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By Matthias Pulsfort, Jiarui Du, Torsten Wichtmann, Achim v. Blumenthal, Diethard König, Rowena Verst

The influence of the interaction between support fluid and soil, e.g., filter cake formation, on the shear stress transfer in the soil-concrete interface of diaphragm walls and bored piles is still controversially discussed. Actual research on the soil-concrete interface using bentonite suspensions indicates that shear stress transfer is underestimated by existing standards. Investigations on the soil-concrete interface using polymer solutions are rare. Therefore, complementary field investigations and systematic laboratory studies were conducted to analyse the soil-concrete interface using both bentonite suspensions and polymer solutions. Thickness and composition of real-scale filter cakes were investigated on several slurry wall construction sites, where bentonite suspensions were used. Direct shear tests (60 mm x 60 mm) were executed for soilbentonite mixtures with varying amounts of bentonite and different granular fines representing a realistic bandwidth of in-situ filter cake compositions. Larger direct shear tests (300 mm x 300 mm) with preceding horizontal penetration, subsequent vertical tremie concrete placement, and filter cake consolidation were performed using both bentonite suspensions and polymer solutions. The results support the view that shear stress transfer in the soil-concrete interface can be described by a wall friction angle in a range of 25° to 30° for bentonite suspensions and between 35° and 40° for polymer solutions in non-cohesive soils.

May 1, 2022

By David Sherwood

The paper has been prepared as the basis for the 2008 John Mitchell Memorial Lecture. It reviews major developments in ground engineering over the last 20 years, not from the point of view of technical processes, but from the drivers that have driven these developments and the needs that they have met. It concludes with a glimpse into the future and suggests to where current trends will probably lead us. By its nature such a review is closely aligned with personal experience and it relies heavily on case histories largely from within the writer?s own experience over that period.

Jan 1, 2008

By Takefumi Takuma, Ali Fayad, Shigeru Kambe

"This paper discusses the unique design and construction circumstances of the cantilevered dual sheet pile walls and the Accordion Sheet Pile Wall for the repair and upgrade of the East Garden Grove-Wintersburg Channel in Huntington Beach, California that was concluded in 2014. It also describes the 2008 Emergency Sheet Pile Project for the same channel. Both projects utilized the Press-in Piling Method for its low noise and almost no vibration advantages.BackgroundThe East Garden Grove-Wintersburg Channel is part of the Orange County Flood Control District (OCFCD) and is operated and maintained by OC (Orange County) Public Works (see Figure 1 for its location). The channel, referred to as OCFCD facility # C05 (C05), had suffered significant toe undercutting and slope erosion of its levee due to a series of storms. These began after the facility was constructed in the 1960’s and culminated in 2005. Consequently, the levee was deemed significantly deficient and was eventually declared as a local emergency in 2007. C05 was an incised channel and its levee was constructed primarily from native materials. Operation and Maintenance (O&M) personnel notified the design staff at OC Public Works to be aware of major consequences associated with the dilapidation problem in the most downstream reach of the channel in the vicinity of the Bolsa Chica Wetlands Restoration Project. In 2007, the Orange County Board of Supervisors declared a local emergency to fix the levees with sheet piles to be driven by the Press-in Piling Method, hydraulic pushing piles into ground by holding onto previously installed piles. The project that ensued represented the first in-tandem use on the West Coast of the United States of the Press-in pile driver with its GRB System (Press-in pile driver, a support crane and pile transporter travel on top of already-driven sheet piles). This is further discussed in this paper in the sections titled “Press-in Piling Method” and “GRB System”, respectively. The project repaired approximately 3,800 feet of erosion on the north levee of C05 with 45-foot long cantilevered sheet piles. The sheet piles design constraints are discussed in this paper in the section titled “C05 2008 Emergency Sheet Pile Project (Phase 1)”. Between 2012 and 2014, another mile’s worth of levee reach was improved with the Soil-Mix-Sandwich (SMS) Method. This concept consisted of deep soil cement mix (DSCM) columns sandwiched within the dual rows of sheet piles. Additional details on the SMS, its DSCM construction, and its hybrid geo-structure design concepts are well beyond the scope of this discussion, which is primarily focused on sheet piles. Instead, the interested reader is referred to two papers on the SMS and its DSCM metrics (Fayad, 2015; and Arora, et al., 2015). These were presented and published in the Proceedings of the Deep Foundations Institute (DFI) 2015 Conference on Deep Mixing. Hence, in the section of this paper titled “C05 SMS Dual Sheet Piles Project (Phase 2)” only the sheet pile design constraints of the SMS are covered. Finally, in the area where the project traversed the Alquist-Priolo zone of the Newport-Inglewood tectonic fault, an expandable and deflectable sheet pile wall was used to isolate the flood channel from the Bolsa Chica wetlands. Its details are addressed in the section titled “C05 Accordion Sheet Pile Wall (Phase 2)” of this paper."

Jan 1, 2017

By Shahriar Vahdani, Andy Herlache, Andrew Bro, Wei-Yu Chen

"The Presidio Parkway Project will reconstruct approximately 1.6 miles of highway, including seven bridges, three cut-and-cover tunnels, and an undercrossing connecting the Golden Gate Bridge to the City of San Francisco, California. The project site is approximately 5.6 miles from the San Andreas Fault, which is capable of producing magnitude 8 earthquakes. Seismic hazards include strong ground shaking, soil liquefaction, ground settlement, and lateral spreading. At the Tennessee Hollow bridge section up to 30 feet of loose sands and soft clays are present. Concerns are raised that standalone drilled piers will experience excessive lateral soil loads from liquefaction-induced lateral spreading pressure resulting in excessive pier head displacement of up to 8 inches. Ground improvement by Cement Deep Soil Mixing (CDSM) is proposed to provide additional foundation stiffness. This paper presents the methodology to: 1) assess the effectiveness of the ground improvement in resisting lateral spreading, and 2) optimize ground improvement design at individual bridge bents based on local site condition. A series of 3-D numerical analyses are conducted and the results show that drilled piers with CDSM ground improvement are capable of withstanding seismic demands from lateral spreading and the lateral pier head displacement is reduced to less than 2 inches. The adopted analytical approach is efficient at modifying design for individual bents and can be considered for future pier foundation design in seismically active areas. IntroductionThe Tennessee Hollow bridge section (Low Viaduct) is an integral component of the Presidio Parkway project which will replace the existing facility with a new multi-lane roadway between the Golden Gate Bridge and the City of San Francisco. As shown on Figure 1, the project site is located about 5.6 miles east of the San Andreas Fault and 12.5 miles west of the Hayward Fault. The Low Viaduct will span over a future wetland habitat subject to tidal fluctuations and potential scouring."

Jan 1, 2014

By George J. Tamaro

The design and construction of foundations in the New York City area are usually dictated by the widely varying geologic conditions encountered in the five boroughs, particularly along the spine of Manhattan Island. Rock extends well above sea level at the northern reaches and falls to depths in excess of 250 m at the barrier islands at the southern extremities. These highly variable geologic conditions, significantly affected by glacial activity, dictate different design and construction approaches throughout the five boroughs of New York City. Extensive rock removal is required at the north while long piling is dictated in the south. Similar changes can occur within a project site on Manhattan Island. This paper will describe these conditions in general, will identify the various solutions used to solve these problems and will summarize various foundation types used in the New York City area.

Jan 1, 2000

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 Stephen Darmawan, Mahdi M. Disfani, Arul Arulrajah, Alireza Mohammadinia

Deep mixing using cementitious compounds is an in-situ method of ground improvement for improving the strength, compressibility of loose sand. Artificial light cementation can increase the stiffness of loose sands significantly and reduce the settlement of loose deposits. The increase in contact area between the particles with a thin layer of cementitious agent depends on the confinement and void ratio of the soil mass. Hence, the stiffening effect of cementation not only depends on the type and amount of cementing agent and inter-particular force chain of loose deposit but also depends on the stress level at the time of cementation. In addition, the cementation effect in loose deposits can be deteriorated at relatively low strain levels. Decementation softening can cause detrimental and irreversible impacts on the soil deposit. This study investigates the effect of initial confinement and subsequently the initial void ratio at the time of cementation on small strain behaviour and decementation softening of cemented loose sand under ko loading. The effect of inter-particular contact of sand particles based on the specific surface area and also soil density was also investigated by means of shear wave propagation. This study present insightful information on effect of primary consolidation stress levels, density of soil and cementation level on softening and collapse of loose deposits improved using deep soil mixing technique. Better understanding of soil-cement interaction by optimization of binder content for deep mixing activation can lead to increasing the level of confidence in using this technique in ground improvement applications.

Jan 1, 1900

By Ground Improvement Committee

The evaluation of earthquake-induced liquefaction has become a routine part of geotechnical engineering design. For a given project, if an analysis identifies a potential for liquefaction and the consequences of liquefaction are deemed unacceptable, then some form of hazard mitigation is required. Mitigation efforts may consist of removing the liquefiable soils, bypassing the liquefiable soils with deep foundations, structurally accommodating the deformations or strength loss caused by liquefaction, or preventing the onset of liquefaction through ground improvement. The fundamental ground improvement mechanisms for liquefaction mitigation include densification, drainage, and reinforcement. When evaluating, recommending and specifying various ground improvement methods for liquefaction mitigation, practitioners should understand the fundamental mechanics involved and applicability and limitations of the various methods. The DFI Ground Improvement Committee offers a review of the fundamental mechanics and commentary on the applicability and limitations of each method to provide clarity and guidance on the issues related to ground improvement for liquefaction mitigation.

Aug 1, 2013

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 Rob Jameson

"Although seismic retrofit is recognized as a key micropile application, widely-used reference documents do not clearly address design and testing recommendations for micropiles that are loaded primarily under seismic conditions. The principles of micropile design and construction and their application to seismic retrofit projects are well understood and executed by leaders in the field. As the micropiling market grows, a wider audience relies on the information presented by DFI and similar industry groups. State-of-practice updates appear periodically in conference proceedings, but examination of recent bid documents makes it clear that there are opportunities to improve the specification of load, deflection, testing and acceptance criteria on many seismic retrofit projects. Updates to the FHWA Manual or DFI Sample Specification that specifically address seismic retrofit cases would be useful tools to disseminate information and enhance the state of practice.Micropile Survey UnderwayAs one step in this process, I am distributing surveys to contractors and designers prior to DFI Super Pile ’09 (June 4-6, San Francisco) seeking recommendations for design and testing procedures applicable to seismically loaded micropiles. I am also requesting any existing references that could be promoted as a standard for these cases. Anyone interested in participating in this survey, should contact me at rjameson@malcolmdrilling.com. Seismic RetrofittingMicropiles are ideally suited to seismic retrofit applications. Their high-tensile and compressive capacity can sustain the large concentrated loads induced during seismic events. They can be installed within and around the access limitations of existing structures, and can be drilled through and grouted into the wide variety of soil and rock materials encountered in seismically active zones.Seismic retrofits have included micropiles since the early 1990s, and they are now widely specified in the Western U.S. In the San Francisco Bay Area alone, thousands of micropiles have been installed for seismic upgrades of highway and transit aerial structures, and retrofits of commercial, residential and public buildings. Micropile use is growing in both public and private sectors, with large-scale retrofit projects currently underway for both the Bay Area Rapid Transit (BART) system-wide upgrades and renovations at San Francisco Airport."

Jan 1, 2009

By A. Rod Kern, Michael A. McNicholas, Yaser Taheri

Deep foundations were required for construction of an 18,000 ft2 (1,672 m2) 4-story office building and an adjacent 23,750 ft2 (2,206 m2) 5-story parking garage in Queens, New York due to an existing uncontrolled fill layer ranging from 15-20 ft (4.6 - 6.1 m) in thickness beneath the building footprint. The geotechnical engineers for the project initially selected auger cast-in-place (ACIP) piles over driven piles to limit the impact of noise and vibrations on the surrounding neighborhood. Ultimately, drilled displacement piles (DDP) were installed since this method offered a more economical solution that would generate the required pile capacity with shorter drill depths and would also mitigate spoils volume. During installation of test piles by the geotechnical contractor retained for the foundation work, multiple unanticipated soil conditions were encountered that would adversely affect the constructability of the piles. The existing fill contained significantly more natural and manmade obstructions than expected and the underlying glacial soil became too dense to penetrate at shallower depths than anticipated. This paper discusses how these issues were overcome through pre-drilling and the use of detailed instrumented test pile data coupled with in-house engineering capability to proactively re-evaluate minimum pile lengths at any given location and keep the project on track. INTRODUCTION Geotechnical work in the New York City market presents soil conditions that can be highly variable and challenging due to the presence of uncontrolled urban fill placed over the native soils. Construction in this area can therefore pose many unforeseen challenges, even with detailed geotechnical analysis being performed at project sites. A case in point is a construction site in Queens, New York. The proposed site development consisted of construction of a 4-story office building with a footprint of 18,000 ft2 (1672 m2) and a stand-alone 5-level parking garage with a footprint of 23,750 ft2 (2206 m2), together with associated new pavements and utilities. The site is bordered by a mix of commercial buildings and residential properties on all sides. Depth of the uncontrolled nature of the fill extended up to 20 ft (6.1 m) below street grade. Given the significant cost associated with removal and replacement, deep foundations were recommended to bypass the unsuitable soils and support the structures at depth where good bearing material existed.

Jan 1, 2019

By Stefan Larsson, Jan Ekström, Jennie Kock-Larsen, Håkan Garin

"This paper describes the testing procedure (or protocols) for quality control of dry deep mixing columns in a major ground improvement project carried out in Sweden. Quality control was mainly based on column penetration tests performed at different stages in the project and on two occasions after installation. In the paper, the results from the tests are compared with tests on the unimproved clay. As expected, the results show that the correlation between undrained shear strength in the columns and in the unimproved soft soil depends mainly on the in-situ stress. However, the correlation probably depends on when the tests were performed after mixing. When the influence of the in-situ stress was excluded from the analysis, no significant correlation could be identified. This means that the undrained shear strength in the columns and in the unimproved soft can be considered to be uncorrelated when the strengths and the corresponding variability are evaluated with depth from groups of tests.INTRODUCTIONQuality control and quality assessment of deep mixing (QC/QA) constitute a key component in verification of the limit state design. Due to the complex mixing process and varying geological conditions, it is normally not possible to sufficiently assess the strength and deformation properties in advance. In Sweden, the most commonly used QC/QA method for verification of the limit state is the column penetration test (Axelsson and Larsson 2003; Bergman et al. 2013). The method works well but is time-consuming and requires many tests since property variability is normally high. The column penetration test can be used to assess the undrained shear strength Cu,col. However, it is not clear how the strength correlates to the undrained shear strength of the unimproved soil Cu,soil. There are common factors such as the in-situ stress state and the natural water content, which makes a positive correlation probable, i.e. as Cu,soil decreases, Cu,col also decreases and vice versa. The unimproved soil has a natural spatial variability, but it is not known if the improved soil follows the same variation. The mixing process has a substantial influence on the strength variability and may supersede the influence of other factors. However, if a sufficiently good correlation exists between Cu,col and Cu,soil, information from the geotechnical ground investigations can be used in the design and planning of QC/QA of deep mixing in a more stringent manner. Information about the correlation is also essential in reliability based design, where a strong positive correlation may have a negative influence on reliability. However, as discussed by Al-Naqshabandy and Larsson (2013), this correlation may be weak or insignificant for a representative failure domain where the mixing process may have a dominant influence on the strength variability. It is thus of interest to assess the correlation."

Jan 1, 2015

By Francisco A. Flores, José L. Aguirre, Héctor A. de la Fuente, Erika Bernal, Jorge Arroyo-Esquedla

This paper presents the analysis, design, and construction of soil improvement for storage tanks foundation support at a site in Tabasco, Mexico. A total of 980 Rammed Aggregate Piers of 12.5 m in length and 0.5 m in diameter were designed and constructed to support four storage tanks. The soil conditions at the site generally consist of loose to medium dense silty/clayey sand to about 8m depth, underlain by very loose to medium dense silty/clayey sand with seams of very soft clay. The use of Rammed Aggregate Piers induced densification of the soil to increase its stiffness and reduce the liquefaction potential to control both static and dynamic induced settlements. Standard Penetration Test (SPT) and Cone Penetration Test (CPTu) explorations were performed prior to and post soil improvement to compare the liquefaction potential and the Factors of Safety associated with the two conditions. Finally, the soil improvement installation rate is presented. Soil improvement using Rammed Aggregate Piers represented a suitable alternative to support storage tanks foundation in potentially liquefiable areas.

Oct 1, 2022

By Takefumi Takuma, Hiroyuki Nishimura, Shigeru Kambe

"Japan’s Great Tohoku Earthquake and the immediately following tsunami of March 11, 2011 killed more than fifteen thousand people and destroyed numerous buildings and infrastructures in the northeastern part of the country.In addition to reconstruction projects in the areas where the earthquake and tsunami hit, other seismically vulnerable regions in the country have started building new and more robust facilities as well as upgrading existing coastal structures so they will be able to cope with such deadly seismic and hydraulic force. This paper will highlight two different types of aseismic and anti-tsunami levee upgrades currently under construction on the coast of Kochi Prefecture, approximately 500 miles west of Tokyo. The first type is the installation of double sheet pile walls in existing seawalls. The second type is to drive tubular piles into existing levee structures for reinforcing them. Both sheet and tubular piles are being driven by the Press-in Piling Method without removing or compromising the function of the existing structures. 1. BACKGROUNDGreat Tohoku Earthquake of March 11, 2011 caused severe damage to many structures. ASCE’s survey of damaged coastal structures conducted immediately after the disaster by Ewing, et al. (2014) categorizes failure modes of the structures in the following manner.?Overtopping without structural failure.?Overtopping with structural damage or failure.?Wave uplift forces.?Movement of structure off foundation from sliding, rotation, or overtopping.?Impact loads.?Hydrostatic pressure.?Supercritical flows.?Scour.?Erosion.?Abutments end effects.?Subsidence."

Jan 1, 2017

By Clayton A. Signor

Abstract: Expansive soils cause more damage to structures annually than a combination of other major natural disasters. Because of the cost to our society, all means and methods need to be fully explored to mitigate the problems associated with expansive soils. This study will present a foundation design approach that is underutilized in this application, driven piles. The main objective of the study is to present pile test results and analysis from four driven pile project sites in three types of expansive soils found in central Texas: Del Rio formation, Taylor/Navarro formation, and expansive alluvium. High strain dynamic pile tests were conducted on each of the four studies with rigorous signal matching analysis from the CAse Pile Wave Analysis Program (CAPWAP). Ultimate pile capacities ranged from 73 to 311 kips with an average of 61% of the total capacity coming from the pile shaft and were two to six times the structural capacity needed. Allowable loads calculated from Modified Gates dynamic formula best modeled allowable test results. Average unit skin frictions ranged from 0.50 to 4.71 ksf. Restrike pile tests of 1 to 17 days after initial driving reported 30 to 100% shaft capacity gain. All open-ended pipe piles driven produced soil plugs ranging from 4 to 14 feet thick. Small diameter, thick-walled, open-ended pipe piles reached penetration of twice the depth of designated zone of seasonal moisture change without problem. The observed production rate of the driven piles was on average 8 minutes, which implied daily production of 15 to 40 piles. Predrills or augered holes should be specified for underground obstructions found in soil investigation.

By Abolfazl Eslami, Masoud Zare, Ali Asadi, Ali Abrang

"Physical small scale models for study of deep foundations can be performed in simple chambers (1g), calibration chambers (CC), and centrifuge apparatus (ng) which involve some limitations and difficulties. In recent years, Frustum confining vessels (FCV) have been developed for physical modeling of deep foundations. This device is frustum of a cone shape that applies a steady pressure on its bottom and creates a linear stress distribution along its vertical central line. A new FCV which has been built in AUT is introduced. This device has a height of 1200 mm, top and bottom diameters of 300 and 1300 mm, respectively. Through the application of bottom pressure up to 300 kPa, the insitu overburden stress conditions equivalent up to 40 m soil deposits consistent to the embedment depth of commonly used piles. Observation indicated that there is approximately a linear trend of stress distribution, and this device can create realistic overburden stress in the desired control volume along the central line. Moreover, a couple of compressive and tensile load tests were performed on steel tubular open end model piles driven in sand with length of 750 mm and different diameters and L/D ratio between 8-15. Comparison of load capacity between tested and full scale piles demonstrate a suitable conformity for similar confinement conditions. Therefore, the FCV can be realized as an appropriate apparatus for investigation of piling geotechnical behavior and examination of construction effects.IntroductionDeep foundations are designed as foundation system for supporting heavy loads, high rise and important structures. Different theoretical, numerical and experimental approaches have been developed to study the geotechnical behavior of deep foundations. Experimental methods are employed to clarify directly pile-soil interaction and because of repeatability, analogy, rapid measurement and cost efficiency, physical modeling can be realized as an intermediate technique compared to element testing and full scale load tests."

Jan 1, 2015

By Monica Prezzi

"Auger cast-in-place (ACIP} piles and drilled displacement piles are being increasingly used as foundation elements for structures, particularly in projects requiring accelerated construction or involving the rehabilitation of foundations of existing, overstressed structures. Auger cast-in-place piles (also referred to as continuous-flight-auger piles) are widely used to construct the foundations of all types of structures. There are many different types of drilled displacement piles, with the installation methods varying according to the equipment used. Depending on the specific rotary piling technology used, responses ranging from those associated with non-displacement to those associated with full-displacement piles are obtained. Conventional pile design methods do not account for how the various construction techniques involved in auger piling change the soil state around the pile during installation and, hence, cannot accurately estimate the pile resistance in a consistent way. Research on this subject, identifying the different variables that must be accounted for in design and linking these variables to installation methods, is lacking. This paper describes the different piling methods available for auger cast-in-place and drilled displacement piles, the equipment used to install them and the quality control processes typically used. It also reviews some of the design methods currently used.IntroductionDeep foundations are extensively used in geotechnical engineering practice. The wide spectrum of piling methods results in a variety of pile types. Each type behaves differently, depending on the installation or construction methods. On one end of the spectrum are non-displacement piles, the classicql examples of which are bored piles or drilled · shafts. These piles are constructed by removing a cylinder of soil from the ground and replacing it with concrete and reinforcement. On the other end are full-displacement piles, such as closed-ended pipe piles or precast reinforced concrete piles, which are typically driven into the ground. Driven piles preload the materials below the toe of the pile and displace the soil surrounding the pile shaft laterally during the installation process. Therefore, displacement piles are, in general, more likely to have a stiffer response than non-displacement piles. This is true particularly in the case of sandy soils where displacement causes densification."

Jan 1, 2005

By Karen J. Dawson, Francisco Johnson

"Pressure-grouted high strength helical displacement piles are a recently developed pile type that can be useful in conditions where noise or vibrations must be low or where access or clearance is limited. However, there is no information in the literature that can be used to estimate the soil resistance of these piles or production rates. To fill this information need, this paper presents a New Jersey installation case history and the results of static axial and lateral load tests on both pressure-grouted and ungrouted high strength helical piles at the case history site and trial installation locations in New Jersey and Washington State. Piles between 25 and 50 feet long comprised of steel shaft diameters of 4.5, 5.5, and 7 inches with equivalent grout column diameters ranging from 12 to 22 inches were tested. Lateral loads of up to 100 kips and axial compression loads of up to 700 kips were applied. The results of the load tests are compared to predictions of lateral deformation and axial resistance.INTRODUCTIONHelical piles have long been recognized as a useful foundation type in situations where noise and vibrations must be limited, or where there are access or clearance restrictions. Relatively well-documented design methods and torque to capacity correlations have been developed for the most commonly used helical piles, which are relatively small (typically shafts of 6 inches or less) with corresponding low load carrying resistance.With the increased need to construct in congested urban environments, there is incentive to develop helical piles with higher axial resistance. Seismic and other loading conditions also require lateral resistance, which is low for the typically small helical pile shafts. One method of increasing the soil resistance, both axially and laterally and at relatively low cost, is to place grout around the shaft. Injecting the grout under pressure through the hollow helical pipe section and out a grout port or ports located near the toe of the pile has the potential to increase the pile resistance significantly above that which can be achieve by gravity grouting. Not only does the pressurized grout push out against the surrounding soil, but the rotating helix helps to distribute the grout laterally. Unfortunately, little information is available in the literature to help designers estimate the resistance of grouted helical piles in general and none is available regarding pressuregrouted helical piles."

Jan 1, 2016

By Arash Saeidi-Rashk-Olia, Dunja Peric

Energy piles are gaining increased popularity due to a growing demand for clean energy. To further advance the understanding of soil-structure interaction in energy piles, recently-derived analytical solutions have been implemented to investigate the impact of stratigraphy on the soil-structure interaction. This was accomplished by comparing the measured and predicted head displacements, axial strains and stresses in an energy pile embedded in the actual homogeneous and layered soil profiles, as well as into synthetic homogeneous soil profiles. The analytical solutions for homogeneous soil profile captured the smooth experimentally observed response versus depth very well. In the case of a layered soil profile, the corresponding analytical model was capable of capturing nuances in trends of axial stress and strain versus depth at the interface of different layers. The analytical predictions for the layered profile appear to be slightly less accurate than for the homogenous profile. The experimental data obtained from the layered profile appear to be a bit more scattered than those from the homogeneous profile. In the former case, the interplay of the individual soil layers with the pile occurs while maintaining the continuity of the pile stress and displacement at the interface of different layers. The response throughout each layer of the layered profile is quantitatively different than the corresponding homogeneous response. Nevertheless, qualitatively the response throughout each layer of the layered profile is similar to the response of the pile embedded in the corresponding homogeneous layer.

Sep 8, 2021

By Gang Guo, Zhong Liu

"In response to an increasing demand of anchored structures for underground space and transportation infrastructure in China, an innovative underreamed ground anchorage system was created. The novel anchorage system has provided more efficient functions with higher capacity at lower cost, because of the enlarged cylindrical body (known as ECB) sealed in capsule at bottom of anchorage. This paper presents the detailed structure of innovative anchorage system and its special features. To investigate the bearing mechanism of new anchorage, we evaluate its performance and failure mode based on the experimental results, and also indicate its strain-hardening load-displacement relationship. Unlike the shaft anchorages, it is identified no overall failure to be found in soil surrounding the underreamed anchorage. More importantly, the anchorage capacity is governed by the base resistance, which takes more than 80% of total pullout capacity resulting from the contribution of ECB. Finally a case history of anti-floating project introduces the new combined construction approach and procedure, which has provided the contribution to the quality control and cost efficiency.INTRODUCTION AND BACKGROUNDThe construction boom over two decades in China has resulted in an increasing demand for underground space and slope stability. The infrastructures market requires the more efficient anchorage systems for retaining structures, resisting uplift forces and slope protection. The major concern focuses on gaining higher capacity and lower cost resulted from perfecting anchorage systems. There are three main anchorage systems designed to achieve the above objectives: ? single bore multiple anchorage system (Barley 1997), ? regroutable anchorage system (Smoltczyk 1991), ? underreamed anchorage systems (Xanthakos 1991). Generally, the concept ? comparing with the other two, can be more competitive due to its distinct advantages. To improve the performance and durability of ground anchorages under the complex geological conditions and diversified engineering requirements, a number of different underreamed anchorage technologies had been used, which included cone - shape anchorage described by Liao, Wu and Shu (1997) in Taiwan, Soilex anchorage developed in Sweden (Massarsch et al. 1997), Soletanche anchorage proposed in France, blasting anchorage used in Czechoslovakia (Hobst and Zajic 1986), jet-grouting anchorage innovated in Europe (Anon 1988), as well as deep mixing anchorage created in Japan (Cheng et al. 2000).The underreamed anchorage systems have the remarkable advantages compared to the shaft anchorage system. However, there are also some weaknesses inherent in the underreamed systems. For instance, the mechanical underreamed anchorage is unsuitable in sand or waterbearing ground, because the enlarged hole is easy to collapse, and it is hard to ensure the quality of anchorages. On the other hand, relying on the blasting in deep hole, the geometrical space and dimension of enlarged hole is uncontrollable, meanwhile, the continuous blasting operations may easily cause the serious ground deformation and the negative effects to the completed anchorages."

Jan 1, 1900