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By WenJun Dong

This paper presents the stability assessment of the steel pipe piles that are used to support a deadman beam to anchor an adjacent bulkhead wall. Finite element analyses are performed to assess the stability of the bulkhead wall and determine the required tie-back force to the pile. The piles are relatively close to the bulkhead wall such that their soil resistance wedge zones are not fully developed but truncated by the bulkhead wall. The reduced lateral resistance capacity of the anchor piles is determined by applying the Coulomb wedge method on the truncated soil passive zones between the pile and wall. Both the conventional soldier pile stability (in terms of force and moment equilibrium) and Winkler soil spring (for soil-pile-interaction) analyses are used to assess the stability of the anchor piles.

Sep 8, 2021

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

Jan 1, 1996

By Mu Chen, Ye-Shuang Xu, Dong-Wei Hou, Shui-Long Shen, Huai-Na Wu

"This paper presents a laboratory investigation on the mechanical behaviors of the cement-clay admixture improved by polypropylene fiber. Cement can significantly improve the clay admixture. The fiber additive also improves the strength and ductility of the improved clay. The Unconfined Compression Strength (UCS) of the polypropylene fiber-reinforced cement-clay presents an overall trend to grow with the increase of fiber length. The improved clay reached its peak strength at the fiber content of 0.5%. Then the UCS of the improved clay will slowly reverse if the fiber content continues to rise. For study of curing time, improved clay behaves better in its early strength, but an inhibition will be brought about if fibers are excessive.INTRODUCTIONGround improvement technology is essential for construction of structures in soft ground. Some traditional techniques often cost much but result in little. For instance, along the coastal region of China, soft ground is often improved by backfill with high quality sandy soil transported far away, leading to high additional haulage costs and long construction period. Reutilizing the excavated soil as backfill or subgrade after treatment, by contrast, will be more economical and effective (Hufenus et al., 2006). Many researches have been conducted to improve the compression strength of soft soil, among which, the method of mixing the soft soil with cement and fly ash is one of the most common ways (Kolias et al., 2005; Horpibulsuk et al., 2009; Porcino et al., 2012). It is known that soil resists well against compression and shear force but behaves poorly in resistance to tension. Therefore, utilizing tensile elements such as fibers and strips to improve the tensile strength will be effective because of its strength isotropy, better durability and cost effective (Haeri et al., 2000; Kaniraj and Havanagi, 2001; Consoli et al., 2010)."

Jan 1, 2015

Pier, well cap and steining junction is a complicated 3-d re-ion. The prevalent design procedure for the pier, well cap and steining in isolated manner is not rational. In absence of an integrated approach for design of the junction structure, the well cap is designed uneconomical and at the same time pier and steining are left relatively unsafe. Strut-and-Tie Model based design is a simple solution to this problem. An example illustrating design of the junction structure using STM is presented. On comparison of the outcomes of the STM based design with the prevalent design, the following anomalies are found: i) For smooth flow of forces, length of pier at its base should preferably be made equal to the outer well diameter, ii) STM based design for the pier is more rational, economical and safe. iii) Due to presence of hoop stress, as indicated by the STM, the steining concrete in a depth of p times outer diameter of the well from the well cap level should be limited to M15 grade, iv) STM based design for the steining is more rational, economical and safe.

Jan 1, 1996

By Karen Talbot, Noah Maier, Rob Jameson, Giuseppe Gaspari

A storage and drainage tunnel advancing below I-75 in Detroit, Michigan experienced sudden subsidence. The Tunnel Boring Machine (TBM) was damaged to the extent that its shield, cutting head and extensive interior components needed to be extracted and replaced along with several completed tunnel segments. The tunnel was 16 feet (4.9m) in diameter with crown over 79 feet (24m) deep at the time. The tunneling contractor immediately engaged their designers and specialty subcontractors to develop a scheme to access the machine and repair the tunnel. They required a shaft 99 feet (30m) deep, with unobstructed plan dimension of 50 feet (15m) to accommodate the large components that needed to be removed and replaced. This precluded the application of an internally braced excavation and instead earth support solutions focused on use of a compression ring. Since the completed tunnel section behind the TBM obstructed closure of the compression ring below its invert, this paper describes the innovative access shaft solution employed. A conventional compression ring was constructed using 5 feet (1.5m) diameter drilled shafts down to the tunnel crown. In front of, and to the sides of the tunnel heading, the secant shafts were extended to over 150 feet (46m) depth, creating a horseshoe of support extending 50 feet (15m) below the planned excavation invert. Larger diameter "King Pile" shafts were drilled immediately to either side of the tunnel, overlapped into each end of the secant "horseshoe". The king pile shafts, together with a heavily reinforced ring beam above the crown elevation, acted as a door frame to transfer hoop loads from the incomplete secant arc into reaction supports above and below the tunnel. These oversize king pile shafts were extended and socketed into rock over 70 feet (21m) below tunnel invert. Very tight installation tolerances were necessary to maintain secant shaft alignment to depths exceeding 150 feet (46m). The project operational, geotechnical, and quality data was managed and visualized using a custom GIS interface. This paper will present the design approach employed and review the construction and quality program selected to repair the tunnel.

Oct 1, 2022

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

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

Sep 8, 2021

By Anburaj C., Srinivas A.

Deep excavation with support system is required to construct various part of underground structures like shafts, stations and entry structures etc. These structures have to be constructed using permanent or temporary embedded retaining walls with support system. The selection of a suitable type of retaining wall will depend upon the geological condition present in the particular location, time, cost and available equipment etc. In Bangalore Metro Rail Project, secant pile wall is adopted as the temporary earth retaining system and depth of excavation is about 20 m. It is designed initially based on bottom up construction methodology with 3 level of struts and 3 level of anchors but at later stage due to time and other construction related issues, it is decided to change the configuration to 6 levels of strut. Generally, in deep excavations, all the underground structures should be designed and checked for the critical forces from both permanent stage and construction stages. Since, secant piles are used as temporary retaining wall, only construction stage analysis is carried out to get the governing forces and deformation. In construction stage analysis, soil layers are defined with boundary conditions and the surcharge during construction and surcharge from actual building near the secant pile are considered. This paper discusses the effect of change in the support system from anchors to struts and how these changes in the support system affect the behavior of secant pile and subsequently adjacent buildings present in the influence zone of the excavation. As a result, in changing from anchors to struts, the wall displacement, strut forces and ground movement on the adjacent ground and buildings increases. The increase in deflection, ground movements and strut forces occurs during backfilling sequence of the underground station excavation. During backfilling, struts has to be removed and this imparts higher magnitude in deflection, strut forces and ground movements.

Nov 1, 2022

By Hugo Meggitt, Damian R. Siebert, Wystan Carswell

Excavation-induced ground movements are a critical component in the design and construction of deep excavations in urban settings due to the potential adverse effects on adjacent structures and infrastructure. Ground movements are influenced by soil stratigraphy, soil properties, adjacent structures, and construction means and methods. The use of empirical relationships, computer models, and reliance on experience with similar excavations in similar soil conditions often provides a basis for predicting excavation-induced ground movements. In this paper, data from 21 deep excavations approximately 20 ft to 75 ft deep supported by concrete diaphragm “slurry” walls in the Greater Boston area are compared to published literature, considering how different foundation systems (e.g. shallow foundations, caissons, and piles) of abutting structures have been affected by adjacent excavations. The influence of construction method (conventional vs. top-down) on adjacent foundation movements indicate that top-down construction typically results in smaller foundation movements. INTRODUCTION Estimation of ground movements due to excavation is a challenging endeavor, even with complex three- dimensional finite element modeling and high-order constitutive models that are increasingly available in modern engineering practice. Aside from the expense of the soil exploration and testing used to inform these higher-order models, the challenges of modeling past stress history, adjacent structures, and the groundwater conditions during excavation require not only large investments of time during design but also validation from past experience (to avoid a “garbage in, garbage out” paradigm). While site conditions such as soil stratigraphy, soil properties, groundwater conditions, and as-built conditions of adjacent structures can be obtained, measured, and estimated, the effects that means and methods of construction have on ground movements are difficult to quantify. During early phase design, assessments of predicted ground movement are unable to account for all aspects of project construction, nor is it cost-efficient to fully design an excavation while project parameters such as site size and excavation depth are under consideration by the design team. While construction is in progress, benchmarking support of excavation performance and associated ground movements in the context of successfully completed projects allows for a more nuanced view of system performance and provides the opportunity for more informed decision-making (if required) as construction proceeds. For these reasons, the use of empirical relationships and the collection of historical support of excavation performance holds high value for the practicing geotechnical engineer at all phases of the project.

Jan 1, 2019

By Clarissa Aguiar, Seok hyeon Chai, Thamer Yacoub, Sina Javankhoshdel

Sheet piles are used as an excavation support for soil retention. They are interlocked systems to form a wall for earth support along with anchors to provide an extra lateral support in excavations. The earth pressure against a sheet pile structure is not unique for each soil, but rather a function of soil-structure system. Movements of the structure with respect to the soil are primary factor in developing the pressure and thus the problem becomes indeterminate. In order to model a sheet pile wall for the analysis, structural element/interface can be used for the sheet pile. However, the use of the structural element with soil model alone is insufficient to simulate this soil-structure system as it fails to capture the slip condition between the sheet pile and the retained soil. In order to capture this slip condition, an interactive element can be used between sheet pile and soil to allow slip to occur. There have been many case studies where this method was used to analyze the response of the retained soil. Numerical studies have shown a good agreement with experimental results, but this stiffness is often not a well-known parameter, due to its complexity in nature of interactive behavior between soil and sheet pile walls. Also, many case studies are carried out with twodimensional analysis of the foundation, where three-dimensional analysis may be more suitable in some practical applications. In this paper, the interactive behavior of the element between sheet pile and soil is investigated with case studies for staged excavation using sheet piles and anchors. Then, investigation of a three-dimensional model is carried out by comparing with two-dimensional analysis.

By Rohrbach

Crosshole Sonic Logging (CSL) testing is commonly used to verify the integrity, quality and ultimately the acceptability of the concrete in structural elements such as drilled shaft foundations, secant pile cutoff walls, and secant/tangent pile earth retention structures. Besides concrete quality, many factors can impact CSL test results (e.g. laitance, air temperature, access tube spacing, access tube debonding, etc.). Effective use of CSL testing requires fully informed qualified practitioners capable of distinguishing between abnormal readings unrelated to deficiencies in the drilled shaft concrete and similar readings indicating the presence or possible presence of drilled shaft defects. Based on data and experience gathered from CSL testing of thousands of drilled shafts across North America, this paper discusses such factors and other information useful when evaluating CSL test results, and provides practical recommendations intended to reduce the potential for incorrect test data interpretation. The CSL testing industry is lacking in a clear, universally accepted guideline for the interpretation of CSL data and acceptance criteria of these concrete elements. This paper proposes terminology and a streamlined process for use when atypical results are obtained. The proposed terminology and method are intended to simplify and expedite the submittal review and approval process. Because construction activities for these elements are often on the project?s critical path, the benefits obtained in terms of project savings and reducing costly delays are undoubtedly valuable.

By Patrick Wong

The design of piling platforms is addressed in BRE (2004) for both fine grained and coarse grained subgrades. However, for coarse grained subgrades, piling platform designs can often be overly conservative due to either conservative assumptions on soil friction angle, or concerns over density variations of granular fill, particularly for made-ground. This paper provides guidelines on economic design of piling platforms on coarse grained subgrade by providing recommendations on ground characterization, assessment of soil properties and the use of non-linear stiffness soil behavior. An innovative performance-based design approach is also introduced, utilizing proof rolling with associated testing and interpretation using small strain theory to overcome concerns regarding potential ground variability of made-ground. A case study is presented to demonstrate the successful application of this performance-based approach to avoid having to construct a new piling platform over a 2 ha area. Small strain, non-linear stiffness theory was used to enable a practical proof rolling pressure to be adopted without having to reach the design or ultimate operating pressure. The author considers that the performance-based approach adopted on the case study may be similarly applied to a range of other projects to derive economic solutions.

Nov 1, 2022

By R. B. King

This document was prepared by the DFI International Grouting Committee with the intent to provide a summary of main Standards and Guidelines available for the North America and Europe grouting industry. This document highlights the different approaches, methods and tools used internationally. The DFI International Grouting Committee comprises all parties involved on a grouting project: Owners, regulators, engineers, contractors, and manufacturers (equipment and materials). This document is not intended to cover every conceivable application or requirement of grouting. However, it does provide standard practice requirements for qualifications, materials, equipment, testing, and production procedures for the professional engineer to incorporate into their project specific requirements.

Jan 1, 2021

By Robert Bachus, Jamey Rosen, Fabio Santillan, Georgette Hlepas

"A seepage barrier of length 4,800 feet and maximum depth 144 feet is being installed at Bolivar Dam in Ohio. This project is owned by the United States Army Corps of Engineers and contracted to Treviicos South. Many data types are being collected, synthesized and analyzed on a nearly real-time basis to monitor and track dam construction using several technologies including an enterprise relational database and web-based Geographical Information Systems. These data are being collected by both the owner and contractor and managed by the data subcontractor, Geosyntec Consultants. Each of the owner and contractor brings their own list of goals and desires to the data management program, and the subcontractor’s duty is to address these goals with minimal compromise by either party. The owner requires comprehensive, transparent and timely access to data in both “executive summary” and detailed formats. The contractor requires immediate analysis of disparate data to determine (for example) if a given excavation meets the specified tolerance and continuity requirements. This paper will describe the tools and methods used to store, analyze and visualize these data and discuss how each party’s needs were met in a collaborative system.INTRODUCTIONThe 4,800 foot long seepage barrier under construction at Bolivar Dam requires the collection, organization, and sharing of several types of data. These data include drawings and borehole logs that existed prior to construction; data collected during construction (seepage barrier panel composition and verticality data, slurry quality control and quality assurance data, grouting records, etc.); and instrumentation data collected and reviewed throughout and beyond construction. Each of these data streams require input and review from the Owner (United States Army Corps of Engineers (USACE), responsible for quality assurance and the ultimate consumer of the data), the Contractor (Treviicos South, responsible for the construction of the seepage barrier, its quality control and analysis of the data per the Contract Specifications), and the Data Management Subcontractor (Geosyntec Consultants, responsible for organizing and presenting the data to meet the needs of the Owner and Contractor). While all parties work with the same common goal, i.e.: producing a high quality product in an efficient manner making dam safety paramount during construction, and require immediate and comprehensive access to these data, the needs and desires of the parties differ. The challenge presented to the Data Management Subcontractor is to synthesize these data into a series of tools and reports that meet each of these needs."

Jan 1, 2017

By Mark A. Rohrbach, Timothy R. Kovacs, PhD Saidin

"Crosshole Sonic Logging (CSL) testing is commonly used to verify the integrity, quality and ultimately the acceptability of the concrete in structural elements such as drilled shaft foundations, secant pile cutoff walls, and secant/tangent pile earth retention structures. Besides concrete quality, many factors can impact CSL test results (e.g. laitance, air temperature, access tube spacing, access tube debonding, etc.). Effective use of CSL testing requires fully informed qualified practitioners capable of distinguishing between abnormal readings unrelated to deficiencies in the drilled shaft concrete and similar readings indicating the presence or possible presence of drilled shaft defects. Based on data and experience gathered from CSL testing of thousands of drilled shafts across North America, this paper discusses such factors and other information useful when evaluating CSL test results, and provides practical recommendations intended to reduce the potential for incorrect test data interpretation. The CSL testing industry is lacking in a clear, universally accepted guideline for the interpretation of CSL data and acceptance criteria of these concrete elements. This paper proposes terminology and a streamlined process for use when atypical results are obtained. The proposed terminology and method are intended to simplify and expedite the submittal review and approval process. Because construction activities for these elements are often on the project’s critical path, the benefits obtained in terms of project savings and reducing costly delays areundoubtedly valuable.1. INTRODUCTIONCSL testing is used extensively throughout the world on many projects to verify the quality of concrete used for drilled shaft foundations, secant pile walls, diaphragm walls, etc. In this paper, these structural elements will be referred to as “drilled shafts,” as they are the most common subject of this test method. In the United States, CSL testing is frequently specified by state and regional transportation agencies, ports, design builders, and others. Although other methods are currently available such as Gamma-Gamma Logging and low-strain Impulse-Echo or Sonic-Echo testing, and new methods are under development such as the Thermal Integrity testing, CSL testing is likely to remain one of the most useful tools for evaluating the acceptability of constructed drilled shafts for quite some time. The popularity of CSL as a testing method can be attributed to two main factors: 1) there is no depth limitation to the method and 2) the apparent ease of interpreting the results. A third advantage of CSL testing is that, when correctly interpreted and with adequate test coverage, it is unlikely to misrepresent a defective profile resulting in acceptance of a defective or inadequate drilled shaft. In other words, CSL testing is very likely to underestimate concrete quality/drilled shaft acceptability within its area of coverage."

Jan 1, 2017

By Leena Korkiala-Tanttu, Noora Lindroos, Juha Forsman

"Construction works at the Helsinki city sea shoreline requires dredging and handling of contaminated sediments. Most of these soft dredged sediments are regarded as too poor quality material for earth construction purposes. Mass stabilization technology has been applied to improve the technical and environmental properties of the dredged sediment in order to utilize the material in construction. The treatment site presented in this article is placed in the West Harbor where the dredged sediments are disposed in basins, mixed with binders by mass stabilization and transported to utilization sites. The volume of these basins is about 90 000 m3. So far these basins have been used three times during the years 2011-2014. The most applied binder has been cement. Its high price and carbon footprint have encouraged use alternative binders. Other used binder materials include fly ash and end product of desulphurization from coal combustion, and fly ash from combustion of Estonian oil shale. The technical and environmental properties of stabilized sediments have been studies in the laboratory and in situ thoroughly. Some properties of the stabilized sediments which have been studied are: compression strength, modulus, hydraulic conductivity, leaching of contaminants, etc. The leaching test results show that heavy metal leaching is very low with all binder materials tested.1. INTRODUCTIONContaminated marine sedimentsMarine sediments in the coastal areas are often contaminated as a consequence of industrial and port activities, as well as the influence of cities located there. Construction activities and reclamation of shore line require dredging and handling of contaminated sediments since the level of contamination inhibit dumping of dredged sediments into the sea. Based on their technical properties, most of these dredged soft and watery sediments (clay, gyttja, etc.) are regarded as too poor quality material for earth construction purposes. Economic, sustainable and environmentally safe management of contaminated, dredged sediments is a key issue in many construction sites.In the City of Helsinki, mass stabilization technology has been applied to improve the technical properties of the dredged sediments in order to utilize the material in construction. Owing to stabilization / deep mixing / solidification, also the contamination is encapsulated in a monolithic solid of a high structural integrity. Thus, contaminants migration is restricted by the decreased surface area exposed to leaching.The treatment site presented in this article is placed in the West Harbor (a place of Helsinki called Jätkäsaari) where dredged sediments are disposed into stabilization basins, mixed with binders by mass stabilization and then transported to final utilization sites. The location and principle of these basins is presented in Figures 1-4. The overall volume of these four stabilization basins is about 90 000 m3."

Jan 1, 2015

By Sven Schröer, Lilma Schimmel, Dimiter Alexiew

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

Jan 1, 2016

By Mary Ellen Bruce Large

"In partnership with California Department of Transportation (Caltrans), Federal Highway Administration (FHWA), and with support from International Association of Foundation Drilling (ADSC), Deep Foundations Institute (DFI) organized a workshop on quality assurance (QA) practices for acceptance of post-grouted drilled shafts in conjunction with DFI’s 40th Annual Conference on Deep Foundations. The 1½-day workshop was held on October 15-16, 2015 at the Oakland Marriott City Center in Oakland, CA.Post-grouting, in the context of this workshop and report, refers to the alternative design and construction of base-grouted drilled shafts wherein a grout distribution system is installed during construction and used to grout the base under pressure after the drilled shaft concrete has gained adequate strength, resulting in a stiffer axial-compression load-displacement relationship and additional possible ground improvement effects.The primary goals of the workshop were to•?Identify and summarize the state of the practice for design, construction, inspection, verification, acceptance criteria, reliability and performance of post-grouting.•?Identify gaps and needs in quality assurance that should be addressed for successful use of post-grouting.This report is structured to follow the workshop program: workshop presentations outlined the state of practice and views from owners, engineers and contractors on acceptance of post grouting methods for drilled shafts; and subsequent workshop discussions attended by a small invited group of participants focused on identifying areas of agreement and disagreement on post-grouting best practices, acceptance criteria, design and verification procedures, and inspection requirements. A partial list of attendees of the open and closed sessions is provided as Appendix A, and copies of presentations are included as Appendix B.FHWA and Caltrans are the primary audiences for this report, and its content will be used to develop a roadmap for deploying the findings into policy and practice. The secondary audience is the broader industry group, and the report content will be disseminated in a variety of formats."

Jan 1, 2016

By Mary Ellen Bruce Large

"INTRODUCTIONIn partnership with California Department of Transportation (Caltrans), Federal Highway Administration (FHWA), and with support from International Association of Foundation Drilling (ADSC), Deep Foundations Institute (DFI) organized a workshop on quality assurance (QA) practices for acceptance of post-grouted drilled shafts in conjunction with DFI’s 40th Annual Conference on Deep Foundations. The 1½-day workshop was held on October 15-16, 2015 at the Oakland Marriott City Center in Oakland, CA.Post-grouting, in the context of this workshop and report, refers to the alternative design and construction of base-grouted drilled shafts wherein a grout distribution system is installed during construction and used to grout the base under pressure after the drilled shaft concrete has gained adequate strength, resulting in a stiffer axial-compression load-displacement relationship and additional possible ground improvement effects. The primary goals of the workshop were to•?Identify and summarize the state of the practice for design, construction, inspection, verification, acceptance criteria, reliability and performance of post-grouting.•?Identify gaps and needs in quality assurance that should be addressed for successful use of post-grouting.This report is structured to follow the workshop program: workshop presentations outlined the state of practice and views from owners, engineers and contractors on acceptance of post grouting methods for drilled shafts; and subsequent workshop discussions attended by a small invited group of participants focused on identifying areas of agreement and disagreement on post-grouting best practices, acceptance criteria, design and verification procedures, and inspection requirements. A partial list of attendees of the open and closed sessions is provided as Appendix A, and copies of presentations are included as Appendix B.FHWA and Caltrans are the primary audiences for this report, and its content will be used to develop a roadmap for deploying the findings into policy and practice. The secondary audience is the broader industry group, and the report content will be disseminated in a variety of formats."

Jan 1, 2016

By Racquel Nottingham, Marc Mastrantuono, Freddy Lopez

In the digital era that we live in, connectivity and mobility play a decisive role in our daily activities. In this context, insufficient telecommunication infrastructure gives origin to the so called “dead zones” (areas with poor or non-existing cell phone reception), which hinder economic development in small communities and in many rural areas, since they remain invisible to a larger marketplace due to the inadequate cellular coverage. Several countries are working to identify these dead zones and with this information, establish strategies together with mobile providers in order to improve the existing mobile networks by expanding the coverage areas. As a result of the analysis, it is expected that thousands of telecommunication towers for 4G and 5G networks will be erected in the coming years. Telecommunication towers are slender elements that require large shallow foundations to verify primarily the safety against overturning. However in remote areas, it can be advisable to consider alternatives to the conventional shallow foundations, in order to optimize the use of materials (concrete, reinforcement steel, etc.). The following article presents an overview of intervention projects, where telecommunication towers were founded on micropiles. The micropiled foundations allowed to reduce considerably the dimensions of the originally planned shallow foundations. Furthermore, the use of micropiles allows for additional optimization, in combination with pre-fabricated foundations (i.e., precast concrete elements, etc.). This paper will focus mainly on the design and the execution of the micropiled foundation.

Sep 8, 2021