Search Documents

By Hubert Law, Amin Rahmani

This paper evaluates the effects of pile diameter on the initial modulus of subgrade reaction and proposes modifications to the subgrade reaction moduli that are commonly used in the current state of practice based on American Petroleum Institute (API) guidelines. Three-dimensional continuum finite element model of a soil-pile system is simulated under monotonic lateral loadings to develop benchmark data. The benchmark data, which includes small (0.5 ft) to large (10 ft) diameter pile responses, is used to estimate the initial modulus of subgrade reaction for each of the considered pile sizes. The study shows that the subgrade reaction moduli provided by API may underestimate the actual soil stiffness at the soil-pile interface for large diameter piles and may overestimate it for piles smaller than a certain diameter. A simple equation is proposed herein to adequately estimate the initial modulus of subgrade reaction for all pile diameter ranges. The proposed equation is validated by the measurements of full-scale field tests.

By Dan Brown

Renewal and revitalization of transportation presents a challenge in the need for replacement, repair, and improvements of existing bridges, as well as increased construction of transit systems within existing transportation rights of way. Difficulties with conventional deep foundation systems occur because of the limited site access, adjacent structures, the need to maintain traffic, and other constraints on construction activity. Major projects are often performed in a design-build contract environment in which the schedule is aggressive, and where speed and reliability represent major considerations. Foundation designers are confronted with a need to solve problems with a construction-oriented mindset, where typical experience with lowest cost solutions may not reflect the most effective approach. This presentation presents an overview of the challenges that may affect design and construction of deep foundations in this environment and the methods that have successfully been employed on several large transportation projects in the U.S.

Jan 1, 1900

By Alexander Blatt, Franz-Werner Gerressen

Diaphragm wall technique is usually used to construct structural elements in the ground, commonly used for retention systems, permanent foundation elements or deep groundwater barriers, named Cut-Off-Walls (COW). Recent developments proof, that the technology also satisfies the demands for using the diaphragm wall technique for bulk sampling purposes. Such kind of new ideas required the adaption of equipment and tools for a depth capability never reached before by a trench cutter in any commercial application worldwide. Compared to the development of increasing depths, especially inner-city applications with limited space, demand a minimization of equipment to accommodate such projects. The paper will focus on the developments and solutions generated to fulfill these requirements and will give an outlook to future developments. Further it describes finalized reference projects and will give a general outlook on future trends and developments. The Paper/The Presentation explains as well the installation process in general.

May 1, 2022

By Gerry Houlahan

"The 2015 Outstanding Project Award (OPA), which recognizes the superior work of DFI members, was awarded for the San Francisco- Oakland Bay Bridge New East Span. The award was presented to representatives from Caltrans and the T.Y. Lin International/Moffatt & Nichol Joint Venture at the DFI 40th Annual Conference on Deep Foundations in Oakland, Calif. A committee selected this project based on size, scope and challenges of the project; degree of innovation and ingenuity exercised; and the uniqueness of the solution to the difficulties of the job. A bridge across the bay between San Francisco and Oakland was proposed as early as 1872, but it took until November 12, 1936, until it became a reality. The bridge spans to the west of Yerba Buena Island were conventional suspension spans, while the east spans used a steel cantilever truss design and simple steel truss spans. This double-deck bridge served the Bay Area well until 1989. In that year, the magnitude 7.1 Loma Prieta earthquake damaged the East Span of the San Francisco-Oakland Bay Bridge. The resulting interruption to service across the bay demonstrated the vital role this bridge plays in the economic and life safety activities of the Bay Area. The project owner, California Department of Transportation (Caltrans), determined that the safest, most cost-effective solution was a total bridge replacement. The Engineer-of-Record, T.Y. Lin International/ Moffatt & Nichol Joint Venture, working closely with Caltrans, the Metropolitan Transportation Commission (MTC) and the California Transportation Commission (CTC), was charged with developing a comprehensive design strategy that met the project’s stringent criteria for seismic safety. These criteria included the new bridge’s designation as a regional Lifeline Structure that must open to emergency traffic shortly after the occurrence of a 1,500-year return period earthquake"

Jan 1, 2015

4.5.1 General The provisions of the article shall apply to the design of axially and laterally loaded driven piles in soil or extending through soil to rock. 4.5.1.1 APPLICATION (Revised Article 4.3.1.1) Piling may be considered when footings cannot be founded on rock, or on granular or stiff cohesive soils within a reasonable depth. At loca-tions where soil conditions would normally permit the use of spread footings but the potential for scour exists, piles may be used as a protection against scour. Piles may also be used where an unacceptable amount of settlement of spread footings may occur. 4.5.1.2 MATERIALS Piles may be structural steel sections, steel pipe, precast concrete, cast-in-place concrete, prestressed concrete, timber, or a combination of materials. In every case, materials shall be supplied in accordance with the provisions of this Article.

Jan 1, 1989

By Timothy C. Siegel, Paul J. Axtell

The Missouri Department of Transportation (MoDOT) recently replaced the Hurricane Deck Bridge that carries Highway 5 traffic across the Osage Arm of the Lake of the Ozarks in Camden County, Missouri. The former bridge was constructed in the 1920's and was supported on pneumatic caissons bearing on dolostone bedrock. The replacement structure is founded on drilled shafts socketed into the bedrock. During the design phase of this bid-build project, a baseline design was developed and Alternative Technical Concepts (ATC's) were allowed from approved contractors. Those ATC's were confidential and not shared between teams. Either the baseline design or the approved ATC design could be bid by the respective contractors. The baseline design included re-use of the 90-year old caisson foundations. Accordingly, an extensive evaluation of the caissons and underlying bedrock were conducted by coring, laboratory testing, acoustic tele-viewer (ATV), and cross-hole sonic logging (CSL) methods. The results of the investigation indicated the caissons were in excellent condition and suitable for re-use. However, a more cost-effective ATC was submitted, awarded, and constructed that did not re-use the existing caisson foundations but rather reduced the span lengths, increased the number of piers in the water, and supported those piers on drilled shafts. Interestingly, the difference in low bid price between the awarded ATC and the baseline design was less than one percent of the construction cost. This paper describes the multiple foundation designs that were necessary for this interesting project. The various foundation evaluations include the existing pneumatic caissons, large-diameter open-ended pipe piles to support the baseline design, and the design of rock-socketed drilled shafts that were successfully constructed in 2012.

Jan 1, 2017

By Michael J. Marasa

"Geotechnical engineering and construction primarily relies on the subsurface characteristics of the particular site; however, obtaining both accurate and precise information on those features is challenging due to the numerous factors involved in testing procedures used to analyze varying site geology. This includes a detailed and thorough geotechnical investigation to understand the site conditions, allowing the implementation of the most practical and economical solution.This paper presents a case history of the installation of wick drains and construction of aggregate piers on the site of a large facility to be constructed in Memphis, Tennessee. Throughout intensive subsurface investigations, highly variable soils were encountered, requiring settlement control and increased bearing capacity. This paper will discuss the design and installation of the systems constructed, and procedures and execution of the work to ensure design specifications were achieved.BackgroundA 1.4 million square foot expansion directly adjacent to an existing 1.1 million square foot distribution facility in Memphis, Tennessee was planned to serve as a centralized facility for increased production. The first phase of construction included an 858,000 square foot warehouse and parking lot for approximately 400 trucks to the north of the existing structure. The anticipated column load for the warehouse was 125 kips; slab design bearing pressures ranged from 200 to 500 pounds per square foot (psf) and elevations ranged from EL. 264 to 282. Parking lot elevations ranged from EL. 264 to 290, requiring a design life of 10 years with an estimated 100 in- and out-bound trucks daily and maximum weight of 80 kips per truck. The second phase of construction took place east of the existing structure, and included a 794,000 square foot multi-level warehouse, a 100,000 square foot office, and additional employee parking. The anticipated column load for the second warehouse was 225 kips and slab design bearing pressures ranged from 200 to 500 psf. Elevations ranged from EL. 267 to 282. Anticipated column loads from the office were 25 125 kips, with slab design bearing pressures ranging from 100 to 200 psf. Due to the varying elevations within each planned footprint, up to 18 feet of new fill was required to match the existing structure’s finished floor elevation (FFE) at EL. 282."

Jan 1, 2017

By Jorj O. Osterberg

This paper is for presentation at the 14th Annual Members Conference of the Deep Foundations Institute held at the Hyatt Regency Hotel, Baltimore Maryland on October 10, 1989. This is an introductory presentation of a one hour symposium on the applications of a new testing device. This paper discusses how the device works and its uses. Papers following this describe: - How the cell is constructed and calibrated - Two projects on which the device was used on long driven piles to determine the frictional capacity - A bridge project on which the device was used on an instrumented test drilled shaft and a working drilled shaft

Jan 1, 1989

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 J. W. Slatter

Cast in situ screw piling techniques (both displacement and non displacement) have seen considerable growth in recent years due to competitive production rates, low noise and vibration free installation. However the discussion on the mechanics of auger installation, which has implications on the installation effects and installation forces of screw piling augers, has been almost exclusively targeted towards non displacement techniques and in particular continuous flight augers (CFA). This paper discusses the historical development of the understanding of screw piling auger mechanics in sands and presents a new theoretical model to predict the soil transport and displacement characteristics of both displacement and non displacement augers with variable geometry.

Jan 1, 2000

By Kyle A. Kershaw

The City of Grand Forks, North Dakota obtains drinking water from both the Red River and Red Lake River through a system of raw water intakes, shallow pipelines, and pump stations. However, during flood events, the City often loses access to the system, as evidenced during the record flood event in 1997. As a result, the City decided to construct a new gravity raw water intake system, including a pump station at the base of a 65-foot-deep, 60-foot-diameter caisson, behind a new levee system. Because of high design flood elevations and connectivity of river head to underlying soils, uplift resistance was required for the caisson. A total of 37, 2-foot-diameter, augered cast-in-place (ACIP) piles were chosen to provide uplift resistance. Because of the difficulties associated with installation of piles within the confined space of the constructed caisson and basal stability concerns, installation was completed from the existing ground surface to a depth of 120 feet. Several design and construction issues arose, including squeezing ground during pile installation, placement of long reinforcing bars, and installation of a dual material pile. A dual material pile was required to ensure that the ACIP pile below the base of the caisson was structurally sound and the pile above the base of the caisson could be easily excavated during sinking of the caisson. This paper discusses the solutions to each of these issues, as well as construction sequencing, load testing and integrity testing of the ACIP piles, and the successful completion of the project.

Jan 1, 2003

By John R. Grillo, Gordian Ulrich, Franz-Werner Gerressen

Most geotechnical construction professionals are aware of piling using hydraulic drill rigs and the so-called Kelly drill mode. Kelly drilling has many advantages as it can work with a wide range of tools facing almost all types of soil and rock conditions. Kelly drilling can also deal with diameters up to 10 ft (3.00 m) and bigger or depths of more than 330 ft (100 m). Nonetheless, there is a concern about Kelly drilling as it is a relatively slow installation process. Therefore, an alternative piling method like Cased CFA (CCFA) Piles (Cased Auger Cast Piles) provides a significant advantage in terms of installation performance, schedule and cost saving potentials. Major application for the Cased CFA system is the secant pile wall construction. Against the traditional secant pile wall systems like fully cased bored piles or CFA secant piling the Cased CFA secant pile wall system has the advantage in cost and time against the fully cased system and in quality against the standard CFA system. This paper will describe the methodology and installation process in general as well as first reference projects carried out in the United States. This paper will present the results in cost and schedule saving using this method. In addition, we will also describe the limitations of this method. INTRODUCTION In the changing construction environment, companies are searching for new technologies or improvement of existing technologies to complete their projects in shorter time frames to provide a good economic solution. Especially with the focus of increasing urbanization, the aim of fast construction becomes more and more important. When thinking of piling, most people will have the same picture in mind: that of a hydraulic drill rig working in Kelly drilling mode; however, the perpetual drill rig development provides a number of options for the execution of specialist foundation projects, either for foundations or for pile walls when using single pass applications like CFA, Cased CFA and Full Displacement Piling (FDP). Single pass means, in general, that the tool is pushed and rotated into the ground to the final depth in one stroke. After reaching the final depth, concreting is started and concrete is pumped continuously while the tool is withdrawn.

Jan 1, 2019

By Jim Bruce, Peggy Hagerty Duffy, Mary Ellen Large, Allen Cadden

"Over the past 40 years, Deep Foundations Institute (DFI) has executed its mission “to bring together multi-disciplined individuals and organizations to find common ground and create a shared vision and consensus voice for continual advancement in the deep foundations industry”. Like DFI, micropile technology began a significant growth path in the mid-1980s. This paper highlights how DFI’s mission was executed in the deployment and expansion of micropile technology.INTRODUCTIONMicropiles are small diameter foundation elements constructed using specialty drilling and grouting methods. Micropiles have evolved since their introduction into the North American market in the 1970s from being lightly loaded (less than 30 kips) elements used primarily for remedial applications, to today’s high-capacity, often hybridized foundation systems, for both remedial and new-build projects. Micropiles now occupy a substantial market segment in North America.For 40 years, DFI has aimed to be the forum for discussion of all issues related to deep foundations design and construction. DFI now supports 21 technical committees and working groups on all deep foundations technologies and has expanded to include regional chapters in Europe, India and the Middle East.Several key steps are required for the successful execution of DFI’s mission, including identifying a need, engaging dedicated and knowledgeable people, developing effective vehicles and resources for information sharing, cultivating stakeholder contributions and advancements, stimulating influence/impact on deep foundations market, and expanding approaches to continue progress. Pile drivers in New York City (the original organizers of DFI) positively affected their market using these same steps: they recognized a specific need, gathered the people who could affect change, convened a discussion forum (which is common today, but was innovative at the time), defined tasks to address the issues, and influenced their market by improving means, methods and owner perception of their services. These forward thinking, proactive members created a mechanism for communication among all related parties that would advance the profession by improving safety, quality and value of pile driving construction.Micropile technology has evolved in the United States and around the world for the past four decades. The accumulated efforts of DFI and other, similar organizations such as The International Association of Foundation Drilling (ADSC) have contributed to this evolution. The advancement of the micropile industry – and consequently the micropile market – has been intimately tied to the execution of the mission of DFI."

Jan 1, 2017

By Leonhard Weixler, Alexander Blatt, Franz-Werner Gerressen

Diaphragm wall technique is usually used to construct structural elements in the ground, commonly used for retention systems, permanent foundation elements or deep ground-water barriers, named Cut-Off-Walls (COW). It can be anticipated that global urbanization and increasing demands on environmental considerations will need to be accommodated in underground space in the future. These trends show an increasing requirement for diaphragm walling in even more complex conditions, especially in inner-city applications with limited space. Therefore, there is the demand to minimize the size of equipment to accommodate such projects. Following this demand, a new trench cutter system, the so-called CUBE System, was recently developed. The complete trench cutter system has been fit into container size dimensions so that it can work in very limited space conditions. In addition, complex conditions in terms of space limitations require specifically adapted solutions for slurry, spoil, reinforcement and concrete handling and the related logistics to ensure smooth production. Due to the limited space requirements, the impact on the surrounding environment is limited. As the system is electric driven, an additional reduction of carbon footprint can be expected. First tests of the system have been carried out and the results will be shared. The paper will explain the construction process and the specific challenges and experiences made for these extreme conditions.

Oct 1, 2022

By James M. Tantalla, Roderic A. Ellman, W. Allen Marr, Scott R. Bamford

"Construction of the powerhouse for the Willow Island Hydroelectric Project required a 100-ft deep excavation inside the limits of a cofferdam and embankment-seepage cut-off wall through soil and rock adjacent to the Ohio River. Portions of the rock had preexisting weak plans and slickensided surfaces with low frictional strength. Stability analyses were performed for critical sections of the excavation to evaluate the stability of the soil slopes and rock cuts using buckling, tension crack, and limit equilibrium analysis techniques. Loading conditions included the 100-yr and intermediate floods, normal pool, sudden drawdown, and seismic design conditions.Stability analyses indicated adequate factors of safety for soil slopes and for rock cuts through the landside embankment sections. However, the results of deep-seated stability analyses through the rock supporting the riverside cellular cofferdam indicated unacceptable factors of safety. Consequently, the riverside portion of the excavation required measures to increase stability. Long, high-capacity rock anchors and deep dewatering wells to lower the site piezometric head were chosen for this purpose.Thirty high-capacity rock anchors were installed on the upstream, riverside, and downstream sides of the cofferdam rock cut. Required rock anchor loads varied from 1,968 to 2,074 kips. The designed anchors consisted of multiple, seven–wire strands with up to 59 strands per anchor. Bond lengths used an allowable bond stress of 100 psi based on the rock bond measured with pull-out tests. Maximum bond and anchor lengths were 50 ft and 140 ft, respectively. Measurements of forces in selected strands and displacements of the excavation showed excellent performance."

Jan 1, 2017

By Douglas G. Baker, Jason K. Braund-Read, Megan R. Sheffer

"Mica Dam, owned by British Columbia Hydro, is an 820 ft high earthfill embankment dam that was completed in 1973. The dam consists of a thin central impervious till core supported by upstream and downstream compacted sand, gravel and cobble shell zones, founded on bedrock and valley bottom alluvium deposits. In 2012, a project was started to install new piezometric instrumentation within the dam’s foundation and downstream shell zone.Deep drilling in large embankment dams is very difficult and requires careful planning to select a methodology capable of reaching the target locations, while ensuring that no damage is done to the surrounding dam fill zones. At Mica Dam, the drilling could only be carried out from the Dam Crest and drillholes had to be carefully oriented to avoid intersecting any existing dam instrumentation. The drilling work therefore required angled drillholes, at depths of up to 855 ft, through heavily compacted sands, gravels and cobbles, and to significant depths below the standing water table.During the planning stages for the Project, in early 2013, the preferred drilling method was selected and a drilling contractor was engaged for the drilling work. Critical dam safety concerns were identified and addressed during the design stage of the Project with the drilling contractor, so that risk mitigation measures and response plans could be effectively developed.This paper explains how background information and prior drilling experience influenced the final design and implementation of the drilling techniques used in 2013 to successfully drill the deep holes and carry out the piezometer installations in Mica Dam. Drilling procedures, instrumentation design and installation methods, as well as risk mitigation measures, are discussed."

Jan 1, 2017

By Ronald E. Walkington

The U.S. Department of Energy (DOE) is building the world's newest accelerator-based, pulsed-neutron system, called Spallation Neutron Source (SNS). The facility, located in Oak Ridge, Tennessee, is a partnership of six DOE national laboratories - Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. Oak Ridge has the responsibility for managing the partnership and ultimately operating SNS. SNS will provide opportunities for up to 2,000 researchers each year from universities, national laboratories and industry from around the world for basic and applied research and technology development in the fields of materials science, magnetic materials, polymers and complex fluids, chemistry and biology. When completed, this state-of-the-art research facility will provide neutron beams that are 12 times more intense than any other such source in the world. Most of the world's neutron sources were built decades ago. Therefore, it is easy to understand how SNS will provide new research opportunities unavailable elsewhere, and at the same time restore United States leadership in neutron sciences. Neutron scattering research provides valuable information about materials that cannot be obtained through microscopy, X-rays, spectroscopes, or other techniques. The information gained from neutron scattering research leads to improved materials that are used in high-temperature superconductors, powerful lightweight magnets, aluminum bridge decks, jet aircraft, compact and computer discs, magnetic recording tapes, shatter-proof windshields, and many other applications. SNS is like a flashing strobe light providing high-speed illumination of an object and will record the structure of physical and biological materials from plastics to proteins. Because neutrons have no charge, they can penetrate more deeply into materials than do X-rays, light, or electrons and thus reveal bulk structure and properties of materials. SNS will help to understand and "engineer" better materials and the manufacture of better products at the atomic level. Our high-technology society demands new materials that are stronger, lighter, and cheaper yet perform well under severe conditions. SNS, which is designed with the future in mind, will be the leading neutron research facility for many years to come.

Jan 1, 2001

By Gary L. Seider, Dana A. Wesolek, Fred C. Schmednecht

"A new condominium project, The Atelier, developed by Pickus Companies located at the corner of Bryn Mawr and Sheridan in Chicago, IL required an earth retention system to protect the surrounding roads, alley, and existing neighboring apartment bui lding during its construction. Slurry Systems, Inc. (SSI) and Ground Engineering Consultants, Inc. designed the earth retention system using cantilevered sheet piling for three of the four sides: two sides bordering major streets and one side bordering an alley. For the fourth side, which borders an existing occupied brick building, a combination of sheet pil ing and AB. CHANCE® helical screw piers were used. SSI was actively involved in the review process of its earth retention system with the City of Chicago and quickly learned that there was no specific code for hel ical piers/anchors. (It appears that this is the case with most metropolitan cities throughout the United States). Consequently, the approval of underpinning for this project became the critical path, as much testing, calculations, meetings, and other details were required prior to its approval.SSI and AB. CHANCE® recognized that this process for underpinning approval must be seen by other contractors/suppliers who wish to use helical piers/anchors in the City of Chicago. Consequently, this project served as an opportunity to work with the City of Chicago and the City's Building Code Committee in furthering the development of the Helical Piers/Anchors Code, Section 1814. INTRODUCTION - HELICAL PIERSDefinition. A helical pier or anchor consists of one or more helix-shaped steel bearing plate(s) attached to a central steel stem (solid bar or pipe), which is installed by rotating or ""torquing"" into the ground. Each helix is attached near the tip, is circular in plan , and is formed into a screw thread with a defined pitch. Helical piers/anchors are pre-fabricated and can derive their load-carrying capacity through both end bearing and skin friction. The helical piers/anchors can be augmented with grout."

Jan 1, 2005

By Karsten Beekhaus, Sander W. Odijk, Rabea Bahlum, Mazin Adnan, Ayman Abdelh Al Nuaimat, Hassan Farhat

The Arab Potash Company, APC, is one of the 10 largest potash producers of the world. The solar ponds at the Dead Sea, used for the enrichment of the salt content in the brine, are of crucial importance for the first step in the exploitation of the potassium salt. Targeting at the expansion of production in the since over 50 years utilized facilities, the increase of the brine exploitation capacity, reducing the substantial brine seepage losses from the ponds, becomes a crucially required measure. In this context, the remediation measures on the over 11 km long Dyke 1, being a main dyke of the solar ponds system, became inevitable to reduce the brine losses, prevent further development of sinkholes and cavities and hence assuring the stability of the dyke. The highly aggressive environment, the acting hydraulic conditions and the sensitive stratification and nature of the existing ground represented remarkable challenges for the design, as well as its implementation by the construction activities. Royal Haskoning developed a solution addressing the challenges above and targeting at a high sustainability of the executed structure, especially in view of the various geological and hydrological hazards repeatedly occurring in this Dead Sea region, including sinkholes of several meters by diameter and depth. The construction works, consisting of a cut-off wall, with depths reaching down to 31 m, were awarded to Bauer International FZE, a subsidiary of Bauer Spezialtiefbau GmbH. Upon the execution of the first section of 4.2 km length, additional sections were subsequently commissioned, also on further dykes, totaling to about 300,000 m² of cut-off wall. The specific project conditions, such as utilization of cutter technique for the excavation in Halite rock, the stability of open trench exposed to hydrostatic pressure of salt-saturated ground water, resulted in unconventional requirements towards the supporting fluid. The extremely aggressive saline conditions –with a Dead Sea water density of 1.25 tons/m3; one of the world's saltiest water–, were further a decisive factor for the definition of the backfill material concept. Despite its clear advantage for construction of cut-off walls with installed sheet piles, the single-phase system with hardening slurries, fulfilling both functions of excavation support and cut-off wall backfill material, had to be abandoned in favor of the two-phase system, to construct a hybrid cut-off wall made of sheet piles and plastic concrete.

May 1, 2022

By Athul Prabhakaran, Ramin Motamed, Ahmed Elgamal, Milad Jahed Orang, Reza Boushehri

Documented case histories from past earthquakes have exhibited the devastating effects of the liquefaction phenomenon on the performance of buildings that are often presented in the form of excessive settlement of shallow foundations. Example earthquakes include the 1964 Niigata earthquake in Japan, and more recently the 2010-2011 Canterbury Earthquake Sequence in New Zealand, and the 2011 Tohoku earthquake in Japan. All of the listed events comprised several examples of severe liquefaction-related damage to the buildings founded on shallow foundations. Although the liquefaction-induced building settlements have been experimentally studied extensively since 1964 using shake table tests and dynamic centrifuge experiments, studies focusing on cost-effective mitigation strategies are still limited. In this study, the performance of helical piles as a cost-effective countermeasure to minimize the damaging effects of liquefaction-induced ground settlements on buildings founded on shallow foundations is studied. Two large-scale shake table experiments were conducted at the University of California, San Diego (UCSD) to investigate the effectiveness of helical piles in liquefiable grounds. Results from these two experiments highlight a highly improved performance of a shallow foundation supported on helical piles. These largescale shaking table experiments demonstrate the efficiency of using helical piles as a cost-effective countermeasure to reduce the liquefaction-induced building settlement.