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By Pete Howell, Patrick Granitzki, Alicia Plinio, Janitha Batagoda

The New York City Housing Authority (NYCHA) Red Hook Houses was subjected to damage during Superstorm Sandy. As a result, the NYCHA has an ongoing project known as Restoration Associated with Sandy Recovery Program to improve the resistance against future storms. The specific project included 28 residential buildings and several service buildings within the Red Hook Development. The subsurface conditions within the eastern portion of the site included existing fill material underlain by varying stratums of very loose, loose and medium dense silty sands followed by very soft to medium stiff clay or dense silty sands. The western portion of the site included existing fill material, very loose to medium dense silty sands and organic clayey silts underlain by very soft to medium stiff sandy silts. Based on the geotechnical report, a conventional driven steel pile system was specified containing two pile depths. As part of the project bidding, an alternative pile type was recommended and analyzed to provide quicker installation, reduce vibrations, reduce noise, and provide relatively large cost savings. Due to relatively high lateral loading, an innovative double steel casing drilled displacement piles was proposed as the alternative pile option. Field testing proved the piles capable of the required project capacities and the use of drilled displacement piles as the best alternative for the project and accepted by the NYCHA.

Oct 1, 2022

By Thomas Hyatt, Brandon Phetteplace, Camilo Alvarez

A test pile program was undertaken at a project site in Ain Sukhna, Egypt for an import/export oil jetty. Two 1219 mm diameter open ended steel pipe piles were evaluated at two separate test locations. Each test pile was dynamically tested during initial drive utilizing a Pile Driving Analyzer (PDA). Restrike testing was also performed to evaluate the time dependent soil setup. One static compression test and one static tension test was performed at each test location. A correlation of the static and dynamic load test results was established to develop a driving criteria for the piling across the two kilometer project. The constructability benefits of shorter piles will be discussed in more detail, given that the pile lengths were shortened by 9 to 10 meters on average. Lastly, the use of a four pile linear layout to perform both compression and tension tests will be covered. INTRODUCTION With the increased number of Very Large Crude Carriers (VLCC) & Ultra Large Crude Carriers (ULCC) being used to transport oil products around the world, companies and/or nations are presented with the challenge of transferring these products to and from the carriers in deep water scenarios, typically 15 to 20 meter depths, to accommodate the vessels draft. One option for loading/unloading the oil products from a VLCC or ULCC would be to transfer to/from smaller vessels several miles offshore, whereas the most economical option is to unload directly to a pipeline via a berth/jetty platform near shore. These berth platforms must be designed to withstand multiple loading scenarios while these carriers are moored and transferring their products. The use of Large Diameter Open Ended Pipes (LDOEP) piles are a common foundation choice for this offshore application. One of the drawbacks of LDOEP piles, especially across a large project site, is that there can be extreme variability in the pile driving behavior. This can be caused by either a change in soil conditions or the performance of the soil plug. Due to this variability, it is important to verify throughout the duration of the project that the piling is being installed to the correct criteria as established during the load test program. A well designed driven pile load test program, preferably with the combination of Static Load Testing (SLT) and Pile Driving Analysis (PDA), should develop a driving criteria that can allow the contractor and owner to monitor any change in driving behavior.

Jan 1, 2019

By Sarah Ramp, Daniel V. Cacciola, Justin Labrozzi, Shafiq I. Siddiqui, Faisal Ahmed

"Construction of embankments up to 34 ft in height for twelve ramps and roadways needed for the New Jersey Turnpike Interchange 14A project required ground improvement. The subsurface conditions, consisting of up to 30-ft thick layer of highly-compressible peat and organic soils, would induce up to 8 ft of primary and 4 in. of secondary consolidation settlements to the embankments over a long period of time. Innovative ground improvement solutions were needed to meet unique challenges posed by the poor subsurface conditions, space and existing utility constraints, aggressive construction schedule, and massive size of the project. A variety of ground improvement techniques were utilized in six different zones of the embankments to limit settlements and ensure stability of the embankments. These techniques included preloading with surcharge and prefabricated vertical drains (PVD), load balancing using light weight fill, and concrete column rigid inclusions (RI). Additionally, augercast piles with load transfer platform were used under an existing bridge with low vertical clearance. An innovative approach consisting of preloading with surcharge and PVDs followed by installation of RI was needed in one of the six embankment zones with the worst, i.e., very soft, soil conditions. The design of the RI was performed by a specialty ground improvement contractor (SGIC) using Plaxis 2D and 3D softwares. The performance of the ground improvement systems was verified and monitored by load tests and instrumentations. This paper presents details of the ground improvement design, construction, monitoring results, and lessons learned, with a focus on the RI.INTRODUCTIONNew Jersey Turnpike Interchange 14A is located within the cities of Bayonne and Jersey City, in Hudson County, New Jersey. The New Jersey Turnpike Authority (NJTA) identified Interchange 14A as an area of mass congestion in need of redevelopment to improve the increasing demand of traffic and roadway safety. The New Jersey Turnpike Interchange 14A project included the construction of twelve (12) new roadways, in addition to the construction of four new bridges. The limits of construction are shown in Fig. 1.The fill height required to construct the roadway embankments varied from 2 to 34 ft. The proposed embankment side slopes varied from 6H: 1V to 2H: 1V. Additionally, mechanically-stabilized-earth (MSE) walls were utilized to retain the embankment fill along some segments of the roadways. As shown in Table 1, the proposed roadways were divided into six zones, based on location, subsurface condition, and embankment height."

Jan 1, 2017

By P. Kiruthika, A. Murali Krishna

Soil liquefaction is a dangerous phenomenon that involves huge damages during strong earthquake ground motion event. Stone columns (SCs) are widely used as liquefaction mitigation element which is expected to perform the improvements against liquefaction hazard by densifying, increasing the stiffness and rapid dissipation of excess pore water pressure in the surrounding soil. Although in the recent times few studies on the behaviour of stone columns in the seismic zone has evolved, the performance of SCs in the multi-layered soils is not extensively examined. This paper presents the numerical investigations on the performance of SCs installed in the multi-layered soils as a liquefaction mitigation measure against the seismic loading. The acceleration time histories, Excess Porewater Pressure (EPP), vertical displacement and stress ratio evaluated along different depths using PLAXIS 2D. With the installation of stone column there is a considerable reduction in the acceleration amplitude, which in turn reduces the EPP and vertical displacement at different locations and the amplitude of reduction depends on the soil stiffness levels at the depth.

Sep 1, 2022

By J. Erik Loehr, Minh Uong, Andrew Z. Boeckmann, Sarah G. Myers

"The University of Missouri performed a lateral load test program involving 32 drilled shaft load tests for the Missouri Department of Transportation (MoDOT). Tests were performed at two MoDOT geotechnical research sites, and all shafts were founded in shale. Shafts were instrumented to measure the displacement of the shaft head, and the structural response of each shaft was interpreted from strain gage data and from ShapeAccelArray (SAA) data. The SAA is a chain of rigid segments with sensors that use MEMS (microelectromechanical systems) technology to measure the tilt of each segment/joint. The measuring principle of the SAA is therefore similar to that of an inclinometer. The SAA device was placed in a casing installed in the center of each test shaft to provide a continuous record of deflection along the length of the shaft throughout each test.Bending moment profiles were calculated from strain gage data and from SAA data. Interpretation of bending moments from measurements of strain (via strain gages) and displacement (via SAA) is a nontrivial exercise, primarily because the bending stiffness, EI, is nonlinear and greatly influenced by concrete cracking, which is difficult to predict. The procedure used for this work predicted values of bending stiffness along the length of the shaft as a function of the bending curvature, which was interpreted from the SAA data. Values for bending stiffness as a function of curvature were computed using Ensoft LPile v2012. Bending moment profiles from SAA data were typically similar to those from strain gage data. The SAA bending moment profiles were often “noisier” than the strain gage bending moment profiles, but the SAA bending moment profiles had more data points since the SAA chain was continuous from the top to the bottom of each shaft."

Jan 1, 2017

By Emad Farouz, Ehab S. Shatnawi

"The increasing demand for small deformations and high-capacity drilled shafts without enlarging drilledshaft diameters has motivated the development and increasing use of a base grouting (BG) technique. This technique has been demonstrated to improve drilled-shaft capacity, especially for shafts tipped into loose cohesionless soils. Nevertheless, there remains considerable uncertainty in predicting the performance of base-grouted shafts, particularly for shafts tipped into cohesive soils. To date, there are only two documented design methods for estimating the axial geotechnical resistance of base-grouted shafts: Tip Capacity Multiplier (TCM) and Axial Capacity Multiplier (ACM) methods. A comprehensive test program was carried out during the design phase of the Wisconsin Zoo Interchange project to help optimize the flyover ramp’s foundation design. The test program included installing and testing one base grouted shaft and one ungrouted shaft at two sites with different ground conditions. Based on test results, it was concluded that prediction of the TCM method is well correlated with the measured values for both cohesive and granular soils; however, both methods tend to underestimate the axial resistance. Results also highlighted the importance of the base-grouting criteria in taking full advantage of the base grouting.INTRODUCTIONBase-grouted drilled shafts (BGDS), also known as post-grouted drilled shafts, consist of conventionally installed drilled shafts that contain access grout tubes placed within the shaft during construction. After installing the drilled shaft and achieving the pre-established concrete strength, grout is injected at the shaft tip through the access grout tubes to improve soil behavior around the drilled-shaft base. The tip grout injection improves the overall shaft capacity and reduces settlement through Densifying the in situ soils, compressing any debris left by the drilling process, preloading the soil beneath the tip to mobilize the shaft base resistance within service limits, increasing the tip area, and increasing the side resistance in the lower portion of the shaft."

Jan 1, 2016

By Chris Leach, Lucie Spencer

This case study describes the geotechnical aspects of the basement construction for a multi-storey, residential and hotel complex located in the newly developed Elizabeth Quay precinct in Perth, Western Australia. The development included a three-level basement for car parking covering the full site area which was constructed using the top-down construction sequence. Soil conditions generally comprised 2m of fill overlying medium to dense clayey sands that in turn were generally overlying a very stiff clay stratum at approximately 13m depth. Bedrock level was generally encountered at approximately 22m to 35m below ground level. The ground water table was at a depth of approximately 1m below the existing ground surface level. A site boundary basement wall was constructed using a diaphragm wall retention system. The majority of the vertical loads from the building were transferred to the Kings Park Formation (KPF) bedrock through the use of foundation piles constructed by the CFA method. The CFA piles were installed from existing ground level, resulting in approximately 9m sacrificial concrete length from pile platform level to basement 3 (B3) level. The permanent column loads are such that a single CFA pile was not structurally adequate. To allow a full CFA foundation system to be adopted, an innovative design and construction approach was developed for these heavily loaded columns. This paper discusses the site technical details and the design and construction aspects required to meet the challenges offered by this project.

Nov 1, 2022

By Alexander Filotti, Richard Kalson

"In the last decade, the construction industry has witnessed significant changes in the project delivery systems and contractual relationships between the general contractors (GC) and Deep Foundation Specialty Contractors. The Deep Foundation industry, especially including industry specialty subcontractors, have experienced a significant increase in requests that project risks be transferred through contract documents to subcontractors and suppliers with a decrease in margins for the industry. GCs regularly revise their form subcontracts to take into account recent experiences/contractual trends and newly issued judicial precedent, an exercise that is less frequently undertaken by subcontractors and suppliers. These contradictory trends are at the base of the ethical analysis of subcontracts that comprises the subject matter of this paper. Using contracts as a risk management tool in order to mitigate the general contractor’s risks in the context of dynamic changes in the legislative environment will also be addressed. Furthermore, another possibility for risk mitigation for the industry is to actively promote the introduction of the latest technical developments into the contract documents.CONTRACTS’ ETHICSFor thousands of years, ethics have been a constant presence in our lives and have been debated by different branches of philosophy. In modern times, ethics in business started to be an imperative for the success of a globalized economy.“Ethics are standards by which one should act based on values. Values are code beliefs such as duty, honor, and integrity that motivate attitudes and actions.” (Rumbaugh 2004). Some of these values and actions have been carved in legislation in general and in business legislation in particular. More and more, unethical business practices (e.g., corruption) are identified as the root cause of poverty, underdevelopment, and war around the world. In the context of contract ethics, three aspects are of interest:•,Ethics of contract construction•,Ethics of contracting processes•,Ethics of risk allocation in contracts"

Jan 1, 2016

By Hyu-Soung Shin

This study is concerned with the characteristics of the behavior of steel-concrete composite drilled shafts, a material that is used for large bridge foundations, and especially for weak submerged ground conditions. Depending on the loading or boundary conditions considered, the behavior of foundation will vary. The bearing capacity of steel-concrete composite drilled shaft is influenced by initiation and propagation of fractures along the interface between steel casing and filled concrete. The interface effect is taken into account with the following two simplified cases: (1) detached model with free interface (no shear stiffness of interface) between concrete core and steel casing, (2) confined model by an upper steel cap with free interface. In the confined model, it is intended to have an unified behavior of composite shaft between concrete core and steel casing but there is interface between them. Intensive numerical studies have been undertaken to investigate detailed behavior of the composite shaft. In this study, 3-D finite element analysis is employed. Ground conditions typical of those encountered for the design of drilled shaft under water are considered affecting the behavior. Also, an attempt is made to generate possible combinations of the loads which have been considered in fields. Detailed characteristics of the stress and displacement distributions are evaluated to understand the mechanisms of composite shafts.

Jan 1, 2007

By Mario A. Terceros Herrera, Mario Terceros Arce, Antonio Marinucci

This paper describes the general principles of the expander body with post-grouting (EBI) system, and how it is similar in nature to a large-scale pressuremeter device. The results from the installation of an EBI can be used to provide information about the stress-strain characteristics of the soil adjacent to the device and to compute estimates of nominal axial resistance. As the EBI expands during grouting, pressure is applied to the in-situ soil surrounding the device thereby compacting/densifying the soil. The nominal axial resistance for small diameter piles/ground anchors can be increased due to the greater soil stiffness and shear strength around the device, larger surface and end area, and improved soil-to-EBI interaction in side resistance. The shape of the response curves depends on the geotechnical conditions of the soil (e.g., in-situ stress state, strength, and stiffness) and the installation method of the piling/ground anchor. This technique has been used successfully with different pile types and ground anchors in a wide range of conditions from very loose sands/silts to very dense sands and medium-dense gravels as well as in soft to stiff clays. This paper also describes a mini case history in which 80 piles were installed to support an office building, and the results of the static axial compression load tests performed on a production FDP+EBI pile is also included.

By Henry H. Tayler, Eric Sturel

1 Triton Square was originally a six-storey building with a one-level basement located within a commercial development near Euston, London. It was designed and constructed in the 1990s and the foundation scheme comprised straight shafted London Clay piles arranged singly beneath columns. The scheme added three storeys and a five-storey infill in the central atrium area to increase the building floorplate by 70% and maintained the usability of the basement space. As the loads to support the additional floorplate area were greater than the capacity of the existing foundations, an optimised strengthening scheme of small diameter piles installed within the existing basement and a slender retro-fitted raft was installed to augment the existing piles. The re-use and strengthening of almost all of the existing foundations enabled re-use of a very high proportion of the superstructure and in approximately 35,000 tonnes of concrete and 1,900 tonnes of reinforcement and structural steelwork being re-used. The structural embodied carbon for the refurbished building scheme is estimated at an average of 136 kgCO2e/m2, achieving a Structural Carbon Rating Scheme (SCORS) “A” rating with components detailed in the paper.

May 1, 2022

By Alexander Filotti, Richard Kalson

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

Jan 1, 2017

By Anahita Modiriasari, Benjamin S. Rivers

Measurement while drilling (MWD) is a subsurface exploration technique associated with real-time and continuous monitoring and recording of drilling data during the drilling process. This technique can be used for underground investigations to differentiate ground strata, detect the presence of fractures and voids, and evaluate geological features and mechanical properties of geomaterial. When MWD is used for geotechnical investigations, it can improve site characterization, identify variable conditions, improve design and construction, lead to shorter project delivery times, reduce the cost and risks associated with limited subsurface data and geotechnical uncertainties, and maximum return-on-investment. Given these benefits, MWD is gaining attention among transportation agencies and the geotechnical industry. Federal Highway Administration’s (FHWA’s) innovation deployment program “Every Day Counts (EDC-5)” includes the implementation of Advanced Geotechnical Methods in Exploration (A-GaME), which aims to implement effective, underutilized subsurface exploration methods, including MWD, in U.S. practice. This paper provides an overview of the MWD technology for geotechnical site investigations and presents a case history where MWD was employed to design deep foundation for the construction of a building in Massachusetts. The advantages of this technology for risk reduction and project cost and time saving are also discussed.

Oct 1, 2022

By Ambarish Ghosh, Chitralekha Ghatak, Tanumaya Mitra, Tarun Sengupta, Sajib Das, Sankar Kumar Nath

"Currently construction of important structures like bridges, flyovers and high rise buildings in and around Kolkata are in full swing. These structures have mostly pile or well foundations. The design methodology and construction techniques are being employed keeping in view both the safety and economy of the project. The data presented in this investigation have been taken from Geotechnical Investigation report of Component B in connection with construction of Extradosed Cable Stayed Bridge over River Hooghly in Hooghly and Nadia district of West Bengal, India. The investigation site is located within close proximity of Eocene Hinge Zone which is being taken as the principal contributor of Earthquakes in and around Kolkata. Considering the importance of the project detailed and exhaustive geotechnical investigation has been carried out and site specific response spectra have been generated for analysis and design of the bridge. This paper presents site specific response spectra, liquefaction analysis and comparison of lateral load carrying capacity of pile using Winkler approach and IS 2911 guidelines.INTRODUCTIONPile foundations are used to transfer the load of the super structure through soft soil deposit to deeper bearing stratum by means of skin friction or end bearing or both. Pile foundations are regarded as a safe alternative for supporting structures in seismic areas and have been used for this purpose in non-liquefying as well as liquefying soils. But their design in case of potentially liquefiable soil is quite different from that of non liquefiable soil. In liquefiable soil the progressive buildup of excess pore water pressure will cause stiffness degradation and loss of strength which in turn will induce additional shear force and bending moment in the pile. The mechanism of pile behavior in liquefying soil has been investigated by several investigators in the recent years based on observations of pile performance during earthquakes and studies in the centrifuge and Shake Table tests. Exhaustive geotechnical investigation has been carried out along the proposed alignment of the Extradosed Cable Stayed Bridge i.e., along Baropara, Bansberia ROB, Ishwar Gupta Bridge, Saraswati River to collect disturbed as well as undisturbed soil sample, to develop average soil profile and to determine the design parameters. The proposed project site is very close to Eocene Hinge Zone, which is basically a strike slip fault, capable of generating an earthquake of Mw 6.7. Thus it is evident that the proposed Bridge needs to be designed considering the adverse geo-hydrological condition as well as the earthquake aspects needing special attention following the state-of-the-art technology as guided by relevant codes and published literatures. Considering the soil profile of these locations ground response analysis has been carried out using equivalent linear method to determine the site amplification. Site specific response spectra have been developed for the four zones and zone factors have been determined. The computed zone factors are 0.198g, 0.195g, 0.195g and 0.20g for the four zones respectively, much higher than the zone factor 0.16g, which is for zone III, as stipulated in IS 1893:2002."

Jan 1, 2015

By Scott Webster

Dynamic pile Monitoring Services (DMS) have been used for testing of offshore piles for several decades. However, most of this testing was to measure hammer performance and pile stresses rather than pile capacity or soil resistance. As the need for more economical solutions for foundation support increases, the use of DMS has provided a better means of evaluating in-place pile capacity for offshore structures, and therefore a method of determining pile acceptance. The authors have been involved in several offshore projects where DMS has been the primary source of data for acceptance of the driven pile foundations. The use of DMS for evaluation of offshore foundations requires considerations quite different from land applications and these considerations are often necessary for the careful and thorough analysis of the collected data in nearly real time for determination of pile acceptance. Case Method capacity estimates are often of little use due to the non-uniform cross sections of the foundation piles and their deep penetrations. Therefore, capacity assessments should be made using CAPWAP which is a signal matching program whose utility and reliability has been proven on thousands of projects every year, both on land and offshore. Depending upon the soil conditions at a given location, capacity assessment after soil setup effects may be necessary. In addition, tension capacity is often critical when pile refusal occurs significantly before the design pile penetration depth. Evaluation of uplift capacity can be accomplished by a CAPWAP analysis, which results in a total capacity prediction and its shaft resistance component. The use of hydraulic hammers for driving of these piles also adds the requirement of controlling hammer energy such that over-stressing of the pile is avoided. The calculation of non-axial stresses such as bending or eccentric stresses may also be involved in order to prevent pile damage.

Jan 1, 2010

By Brandon Buschmeier, Frederic Masse

"Inclusions are a type of ground improvement that provide an improvement of a soil mass by insertion of a material with better characteristics than the surrounding soils. There are primarily two types of inclusions: “Soft” inclusions which are constructed of granular material (Stone Columns, Rammed Aggregate Piers, VibroPiers...), and “rigid” inclusions which are constructed of grout inserted with or without pressure (VibroConcrete Columns, Controlled Modulus Columns, Soil Mixing Columns).While the central principle of the inclusions is similar (i.e., overall improvement of characteristics of the soil mass below the structure), the load transfer mechanism is radically different for each technique. Therefore, the applicable design methodology is specific to the type of inclusions and there exists no universal method of design which spans across all inclusions.This paper will present an in-depth comparison between the standard design methods used for “soft” granular-type inclusions (Priebe modified, Balaam & Booker, Goughnour & Bayuk...) and the methods used for “rigid” inclusions which mainly rely on finite element analysis. The paper will explain why the design for soft inclusion methods cannot be applied to rigid inclusions and vice-versa. Each design method will be reviewed in detail to better emphasize its limitations and advantages.Two case histories will also be presented; one for each type of inclusions in order to illustrate the concepts developed in the first part of the paper.1 INTRODUCTION1.1 GENERAL OVERVIEW OF GROUND IMPROVEMENT WITH INCLUSIONSThe use of ground improvement methods to provide the appropriate amount of foundation support is a growing and constantly evolving industry. Traditional structural foundation methods including ‘shallow’ and ‘deep’ foundations do not adequately address the wide range of settlement tolerances, soil conditions, and loading considerations inherent to each unique potential project. In some instances, ‘shallow’ foundation solutions are simply not feasible due to soil and loading constraints. Furthermore, ‘deep’ foundation solutions are used to ‘bridge’ the soft compressible soils, ensuring that the entirety of the load in the structure is transmitted through individual elements into competent layers below the ground surface (bedrock, dense residual soils). Highly concentrated structural loads are transferred into the individual elements by means of direct contact requiring the use of structurally rigid surficial components (structural slabs, grade beams, and pile caps).Ground improvement bridges the gap between these two traditional methods, offering adequate foundation support while using more costeffective techniques and design methodologies. Inclusions are a type of ground improvement used to provide a reinforcement of the soil mass through the vertical insertion of a material with better characteristics than the surrounding soils. Much like deep foundations, inclusions are installed through soil layers with high compressibility and/or low bearing capacity and terminated in a suitable bearing stratum. However, unlike deep foundations, ground improvement inclusions rely on a distribution of load between the soil and the inclusions. By doing so, some of the structural load is applied directly to the soil in a proportion equal to its bearing capacity and compressibility limits, while the rest of the load is shed into the vertical inclusions down to the bearing stratum. Load sharing is a critical aspect in the performance and design of the various ground improvement methods."

Jan 1, 2015

By George Filz, Morales, Carlos, Bertero, Filippo Maria, Alessandro, Leoni

"The Deep Mixing Method (DMM) represents a viable solution to improve adverse geotechnical properties of foundation soils for many practical applications. A pre-construction soil investigation campaign is necessary to assess soil properties and to retrieve samples of different soil layers for a laboratory Bench Scale Testing program (BST). The BST has to be designed using various binder types, binder contents, and water/cement ratios in each of the soil types. Following the laboratory program, a full scale Field Test (FT) is typically necessary to verify the results of the BST. This paper will highlight the differences and the importance of performing both pre-construction laboratory tests and field tests to ascertain the proper mixing parameters in the different soil layers. Comparative analyses and interpretations between the lab and field stages, along with accumulated information about soil properties and quality control (QC) results, allow fine-tuning the production parameters throughout a project. Three Deep Mixing Method projects, where both laboratory and field tests were executed, are illustrated: (1) The LPV 111 Project (New Orleans, LA, USA): DMM was used for ground improvement/foundation strengthening to stabilize and support the burden of a new levee raise; (2) The Rio Puerto Nuevo Project (San Juan, PR, USA): DMM was applied to improve the soils adjacent to a 90"" forced sewer main relocation and to improve the soils for the base of a new drainage channel; and (3) State Road 83 (US 331) over Choctawhatchee Bay project (Walton County, FL, USA): DMM was applied to stabilize the causeway sections of the bridge enhancement project. Data recorded during laboratory and field tests for these projects were analyzed and interpreted to select the most appropriate construction parameters to provide a final high-quality product.INTRODUCTIONThe Deep Mixing Method (DMM) represents a viable solution to improve adverse geotechnical properties of foundation soils in many situations. The effectiveness of working parameters depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product.Generally a pre-construction soil investigation campaign has to be performed to assess soil properties and to retrieve samples of different soil layers for the laboratory Bench Scale Testing programme (BST). The BST has to be designed using various binder types, binder contents (or cement factors - CF), and grout water/cement ratios (W/C) in each of the soil types; the selection of the different combinations and dosages for the BST is based on past extensive experiences on similar materials. Following the laboratory programme results, a full scale Field Test (FT) has to be designed and executed, installing several DMM elements to verify the results of the BST and fine tune the construction parameters, with the appropriate binder type and dosage and the most effective equipment and tool configuration."

Jan 1, 2015

By Joseph A. Mann

"Soil mixing is a proven solution for the construction of ground improvement adjacent to sensitive structures due to the use of computer controlled and monitored equipment. The precision to which geometry is controlled can often be the deciding factor for selection of soil mixing versus other means of ground improvement. Protection of existing structures and utilities requires careful planning, investigation, and may demand supplemental control measures. During planning, it is imperative that the process be fully developed by the project team to ensure proper control measures are budgeted; otherwise, the success and safety of a project can be jeopardized.This paper discusses case histories of soil mixing performed in close proximity to large, sensitive, and critical utilities, including foundation support for an existing earthen dam impounding a water reservoir in upstate NY, a buffer zone for a tunnel drop shaft at an operating wastewater treatment plant in Washington DC, and a containment system to protect a major water line along an interstate widening project in Baltimore, MD. The function of soil mixing as ground improvement varied; however, the selection and application of the technique versus other means of ground improvement was specific due to the controlled manner of construction with soil mixing. Through the three case studies, small diameter (3- ft [0.9 m]), large diameter (8-ft [2.4 m]), and mass mixing applications will be discussed. Furthermore, the case studies offer insight into how the geotechnical community in the Mid-Atlantic utilizes soil mixing technology for widely varying applications. Additional topics of discussion will be the design and construction of the ground improvement systems, procedures and execution of the work to protect existing structures, and the QA/QC methods, procedures, and results from the projects.INTRODUCTIONWet soil mixing, also known as the Deep Mixing Method, is a ground improvement technique that improves the characteristics of weak soils by mechanically mixing them with cementitious binder slurry. To construct columns, a powerful drill advances a mixing tool with radial mixing paddles located near the bottom of the drill string. The binder slurry is pumped through the drill string to the tool as it advances and additional soil mixing is achieved as the tool is withdrawn.Wet soil mixing is applicable in a wide range of soils. Soil mixing has been performed at depths more than 100 lf (30 m). Soils vary widely in their ability to be mixed, depending on the soil type, strength, water content, plasticity, stratigraphy, and texture. Almost any soil type, including organics, can be treated with certain soil mixing technologies, although they may require high binder contents and/or pretreatment to achieve the required results. In cases when the target soil is very soft, including some very weak clays and peats, 100% of the soil may require treatment. This complete coverage of soil mixing is referred to as mass mixing."

Jan 1, 2015

By Steven R. Ahlfield, Ali Ghandeharioon

A wastewater treatment plant commissioned in 1978 is undergoing a major expansion. Planning various phases of the 8-hectare expansion at this site requires an understanding of the site response during and after construction, and the potential impact on adjacent properties and infrastructure. The expansion project requires nominally 5 m of site grading fill for flood protection. The site is underlain by loose to compact fine sand over firm to very stiff clay stratum that extends to great depths. Ground improvement is required to mitigate the liquefaction hazard in the fine sand stratum, and preloading is proposed to reduce post- construction settlements in the deep clay. Site development and foundation systems for the plant expansion project were evaluated by conducting settlement analyses which accounted for the historic and future site loading and 3-D modeling of soil layers with interpolation between borehole and cone penetration test (CPT) locations. The numerical model was calibrated to match short-term and long-term settlements measured at the plant site. The analyses were carried out to assess the effects of past loading, proposed preload and surcharge heights, lateral extents and durations as well as vibro-replacement ground improvement on post-construction settlements. Two design options were considered for the preload footprint across the site and foundation system for proposed facilities. It is shown that limiting the preload extent and founding some of the proposed structures on deep friction piles reduce the predicted settlements of adjacent infrastructure and result in reasonable performance for the proposed facilities. INTRODUCTION A wastewater treatment plant commissioned in 1978 will be replaced with a new plant on an undeveloped portion of the site to provide wastewater treatment for an expanded service area. The existing facilities must remain in operation until completion of the new plant. The site grade will be raised nominally 5 m for flood protection. The large areal extent of the site grading fill and plant structures will cause stress changes extending to great depths in the underlying soils and result in settlement of the existing and new structures. Historic settlement of the existing facilities has been tolerable for plant operations, but no settlement performance data was recorded during site development and post-construction from 1978 to 2007. Development of the 8-hectare expansion at this site is planned in three phases to reduce the overall construction schedule. Planning for each phase requires evaluating the effects of various site development activities from start to completion of expansion and during the design life (i.e. post-construction period), and the potential impact on existing wastewater treatment facilities and adjacent properties and infrastructure including an adjacent viaduct structure. Figure 1 presents the site plan and three distinct site development phases considered for the plant expansion.

Jan 1, 2019

Jan 1, 1998