Abolfazl Eslami, Fatemeh Valikhah

"Complexity in soil-foundation interaction and subsoil nonlinear behavior cause difficulties and uncertainties in evaluating the actual values of foundation design factors such as settlement. The acquired continuous records of Cone Penetration Test (CPT) can be used to determine the soil profile and characteristics those are applicable in the geotechnical design. In this paper, it has been attempted to present a new non-linear stress-strain approach to estimate the foundations settlement by using CPT data in the form of soil behavior classification charts. This new approach is based on Janbu method (1960s and also 1998). Instead of using fixed and constant values for stress exponent (j) and modulus number (m), continuous coefficient variations can be used. The proposed approach also can be used as a new method to predict pile group settlement. A data bank has been compiled containing twenty-two practical case histories to investigate the accuracy of the predictions made by the proposed and available common methods. The comparisons indicate that the proposed approach is relatively able to predict the settlement close to their real values. Therefore, it can be considered as an alternative method based on valuable CPT data and nonlinear stress-strain approach for foundations and pile groups settlement estimation.INTRODUCTIONComplexity in soil behaviour for settlement analysis is the result of non-linear and time dependent stressstrain behaviour of soils, their elasto-plastic performance under loading and unloading situation and also effects of stress history (Holtz et al., 2011; Fellenius, 2015). Hence, many relations and equations have been proposed to predict foundation settlement, where most of them are based on typical different parameters such as soil stiffness (E), foundation width (B), contact pressure (q) and pressure developing in depth (Janbu, 1967 also 1998; Briaud and Gibbens, 1999; Uzielli and Mayne, 2012).The Janbu approach for settlement estimation, proposed by Janbu in the early 1960s, combines the basic principles of linear and non-linear stress-strain behaviour of material. The method is applied to all types of soils. The relation between stress and strain is a function of two non-dimensional parameters which are unique for any soil: a stress exponent, “j”, and a modulus number, “m”. The Janbu relations are derived from the definition of tangent modulus by the following expression:"

Jan 1, 2017

By Steve Davidow, Ashely E. Evans, Peter M. Kandaris

"Annually thousands of deep foundations are constructed across North America supporting high voltage transmission line structures. However, a recent state of the practice survey by the Deep Foundation Institutes’ Electric Power Systems Foundation Working Group discovered that the electric power utility industry lacks consistent foundation design guidelines. The survey identified a wide variability in design assumptions, a minimal understanding of risk based analysis, and a need to standardize design methodologies. This paper summarizes the state of practice in electric system foundation design and proposes a framework for risk-based foundation design by accounting for uncertainty from both loads and resistances. Loads derived from electric system codes do not necessarily provide a compatible level of reliability for the design of foundations, as they are a mixture of probabilistic and deterministic values. Load uncertainty is derived from variability in weather conditions, structural models and material properties, typically accounted for by code derived overload factors. Resistance uncertainty arises from variability in natural soil properties, resistance models, subsurface construction techniques, material sampling methods, and limited observations. A consistent methodology is offered relating nominal resistance capacity (strength) to structure loads and service state criteria. Discussion also includes the need for risk-based assessments to account for non-structure load influences (fluvial loads, scour ground loss, liquefaction, etc.).INTRODUCTIONNearly 40 years ago the Electric Power Research Institute (EPRI) embarked on a major research effort to optimize reliability and economics of transmission line foundation design. Strategies focused on improvements in design models, site characterization, exploration strategies and testing to reduce uncertainty and variance in analysis. Transmission line engineers realized that safety and reliability advancements in design based on probabilistic approaches, with a focus on the unique nature of transmission line, could better control risk and cost.Some transmission line professionals took full advantage of these advancements, particularly where research led to improved software and models. Yet, even after two decades of extensive research, by 1995 the industry still had made little progress in changing design habits. The majority of designers were still characterizing sites via deterministic methods, using loads that may or may not relate to a consistent probability of occurrence, and applying a traditional global factor of safety approach (Phoon, et al. 1995). The following two decades have seen even greater developments in software and reliability-based analysis methods, but old habits seem to die hard as recent surveys show less than half of design professional quantitatively assess risk in their design process."

Jan 1, 2017

By Eleonora Di Mario, Colin B. Turnbull, Matthew G. Mills, Chengbin Miao, Wilhelm S. Degen

"In the past decade, the ‘zero-dredge’ philosophy has become the preferred option for the formation of marine seawalls and reclamations, compared to the partially or fully dredged options, as this solution presents several environmental advantages. Recent relevant project experience is presented herein in order to highlight key design principles and construction issues central to the successful construction and performance of a sloping rubble seawall founded on soft soil improved by stone columns. If designed and installed with proper quality control, correct treatment intensity and sensible construction staging, stone columns are a safe and cost effective method for seawall foundations. This paper provides guidelines with regards to the design, construction and quality control for the correct implementation of stone columns as a foundation element for sloping rubble marine seawalls.INTRODUCTIONBenefits of sloping marine seawalls founded on stone columnsTo suit the current environmental requirements in Hong Kong, recent projects are tending to favour zero-dredge solutions, such as the Hong Kong Boundary Crossing Facility and the forthcoming Three-Runway System. The installation of stone columns allows the underlying deposits, generally consisting of very soft to soft clay and silt (soft soil), to improve in strength to the extent that the seawall can be directly placed on the seabed. This negates the need to dredge the soft soil and, therefore, this ground improvement technique represents an ideal solution for zero-dredge projects.Stone columns can also provide several other beneficial effects, including: accelerated drainage, reduced settlement, increased slope stability and soil reinforcement in the event of an earthquake. Stone columns, in contrast to competing cementitious methods, are a very ductile foundation method. This ductile behaviour is part of the design concept of stone columns in soft soil. Past projects located in Hong Kong and elsewhere, with an improved soft soil layer thickness of over 15m, have shown that stone columns can remain fully functional in terms of both drainage and horizontal reinforcement, even after settlements of over 3m and lateral displacements of up to 1m have occurred."

Jan 1, 2017

By A. J. Monhemius

This paper reviews the history of modern iron-control processes in hydrometallurgy. Attention is paid to processes developed in the electrolytic zinc industry for removal of iron from zinc sulfate leach liquors and the problems faced by the industry in the safe disposal of the iron residues produced by these processes. Past lessons learned are projected onto current efforts to develop hydrometallurgical processes for treatment of copper sulfide concentrates. It is argued that any attempt to create a \u201chydrometallurgical copper smelter\u201d will fail, unless methods are developed that can recover iron in a form that can be directly used by the steel or pigment industries.

Jan 1, 2017

By M. Hitch, M. B. Lytle

Resource development conflicts arise largely due to differences in worldview between those who support and those who oppose development. This paper illustrates how societies and civilizations with different worldviews produce different levels of creative and economic energy. A questionnaire was created to build a database of responses to test whether worldview and resource development are correlated. Factor and multivariate regression analysis determined correlations for respondent groupings. Results showed a positive correlation between the respondents\u2019 worldviews and their attitudes toward resource development. Correlations became stronger as the homogeneity of the sample subgroups increased.

Jan 1, 2017

By L. Zhou, J. P. Rider, T. W. Beck, J. A. Organiscak, Y. Zheng

The U.S. National Institute for Occupational Safety and Health (NIOSH)’s Pittsburgh Mining Research Division (PMRD) recently developed a series of models using computational fluid dynamics (CFD) to study gas distribution around a continuous mining machine with various fan-powered flooded bed scrubber discharge configurations in an exhaust curtain working face. CFD models utilizing species transport model without reactions in FLUENT were constructed to evaluate the redirection of scrubber discharge toward the mining face rather than behind the return curtain. The study illustrates the gas distribution in the slab (second) cut. The following scenarios are considered in this study: 100 percent of the discharge redirected back toward the face on the off-curtain side; 100 percent of the discharge redirected back toward the face, but divided equally to both sides; and 15 percent of the discharge redirected toward the face on the off-curtain side, with 85 percent directed toward the return curtain. These models are compared against a model with a conventional scrubber discharge where air is directed away from the face into the return. The models were validated against experimental data, proving to accurately predict sulfur hexafluoride (SF6 ) gas levels at four gas monitoring locations. This study includes a predictive simulation examining a 45° scrubber angle compared with the 23° angle for the 100 percent redirected, equally divided case. This paper describes the validation of the CFD models based on experimental data of the gas distribution results.

Jan 1, 2017

By M. E. Buzon, M. E. Gunter

Talc has been the focus of recent civil litigation based on claims that asbestos minerals exist in talc deposits and therefore have caused asbestos-related diseases in those who have regularly used talc products. Such litigation, and ensuing confusion over the petrology and asbestos content of these deposits, challenges the talc mining industry in Montana and elsewhere in the world. The talc deposits in southwest Montana were formed by hydrothermal alteration of dolomitic marbles and are still actively mined. In general, talc formed by hydrothermal alteration of preexisting carbonate rocks is known to be nearly monomineralic and lacking in amphiboles. This paper includes data from analyses of representative ore samples from this mining region in southwest Montana. The results conclude that the presence of asbestos minerals — both amphiboles and chrysotile — is unlikely and that the ores are nearly monomineralic, as expected. Samples were characterized using a suite of analytical methods, namely, powder X-ray diffraction, X-ray fluorescence spectroscopy and electron microprobe analyses, which allowed us to determine the minerals present and the formation process. Our data and interpretations suggest that previous identification of asbestos minerals in these deposits is not accurate.

Jan 1, 2017

By M. Hepokoski, M. Klein, D. S. Yantek, L. Yan

Research by the U.S. National Institute for Occupational Safety and Health (NIOSH) has shown that heat/humidity buildup is a major concern within coal mine refuge alternatives. High temperature and humidity levels inside a refuge alternative may expose occupants to heat stress. Due to the safety risks associated with testing using human subjects, NIOSH partnered with ThermoAnalytics Inc. to create detailed thermal simulation models of refuge alternatives with human occupants. The objective of this effort was to predict a miner’s core temperature response and moisture loss in environments that may be encountered in a coal mine refuge alternative. These parameters were studied across a range of temperatures and relative humidity values to determine if the current 35 °C (95 °F) apparent temperature limit for refuge alternatives is reasonable. The results indicate that the apparent temperature limit is protective, provided that miners are supplied with sufficient water. The results also indicate that the body core temperature does not reach dangerous levels even at an apparent temperature of 54 °C (130 °F). However, the results show that moisture loss increases with apparent temperature. Therefore, if the apparent temperature limit were raised, the water provided in a refuge alternative would have to be increased to offset moisture loss.

Jan 1, 2017