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By Ryan Weaver, Travis Coleman

The drilled shafts that support transmission lines and substations have been increasingly subject to testing to assess the integrity of placed concrete. Cross-hole Sonic Logging (CSL) has been used, but large diameter shafts with challenging site access are generally more favorable to Thermal Integrity Profiling (TIP) testing. TIP testing assesses the shafts based on measurements of the concrete temperature during curing. The TIP results provide assessment of integrity both within and outside the cage, along with information about the alignment of the cage and concrete cover. This data has allowed shafts with imperfect results to be subject to more detailed structural evaluations. However, it may not be well understood how to use this additional information by designers and engineers. The purpose of this paper is to present TIP results of transmission line foundations, both with and without issues with integrity, including cage shifting, minimal concrete cover, or soil inclusions. The intent is to provide general guidelines of the issues that merit additional investigation and those that should be recognized as inconsistencies inherent to underground construction. BACKGROUND This paper is intended to discuss some of the drilled shaft evaluations made when TIP testing is performed. The authors of this paper were recently involved with a transmission line project that was designed and constructed for a Confidential Utility Client located in the Midwest United States. The project was delivered as an Engineering, Procurement, and Construction (EPC) contract with the electrical line construction company as the prime contractor. The contractor then subcontracted several parts of the work which included engineering for transmission line and foundation design, foundation construction, and third-party testing intended to evaluate the concrete homogeneity and integrity of the place concrete in the deep foundations. The testing method selected was Thermal Integrity Profiling Method B, which uses thermal sensors embedded in the concrete. The TIP testing was administered by Mr. Travis Coleman with GRL Engineers, Inc. Mr. Ryan Weaver with Burns & McDonnell served as the owner’s engineer and technical consultant for the utility and was responsible for reviewing submitted TIP reports and providing recommendations to the utility on their acceptance, and if there were any issues that would warrant further discussion and analysis.

Jan 1, 2019

By Stephen Darmawan, Mahdi M. Disfani, Arul Arulrajah, Alireza Mohammadinia

Deep mixing using cementitious compounds is an in-situ method of ground improvement for improving the strength, compressibility of loose sand. Artificial light cementation can increase the stiffness of loose sands significantly and reduce the settlement of loose deposits. The increase in contact area between the particles with a thin layer of cementitious agent depends on the confinement and void ratio of the soil mass. Hence, the stiffening effect of cementation not only depends on the type and amount of cementing agent and inter-particular force chain of loose deposit but also depends on the stress level at the time of cementation. In addition, the cementation effect in loose deposits can be deteriorated at relatively low strain levels. Decementation softening can cause detrimental and irreversible impacts on the soil deposit. This study investigates the effect of initial confinement and subsequently the initial void ratio at the time of cementation on small strain behaviour and decementation softening of cemented loose sand under ko loading. The effect of inter-particular contact of sand particles based on the specific surface area and also soil density was also investigated by means of shear wave propagation. This study present insightful information on effect of primary consolidation stress levels, density of soil and cementation level on softening and collapse of loose deposits improved using deep soil mixing technique. Better understanding of soil-cement interaction by optimization of binder content for deep mixing activation can lead to increasing the level of confidence in using this technique in ground improvement applications.

Jan 1, 1900

By Matthew Janes

The RC Harris Filtration Plant, which treats the majority of the fresh water for over 2.5 million Torontonians, is a Canadian Architectural Heritage site demonstrating a classic example of Art Deco Architecture. The facility is undergoing an expansion to install an underground sludge treatment capability. Perched atop a bluff on the North shore of Lake Ontario the structure enjoys a commanding presence on the Lake Ontario shoreline. A series of underground tanks were proposed for the hillside below the structure, which when covered would preserve the building?s architectural presence. However, the plan required two, stepped excavations 12 m and 10m deep into compact, wet sands over stiff clays and clayey silts. Concerns regarding the original structure influenced designers to set the lateral deflection limit for the front footing of the existing structure at 4 mm, (0.03% excavation depth). The design-build team indicated at the time of tender that the movement criteria was unattainable using the tender design. Analysis indicated installation effects and overall elastic movement of the soil mass beneath the building would result in movements of 7 to 9 mm at the structure. Through extensive FLAC analysis and a novel construction geometry the design-build team crafted an alternative that produced significant savings over the original concept. Based upon the analysis the design-build team negotiated a new deflection criteria dictating a maximum of 2.0 mm of movement across the critical expansion joint between the Filter Building front footing and the tank slab beyond. The contractor invested in additional pre tender soils investigation to support the refined design process. The FLAC analyses indicated the Filter Building movements would be elastic and distributed up to 50 m back beneath the front footing of the structure. An extensive precision monitoring program proved construction related movements of 6 to 10 mm horizontal at the front footing. Extensometers placed at two locations over the critical interior tank expansion joint showed no measurable movements. The overall monitoring program, including inclinometers, tilt meters, tie back extensometers (smart cables) and tie back load cells indicated a good match between recorded movements and loads and those predicted by FLAC Analysis.

Jan 1, 2006

By Garland Likins, Gray Mullins, George Piscsalko

"Quality control of drilled shafts is greatly dependent upon the practices of the site personnel. For drilled shafts cast under slurry, inspection of the hole prior to concreting is very difficult or impossible. There are numerous non-destructive test (NDT) methods currently available to assess the integrity of drilled shafts. This paper will discuss the theory and use of an emerging NDT technology known as Thermal Integrity Profiling (TIP). The Thermal Integrity Profiling method measures the elevated concrete temperatures that occur during the hydration process. These temperature measurements are made along the length of the pile and can determine the integrity over 100% of the pile cross section, both inside and outside the reinforcing cage. With the known shaft volume information, TIP can evaluate the effective shaft radius at each measurement location. With the increased use of TIP on highway projects, there is a need to have standard criteria for shaft acceptance. Shaft acceptance criteria can be based upon thermal measurements and subsequent analysis of the data to determine the average shaft radius, local concrete cover, and cage alignment. With this additional information obtained via the thermal testing method, acceptance methods based upon concrete cover can be developed. In this paper the Thermal Integrity Profiling method will be described, results from a case history will be discussed, and an acceptance criteria based upon concrete cover will be proposed.INTRODUCTIONDrilled shafts are an attractive foundation element in many applications due to their large axial and lateral capacities. When drilled shafts are cast in a dry hole, it is possible to inspect the hole prior to casting, allowing for very basic level of quality control, although the shape of the completed element is still unknown without some form of post construction testing. When drilled shafts are installed where soil conditions are unstable, the shafts will often be cast under slurry to support the surrounding soils during the construction process. When casting a drilled shaft under slurry, it is very difficult to impossible to accurately and efficiently inspect the hole prior to casting concrete and it is equally difficult or impossible to inspect the shaft during the casting process"

Jan 1, 2016

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Sep 8, 2021

By Siavash Mahvelati, Alireza Kordjazi, Joseph Thomas Coe

Deep foundations are often constructed as end bearing members with a significant amount of their capacity derived from bedrock. Sites with highly variable bedrock conditions therefore present a unique challenge when attempting to estimate the design elevation of deep foundations. Typical subsurface characterization techniques such as drilling, standard penetration testing (SPT), and cone-penetration testing (CPT) may fail to adequately establish top-of-rock elevation in geologic settings prone to karst and/or significant amounts of residuum, saprolite, and deformed bedrock. Seismic surface wave geophysical methods have been increasingly used to map bedrock topography in such settings. However, the current standard of practice for these methods introduces resolution limitations in spatially variable subsurface conditions due to averaging effects from the analytical framework used to process the acquired data. This study explores the use of a tomographic approach with full waveform inversion (FWI) to map top-of-rock elevations at a numerically simulated site representative of highly variable bedrock topography. Comparisons are made with seismic refraction (SR) and a dispersion-based multichannel analysis of surface waves (MASW) approach as more commonly used in geophysical subsurface investigations. The results highlight that FWI provides a superior estimate of top-of-rock topography than SR and MASW at a cost of a significant increase in the required computational resources and time.

Oct 1, 2021

By Nick Hytiris, Mohammed Al Maadheedi, Slobodan B. Mickovski

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Mohammed Al Maadheedi

This paper explores the capacity effects of a square steel plate welded at the ground surface on a driven open-ended steel pile (i.e. the plate would touch the ground surface after the pile achieves the required penetration). A series of strain-controlled, 1-g laboratory tests were undertaken on piles with and without a square steel plate attached. The piles were driven in dry, loosely packed, uniform sand. Two plates were used, one with a breadth equal to two times the diameter of the pile (2D) and the other with a breadth equal to three times the diameter of the piles (3D). A 20% increase in capacity was recorded for the 2D plate, and a 110% increase in capacity was recorded for the 3D plate when compared to the pile without an attached steel plate. The back-analysis of the results allowed the derivation of a new expression to calculate the capacity of bearing plates, which accounted for the effects of sands compaction and dilation. By extrapolating the findings of these tests to a hypothetical scenario, a model design problem was described where the length of a pile can be reduced by 20% to 60% (depending on the load) by using a plate attached to the pile. The results of this study can help designers to minimise penetration depth; thus, achieving a more economical and sustainable design.

By Stephen Buttling, Zhong Rui

"A single unit gas fired power station was being built on the edge of the Gulf of Thailand in 2001. The soil conditions consisted of very soft to soft Holocene Marine Clay, and the site was part of a coast line which had been subsiding below high water mark for some time. In order to provide access around the power station a road system in a figure-of-eight formation was required, and this also needed to be above the design flood level, allowing for future settlement. A ground improvement scheme was proposed and constructed, which consisted of two spacings of prefabricated vertical drains (PVD) over two depth ranges, vacuum consolidation and pre-loading, and rigid inclusions.During the construction phase, the vacuum consolidation was applied for 202 to 221 days in different zones, and monitoring allowed a prediction that the future settlement, including secondary consolidation over a period of 25 years, would be within the range of 175 to 355 mm, which met the contract requirement of less than 400 mm.The power plant was completed and became operational in 2003. Monitoring of the road levels continued, as did the settlement, and in early 2010 the total settlement since the end of vacuum consolidation had reached about 800 mm. The monitoring data both during the ground treatment and for the following 7 years is presented and analysed. This is supported by numerical analysis using 3D finite element methods which shows good agreement with the measured data, and allows a preliminary explanation as to why the predictions were so far out.BACKGROUNDAfter a period of bidding and negotiation, the Eastern Power and Electric Co Ltd (EPEC), an Independent Power Producer, entered into an agreement with the Electricity Generating Authority of Thailand (EGAT) in November 1997 to sell them power. In 1999 an Engineering, Procurement and Construction (EPC) contract and an Operation and Maintenance contract were signed with a supplier to provide a gas-fired (with oil as a back-up fuel) 350 MW combined cycle power plant in Bang Bo, Samut Prakarn Province, east of Bangkok. The site of the plant at Bang Bo is located immediately to the east of the Samut Prakarn Wastewater Treatment Plant, adjacent to the Gulf of Thailand (see Figure 1) in an area of very soft to soft marine clay (Bangkok clay) having low shear strength and potential for excessive settlement. The site layout comprises the main Power Plant components of generating block, cooling towers, fuel unloading area and storage tanks, switchyard and administration block, separated by access roads."

Jan 1, 1900

By Chu E. Ho

This paper reviews the design of jet grouting at re-entrant corners of excavations where the diaphragm wall and secant pile wall installation were interrupted by existing utilities in the streel sidewalk. Jet grout blocks were formed to seal the gaps in the walls for excavation support, consisting of four to six columns in clusters. Jet grouting was performed around an electrical duct bank which had to be maintained. Jet grouting was executed through stratified soils using various combinations of jetting parameters for different soil strata. The installation sequence and age of the neighboring columns within a cluster will affect the jet’s ability to form subsequent columns. When jet cutting is limited next to hardened grout columns or embedded obstructions (such as diaphragm walls or secant pile walls in this case), the specific gravity (SG) of spoils would be reduced and tend toward the value of the injected grout SG. The magnitude of spoil SG is also influenced by the variability of the grout mix supplied. Specific Gravity Ratio (SGR) defined as the ratio of spoil SG to the actual grout SG at the time of jetting can be used as an indicator of successful treatment, with SGR > 1.0 indicating effective soil erosion. Verification coring and testing were implemented to confirm target column diameter and strength of grouted soils have been achieved.

May 1, 2022

By A. Daugiala, D. Coleman

In 2014 the New York State Department of Transportation (NYSDOT) awarded a Design-Build contract to the joint venture team consisting of Skanska which is the managing partner; Kiewit Corporation and Ecco III (SKE) and HNTB as the lead design firm. The design build team employed methods to provide schedule savings and commercial benefits to the owner NYSDOT. This paper presents the design approach and construction methods used to accelerate drilled shaft installation supporting the main span foundation for the cable stayed bridge. The drilled foundation contractor Underpinning and Foundation Skanska, a division of Skanska was responsible for assisting with design, budgeting and construction of the drilled shaft foundation construction. As part of the Request for Proposal (RFP) bid process, Alternate Technical Concepts (ATC) was encouraged by the NYSDOT. The JV team proposed an ATC which involved a scaled production shaft testing method to simulate the ultimate load level, commonly referred to as the “Chicago Method” was used in the rock socket employing the Osterberg Cell (O-Cell) testing procedures. To the authors knowledge this was the first NYSDOT project where this approach was utilized on a Demonstration/Production installation to validate construction procedures and load bearing capacities. Construction procedures, challenges and solutions are discussed in detail. Upon completion of successful drilled shaft construction, concrete integrity is verified using two methods – Cross Hole Sonic Logging (CSL) and Thermal Integrity Profiling (TIP). A comparison from the contractor’s perspective is provided. Finally the drilled shaft rock socket is tested to ultimate end bearing values while rock socket side shear stresses are not exceeding the service level loading. Lateral load test was also a RFP requirement; the test arrangement and performance are discussed in detail as well. The Kosciuszko Bridge location poised unique geotechnical challenges on many levels shifting towards an extreme boundary of parameters encountered in New York City Area for drilled shaft construction. The JV team and specialty drilled shaft contractor actively participating in the shaft design and construction practice coordination and working with NYSDOT yielded a successful foundation solution which provided cost and schedule savings to the project.

Jan 1, 2016

By Amanda R. Parry, Chris R. Pray

Predicting and modeling the soil structure interaction of laterally loaded piles with significant unbraced lengths is one of the challenges faced in designing many waterfront structures. Designers often rely on pile specific design software to calculate forces in an embedded pile and then couple that with either a structural design software to capture the behavior of the rest of the structure or use potentially overly conservative assumptions to omit modelling the piles entirely. Given that some projects have hundreds of piles coupled with hundreds of loading conditions, the shuttling of results from the structural analysis software into the pile analysis software can become cumbersome, difficult to track and manage, and prone to user input errors. An alternative approach recently used on two large marine infrastructure projects consisted of calibrating a structural analysis software to replicate the resultant outputs from a software developed specifically for pile analysis. This calibration was done using thoughtfully placed springs along a pile modeled in the structural analysis software to replicate the soil-structure interaction of the piles. The focus of this paper will be on the methodology used to calibrate the two software programs and an evaluation of the results which showed close agreement. Based on the two case studies, calibrating a generic finite element analysis software via this method should be considered as a reasonable and time saving design approach for pile-supported structures.

Sep 8, 2021

By K. Madhusudan Reddy

Pile response under combined uplift and lateral load is very important and it is imperative to evaluate the effect of combined loading and only few studies were reported on pile behavior under combined uplift and lateral loads. Model pile made-up of aluminum having an outer and inner diameter of 25.4 mm and 19.4 mm respectively is used. Dimensions of the model steel tank are fixed as 1.0 m x1.0 m x 1.2 m (depth) to avoid the boundary effects under combined lateral and uplift loads. Experiments were carried out on single piles at isolated uplift, isolated lateral loading and combined lateral and uplift loading, embedded in sandy soil. Results indicate that load?deflection behavior is nonlinear for isolated uplift and lateral load tests as well as in case of combined loadings. It is also observed that the behavior of piles under isolated loadings is substantially different when compared to combined loading.

By Alessandro Bertero, Stefano Valagussa, Filippo Maria, Wesley Schmutzler, Leoni

"Abstract The Deep Mixing Method (DMM) represents a viable solution to improve the adverse geotechnical properties of foundation soils. Differences and the importance of performing pre-construction laboratory and field tests will be highlighted. Comparative analyses and interpretations between the various lab and field stages, along with accumulated information about soil properties and QC results, allowed fine-tuning of the production parameters throughout almost the entire project.Two projects where the US Army Corps of Engineers selected the Deep Mixing Method (DMM) for the required stabilizations, and a third project completed in Italy, will be illustrated:•,?the LPV 111 Project (New Orleans - LA – USA); DMM was used for groundimprovement/foundation strengthening and consequently stabilize and support the burden of the new levee.•,the Rio Puerto Nuevo Project (San Juan - PR - USA); DMM was applied to improve the soils adjacent to a 90” forced sewer main relocation and to improve the soils for the base of a new drainage channel•,the new Italian high speed railway project (Florence Italy); DMM technology was applied to realize a a TBM break in/break out, foreseen originally by jet-grouting.IntroductionThe Deep Mixing Method (DMM) represents a viable solution to improve the adverse geotechnical properties of foundation soils. The effectiveness of working parameters depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product."

Jan 1, 2014

By Adam Zagorski, Rusty Lucido, Curt Scheyhing

"The current California Department of Transportation (Caltrans) practice based on AASHTO LRFD Bridge Design Specifications is to use the O’Neill and Reese method (FHWA, 1999) for calculating the side resistance and base resistance of Cast-in-Drilled-Hole (CIDH) piles / drilled shafts. In this calculation, end bearing is typically neglected for piles constructed using a wet method due to questionable reliability of end bearing resulting from soil disturbance and inadequate cleaning of the base. Pressure grouting below the tips of drilled shafts in cohesionless soils has long been used worldwide to provide reliable end bearing capacity, but for decades it was relatively unused in this country. It has been used increasingly in the United States over the last decade. Before this project tip grouting has not been utilized on or accepted by Caltrans to maximize piles end bearing capacity. This project proved that tip grouting to mobilize reliable base resistance can be successfully implemented on a full-scale bridge project requiring over 350 large diameter shafts.For the Gerald Desmond Bridge Replacement Project, Shimmick/FCC/Impregilo, JV utilized a temporary Oscillator casing to the full depth to install CIDH piles. Piles were constructed by the wet method and then pressure grouted below the pile tip. A tip grouting procedure for these large diameter shafts was developed and tested to specifically address the geology and constraints of the project. This procedure was then proven during the Load Testing of test piles during the Test Shaft construction phase of the project. Tests showed a minimum reliable base resistance of 150 ksf could be mobilized in very dense sand at a downward movement of 5% of the pile diameter for piles ranging from 4.9 to 8.2 feet in diameter. By tip grouting, the length and diameter of the piles were significantly reduced."

Jan 1, 2017

By A. Paviani

The subject of this session is "Equipment Installa­tion, Recent Developments". This is a subject which is not usually addressed at conferences of Foundation Engineering. It is rare to find sessions dealing with the technological side of deep foundations, a subject which only recently seems to have aroused sufficient interest at national and international conferences. It is therefore natural for the subject of "Equipment", or the tools used to implement the various "technologies", to be over­looked or mentioned only occasionally during the discussion of other issues. At conferences, most of the attention is attached to research and to the theoretical interpretation of the performance and behaviour of deep foundations, as well as to establishing the most suitable calculation algorithms and approaches for the study, design and control of foundation structures. It is almost as if the subject of equipment is felt to be less important or, perhaps, that it is considered to belong more strictly to mechanical engineering than to civil engineering.

Jan 1, 1994

By I. D. McPherson, Dominic P. Mahoney

The Metro Sports Facility is currently under development in Christchurch, New Zealand and is a key Anchor Project in the city’s post-earth quake recovery. When completed it will be largest indoor sports and swimming pool complex in New Zealand, with a building footprint in the order of 22,000m2. The site is underlain by poor performing soils comprising interbedded layers of soft compressible silts and loose liquefiable sands to over 20m depth. The site is typical for Christchurch with a shallow groundwater table and artesian conditions. The site performed poorly during the 2010-2011 Canterbury Earthquake Sequence with extensive liquefaction, and associated ground damage. To provide a resilient and economical foundation system for this key development project, deep ground improvement comprising of a uniform grid of some 7,200 stone columns in conjunction with robust shallow foundations has been adopted. This paper discusses the geotechnical site constraints, and ground performance under earthquake loading and describes the various options considered for the development. The foundation option selected, the design considerations of the adopted stone column ground improvement, and foundation solution are described in detail, as well as, construction observations. The paper aims to provide insight into an urban large-scale ground improvement project for the engineering practitioner.

Nov 1, 2022

By Dzianis Proshchanka, Yoshi Izumi, Koji Mitani, Ayuna Kitaura

"A new pile driving and drilling navigation system has been developed. It utilizes the commonly used surveying total station, combined with an innovative reticle. Conventional crosshairs have been replaced by a concentrically circular reticle called Baum. It allows for easily performed measurements of central axes of cylindrical objects such as piles, chimneys, electricity poles, etc. This provides several significant advantages compared to other existing systems. It is cost-effective as only one operator is required to control deviations in positioning and inclination. Furthermore, repetitive reinstallation of the instrument is not required for every pile driven or hole drilled. It is also a safer method, as workers have no need to be near a pile driver or drilling machine to perform the measurements. With Baum Station, necessary measurements can be performed away from the actual work area. Moreover, it is highly accurate with real-time solutions, as three-dimensional orientation information for the pile/drill is obtained simultaneously with the pile being driven or the hole being drilled. This allows for the highest levels of precision-control and correction to minimize eccentricity of the intended center positioning.INTRODUCTIONBackgroundIn foundation construction for structures, pile foundations are widely used for deep bearing strata. There are two patterns to driving piles: vertically or obliquely to the ground. The shapes of the piles are normally cylindrical. Vertical pile foundations are employed as the foundations of many structures due to their high workability. There is a problem however, which is that this method does not bear measurement data as construction accuracy is visually checked. On the other hand, tilted pile foundations are rarely employed because it is too difficult to ensure construction accuracy. In addition, commonly used percussion methods create noise and vibrations when the piles are hit, while there are advantages that thinner piles are available, ensuring earthquake-resistance, as tilted piles curb horizontal displacements of structures, which may be caused by earthquake ground motion. However, current requirements of cost reduction bring professional attention to tilted pile foundations, which can be driven reasonably and economically with much research of tilted piles having been carried out to improve their capacity. Also, a method of screwing piling has been developed, which produces small amounts of noise and vibrations. This method has solved tasks of workability and environmental burdens, and is becoming more and more common. However, there is a necessity to develop a method to accurately measure angles of piles’ axes in order to drive piles into the ground with appropriate angles. It is also expected to find out a way to control construction information, such as correction amount and driving record."

Jan 1, 2017

By Ben M. Lewis, Yogesh Prashar

"The East Bay Municipal Utility District (EBMUD) is a major water utility service providing water to over 1.3 million people in the eastern San Francisco Bay Area. EBMUD manages 28 dams at 5 terminal and 23 open-cut reservoirs within a 331-square-mile customer service area. As part of a 2012 update on EBMUD’s Infrastructure Rehabilitation Plan for Distribution Reservoirs, EBMUD has decided to replace Central Reservoir, a 152.8 milliongallon open cut reservoir, with optimally sized tanks. This paper presents the results of an analytical comparison of various foundation reinforcement solutions for the proposed tanks including: Cement Deep Soil Mixed (CDSM) columns, vibro stone columns, rammed aggregate piers, and lightweight cellular concrete fill. The computational program GeoMat (www.ensoftinc.com) was used to perform simplified soil structure interaction analyses. Settlement estimates were developed for each alternative with the proposed loading and compared to an allowable differential settlement criterion established at 0.3-inches over a 50 foot length. The authors wish to present the importance of considering mat and soil interaction along with various settlement mitigation methods considered for this challenging project.INTRODUCTIONProject BackgroundCentral Reservoir is an operational open-cut reservoir located north of the intersection of 25th Avenue and East 29th Street in Oakland, California. The reservoir is bound by 23rd Avenue to the west, Sheffield Avenue to the east and Interstate Highway 580 to the north. Originally, the Central Reservoir site was a drainage swale incising into weathered bedrock formed from Pleistocene alluvial deposits. The reservoir was first constructed in 1910 by excavating a basin below grade and constructing an embankment dam on the south and cutting/filling the bedrock and alluvial deposits from the drainage swale. The main dam at the Central Reservoir site is also a DSOD (Department of Safety of Dams) jurisdictional dam and as such is regularly monitored by the EBMUD Materials Engineering Section and the California DSOD.In a 2012 update to EBMUD’s Infrastructure Rehabilitation Plan for Distribution Reservoirs, Central Reservoir was identified as a critical facility that has reached the end of its useful life and must be replaced due to: a failing panel craft lining which contains polychlorinated biphenyls in the interior coating, a roof that does not meet the current seismic code, and reduced operating levels due to potential leakage in the upper portions of the panel craft lining. Furthermore, Central Reservoir is about three times larger than required and is located at a lower elevation than other regional reservoirs in the pressure zone resulting in increased labor-intensive operational challenges and water quality operations.This project presents some challenging geotechnical demands – the site is founded on weakly consolidated Holocene Alluvium overlying weathered bedrock, the proposed structural loads are large, and the new Central Reservoir is to be placed on a pad at an elevation of 182 feet, required placement of up to 30 feet of fill over the current basin. Additionally, the project aims for a long-term foundation solution that will outlive the new replacement tanks and accommodate future site upgrades. In order to meet this goal, the differential settlement criterion for the tanks was ¼ inch over 50 feet length. Lastly, the project also aims to address EBMUD’s increasing trench spoil stockpiles by recycling discarded trench spoils as fill for the proposed tank pad."

Jan 1, 2016

By Lorie M. Dilley

Alaska Village Electric Cooperative (AVEC), an electric utility cooperative providing power to 51 Alaska villages, has made a concerted effort to install wind turbines in the villages they serve in an effort to mitigate the growing costs of electrical power generation. The subsurface soils in several of these villages consist of sands and silts with ground temperatures of between 30°F and 32°F. The presence of warm, degrading permafrost in three of the villages has required innovative foundation designs, including the use of helical piers and piles to support steel and concrete wind turbine foundations. The design of the deep foundations had to account for the effects of degrading permafrost likely resulting from observed climate change patterns. Uplift forces imposed on the foundations were approximately 100 kips per pile. Uplift pile load testing was conducted on the installed piers and piles in order to determine the actual working load that each pier or pile could sustain. In addition, pile driving analyzer testing was conducted on several piles installed in the permafrost and compared to pile load tests. Results indicated that the installed piers and piles achieved the necessary capacity with sufficient factors of safety. Thermosyphons were installed near the foundations in order to limit the effects of climate change on the permafrost. The two to four wind turbines in each of the three villages are currently operational. Refinement of the design based on the pile testing from the first village to the third has decreased the cost of the tower foundations and improved our understanding of designing for warm, degrading permafrost.

Jan 1, 2010