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By Fredrik Sarvell, Harald. Ihler, Veli-Matti Uotinen, Jukka Rantala

"Many of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The ultimate structural load bearing capacity of a pile in a cohesive soil is decided by examining which gives the lowest value, the peak buckling load and the resisting moment provided by the surrounding soil medium or the structural capacity of the pile cross section. In both cases, the initial deflection of the pile is a significant factor when the axial load bearing capacity of the pile is determined. Steel micropiles are joined commonly with mechanical splices. A less rigid mechanical splice is often a weaker hinge that allows the pile to bend and deflect more during installation increasing the initial deflection of a pile. In addition the less rigid splice element decreases the bending capacity of a jointed pile section and the ultimate axial load capacity of the entire pile. A series of FE analysis performed for various pile sizes suggest that the steel pipe piles including separate pile sections and mechanical splicing elements should have the combined bending stiffness of EIshaft = 0,75 × EIpile. This requirement yields to the buckling resistance of at least 96 % of the solid reference pile with the sameinitial eccentricity in similar soil conditions.IntroductionMany of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The potential buckling of these very slender high capacity piles in soft soils may in many cases be the controlling design factor of the pile, especially with end bearing micropiles.A typical sequence of soil strata in Nordic countries, such as Norway, Finland and Sweden, constitutes of friction soil or dry crust clay on top of soft clay followed by till. This soil stratum often rests on solid bedrock of granite or gneiss. Conditions like these are suitable for slender end bearing piles subjected to buckling and especially steel pipe piles where most of the material is located at the edge of the cross section. Other reasons for using slender steel pipe piles are for example fast installation with minimal waste, efficient manufacturing and relatively well established design and execution procedures. Minimum quality criteria’s regarding splices for steel pipe piles are recommended to be set as national provisions to ensure quality and comparable procurements in foundation business."

Jan 1, 2014

By Rob Jameson

"San Francisco is 49 square miles surrounded by reality." So said Paul Kantner of the local '60s icons, Jefferson Airplane, and his words have still held true. The rate, scale and complexity of recent construction in this city has been remarkable, even compared to the Gold Rush or reconstruction after the 1906 earthquake. This article will address developments in soil mixing in San Francisco since 2011, and how the marked settlement of a downtown high rise has influenced this booming construction market.

Jul 1, 2022

By Yuji Yamashita, Kazuyoshi Kamimura, Tsuyoshi Takahashi, Naoya Matayoshi

"The CDM-LODIC method (cement deep mixing - low displacement and control) method enables ground displacement to be reduced by removing an amount of soil equivalent to that of injected cement slurry and the volume of the plunged mixing tool, which causes a certain degree of ground displacement. Since the CDM-LODIC method was developed in 1985, it has been applied to over 930 sites and the accumulated volume of stabilized soil has now reached 7.6 million cubic meters.In the CDM method, the number of blade rotations per unit depth in the ground when the mixing blades are withdrawn is considered a construction item. The blade rotation number depends on the degree of mixing between the cement slurry and the ground Some field tests were performed based on the degree of mixing between the cement slurry and the ground. In these tests, a new concept of evaluating the blade rotation number when the screw rod penetrates to a given depth without injecting cement slurry has contributed to the degree of mixing. Furthermore, a correlation exists between the coefficient of efficiency of soil removal and the cement slurry admixture rate. In this paper, we discus the data collected in those field tests and present some application examples.OUTLINE OF CDM-LODIC METHODThe injection of cement slurry may cause some ground displacement during Cement Deep Mixing (CDM). In recent years, due to an increased demand for ground improvement work in urban areas, there is increased concern that buildings near any CDM site may be adversely affected. The deep mixing method which reduces displacement due to mixing (CDM-LODIC method) enables ground displacement to be minimized by removing an amount of soil equivalent to the injected cement slurry and the volume of the mixing tool, which itself causes some ground displacement. When the construction site is near other structures, regardless of whether on or under the ground, the CDM-LODIC method can be used in order to minimize any ground displacement. There are considered to be two main causes of ground displacement as shown in Figure 1. Displacement A indicates ground displacement caused by the volume of the inserted mixing tool during the penetration stage and displacement B indicates ground displacement caused by the volume of the injected stabilizing agent. Thus, by removing soil equivalent to the volume of the inserted mixing tool and the injected stabilizing agent, ground displacement can theoretically be minimized. Figure 2 shows the amount of observed ground displacement in the cases of CDM and CDM-LODIC at an actual site. These case studies indicate that ground displacement can be reduced by removing the soil."

Jan 1, 2015

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 M. Hesham El Naggar, Tony Sangiuliano, Alper Turan

"Bridge abutments supported on pile foundations are often constructed over weak and compressible soils. The consolidation settlements induced by the embankment loads are known to result in downdrag and lateral forces on the piles supporting the bridge abutments. The performance of a pile group including inclined piles embedded in consolidating soils was investigated numerically considering surcharge loads from approach embankment construction. A two-dimensional numerical model was constructed using commercial finite element software PLAXIS and calibrated against field measurements of the abutment movements observed on Brookdale Avenue Underpass Structure located on the Macdonald-Cartier Freeway in Ontario between Cornwall and the Quebec border. The soft soil model (SSM) was used to simulate the constitutive behavior of the compressible soil deposit. The SSM model parameters were determined based on the laboratory tests. Subsequently, time dependant development of downdrag effects was comparatively evaluated for vertical and inclined single piles as well as a pile group that included both vertical and inclined piles.Results showed that drag loads increased with the consolidation time. However, majority of accumulation of drag loads took place within first 120 days after installation of piles. The results also indicated that the shear forces and bending moments are controlled by the lateral spreading of foundation soil and their accumulation is proportional to consolidation time. The large axial strains caused by large downdrag forces are considered to have yielded the piles and this is a possible reason for unusual abutment movements. The results presented in this study are considered to be of interest to researchers and practitioners.1. IntroductionDeep foundation units are widely used for supporting bridge piers and abutments, where weaker surficial soils preclude shallow foundations. Particularly in Ontario, semi-integral and integral abutment bridges are typically supported on end-bearing steel driven piles. The construction of approach embankments over weaker, compressible soils results in significant vertical and lateral soil movements, which induce additional loads on piles supporting the abutments. In order to minimize such effects, preloading and surcharging are commonly employed approaches to avoid unanticipated settlements prior to the installation of piles. Other alternatives such as aggregate pier supported approach embankment are also being studied as the schedule restrictions imposed by preloading and surcharging becomes cost prohibitive (Turan et al. 2012)."

Jan 1, 2015

By George J. Tamaro

In 1967 the Port Authority of New York and New Jersey undertook the construction of the World Trade Center (WTC) diaphragm walls, installation of the lateral support system and the excavation of the site, commonly referred to as the "Bathtub". The work took two years to complete. In 2001 the City of New York undertook the re-excavation of the site after the terrorist attacks. The recovery work will take eight months to complete. This paper describes the initial work on the WTC "bathtub" in the late 1960s and the recent work during the recovery.

Jan 1, 2002

By Takeo Asanuma, Sachihiko Tokunaga, Hirofumi Taguchi, Yasuhiro Ootsuka, Yosuke Tanaka

The Cement Deep Mixing Method (CDM Method) is a ground improving method that has been used for mainly offshore sites to strengthen the soft ground below the sea bottom by injecting and adequately mixing cement slurry with soft soil into the ground to form a ground-improving column. In recent years, the CDM Method has increasingly been adopted for ground- improving work as part of liquefaction countermeasures and earthquake-resistant reinforcement in the shallow waters of river mouths and inland waters. In consequence of that, a pontoon-mounted CDM Method (CDM- FLOAT Method) has been developed for shallow waters, which is equipped with a land-type mixing machine combined with system management equipment and a tide level-based control function. This CDM-FLOAT Method can be deployed at work sites where the conventional offshore-use CDM barge cannot be employed. This report describes the CDM-FLOAT Method and the scope of applications together with construction work procedures, and a representative case of use of the CDM-FLOAT Method is introduced as an example of earthquake-resistant reinforcement of the existing embankment of a canal.

Jan 1, 2015

By Martina Balic

Dynamic properties of the drilled shaft foundations supporting Doremus Avenue Bridge were determined by forced vibration testing. The main objectives of the substructure testing at Doremus Avenue Bridge were: (1) site evaluation with respect to the dynamic soil properties, and, (2) shaft evaluation for the purpose of definition of their dynamic stiffness. The site characterization entailed crosshole testing for the purpose of evaluation of the shear modulus profile. The drilled shaft impedance evaluation was done through forced excitation using an electromagnetic shaker. The responses of the tested shaft, as well as the response of adjacent shafts, were measured for the purpose of evaluation of the shaft interaction. To gain a better insight into the shaft dynamics, one of the shafts was instrumented with five triaxial geophones distributed along the full length of the shaft. The scope and results of the site characterization, shaft impedance and shaft interaction evaluation are presented.

Jan 1, 2004

By Charles G. Crans, Naresh Gurpersaud

"Toronto’s Union Station, a National Historic Site occupying an entire city block, is the busiest commuter rail transportation hub in Canada. An extensive project is being undertaken to revitalize Union Station while maintaining the historical significance of the building and minimizing disruption to commuters. A significant stage of the revitalization involves excavation indoors, to a depth of up to 5.5 m below the existing floor level to create space for a new transit concourse and a new lower-level pedestrian retail concourse. A hybrid excavation support system utilizing micropiles as soldier piles was constructed over an 18 month period between 2010 and 2011.Development and testing of connections between the micropiles, shotcrete facing, lagging, walers, and tiebacks presented significant challenges. The existing viaduct structure was constructed in the 1920’s on land reclaimed from Toronto Harbour, so there was significant (and ongoing) uncertainty with respect to buried obstructions including relic timber wharfs and abandoned steel and timber piles. Collectively all these conditions precluded the use of conventional methodology; new techniques, installed using modified equipment, and for the first time in the Greater Toronto Area, were required.Details of the existing site conditions, installation challenges, design, construction and performance of the hybrid excavation support system inside this historic structure are presented.INTRODUCTIONUnion Station in Toronto, Ontario is the busiest passenger rail facility in Canada, with 65 million passengers annually and an average of 200,000 passengers each day. Construction of the station was completed in 1920. It has been designated a National Historic Site of Canada and inducted into the North America Railway Hall of Fame in the Facility and Structure category.The Union Station Revitalization Project (USRP) was tendered in 2010 and awarded as a 6-year, $450M construction management / trade contract package. Included was a large scale grade reduction, referred to as “The Dig Down”, to create two basement levels and this required extensive excavation support constructed entirely indoors within the active station setting."

Jan 1, 2017

By John S. Pack

The application of square shaft helical piers in expansive soils is a standard of practice in many areas of the United States. Over 20 years of performance monitoring show exceptional performance and economy will result if proper design procedures, specification requirements and installation procedures are followed. This is true for new foundations and the repair of existing foundations, including lightly loaded wood-frame structures on expansive soils. Proper design includes: 1) site geotechnical characterization, 2) pier layout such that each pier is loaded to its maximum design capacity, 3) maximize spans between piers, 4) minimize the number of piers, 5) isolate the structure from the expansive soil with an appropriate void zone below all grade beams, slabs or other components that would otherwise be in soil contact and 6) utilize only single helix piers. Proper specification employs a performance specification that specifies: 1) the design load on each pier with a suitable safety factor, 2) the minimum installation torque, typically 4,000 ft-lbs (5.4 kN-m), or refusal, 3) a minimum pier shaft steel Fy = 70 to 90 ksi (483 to 621 Mpa) and pier helix steel Fy = 80 ksi (552 Mpa), 4) 1.5 to 1.75 inch (38.1 to 44.5 mm) square shafts, 5) smooth shaft surface, 6) the ICC Evaluation Report (ER) number of the manufacturer and 7) the manufacturer ISO 9001 certification for material quality control. Proper installation requires: 1) equipment with sufficient axial compression force (crowd) on the pier shaft so the helix engages the soil and advances to the specified minimum installation torque or refusal, 2) additional specialized techniques for expansive soils and 3) qualified specialty helical pier installation contractors experienced in expansive soils who submit and utilize pier configurations, techniques and equipment that will most effectively and economically meet the specified performance.

Jan 1, 2007

By Yahia M. Al-Smadi

Effect of lateral loading against existing sheet pile wall and distribution of gravity loading due to various number of construction loading scenarios were studied. The objective of this effort was to determine the loading case that permits the contractor to utilize a 400 ton crane at the specified location with the existing limitation imposed on site. Staged analysis was determined as the methodology that will more accurately predict the exiting and additional stress due to the impose crane loading. A reliable and robust analysis (ANSYS) software was used to complete both 2D and 3D finite element model and analysis. Analysis model parameters such as material properties, non-linear behavior of the soil, and meshing are presented and discussed. At the conclusion specific range of crane operation and pick weights operating on existing concrete mat supported on top of an existing tunnel was reviewed and deemed acceptable.

Jan 1, 2010

By Lucian L. Bogdan

"SummaryActive loaded strand anchors are often used for slope stabilization, retaining walls or tiedown anchors. Normally, strands are tensioned against the structure and wedges are locked inside the anchorages at a certain lock-off load. During the life of the structure, anchors can receive additional loading during a surcharge, seismic event or other activity on the structure.In order to have a reliable ground anchor system, the strand must not slip through the anchorage wedges during its service life. Strand slippage has been reported during lock-off, when dirty wedge plates and wedges have been used. Low lock-off loads are believed to contribute to strand slippage too. Since the initial lock-off load for a ground anchor is usually lower than the lock-load for an equivalent capacity tendon in other types of post-tensioning construction, there is a concern that strand slippage may occur if the load on the anchor increases above the initial lock-off load.Corrosion protection grout, placed after the anchor is locked off, fills the pocket and surrounds the strand and wedges. Some anchor installers believe that the grout will prevent the anchorage from developing additional capacity if the load increases above the initial lock-off load.The load-carrying capacity of an anchorage depends on several factors. Most important are: initial applied load, anchorage geometry, friction between wedge-anchorage-strand and condition of the contact surfaces.The ADSC Anchored Earth Retention Committee considers that the industry should know how wedges behave once the permanent strand anchors are stressed and grouted inside the transition pipe, between wedges and inside the grout cap."

Jan 1, 2005

By Michael D. Justason

"In January 2009, long-time competitors, Anchor Shoring & Caissons Ltd. of Toronto and Bermingham Foundation Solutions of Hamilton, joined forces to tackle one of the Greater Toronto area’s largest deep foundation projects: the West Toronto Diamond Rail Grade Separation. The two companies formed the “West Diamond JV” and succeeded in winning the contract from the Canadian National Railways. This deep foundations work was the first and most significant part of the $300-million-plus rail grade separation project. A big part of the job turned out to be dealing with local government regulations and citizens’ concerns with noise and vibration.The project is approximately 10 km (6 mi) northwest of downtown Toronto in an area of mixed-zoning including light industrial, commercial and residential buildings. The area is commonly called the “The Junction,” because of the heavy rail- traffic. The “West Toronto Diamond” refers more specifically to the railway junction where the North-South tracks of Canadian National (CN) Railway meet at a level crossing with the East-West tracks of the Canadian Pacific (CP) Railway. The goal for this part of the project was to convert the West Toronto Diamond into a grade-separated junction by depressing the CN lines under the CP lines, thus allowing commuter rail carrier, called GO Transit, intercity carrier VIA Rail, and CN freight trains to pass through the new underpass.Dawn Tattle, president of Anchor Shoring & Caissons says, “not only is the site in a densely populated area adjacent to homes and businesses, the crews worked adjacent to active rail lines with numerous trains passing daily. During the 7-hour working day, approximately 60 trains passed through the site in very close proximity to working crews.” Safety was paramount. While trains were passing through the site, it was a railroad requirement that all equipment and men stop working. In addition, at those times, all personnel were required to stay 6 m (20 ft) from the tracks and were required to face the tracks. For the faster commuter trains, this work interruption could last as little as 2-3 minutes, while interruptions caused by the slower freight trains could last as long as 25 minutes. The most disruption to the site occurred during the morning commute between 7 to 9 a.m., so work did not really get underway until after that time. Once work finally commenced the race was on to finish as much as possible before the afternoon commute – hence the shortened work day. The amount of disruption caused by the trains was a big unknown faced by the JV going into the project, but crews adapted quickly to the very unusual work environment"

Jan 1, 2012

By Dardis J. T. II, P. G. Reinhall

"Impact pile driving of steel piles in marine environments produces extremely high sound levels in the water. It has been shown that current pile driving noise attenuation techniques provide limited noise reduction because significant noise is transmitted through the sediment into the water. To solve this problem, we have developed a double walled pile to decrease the total noise transmitted into the water.The double walled pile consists of two concentric tubes connected by a special driving shoe, allowing for an air gap between the two tubes. The double walled pile is driven into the sediment using traditional equipment by striking the inner tube only. The air gap between the inner and outer tube prevents the radial deformation wave produced by the pile hammer from interacting with the water and the sediment. In one embodiment of the double pile design the inner tube can be removed and repeatedly reused.In this paper we report on the results from a recent full scale field test in Puget Sound, Washington. The use of these double walled piles reduces the peak sound pressure over 20 dB relative to single walled piles. We also show that only a 3 to 6 dB reduction is obtained when a bubble curtain is used on a single walled pile.INTRODUCTIONImpact pile driving of steel piles in marine environments produces extremely high sound levels in the water. It has been shown that current noise attenuation techniques provide limited noise reduction because the noise from pile driving is transmitted through the sediment into the water. In [1,2] we showed, using modeling and field data, that the primary source of underwater sound from an impact driven pile originates from radial expansion of the pile as the compression wave propagates down the pile after each strike. The radial expansion is coupled to the compression wave through the Poisson’s ratio of steel. As discussed in [1], the supersonic radial expansion wave (with respect to the water) produces an acoustic field in the shape of an axisymmetric cone, or Mach cone. We showed in [3] that the ability of any sound shield that surrounds the pile in the water only (such as a bubble curtain or a surrounding double wall engagement) to attenuate the sound in the water is limited by the fact that an upward moving sound Mach wave is produced in the sediment and is transmitted into the water. To improve the performance of bubble curtains and other noise shields in the water, it is necessary to attenuate the noise emanating from the sediment into the water. Figure 1 illustrates how sound from the seabed leaks out from the sediment, limiting the effect of the surrounding bubble curtain."

Jan 1, 2017

By Norm Kirk, Robert Bittner

"The addition of a new powerhouse at the existing Tulloch Hydroelectric site on the Stanislaus River in the western foothills of the Sierras Nevada Mountains of central California required a deep excavation in rock on the downstream face of the dam. A cofferdam (water exclusion device) was necessary to isolate the powerhouse construction site excavation from the existing Goodwin Reservoir and the turbulent discharge from the existing powerhouse. The cofferdam was positioned on a steeply sloping fractured rock surface exceeding 50 degrees.This paper describes the challenges encountered during design and construction of the cofferdam and describes the unique design features used to address these challenges including:•,The use of flat-sheet-piles to form cellular walls on the steeply sloping rock surface.•,The use of 5-ft deep tremie concrete plugs in the bottom of the sheet pocket cells to create the bottom seal of the cellular cofferdam walls against the sloping rock surface.•,The use of vertical post-tensioned rock anchors to provide shear resistance at the contact point between the base of the cellular-wall and the sloping rocksurface.INTRODUCTIONModification or expansion of existing hydroelectric power plants often require downstream cofferdams or water exclusion devices to temporarily separate new construction from turbulent downstream discharge of the existing dam. Most dams are positioned on solid rock in the narrowest and therefore the steepest section of the river. This combination of steeply slopingrock and the need for an exclusion barrier creates a challenge for the design engineer trying to maintain a safe dewatered construction site. Typical cofferdam solutions for hydroelectric dams usually use large granular filled circular sheet pile cells that perform as gravity structures. However, this type of structures is not well suited to steeply-sloping highly irregular rock surfaces in a confined area."

Jan 1, 2017

By James C. Scott

Compression and tension load testing were performed on bored concrete piles installed to depths of 18 to 34 meters below excavation levels for a large mixed-use development in Kuala Lumpur, Malaysia. The 900 mm diameter piles were installed in weathered graphitic schist bedrock. Load testing confirmed the side shear and end bearing capacities of the piles. The work formed part of the investigations for the 56,000 m2 site which includes a 79-story office tower, hotel tower, apartment tower, retail complex, and plaza area underlain by 4 to 6 basement levels. The paper provides the results of the site investigations, pile-load testing procedures, pile-load settlement behavior, and shaft load distribution.

Jan 1, 2007

By Ramin Motamed, Fahim M. Bhuiyan, Raj V. Siddharthan

Numerical lateral load analysis based on the beam on Winkler foundation (BNWF) model (i.e., the p-y method) is a simple, and widely used tool to predict lateral responses of drilled shafts from field load tests. The lack of a site-specific p-y model for cemented soil layers such as caliche is one of the major limitations of simulating lateral load tests conducted in Las Vegas Valley. In this study, some of the existing p-y models for rock materials, such as Florida Limestone and Vuggy Limestone have been evaluated to simulate the lateral resistance of caliche. This has been done in the context of four lateral load tests in caliche-dominant sites from the recently constructed Raiders Stadium project in Las Vegas (NV). The uncertainty in characterizing the material properties of caliche has been addressed. The p-y analyses were performed using NVShaft, a MATLAB-based, comprehensive load analysis program. The applicability of the considered p-y models for caliche material was evaluated by quantifying the normalized error margins between measured and predicted lateral responses from the simulations of the mentioned load tests. Correlations between such errors and the depth and thickness of caliche in soil layers affecting numerical predictions were established, for both up to and beyond design load levels.

Oct 1, 2022

By Charles M. Wilk

"Mass stabilization involves mixing binding agents into marginal or contaminated soil to improve the subject material’s physical and/or chemical properties. This paper concentrates on the principles of soil mixing and benefits and application to new and existing rail right-of-way. Successfully applied in Scandinavia and other European countries, the soil mixing is now being applied in right of way in the northern latitudes of the U.S. and Canada. These regions have significant areas of “peaty” soils that can complicate construction and maintenance of rail and structure foundations. Mass stabilization can be used to improve the bearing strength of these soft soils for subsequent construction of railroads, pipelines, roads, and buildings. In civil engineering, the technology is often used to improve the construction properties such as bearing strength, of a marginal soil. In environmental engineering, stabilization is remediation treatment technology that protects human health and the environment by immobilizing hazardous constituents within the treated material. . The treatment is conducted while the subject material remains in-place (insitu). Mass Stabilization is often used to accomplish both civil and environmental purposes on the same project effectively addressing marginal soil while eliminating the expense of soil removal and replacement. This paper presents the principles of mass stabilization technology, implementation in the field and recent completed railway projects. The example rail projects will present the various benefits that soil mixing provides to railway construction and maintenance. Bench-scale studies and full scale implementation as well as soil construction properties before and after mass stabilization will be discussed. The paper and presentation will include information on the advantages of mixing methods and binding agent delivery systems.INTRODUCTIONNew or existing railroad right-of-ways may cross ground with low bearing capacity. Right of way subgrade undergo deflection (strain) as loads (stress) are applied. The amount of strain or deflection of the subgrade caused by loading of a train is proportional to the stiffness of the subgrade materials. Some soils, such as tamped ballast, are very stiff and resist loads well. Other soils such as soft clay, peat, or loose sand have low stiffness and undergo substantial movement under loads. It is very desirable to have the stiffest possible material in a track subgrade. Stiff subgrade material limits deflection under load, reducing track roughness and occurrence of track defects. Mass stabilization is a geotechnical method that can be used to improve the bearing capacity or stiffness of soil in these right-of-way. Mass stabilization involves mixing binding agents into soil subject to treatment while the soil remains in-place or insitu. Variations in the design or areas subject to treatment can be used to address transmission of vibration to adjacent structures."

Jan 1, 2015

By Michael J. Weaver

Urban redevelopment projects are occurring more frequently than ever before as urban greenfield sites become limited and city planners and devel- opers attempt to revitalize existing underdeveloped neighborhoods. How- ever, because of the past usage of many urban sites (some dating back 100 years or more), designers and construction teams have to not only engineer founda- tions to accommodate the subsurface soil and ground water conditions, but also to work around the relic founda- tions or structures that have been left behind from previous developments. In these cases, a one-size-fits-all approach to foundations may not yield the most cost- and schedule-effective approach, and hybrid foundation systems have to be evaluated.

Apr 1, 2022

By Brian T. Nereson, Michael C. Penney

"This technical paper was prepared to describe the general process by which the authors designed a column-supported load transfer platform (LTP) for support of asphalt-paved runway and taxiway embankment areas over soft organic soils, the major tasks and observations made during construction of the system, and the outcome of the system design and construction. The LTP system was designed using the method described in the BSI Standards Publication Code of Practice for Strengthened/Reinforced Soils and Other Fills, BS 8006-1:2010 (BS8006), to achieve performance objectives for the project. The design also used other criteria based upon the authors’ engineering experience and understanding of the expected interaction between soils, structures and geotextiles. The design and construction process described herein resulted in a successful project. The authors identified that full-time engineering oversight during construction was of high importance and provided a high degree of value to the project. The authors’ intimate knowledge of the potentially adverse effects of variations in construction practices promoted timely identification of construction deficiencies that could have affected the reliability of the system. This resulted in corrections and modifications being made, while materials were still accessible, to protect the intended performance of the finished system.INTRODUCTIONThe site is located in Marshfield, Massachusetts. The surrounding area is flat and contains significant wetlands with a water table at or near the ground surface. Prior to the improvements described herein, the site was already developed as an existing municipal airport with an approximately 3,000 linear-feet asphalt-paved runway oriented in a northeast/southwest direction (northeast end referred to as Runway 24 and southwest end referred to as Runway 6; Fig. 1). The site is located approximately 0.5 to 1 mile (Runway 24 and Runway 6, respectively) from the Atlantic Ocean.The improvement project included total extension of approximately 550 linear feet of asphalt-paved runways and taxiways over existing wetlands that consisted of soft, organic soils with varying but significant depths (Fig. 2). An initial geotechnical assessment performed for the project identified that the subsurface conditions were not suitable to support the proposed runways and taxiways in their existing state."

Jan 1, 2016