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By Abdulazeez Rotimi, Barry Sheppard, Abid Adekunte

Good engineering practice is a function of sound theoretical knowledge, first-hand experience on previous projects of similar scope and scale, good acquaintance with case histories of similar projects completed by others in similar environmental conditions, as well as satisfactory degree of exposure to state-of-the-art methodologies. The four factors itemised above are typically interdependent. They amalgamatively influence the judgement of the Engineer and they ultimately result in the delivery of safe and cost-effective solutions by Professional Engineers. This technical paper presents detailed information on the ground engineering aspects of a large-scale housing development project located on a sloping site that had been presumed to be unstable in West Sussex, England. The ground engineering design package for the scheme comprised of temporary working platform designs & stability assessment for piling rigs and other construction machinery, geostructural designs for approximately 1km total run of permanent bored pile retaining walls to support the split-level construction on the sloping site and geostructural designs for the permanent foundation piles to support the housing units. The paper details how the four factors outlined above were amalgamated by the project’s foundation specialist consultants & piling contractors to deliver safe and practical solutions for the development, with significant savings in materials, cost and project completion time.

Sep 8, 2021

By R. Radhakrishnan, C. Gunasekaran

"Calicut Bypass Phase-II project included construction of 7 m high embankment over soft compressible clays up to 18 m in thickness. Approx 1.5 km length of road out of a total 5 km length consisted of abandoned paddy fields which were low lying, waterlogged and marshy in nature. On the basis of excellent results achieved in earlier phases of the by-pass construction, ground improvement work by installing pre-fabricated vertical drains (PVD) was undertaken to stabilize the embankment foundation along the weak clay areas prior to road pavement construction to avoid large post construction settlement as well as to improve the lateral stability during and after embankment construction. This project perhaps stands out as one of the highway projects completed within a very short time period of total 18 months including four month long heavy monsoon period, when embankment construction was not possible and construction of two bridges across rivers. All activities including the ground improvement had to be programmed and completed within the shortest time period possible. The paper discusses details of the extensive ground improvement and soil instrumentation carried out for the project and will illustrate how careful planning and execution can reduce the period required for highway projects involving ground improvement.INTRODUCTIONPhase-II construction of Calicut by-pass was undertaken on a priority basis by the State of Kerala in 2014. The main contract was awarded to M/S ULCCS Ltd, Kozhikode, Kerala and the ground improvement work was awarded to M/S Geo-Enviro Engineers P Ltd, as specialist agency to design and execute the work.Soil investigation carried out confirmed thick soft clay deposits below GL in three areas along the road alignment totaling approx 1.5 km in length. These areas were low lying, waterlogged and marshy in nature. Highway embankment had to be constructed up to 7 m in height above existing GL to form the proposed road alignment along these areas. On the basis of excellent results achieved in earlier phases of the by-pass construction using pre-fabricated vertical drains or PVD (R. Radhakrishnan, 2006), ground improvement using PVD had been included in the contract to stabilize the embankment foundation along the weak clay areas prior to highway embankment construction to avoid large post construction settlement as well as to improve lateral stability during its construction."

Jan 1, 2015

By Bruno Vingiani, Alessandro Bertero

"The use of Artificial Ground Freezing (AGF) for temporary soil strengthening and seepage control is an effective alternative to grouting when dealing with soils whose degree of finesses would imply the use of highly expensive chemical grouts. However, compared to grouting, the application of this improvement technique usually needs a more accurate preliminary soil investigation campaign and a design assisted by specific calculation software. Besides a general description of the main features of this technique, the paper will describe a recent application of AGF carried out in Rome to underpass an existing metro station.INTRODUCTIONNatural ground freezing occurs seasonally or permanently (permafrost) in some areas of the globe close to the poles and can negatively affect the engineering performance of underground structures. On the other hand, Artificial Ground Freezing (AGF) is man-made controllable freezing process that can be used in foundation engineering to temporarily strengthen the ground and create a barrier to the passage of groundwater. During the process, the heat is extracted from the soil in a cylindrical shape around a number of freezing pipes installed into the ground. This action produces columns of frozen soil, which expand gradually till they merge and create continuous frozen wall. The thickness of this barrier can be regulated according to the specific project requirements. Nowadays, AGF technique is applied to a wide range of foundation engineering problems where soil stability and groundwater flows are an issue (Pimentel et al. 2011, Haß and Schäfers, 2013). Typical applications include the temporary stabilization and waterproof of the ground around the excavation profile of mined tunnels until the construction of the final lining (Figure 1).The case history described in this paper deals with a recent application of AGF carried out during the construction of metro Line “C” in Rome. Specifically, this technique has been applied to allow the construction of two single-track mined tunnels running underneath an existing metro station belonging to Line “A”. In that case, the AGF has been evaluated by the Designers as the only possible solution for improving the mechanical and hydraulic characteristics"

Jan 1, 1900

By Brandon M. Robinson, Osman F. Besler, Dominik Gaechter

With the increase in population over the last decade, and anticipated population growth over the coming years, Norway is making significant investments in the Country’s infrastructure. Part of this investment in development starts with the Intercity development project in South-East Norway, which is the largest transport project in Norway. The Intercity Development project consists of 270 km (167 mi.) of new doubletrack rail, capable of train speeds reaching 250 km/h (155 mph). The new stations are centrally located in the major cities, in South-East Norway, to provide the benefit to as many citizens as possible. The goal of the project is to reduce the increase in traffic, which is coupled with an increase in population, and reduce the travel times between the cities. The Intercity Development Project has an anticipated completion date of 2034. The Sandbukta-Moss-Såstad (SMS) project, part of the Intercity development, includes 10 km (6.2 mi) of new double-track railway and is situated on the Østfold Line, near the city of Moss, Norway shown in Fig. 1. The 10 km SMS-section covers three open stretches and two tunnels, including 630 m (2,066 ft) substructure for double-track railways on the open line at Sandbukta. The Moss tunnel is a 1720 m (5,643 ft) long tunnel from Sandbukta to Moss center, including a 420 m (1,378 ft) long concrete culvert. The new Moss station includes an 800 m (2,625 ft) long station area. The Carlberg tunnel is a 2350 m (7,710 ft) long tunnel from Kleberget to Carlberg, including a 200 m (656 ft) long concrete culvert.

Sep 8, 2021

By Bernardo J. Jiménez Vega, Edy L. T. Montalvan

During the last phase of the Circunvalacion Norte project in San Jose, Costa Rica, preliminary designs for an underpass structure of over 16 km (10 miles) considered drilled shafts as an earth retaining system. Since the project’s execution was delayed and close to the deadline, it was necessary to optimize this structure, with the drilled shafts being the most critical aspect. The key element in order to obtain an improved design was characterizing the job site with a specific site study for seismic demand, and the use of advanced numerical modelling, considering soil-structure interaction. The site investigation comprised the CPT, PMT, MASW geophysical tests, deep exploration drilling, and triaxial compression tests. The terrain was modeled using an advanced constitutive model with hardening plasticity calibrated from the triaxial tests. Plaxis software was used to calibrate the seismic model for the terrain and for the dynamic analysis. Two conditions were considered for the retaining structure: free-head and fixed head. A parametric study with drilled shafts of 1.0 m (3.3 ft) and 1.2 m (3.9 ft) in diameter, and center-to-center spacing of 1.3 m (4.3 ft) and 3.0 m (9.8 ft) was conducted in order to obtain an optimized structure. For each condition of the drilled shaft wall, the computed deformations were compared for two spectrum designs: site-specific spectrum and seismic code generic spectrum. Finally, a dynamic analysis was performed to check the performance of the drilled shafts with optimized spacing using a control earthquake. Based upon seismic performance curves, the analysis showed the possibility of greater spacing for the drilled shafts compared to the original design, obtaining a 32% reduction in the total length of the drilled shafts in the project.

Oct 1, 2022

By Seyyed Mehdi Radeghi Mehrjou

The current work investigates the behavior of inclined micropiles under seismic loads. The dynamic finite element method (FEM) was employed. Rayleigh damping was applied to the soil, and elastic beam elements were employed to model the micropiles. The micropile structure was assumed to have one degree of freedom as a column with concentrated mass. The numerical modeling of micropiles was performed to explore the effects of their inclination on their seismic performance within homogeneous soils with uniform stiffness. In addition, the effect of soil stiffness was studied by considering various stiffness in soil depth. The results from the studies have shown significant effects on the dynamic amplification and internal seismic-induced loads of inclined micropiles.

Sep 1, 2022

By Zachary Q. Maassen

Upon approval from the Las Vegas Convention and Visitors Authority (LVCVA), Turner/Martin Harris, A Joint Venture began construction on the estimated $860 million expansion for the Las Vegas Convention Center District Plan. Totaling around 600 shafts (60 feet depth and 3-foot diameter), the foundation installation completed via uncased drilled shaft operation, spanned from October to December of 2018. During this installation, flowback water from the water table was encountered that contained various solids ranging from cobbles to clays to silts, as well as trace amounts of contaminants of concern (COCs) left behind as a result of previous business that used to occupy the same real estate as the current expansion; more specifically, Perchloroethylene (PCE), an organic chemical widely used as a solvent and degreaser. With over 2.5 million gallons of waste slurry to be treated, technologies were deployed to reclassify the waste from liquid to solid waste as well as recover and treat the water for reuse in land spraying applications. Utilizing these technologies, it is estimated that 1.2 million gallons of water was able to be reclaimed along with over 6,400 tons of solids; resulting in hundreds of thousands of dollars in cost and environmental savings. PROJECT OVERVIEW Amidst its famous attractions from gambling to world class entertainment, Las Vegas has long been highlighted as the “No. 1 trade show destination in North America for 24 consecutive years” (LVCVA, 2018). Each year, Las Vegas hosts approximately 22,000 meetings, conventions and trade shows, which support an estimated 65,000 jobs paying $2.7 billion in wages and salaries. In 2017, the Las Vegas Convention Center hosted 21 percent of convention attendees traveling to southern Nevada, which supported approximately 13,800 jobs, paying more than $576 million in wages and salaries. Including indirect and induced impacts, the Las Vegas Convention Center’s attendees generated $2.1 billion in economic impact for the local economy (LVCVA, 2018) . This substantial economic impact of course due in part to the attractions Las Vegas offers to its trade show attendees, along with Las Vegas’ easy accessibility to major metropolises along the West Coast and reasonable travel prices offered if coming in from the East, allows for a very attractive venue. And while being a famous destination is great for business, the city wants to further distinguish itself by offering the best venue as well. For this reason, the Las Vegas Convention and Visitors Authority (LVCVA) approved a three-phase expansion plan for the Las Vegas Convention Center District totaling well over a billion dollars, slated for completion by 2023.

Jan 1, 2019

By Chu E. Ho

This paper describes a case history involving the use of the Equivalent Driving Energy concept for evaluating timber piles that failed to achieve the termination criterion traditionally based on final driving resistance and minimum pile depth. It was assumed that a pile would be acceptable if the overall energy delivered during pile driving was at least equal to that of an ideal pile that achieved the design pile capacity established during an initial load test. The equivalent driving energy was determined by integrating the cumulative driving resistance profile over the embedded length of the pile within the founding soil strata. The required equivalent driving energy was calibrated using representative restrike PDA capacities of production piles as piling progressed. This approach enabled piles that failed to meet the original acceptance criterion to be re-evaluated, resulting in a significant reduction in the number of rejected piles that would otherwise have to be replaced.

By James L. Christensen, Gregory Sanchez, Michael P. Walker

The Fogg Museum expansion project required excavation and construction in a congested urban area in Cambridge, Massachusetts. A soldier pile tremie concrete (SPTC) wall provided the support of excavation and now serves as the permanent basement wall of the new expansion of the museum. The existing Fogg museum had a single basement level. The new expansion has a two-level basement for new exhibit space and an amphitheater. The east side of the site is about 20 feet above the basement level of the existing Fogg structure which resulted in a significant unbalanced load that needed to be resolved without damaging the original Fogg structure. The SPTC wall was supported with a combination of tiebacks and internal bracing. The final depth of the excavation was about 40 feet below street level. Strict movement control was imposed because the existing museum contained an Italian Renaissance-style courtyard. The southeast corner of the SPTC wall had to accommodate underpinning of an historic concrete ramp which was ultimately incorporated into the expansion. Challenges during construction included excavating the SPTC wall panels up to 12 feet into argillite bedrock which had occasional diabase dikes and sills. The following topics are discussed in more detail after a general project.

Jan 1, 2015

By Cheng Lin, Guoming Lin

"This paper presents a case history for the design, construction and long-term performance monitoring of a driven prestressed concrete (PSC) piled foundation supporting a large liquefied natural gas (LNG) tank in Savannah, Georgia, USA. Following a geotechnical investigation, a design stage pile test program was performed with three objectives: to study the densification effect from pile driving on the liquefaction resistance, to test axial and lateral pile capacities, and pile behavior under lateral loads. The test program comprised five piles driven on a test pad constructed adjacent to the tank foundation. Cone penetration testing (CPT) was performed before and after pile installation to test soil densification effects from the pile driving and liquefaction potential was re-evaluated based on the soil densities after pile installation. The axial load tests involved static load testing, high strain dynamic testing, and Statnamic testing. This paper presents the findings of the densification effects, compares results from different axial testing methods and discusses the procedures to use the load test results in the pile design. The paper also comments on the construction issues and presents performance data with 10 years of monitoring.1. IntroductionThe project site is located at the Kinder Morgan’s Elba Island LNG Terminal on the Savannah River which is three miles downstream of the downtown Savannah, Georgia. This LNG terminal was initially developed in the 1970s as an LNG import terminal. The facility includes five LNG storage tanks with two larger tanks which were constructed in 2003 and 2006, respectively. The terminal is currently being converted into a liquefaction and export facility. This paper discusses pile foundations for Tank D4 which is a double walled insulated steel tank built to hold one million barrels of LNG in 2003. This tank has an outer tank diameter of 258 feet, an inner diameter of 252 feet, and liquid height of 113 feet. A number of geotechnical challenges were present in the foundation design and construction.??The site is a typical coastal deposit site featuring a thick layer of very soft under-consolidated clay (up to 40 feet in thickness);??The bedrock is a couple of thousand feet deep;??There is a sand layer that is liquefiable under a high seismic design category (0.5% possibility of exceedance in 50 years)."

Jan 1, 1900

By Jeremy Butkovich

Dynamic soil-structure interaction (DSSI) analyses are becoming more common in bridge designs, especially in seismically active areas. Because of its proximity to two active fault zones, the Evergreen Point west approach bridge replacement will be base isolated, and will be designed using DSSI. The project team completed two independent bridge designs to satisfy peer review requirements. The designs required substantial characterization of the soil dynamic behavior using both laboratory and in-situ testing. The analyses made use of earthquake time histories spectrally matched to conditional mean spectra. This led to reduced, and more realistic seismic demands on the structure, compared to conventional uniform hazard spectrum matching. The bridge analyses suggest that the preliminary bridge design is relatively conservative. This will allow the design team to potentially reduce shaft/column diameters and reinforcement. The design team estimates that the dynamic analysis design could represent a net savings of around $60 to $90 million compared to a conventional design.

By William Billiet

"The Dulles Silver Line Phase II is an 11.4 mile extension of the Washington Area Metro Transit Authority’s Silver line in northern Virginia. There are three miles of elevated guideway, which are supported on 188 large diameter mono-shafts founded within the Triassic Geologic Aged Culpeper Fault Basin. Three lateral load tests were performed on fully instrumented test shafts. The challenge in developing the load testing program was how to reproduce the effects of the extremely high design loads along the test shafts, considering the limitations of the load test equipment. Development, execution, and analysis of the lateral load test program is discussed.INTRODUCTIONPlans for Dulles Silver Line Phase II include two Aerial Guideway sections on elevated track, the Main Line and Yard Leads. The Aerial Guideways are supported on mono-shafts (single, largediameter drilled shafts) socketed into rock. Lateral loads are resisted primarily through the stiffness of the shaft and the geotechnical resistance of the rock socket. The monoshafts were designed in accordance with AASHTO LRFD 2014. Based on our preliminary analyses, the production mono shafts were expected to consist of 6.5, 7.5, and 8.5 foot diameter drilled shafts with rock socket lengths varying between 8 and 34 feet (averaging 14 feet). Table 1 summarizes the maximum service load combinations for each size production shaft along the aerial guideway alignment.GEOLOGYThe project is located within the Piedmont Province, a major physiographic province on the east coast of the USA extending from Alabama to Pennsylvania. Within the Piedmont, a number of Mesozoic basins formed in rift valleys. Dulles Airport is located in the Culpeper Basin, characterized by a relatively shallow siltstone rock surface compared to the adjacent areas underlain by Piedmont crystalline rocks. The geologic stratigraphy at the load test sites generally consist of residual soils and intermediate geo-material (IGM) overlying siltstone rock. IGM is a term used by Virginia Department of Transportation (VDOT) to describe residual material as it transitions between soil and rock. For the purposes of the load test, the siltstone rock is classified as fractured rock (RQD<50), and competent rock (RQD=50). Table 2 summarizes the stratigraphy encountered at each test site."

Jan 1, 2017

By Sven Schröer, Lilma Schimmel, Dimiter Alexiew

"The Geotextile Encased Columns (GEC) deep foundation system for embankments on soft soils was introduced some 20 years ago and is now considered State-of-the-art worldwide.The GECs consist of compacted granular fill, similar to common gravel columns, with one decisive difference: they are confined in a high-strength low-strain flexible geotextile “cylinder” (encasement). This engineered element provides a very efficient tool to control and optimize the behavior of the system. GECs perform very well even in extremely soft soils ensuring bearing capacity (stability) and reducing settlements. Due to the encasement, they a lso provide high lateral ductility. A wide range of fills including sands can be used.The remarkable reduction of vertical stresses in the soft soil surrounding the GECs results in a decrease of lateral pressure as well. Such reduction combined with the lateral ductility allow GECs to be also used for lateral pressure-relief adjacent to sensitive foundations, e.g. rigid piles. The application of GECs as lateral pressure relief was recently used in Brazil and Germany where bridge abutments were built on concrete reinforced-piles. The GECs below the bridge approaches and adjacent to the piles decreased the lateral pressure to acceptable values.This paper presents two case studies for which the most relevant parameters, the geotechnical conditions, specific problems, engineering philosophy, final solution and lessons learned are discussed. Furthermore, instrumentation programs were applied in both projects. The most important results in terms of displacements and stresses are shown, evaluated, summarized and commented upon, focusing on the lateral stress-relief, followed by conclusions and recommendations."

Jan 1, 2016

By Patrick J. Hannigan, Frank Rausche, Rozbeh B. Moghaddam

The Top-Loaded Bi-Directional Test (“TLBT”) is a new method to apply bi-directional loads to a deep foundation element with the loading source located above the foundation head. In the TLBT reusable load assembly, loads are applied to the foundation using the R-System which consists of two stacked steel plates located at the geotechnical resistance balance point or at the foundation base connected to the load assembly via vertical elements. The top plate or the Shaft Bearing Plate (“SBP”) will transfer loads to the foundation upper portion, and the bottom plate or the Base Bearing Plate (“BBP”) will transfer loads to the foundation lower portion as well as the foundation base. At the surface, above the foundation head, a hydraulic jack is located between a Top Load Assembly (“TLA”), and the Bottom Load Assembly (“BLA”). The TLA and BLA are connected to vertical elements which are consequently connected to the R-system. As the jack is pressurized and expanded at the surface, the R-System plates are separated, and the foundation is bidirectionally loaded. This paper presents a brief description of the conventional Bi-Directional Load Test (“BDLT”) including benefits and limitations followed by the TLBT method introduction including its benefits and advantages over other testing methods.

Sep 8, 2021

By Thomas D. Humbert, Christopher J. Ramsey

Construction of a new underground parking structure in State College, Pennsylvania, is situated on a site constrained by limited ROW and required excavations ranging in depth from 25 ft to 40 ft. Additional complications included busy surface streets, an active intersection, and numerous underground utilities that could not be disrupted by construction activities. To combat these challenges, an innovative approach for earth retention was designed that combined multiple types of retention systems. The overall system included alternating sections of soil nail walls and a hybrid system of soldier pile walls (consisting of micropiles) that were partially restrained by a soil nail wall in the lower portions of the excavation. Further, due to the limited space within the property limits that inhibited the length of the permanent nails, the wall design team collaborated with the project designers to develop a solution such that the completed wall became an integral part of the final design/construction of the underground parking structure. INTRODUCTION HERE at State College is a mixed-use, high-rise building in State College, Pennsylvania. The 12-strory building has up to 3 levels of below-grade parking, with the above-grade levels consisting of residential and commercial/retail space. The existing property was a parking lot bound by the streets Calder Way to the north, Garner Street to the east, East Beaver Avenue to the south, and Heister Street to the west. The overall property sloped approximately 20 ft in elevation from southeast to northwest. Excavation for the below-grade levels extended 21 ft to 36 ft (6.4 m to 11 m) below street level. During design-development phases of the project, it became evident that due to subsurface conditions and right-of- way limitations, conventional construction techniques would not be feasible. The full perimeter of the excavation would require earth retention including the weak shale bedrock along the bottom of the excavation. The project developer (CA Ventures) and general contractor (Brinkmann) coordinated with the specialty contractor and wall design engineer to find a solution. At this time, Coastal Drilling East (specialty contractor) and Wood Environment & Infrastructure Solutions (wall design engineer) became involved. The project developer and general contractor were aware they needed an earth retention system, but given the many variables the project faced, a single, straightforward solution would not work in this application.

Jan 1, 2019

By Maurizio Siepi, Bruno Vingiani, Claudio Asioli

"The article describes an emergency rehabilitation intervention executed at Buyo Dam, in Ivory Coast, to intercept a significant water seepage occurring through the foundation of this zoned earthfill retaining structure constructed in the late Seventies. To solve the problem, a 800 mm thick, 400 m long impervious cut-off wall (COW) was constructed on the right side of the embankment, operating from the dam crest and with the reservoir almost at its maximum level. The use of an innovative pre-mixed self-hardening grout, with a target hydraulic conductivity coefficient (k) lower than 10-9 m/s, was considered the only way to match the tight working schedule and the strict requirements for the filling material of the COW.Presentation of the Hydroelectric Scheme of BuyoThe hydroelectric scheme of Buyo, located at 6°14’28” N 7°20’45 W on the Sassandra River, in Ivory Coast (Figure 1), was built in the late Seventies for agriculture and power generation. With a reservoir of 8.3 billion m3 and an installed power capacity of 165 MW, enough to supply electricity to 111,000 homes, it represents an installation of great significance for this West African country."

Jan 1, 2016

By David Corke

The paper presents the development of Federation of Piling Specialists (FPS) calculation of rig track loading, the production of the Building Research Establishment document “Working platforms for tracked plant” (BR 470), working platform testing and considerations of rig stability. The paper also discusses the importance of rigorous and well documented procedures and proposed future development of rapid working platform testing methods. Topics presented include the fundamental requirements and principles involved in the testing, design and maintenance of working platforms, rig track loading, the BRE design method and site testing analysis. The paper stresses the need for testing and design processes to be robust and simple and quick to perform as there is often little time between the award of a contract and the need to start work on site. Also, it is vital that all aspects of working platform design can be carried out with information that is available to the platform designer. Developments in the UK over the last two decades have resulted in improved quality and safety of working platforms that will hopefully be further enhanced as design and testing methods continue to improve.

May 1, 2022

By Filippo Leoni, Wesley Schmutzler

"The LPV-111 East Back Levee Improvement Project lies along the Gulf Intracoastal Waterway (GIWW) in Orleans Parish of New Orleans, La., and is an essential component of the New Orleans Hurricane Protection System. The Hurricane Protection Office of the U.S. Army Corps of Engineers (USACE) attributed failure of the New Orleans East levees system to overtopping, erosion and subsequent breaching of LPV-111 along the GIWW, as well as other sections of flood protection during Hurricane Katrina in 2005. The existing levee suffered extensive damages from Hurricane Katrina, such that the USACE elected to provide earth stabilization and to rebuild the levee sections. Due to the adverse geotechnical properties of the foundation soils, the Corps deemed ground improvement necessary to stabilize the new levee and to limit its footprint. Wet Deep Mixing Method (DMM) was selected as the most suitable technology for this task.ChallengesDesign: This reach specifically protects East New Orleans and the Bayou Savage National Wildlife Refuge, the largest urban wildlife refuge in the U.S. and home to several threatened or endangered species of birds as well as many reptiles, amphibians and small mammals. The Corps chose DMM due to the sensitivity of the protected marshlands and because the method limits the footprint of the raised levees. The increase in the load bearing capacity of the treated soil significantly decreases the footprint necessary to attain the required height increase. This limitation required the new levee to have steep slopes, drastically increasing the surcharge on foundation soils characterized by overall poor geotechnical properties (soft clays and peats). The design also considered the increased horizontal stresses on the levees due to the extreme storm surges during a hurricane.The design of the 1.6 m diameter (5.25 ft) DMM elements called for overlapping them to form a double auger element that formed buttresses perpendicular to the levee alignment. The contractor installed the buttresses at a maximum on center spacing of 4.7 m (15.5 ft). One additional double auger DMM element was midway between consecutive buttresses at the centerline of the levee to further help prevent settlement (Figure 1)."

Jan 1, 2013

By Kazuyoshi Kamimura, Masaya Kawata

"It has been 30 years since the cement deep mixing (CDM) method developed in Japan. CDM method has been applied to many structures. While various technical improvements have been implemented in the meantime, the single-axial and double-axial technologies used at the time of its initial development are still prevalent.In response to the recent trend of reducing construction costs, we developed a triple-axial CDM method called the “Lemni 2/3 Method.” This method uses two lemniscate motions caused by newly developed auxiliary stirring devices and employs a double-axial injection method in which the cement slurry injection takes place only from the outer two axes. In this way, it is possible to create a stabilized body around the three axes. Moreover, this method does not require substantial equipment investment as conventional construction machine and facilities can be used without modification and large volume work is possible.With these technologies, this method can achieve a substantial reduction in the construction period and cost, while ensuring the same level of improvement quality as conventional methods. As a result, this method is being applied to ground improvement work in a variety of places.Lemni 2/3 Method was first put to practical use in 2004. Since then, the method has been used for ten projects. In this paper, we show some application examples of this method.OUTLINE OF TRIPLE-AXIAL CDM METHOD (LEMNI 2/3 METHOD)In the newly developed CDM method (Lemni 2/3 Method), work efficiency is improved by employing triple-axial stirring blades instead of the conventional single- or double-axial type. Existing conventional construction facilities for double-axial type can be used with only minor equipment additions, because the cement slurry injection takes place only from the outer two axes.Construction Machine and Construction MethodThe combination of major construction machines of the Lemni 2/3 Method differs little from the standard specifications of the double-axial type as shown in Fig. 1. Existing work control equipment can be used without modification, which is further evidence of the simplicity, convenience, and economy of the new method. The Fig. 2 photo shows a full view of the construction machine, and the Fig. 3 photo shows the stirring blades and the auxiliary stirring devices. The work procedure for the Lemni 2/3 Method is shown in Fig. 4."

Jan 1, 2015

By Dennis Nottingham

"Increased interest in seismic soil liquefaction and preventative soil stabilization sets the stage for improved deep compaction methods using pile driving techniques. In 1971, L.B. Foster Company personnel patented a method of deep compaction using a vibratory pile hammer and pile probe. The technique had some success, but did not produce consistent results and thus found its way to obscurity. Other patents attempted to modify the technique by various probe modifications, but again without measurable improvement from a practical point of view. Solutions to economical deep compaction up to 100-foot depths particularly in saturated granular soils would have a great impact on the construction industry and new bulkhead structures being developed, thus PND was prompted into related research and development. The advent of higher horsepower vibratory hammers, coupled with PND engineers’ experiments, observations and measurements, led to an “H” pile probe design which has produced measured soil density improvements up to 250% using SPT “N60” values as a measure. Case histories of two projects involving extensive SPT soil sampling comparative measurements will be discussed along with findings that led to the compaction success. Applications to numerous modern “Open Cell” bulkhead projects will be presented and discussed.INTRODUCTIONNecessity often is the basis for innovation and such was the case for needed cost-effective deep soil fill compaction in Open Cell bulkheads where granular fill below water levels was often placed.Open Cell bulkheads were developed by PND Incorporated starting in 1980, for the express purpose of meeting client demands for an economical, easily constructed, extremely strong structure. Earth-filled structures historically have had a long history of problems with stability, scour and settlement.Open Cells are flexible steel sheet pile membranes supported by soil contact with embedded tail anchor walls.This concept creates an integral reinforced soil system. The result is a structure that can withstand large settlement and support a variety of very large loads. In effect, viewed from above the structure becomes a series of U-shaped horizontal membranes that require no toe embedment for stability. The Open Cell bulkhead is constructed of only three components: flat sheet piles, fabricated connector wyes and anchor piles. Compared to alternative structures, several cost savings are realized from this land based construction such as, reduced sheet pile area, greater construction tolerance, minimal pile penetration, and simplified backfilling procedures. In seismic regions or weak soils, the tail walls can be extended as required to guarantee fill mass stability."

Jan 1, 2005