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"1 INTRODUCTIONThe use of nondestructive testing (NDT) methods to evaluate the integrity of Augered Cast-in-Place (ACIP) and Drilled Displacement (DD) piles has been a subject of significant debate among engineers, contractors and NDT practitioners. This guideline document will illustrate the importance of reviewing all available information in conjunction with the NDT records. ACIP and DD piles have unique properties that must be considered when using a specific NDT method. Any evaluation of the integrity of an ACIP or DD pile must also include a thorough review of the detailed pile installation records and the site specific soil conditions. Long or theoretical descriptions of the methods have not been included in this publication. More detailed information about these NDT methods including their theoretical and historical backgrounds can be found in DFI’s Manual for Non Destructive Testing and Evaluation of Drilled Shafts (2004). Additional information can also be found in the more comprehensive textbook Nondestructive Testing of Deep Foundations by Hertlein and Davis (2006).1.1 PurposeThe intent of this guideline is to provide practical guidance for the proper interpretation of NDT results on ACIP and DD piles. Short descriptions of the main integrity methods available are provided along with several examples of how to use all of the information available to make sound engineering judgments about the results. This publication is a state-of-the-practice guideline to promote accurate engineering evaluations.For engineers inexperienced with NDT, these guidelines provide sufficient background information on NDT methods to help understand the limitations of the testing, assess the results presented to them, and formulate appropriate questions. This is particularly important for engineers charged with the responsibility to determine from those results what, if any, consequences there may be on the performance of the structure under construction."

Jan 1, 2016

By Garland Likins

Where soil conditions are favorable, augercast piles have significant economic advantages, but they also have some uncertainty due to the in construction methods. To confirm structural integrity, static testing can be performed on a small sample of piles. Other Non-Destructive Evaluation methods like Pulse Echo are frequently specified for a large percentage of the remaining production piles. However, such NDE methods require testing the pile after the grout/concrete has hardened. If problems are found, then the repair or replacement can be relatively expensive. The confidence in the quality of these piles can be improved by automatically monitoring the grout pumped as a function of depth during the grouting phase of installation. If a low grout volume is detected, the pile can be redrilled and regrouted immediately while the piling rig is still in place and the grout still fluid. This considerably reduces remedial costs. To be effective, such installation monitors must accurately determine both grout volume and depth during installation and be rugged simple to operate. Such an equipment can be of great help to the installation crews. The assurance gained may reduce the need for subsequent NDE tests. The quality of inspection of driven piles depends heavily on the inspection personnel. While inspection is critical in a good installation, it is sometimes assigned a low priority. Inspection personnel in many cases are technicians with little pile experience. They may not understand the project needs or even how the pile driving equipment works. The task is often monotonous and any distraction makes accurate record keeping difficult. In some cases inspection is totally ignored for lack of qualified personnel. Electronic systems can automatically and accurately monitor driven pile installations and include documentation of certain hammer performance parameters. This paper describes equipment available and routinely in use for automated monitoring of both augercast and driven piles and demonstrates applications on typical construction sites. The paper also discusses benefits and limitations of the alternative NDE tests. KEYWORDS: Augercast Piles, Piles, Installation Monitoring, Pulse Echo Method, Integrity Testing

Jan 1, 1999

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 Y. M. Ha, T. D. Nguyen, D. T. Nguyen, H. K. Choi

Conventionally, cement deep mixing (CDM) columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern may be inefficient in cases of spread footings or shallow foundations. This paper first briefly introduces principles of an improved CDM method that can create head-enlarged CDM (termed PF) columns. A simple analysis approach was introduced to obtain optimal shape of PF columns that results in minimum settlement. The effectiveness of this improved method over the conventional CDM method was then illustrated by settlement analysis for an actual footing in a case study using two recommended analytical methods in the literature. Analysis results from the case indicated that by using the same amount of soil-cement mixed volumes, settlement from a footing on PF columns can reduce up to 10 % compared with that from the same footing on CDM columns. In addition, a material quantity comparison for the case indicated that to have the same settlement values the volume of each PF column can be reduced of around 10% compared with that of the CDM column. INTRODUCTION The cement deep mixing (CDM) method is one of the most popular methods in ground improvement works. Details on the method such as construction procedures, necessary equipment and recommendations are described in many references or manuals (e.g. Bruce et al. 2013, BS EN 2015, Kitazume and Terashi 2013). Conventionally, CDM columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern is found inefficient in cases of spread footings or shallow foundations as the upper soil layers are naturally weaker than the deeper ones but are subjected to larger amount of induced stress from the superstructures.

Jan 1, 2019

By D. Barber, A. D. Miller, P. A. Bray

The project was to develop an area within the existing West County Wastewater Treatment Plant which would enable the construction of a new Raw Wastewater Pump Station (RWPS) with a footprint of approximately 85 feet by 190 feet and a foundation depth of about 82 feet below grade and a new Short- Term Detention Basin (STDB) with a footprint of about 80 feet by 130 feet and a foundation depth that varied from approximately 3 to 24 feet below grade.. The excavation support system had to be designed to withstand both normal and the 100-year flood elevations. A Reinforced Soil-Cement Wall (RSW)was chosen to provide a hydraulic barrier which consisted of a single row of soil-cement elements installed along the perimeter of the area to be excavated. Steel wide flange beams were installed on 4 foot centers to support construction loads and be resistant to the lateral forces of the soil and hydrostatic pressures. The RSW was installed to a maximum depth of 104.5ft using a triple-auger drill rig with mixing paddles with a 2ft key into weathered shale providing a cutoff wall consisting of 53,150 square foot of treated soil. The project was to provide the initial design of the excavation support for the pumping station excavation support system and groundwater cutoff. There was 534 linear foot of soil-cement-bentonite wall installed and 106 - 80 foot long W21 x 121 wide flange beams installed on four foot centers into the alignment of the wall. Each element was drilled down into the weathered shale to obtain groundwater cutoff. Derek R. Guthrie Water Quality Treatment Center Pumping Package is the site for a new pumping station that will service Louisville, Kentucky residents. After unplanned long term exposure into the winter, the effects of freeze thaw cycles were evident.

Jan 1, 2017

By Alexander Scheuermann, Martin D. Larisch, David J. Williams

"Drilled displacement piles (DDP) have been used around the world for decades as foundation elements for structures and embankments. Typically the pile toes are designed to penetrate into stiff or dense soil formations to achieve sufficient base resistance. Recent research at The University of Queensland in Brisbane, Australia has discovered that the in situ stress conditions in stiff to hard clays is directly related to pile installation rates, which in turn are a function of the piling rig capacity and ground conditions. With adequate and constant pile penetration rates in situ stress conditions in the stiff to hard clay are increased by about 40%, resulting in significantly higher pile capacities. If pile penetration rates are too slow the in situ stress conditions are reduced considerably by remoulding and shearing of the clay, potentially causing reduced pile capacities. The paper presents the results of full-scale test piles at a stiff to hard clay site installed using different full-scale piling equipment.INTRODUCTIONDrilled displacement piling (DDP) is a piling technique in which a hollow stem, fitted with a purpose built displacement tool at the bottom, is drilled into the ground. Dissimilar to non-displacement piles, like Continuous Flight Auger (CFA) piles or conventional rotary bored piles drilled with kelly bars, the soil is not excavated during the DDP penetration process, but is displaced laterally and to a lesser extent vertically. The cavity created by the drilling tool is filled with highly workable concrete during the extraction process. The DDP technique is very economical providing high production rates and creating only marginal drill spoil, which has led to its increased global usage during the last decade. The typical DDP installation process is described in Figure 1."

Jan 1, 1900

By Kozo Takeda, Arashi Shimano

"Dry Jet Mixing (DJM) technique is widely known as soil mitigation technique with small ground displacement during installation comparing with other techniques. Some projects involving sensitive structures, however, require smaller impact than in conventional technique. In order to reduce ground displacement during DJM installation, this paper introduces systematic mixing technique, RD-DJM (Reducing Displacement – Dry Jet Mixing). RD-DJM is characterized by injection nozzle on the rim of mixing blade and fin plate on mixing shaft. These devices contribute efficient collection of injected air toward mixing shaft and result in reduction of ground displacement. The authors demonstrate successful performance of RD-DJM indicating difference between conventional installation and RD-DJM technique.INTRODUCTIONThe Dry Jet Mixing (DJM) method is one of the most common techniques in Japanese deep soil mixing field and characterized mechanical mixing of powdery binder with in-situ ground (dry-mixing technique). It is widely believed that DJM Method has great advantages in less quantity of binder to achieve the desired strength and less waste generation during installation.DJM method can meet the required strength with less binder content than wet mixing. And volume of binder of dry mixing is absolutely less than wet-mixing injecting considerable volume of binder slurry. This means that dry mixing causes less ground displacement compared with wet mixing.As the medium for forced feeding of the binder, the DJM method uses compressed air, which is blown from the mixing blade nozzles to scatter the binder and then recovered through the periphery of the mixing shaft to the ground surface. Because the binder is injected outward from the injection orifice at the root of the mixing shaft, a part of the air may escape to untreated areas due to the blockage of air recovery path around the mixing shaft. Figure 1 illustrates possible escaped air and leakage around installation location."

Jan 1, 2015

By José L. M. Clemente, John R. Davie

"Abstract An extensive pre-production static and dynamic pile load testing program was conducted for a coal-fired power plant. The static load testing program included axial compression, uplift (tension), and lateral load tests. Three types of piles were tested: Monotube, closed-end pipe, and step-tapered. The load tests were used to (a) determine pile driveability characteristics for each pile, (b) verify pile load response behavior, and (c) provide data to support the selection of a cost-effective piled-foundation system for the plant. A recent publication (Clemente and Lewis, 2013) describes the compression load testing program, the interpretation of instrumentation measurement results, and pile selection criteria. This manuscript describes site subsurface and groundwater conditions and installation of probe piles for testing, focuses on the uplift and lateral load testing program, and provides a comparative interpretation of the load test results.INTRODUCTIONThe pre-production probe pile load testing program described here was conducted for a 202-megawatt, coal-fired power and steam generating (cogeneration) facility. A schematic layout of the main plant (power block area) is shown in Figure 1, which also includes the locations of clusters of preproduction probe piles and boreholes drilled near these clusters.The load testing program included 24 pre-production probe piles driven throughout the power block area. The probe piles were driven at locations T-1 through T-8, shown in Figure 1. Three types of piles were driven at each location: Monotube pile; closed end, straight shaft pipe pile; and step-tapered pile. At each location, the three piles were driven in a row with the pipe pile at the center, and the center-tocenter spacing between piles was equal to about 1.5 m (> 3.5 pile diameters for the largest pile). No pile cap was used to connect the three piles, and the three piles driven at locations T-1 through T-8 will be referred to as pile clusters. A complete suite of static load testing (compression, tension, and lateral) was performed on each individual pile at Cluster T-2 and on the step-tapered piles only at Cluster T-8, shown in Figure 1.Clemente and Lewis (2013) provide details of the compression load testing program, the interpretation of instrumentation measurement results, and pile selection criteria. This manuscript focuses on the uplift (tension) and lateral load testing program. A brief summary of the site geology and existing subsurface and groundwater conditions in the vicinity of the test pile clusters is presented, with emphasis on T-2 and T-8. Probe pile driving results at T-2 and T-8 are also presented. Descriptions of the static uplift and lateral load test program at T-2 and T-8 are given along with a comparative evaluation of the load test results."

Jan 1, 2014

By E. Mongilardi

The construction of large underground openings through cohesionless or weak cohesive soils and under the water table in particular, often requires a ground improvement to be done from the surface or ahead of the excavation face in tunnelling problems. To this purpose various injection procedures have been used in the past and new outstanding techniques have been developed recently, such as "jet-grouting", extending the feasibility range. The paper presents a review of basic principles and practical design criteria with particular reference to the newest trends of development. Case histories have been selected within the experience of specialist contractor Rodio Co. showing the variety of problems solved by manifold grouting procedures and layouts, in widely different soils ranging from the sandy-gravelly alluvia of Milan to the soft marine clays of Singapore.

Jan 1, 2010

By Eric Brandner

Expansive soil formations can be found throughout the United States. When subjected to wetting, many of these formations have the potential to swell and exert large uplift forces which can significantly damage lightly-loaded structures. Designing an economical foundation that can resist uplift forces is critical to prevent damage to these structures. The current solutions to control uplift due to swelling soils, such as over-excavation and replacement of the expansive material, or drilled shafts, can be costly and problematic. Piles made from recycled polymer materials may provide a solution. Due to a lower coefficient of friction along the interface than piles made from traditional materials, solid recycled plastic piles can allow expansive soils to move nearly independently from the pile when wetted. This results in a much smaller magnitude of uplift force being transferred to the structure which minimizes the risk of significant structural damage. This paper presents the preliminary results of research conducted on the use of recycled plastic piles in an expansive shale environment. The preliminary phase of the project involved the installation of six 13 in. (330 mm) diameter recycled plastic piles at a test site on the South Dakota School of Mines and Technology campus. The piles varied in length from 15 ft. to 25 ft. (4.6m to 7.6 m). Two of the piles were subjected to a full-scale compression load test in order to determine ultimate capacity, while the additional four piles are being subjected to long-term monitoring of uplift movement. A cast-in-place concrete pile, with a diameter of 6 in. (152 mm) and length of 15 ft. (4.6 m), was also installed at the test site for monitoring. The preliminary results indicate that the use of solid recycled plastic piles is a viable alternative for support of lightly-loaded structures in expansive soil environments.

Jan 1, 2009

By Chu E. Ho

Jet grout column formation at large depths are prone to several uncertainties, such as inaccuracy in setting out boreholes, drilling deviation, soil variability and reduced jetting energy at the nozzle. This would result in shorter cutting distance of the jet, with potential lack of interlock between grouted columns. A design strategy for mitigating the risk should include a soil investigation program aimed at discovering potential variability in soil conditions at the locations of jetting. Determination of soil strength profiles with depth would be useful for evaluation of jetting parameters and prediction of the achievable cutting distance at any depth. Selection of design column spacing should include allowance for setting out accuracy, verticality of the boreholes and the achievable jet cutting distance. For deep jet grouting operations, it would be necessary to take into account the energy losses at the nozzle inlet; however the increase in the presiding pressure at the nozzle outlet at depth is small relative to the range of jetting pressures commonly employed and would not affect the cutting distance to any significant degree. Design column spacing should not be so close as to cause problems with ?masking? which may lead to localized ungrouted zones of soil. For effective field control, boreholes should be cased up to the top elevation of the grouted zone so that the orientation of the borehole can be measured prior to grout injection. An analytical equation for calculating the cutting distance is proposed for adjusting jetting parameters where necessary to compensate for drilling deviation and changes in soil conditions. It is preferable that jet grouting trials be executed at elevations that correspond to the actual production jet grouting depths for accurate evaluation of jet cutting performance.

Jan 1, 2008

By Robert C. Rabeler

Soil and Materials Engineers, Inc. (SME) has utilized drilled cast-in-place (D-CIP) piles on a number of projects in the midwest. These foundation systems have typically consisted of drilling an 8 to 9-inch diameter borehole with a rotary type drill rig or driving a casing with a small hammer. A structural steel member is installed in the center of the excavated space, and the borehole or casing is grouted to complete the installation of the D-CIP pile. This type of piling system has also been called: mini-pile, micro-pile, or drilled-in pier. The capacity of these piles varies depending upon subsurface conditions, as well as the structural capacity of the pile. The structural capacity can be modified based on the size and yield strength of the structural steel member. SME has used the D-CIP piles for underpinning of lightly-loaded structures for a number of years. Steel brackets can be welded to the structural steel member in the center of these piles, and the bracket extended underneath existing foundations to provide proper foundation support. D-CIP piles have also been used for new construction where access was limited. Recently, SME had the opportunity of providing design as well as construction monitoring services for a unique project where these piles were used, but at much higher capacity. The project involved adding seven additional floors on top of a five-story building (total of 12 stories). New columns were extended through the existing building to support the new floors. Access to construct foundations was available to one level of underground parking beneath the structure, as well as to a basement area. Access required equipment to travel through a 3-foot wide hallway. A special duplex drilling machine was used to access the foundation locations and to install the piles in a limited headroom condition. Eight-inch diameter D-CIP piles were extended to a depth of approximately 40 to 50 feet below grade and socketed into a dense clay till or sandstone, and No. 18 or No. 20 threaded bars were installed in the center of these piles. The design pile capacity was as high as 190 kips and were verified by a compression load test. The load test was performed with limited access and headroom. These piles were installed by Spencer White and Prentis Foundation Corporation (SWP). For conditions where rock or hard soils are encountered at reasonable depths, D-CIP piles can provide working load capacities comparable to larger driven steel piles. The ability of the equipment to access very restricted areas, combined with the high capacities results in a very attractive solution to a number of difficult foundation problems.

Jan 1, 1999

By Swaminathan Srinivasan, Aaron J. Muck

"When an opportunity arises to combine state-of-the-art concepts with advanced modeling tools, engineers need to take what they know and apply forward thinking to geotechnical solutions to promote the state-ofpractice. Such an opportunity was seized during the design and construction of the Great American Tower in Cincinnati, Ohio. The forty-one story Great American Tower at Queen City Square – currently the tallest building in Cincinnati – has not only changed the downtown skyline, it is also contributing to the advancement of the state-of-the-art use of auger cast-in-place (ACIP) piles as settlement reducers. Predicted settlements of a traditional mat foundation were excessive, and the costs and construction time associated with traditional ACIP piles extending to bedrock were not preferred. A mat supported on a limited number of ACIP piles, with the piles primarily acting as settlement reducers, was evaluated as the preferred foundation type.Promoting the unique soil-structure interaction of the foundation system with confidence required the use of sophisticated numerical modeling tools. Traditional standard penetration test boring data (SPT) was initially used to develop a numerical analysis of the soil-structure interaction using FLAC 3D software. The model was further modified with cone penetration (CPT) and pressuremeter testing (PMT), along with actual load test results on several ACIP pile elements of varying lengths, but all tipping above bedrock. Through a combined design team effort, and detailed numerical modeling analysis, ACIP piles were recommended for reducing mat foundation settlement. Instrumentation during and post-construction confirmed design assumptions and predictions. Integrating sound geotechnical concepts, and using advanced geotechnical analysis and design methods, traditional mat and ACIP pile foundations were successfully integrated into a unique foundation support system.INTRODUCTIONThe Great American Tower at Queen City Square in Cincinnati, Ohio is located within a region dissected by historical geologic deviances associated with the meander of the Ohio River and glacial progression/recession. Combining a challenging geology, with the development of a high-rise office building afforded the design team an opportunity to combine state-of-the-art soil-structure interaction concepts and method with traditional geotechnical engineering concepts. Such a combination required a variety of field tests, collaboration with the design team and owner, and geotechnical-structural modeling during the design phase. During construction, in addition to materials testing and observation, a variety of instrumentation systems were employed. Together, the data was used to corroborate the design model and make adjustments during construction and further substantiate design assumptions following construction."

Jan 1, 2015

By Leo Panian, Ryan Nagle, Priyanshu Singh, Gina Carlson, Wayne Magnusen

"This case study presents the design and construction of an integrated foundation and ground improvement solution utilizing deep soil mixing (DSM) and micropiles. 270 Brannan is a midrise office building in San Francisco that straddles the historic shoreline that was reclaimed in the 19th century. Subsurface conditions include shallow bedrock inland of the historic shoreline, and steeply dipping bedrock overlain by 60 feet of compressible deposits and liquefiable fill on the bay side. Project challenges included mitigating the liquefaction and lateral spreading hazards, addressing settlement concerns in the fill and the bay deposits, developing a cost-effective foundation support solution, assuring satisfactory seismic performance, and addressing construction restrictions with existing adjacent structures.DSM combined with micropiles was identified as the most cost-effective solution for the ground conditions. The DSM panels act both as a liquefaction mitigation mechanism and a foundation support system. Resistance to seismic overturning is provided by uplift-resisting micropiles. The DSM-micropile solution allows the use of efficient conventional spread footing foundations, integrating isolated micropile groups to anchor the shear walls. Successful installation of the system relied on a program of field testing to validate the design and conformance with the design criteria.INTRODUCTIONThe regular grid of surface streets within San Francisco’s South of Market (SOMA) district provides little evidence of the geotechnical complexities that lie below. In the late 1800s, sand dunes, bedrock hills, cliffs, marshes, and mud flats were flattened and filled, concealing their locations and characteristics. The 1906 San Francisco earthquake and fire leveled many buildings in SOMA; new buildings were built after 1906 – often on top of rubble and debris from the structures that came before. Locally, the combination of natural geology and historical interventions can produce complex subsurface conditions that vary dramatically over short distances. This is particularly true at locations where tidal mudflats once met bedrock hills at the shore of San Francisco Bay.This case study describes an integrated foundation and ground improvement system implemented for a multistory “Class A” office building at a complex SOMA urban infill site. The system utilizes cement deep soil mixing (DSM) in combination with spread footings and micropiles to address a range of design and construction issues, including liquefaction and lateral spreading mitigation; consistency of earthquake ground motions; shallow foundation support; seismic uplift resistance; and avoidance of loading adjacent basement walls. The system was implemented by a technically-sophisticated owner through a process that included constructive collaborations between the project geotechnical engineer, structural engineer, general contractor, and specialty foundation and ground improvement contractor(s). The system is designed to cost-effectively provide a high level of seismic performance."

Jan 1, 2017

By Patrick K. Wong, Richard Kelly

"The variability in strength and compressibility of in situ deep soil mixing products can be greater than the variability of the natural soil. However, satisfactory performance can be achieved by careful construction and an appropriate QA/QC program. This paper presents a case study on the use of deep dry soil mixing columns to support several embankments over soft clay along a highway project. Post-construction settlement monitoring indicated that good performance is achieved where the acceptance criteria are met, except in an area with high organic content. Embankments with contrasting performance are compared to the quality control test results which comprised laboratory testing of core samples as well as in situ test results such as pull-out and push-in vanes and conventional cone penetration tests. Drawing on the performance results and quality control testing, discussions and guidelines are given on quality assurance acceptance criteria and construction control testing regime for future projects.INTRODUCTIONBetween 2008 and 2012, the largest deep dry soil mixing (DSM) contract during that time in the southern hemisphere was carried out for the Ballina Bypass project. The project, comprising 12 km upgrade of the Pacific Highway located in northern New South Wales close to the border of Queensland, was commissioned by the Roads and Maritime Services (RMS) of NSW. The ground improvement contractor was Keller Ground Engineering (KGE) Australia. Seven different types of ground improvement techniques were employed for the project, ranging from low embankment strategy with nominal preloading, to surcharge with wick drains, light weight bottom ash fill, DSM, vibro-replacement stone columns, dynamic replacement, and vacuum consolidation (installed by Menard Bachy Pty Ltd). Different techniques were chosen depending on time program, cost, and performance requirements relative to proximity to piled structures (e.g. bridge abutments) and post-construction settlement and differential settlement for either rigid or flexible pavements at different locations.DSM was the most utilized ground improvement technique employed on the project, comprising a total of about 285 km of 0.8 m diameter columns to depths up to 18 m for the purpose of supporting bridge approach embankments and culverts with embankment heights up to 6 m. DSM was chosen due to the very soft nature of the clay soil with moisture content practically at liquid limit, and the relative speed and economy of the system. Dry cement powder at rates of 160 kg/m3 to 200 kg/m3 were pneumatically discharged via the hollow stem of the mixing tool, and mixed with the soil (using multiple horizontally mounted paddles on a single vertical stem) at high speed as the mixing tool is withdrawn."

Jan 1, 2015

By Lance A. Roberts

Micropiles are commonly utilized for applications other than foundation retrofit. In bridges, for example, micropiles can serve as the permanent foundation elements or can be used in temporary support applications. In this paper, a case study on the use of micropiles for the 18th Street Expressway Bridge rehabilitation/repair project in Kansas City, Kansas is presented. In the project, micropiles were utilized for support of six temporary jacking structures, which allowed the bridge to be lifted while repairs were completed. A group of six micropiles was required to support each jacking structure. The required compressive service load per micropile was approximately 300 kips (1300 kN) and the settlement of the micropiles under the service load was to be limited to 0.5 in. (12.7 mm). Two field compression tests were conducted as part of the project. The field load test data was integrated within a soil-structure interaction capacity approach in order to analyze and permit the shortening of the design bond length for the production micropiles.

Jan 1, 2009

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

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

Jan 1, 2017

By Vincent Tirolo

Two separate secant pile cofferdams were constructed as part of an extensive rehabilitation and modernization of the New York City Transit's Lexington Avenue/Third Avenue IND Station at 53rd Street in Manhattan. Major high rise structures and outpatient hospital facilities bordered the site. The roadway is an important east-west corridor in mid-Manhattan. In order to perform the construction of new escalator and elevator shafts over 250 linear feet of secant wall was installed to the top of rock or to the existing subway roof. Much of the secant wall was constructed from below a temporary roadway decking system using a low headroom rig. The roadway decking system was supported on shallow spread footings. The secant piles were drilled using crawler mounted hydraulic rotary drill rigs. The secant wall provided a watertight, rigid cofferdam that minimized settlement and other disruptions to existing structures and utilities. During later stages of the project the secant wall also supported the roadway decking system.

Jan 1, 2003

By Chiranjib Sarkar, Sibapriya Mukherjee, N Kumar Pichumani

With the rapid expansion of urban transportation systems, tunnels and cut & cover structures are considered as the only solution in improving the urban space congestion problem in mass rapid transit system. Therefore, it is necessary to accurately design underground structures with realistic assumptions and considerations of design parameters like site geotechnical data, water table, surcharge load etc. Over conservative approach provides not only uneconomical design but sometimes it also causes overdesign of the concerned structures. Water table depth has a significant role in some design aspects of underground structures like floatation check, lateral and uplift pressure on the buried structure, etc. In current practice of tunnel and cut & cover structure design, water table is assumed to coincide with the ground level. Most of the Design Basis Reports & Outline Design Specifications directly mention consideration of water table at ground level for floatation check and load calculations, etc. However, the actual scenario is different in most of the cities specially in northern, central, western and eastern regions of India except the coastal cities. In the present study an attempt has been made to carry out a parametric study on the effect of water table depth in the design of a typical 6.3m outer diameter circular tunnel with 6m backfill. In this study, it is also attempted to establish an analytical method of calculating the most realistic consideration of water table depth instead of the present hypothetical assumption of considering water table to coincide with the ground level. The findings of the current study may be helpful to the researchers and practising engineers in design of tunnel and cut & cover structure for subways and metros.

Nov 1, 2022

By Silas C. Nichols

"Abstract Piling and deep foundations are a staple for transportation projects in the United States (US). Driven or bored piles have been used for everything from support of bridge foundations and retaining structures to support of culverts and embankments on soft ground. Deep foundations have been popular in the US transportation market to better handle large axial and lateral loads, extreme event loading, and to better control structure movement. However, there are challenges in the maintenance of design and construction codes in transportation for consistent and reliable structure foundation elements. A significant amount of effort continues in the US to maintain national codes and specifications at a level consistent with the state of practice, and identify and conduct research for providing safe and cost effective highway structures.IntroductionThe transportation sector in the United States has a hierarchy of design and construction codes that are used for the specification of piling and deep foundations. Any highway or bridge project on the National Highway System (NHS) must be designed and constructed in accordance with a national set of standards approved by the State Highway Departments, and that are acceptable to the Federal Highway Administration (FHWA). However, in any jurisdiction, exceptions are permitted with approval. Therefore, design may be governed by the national standard specification, a state standard specification and design manuals, special provisions, or guideline specifications. Any of these standards, or a combination, may be used depending on the needs of the owner agency.The FHWA and the American Association of Highway and Transportation Officials (AASHTO) have worked together in the development and maintenance of geotechnical design and construction guidance and codes that support the surface transportation community. General geotechnical engineering practice in the United States lacks a singular, national design and construction code that addresses all aspects of geotechnical engineering. As a result, the AASHTO specifications provide the most complete geotechnical specifications focusing on structure foundations, retaining walls, and buried structures for surface transportation applications. This includes piling and deep foundation types commonly used for support of bridges and transportation structures.The FHWA National Geotechnical Team has published several technical guidance documents that include guideline specifications for the design and construction of driven and bored deep foundations. Reference documents published by FHWA summarize the state of practice and provide recommended design and construction guidance. These reference documents have long served as a basis for provisions included in the AASHTO specifications. Maintenance of the design code and specification, and related guidance documents for consistent use on US transportation projects requires a collaborative effort between industry, FHWA, and the member state highway departments that make up AASHTO."

Jan 1, 2014