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By Giovanni Lombardi

In order to get a clear overview of the grouting works carried out, to avoid misinterpretations of the data and functions shown on the display of the grout monitoring device, it is recommended to keep the flow rate as constant as possible. Obviously, at the beginning of the process, the flow rate will increase from nil to the selected "basic" value. An important question frequently addressed is also how to reduce the flow rate in nearing the GIN limit so to finally reach the target intensity. Depending on the actual conditions, there are different manners to proceed. However, the following one appears to be the most convenient. It is represented on Figure 25. Being GIN the target intensity, two new limits at, let's say, 0.95 GIN and at 1.05 GIN as shown in the figure should be defined. The selected basic grout flow rate "q0", is kept as constant as possible all along the grouting process until the 0.95 GIN limit is reached. The flow is then reduced step wise to 2/3 q0, 1/3 q0 and zero at crossing each of the three limits. A similar rule can be used in respect to the maximum pressure, while for the maximum volume the process can be stopped at one time. Obviously the number of successive limits and thus the number of steps in reducing the pressure, as well as the width of the fringes defined in said way may be adapted to the local conditions.

Feb 10, 2003

By James A. Schneider

Selection of resistance factors within Load and Resistance Factor Design (LRFD) requires accurate assessment of uncertainty and bias in load and resistance. To date, many studies have focused predominantly on the assessment of uncertainty, while the potential for bias appears to be the dominant factor in design for consistent levels of reliability under a variety of situations. Bias comes from factors which have been ignored in design method development but significantly influence resistance when extrapolating from conditions typical of databases to those at a given site. Uncertainty and bias can be quantified as the coefficient of variation and mean (or median) of a data set, respectively, for statistical assessment of load and resistance factors. This paper first presents an overview of statistical assessment of resistance factors, and then discusses factors that influence uncertainty and bias when extrapolating to situations outside of conventional databases of driven pile axial capacity.

Jan 1, 2009

By Dimitrios Polantzas P. E., Collin E. Sweeney E. I. T., Franklin M. Grynkiewicz P. E., Leili Javidanian P. E.

In the latest AASHTO design specifications, the Load and Resistance Factor Design (LRFD) method is prescribed for the design of retaining walls. However, inconsistencies arise when LRFD is used for retaining wall design versus the traditional Allowable Stress Design (ASD). Required toe embedment and wall loading demand vary greatly when the two design approaches are compared, all else being equal. This is due to application of linear load factors to properties that vary non-linearly in the design. These inherent inconsistencies are further intensified when introducing factors such as layered soil profiles, different wall types, groundwater elevation, and surcharge requirements. When applied correctly, these two design approaches, in theory, should lead the designer to the same result with little discrepancy, as they do with steel structure design. However, the use of the current AASHTO LRFD method for various geostructural retaining wall designs yields contradictory results that suggest existing retaining walls that have been successfully designed and constructed are unstable. Fundamentally, LRFD should be built on reliability-based calibrations; the successful past performance of existing retaining structures designed using ASD suggests that the LRFD approach requires considerable modification. The authors of this paper recommend that the current LRFD load factors be reviewed and revised based on more comprehensive wall performance data and wall type such that the difference between retaining structures designed using LRFD and those designed using ASD is eliminated.

Oct 1, 2022

By Joseph A. Sopko

There has been a trend in recent years in performing the initial formation freezing using liquid nitrogen (LIN) and then converting the system to circulating refrigerated brine. While proponents of this method state it decreases freezing time, it can also be considered an alternative to inadequate refrigeration capacity. This method was used on several small projects in the 1980s. Problems such as broken pipes, frozen brine, and unsafe work conditions caused contractors to re-think the method. This paper discusses these problems and also presents work schedules showing no schedule reduction. In fact, this method can lead to longer time as well as significantly higher costs. BACKGROUND Ground freezing as a method to provide groundwater control and temporary earth support for excavations is completed using a relatively simple process: drilling and installing refrigeration pipes around the perimeter of the excavation and introducing a coolant into these pipes. The coolant extracts heat from the ground, converting the pore water to ice and forming a strong, impermeable material. A typical ground freezing system is illustrated in Fig. 1. SYSTEMS There are two basic types of coolant systems: circulating and direct expansion. The circulating coolant system is made of two separate, closed systems. The medium circulating is the secondary coolant. It is cooled at a central refrigeration plant, circulated through the pipes, and warms as it extracts heat from the ground. It then circulates back to the plant where it is cooled. This coolant is chilled in a heat exchanger by the primary refrigeration system where a compressor system is charged with a refrigeration gas. The heat is ultimately extracted from the ground and expelled into the atmosphere by an evaporative condenser. Secondary coolants are usually a brine or glycol chemical while the primary refrigeration gas is anhydrous ammonia or another commercially available gas.

Jan 1, 2019

By Timothy L. Roberts

For many years practicing geotechnical and structural engineers in Texas and Louisiana were reluctant to include augered cast-in-place (ACIP) piles as a viable deep foundation alternate. Three primary concerns were the lack of a final driving resistance to confirm adequate capacity, the inability to inspect ACIP piles prior to installation, and the fact that pile integrity is highly dependent on the skill of the ACIP pile contractor's field personnel. The Deep Foundations Institute (DFI) Committee on Augered Cast-In-Place Piles has responded to these quality control concerns by establishing standards of practice for ACIP pile installation and ACIP pile inspection. Regional areas of the country have different subsurface soil and rock conditions and many times this will influence local installation and inspection requirements. The best way structural and geotechnical engineers can address quality control concerns is to be familiar with the DFI standards of practice, to know the special requirements for a particular project site, and to incorporate them into a well-written ACIP pile specification. The purposes of this paper are to: 1) review the main fundamentals of a successful quality control program, 2) describe how these fundamentals can be applied to the installation of ACIP piles, and 3) add personal experiences from ACIP pile projects in Texas and Louisiana. Nondestructive test methods are frequently used as a quality control tool to evaluate questionable piles. An additional brief discussion of two nondestructive test methods is presented to complete the paper.

Jan 1, 1998

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

By Brandon Smith, William Bohlen

Riverbank erosion along the Brazos River has modified the structural support conditions for an existing bridge structure in Southeast Texas. The 8-span, 1,200-foot long bridge was completed in 1992 along Highway 99, a key corridor for the Houston area. Foundation support conditions have been altered due to natural, ongoing river morphology for three bents on the affected riverbank. Recent events include three storms within a three-year period that each exceeded the 500-year return probability. This resulted in accelerated erosion along the northern riverbank. Over forty vertical feet of soil has been removed in some locations. Drilled shaft foundations are now functioning as columns. This review considers the behavior of columns and deep foundation elements due to the modified support conditions. The review ultimately presents a rational methodology for the review of the present and anticipated future bridge configuration with respect to current strength, service, and extreme event limits, with corresponding safety factors for the design. Introduction and Background The Fort Bend Grand Parkway Toll Road Authority (Owner) oversees the State Highway 99 Judge Jodie Stavinoha Bridge over the Brazos River. The 8-span, 1,200-foot long bridge was originally designed with four southern approach spans of 115 feet; a three-span continuous river crossing with span lengths of 195 feet-235 feet-195 feet; and a single northern approach span of 115 feet. Figure 1 provides an overview of the northern portion of the bridge. Table 1 provides a summary of the original bridge substructure configuration. When the bridge was completed, the centerline of the Brazos River was located at midpsan of the main span and the northern high bank was originally located at Bent 7. Erosion process has forced the northern high bank to Abutment 9 (also called Bent 9), and the river centerline during normal flow conditions is located south of Bent 8. The overall estimated river excursion at present day is approximately 270 feet to the north from its original location. An erosion wall that was installed in 2017 limits further erosion of the north river bank within the 300-foot width of the roadway corridor right-of-way. This study was developed to better understand the existing conditions, and to forecast the need, nature, and criteria for potential future improvements.

Jan 1, 2019

By Patrick van der Schaaf

"During 2016, foundation piling works were completed to allow for the construction of a production and storage/handling terminal in Rotterdam. It is there that steel foundations will be produced for offshore wind farms and the oil and gas industry. Several Dutch contracting companies were involved in constructing: foundations for an assembly hall, a barge quay and a deep-sea quay wall. For the hall foundations, cast in situ concrete vibro piles were created. Open ended steel casing piles were also installed due to very high cone resistances which made it impossible to perform cast in situ piles in certain areas. The quay wall was constructed with open ended steel casing piles in combination with sheet piles. A deep-sea quay wall was also constructed to provide enough storage area for the offshore mono piles. This project was unique and challenging due to the use of different foundation technologies in challenging circumstances and soil conditions. This paper will give an insight into the Dutch use of varying foundation piling techniques for deep-sea quay wall constructions. It can be concluded that even experienced local contractors can be surprised by variations in soil conditions. It will also show how the contractors adapted to the difficult circumstances.PROJECT OUTLINEThe project consisted of a barge quay near the assembly hall with a length of 500 metres, width of 42 metres and a height of 35 metres, and a deep-sea quay wall 480 metres in length. This paper concentrates on the foundation works for the construction of the deep-sea quay wall. The construction of the deep-sea quay wall consisted of a combination of open ended steel casing piles with a diameter of Ø 1420 mm and a wall thickness varying between 21 and 23 mm. The lengths of the steel casing piles varied between 32 and 37 metres. Between the steel casing piles triple PU 28 sheet piles were installed with lengths varying between 26 and 29 metres. In the Netherlands, a combination of open ended steel piles and sheet piles is known as a “combi wall”. For the deep-sea quay wall a steel combi wall was shored with steel H- section profiles that were driven in a raked position whilst being injected with grout, so called MV-piles. The MV piles for this project consisted of steel HEB 600 sections with lengths from 52 up to 59 metres and were installed with angles varying between 42.5 and 47.5 degrees. For a detailed overview regarding the project specifications reference is made to table 1 which is presented below."

Jan 1, 1900

By John P. Turner, Steven S. Dapp, Dan A. Brown

"The Goethals Bridge Replacement (GBR) spanning the Arthur Kill Waterway between Elizabeth, NJ and Staten Island, NY consists of a dual-span 1,982.5-ft long cable-stayed bridge with approach spans of 2,545 ft on the NJ side and 2,788 ft on the NY side. The bridge is supported on over 200 drilled shaft foundations ranging in diameter from 4.5 ft to 10 ft and socketed into Passaic Formation siltstone. Drilled shaft resistances for design were based on load tests as described in a companion paper (Dapp et al. 2016). This paper presents the main foundation design considerations and challenges. The approach to construction of the rock sockets, with a focus on quality in order to support the use of high nominal values of side and base resistance, is described. Lessons learned from this project and their application to future similar projects are presented.INTRODUCTION AND BACKGROUNDThe Goethals Bridge Replacement (GBR) project is a Public-Private Partnership (P3) that represents a major milestone for the Port Authority of New York and New Jersey (PANYNJ) in its distinguished history of bridge building in the greater New York City metropolitan area. The new bridge will replace the existing Goethals Bridge, named after Major General George W. Goethals, Chief Engineer of the Panama Canal and the first consulting engineer for the Port Authority. The existing Goethals Bridge along with the Outerbridge Crossing and the Bayonne Bridge comprise the three Port Authority bridges connecting Staten Island with New Jersey. The existing Goethals Bridge and the Outerbridge Crossing are cantilever truss structures and both opened on the same day in 1928. They were designed by J.A.L. Waddell under the supervision of the eminent engineer Othmar H. Ammann (1879-1965), who was the designer of many other iconic bridges in the NY City area including the Bayonne Bridge (1931), the George Washington Bridge (1931), and the Verrazano Narrows Bridge (1964). The designer of record for the replacement Goethals Bridge is Parsons Corporation, which is the successor firm of Robinson & Steinman, whose principal David B. Steinman was also a notable NY area bridge designer and a contemporary and rival of O.H. Ammann.The replacement Goethals Bridge is supported on over 200 rock-socketed drilled shaft foundations. Each main pylon tower is supported on a group of six 9-ft diameter drilled shafts and each anchor pier is supported by two 10-ft diameter shafts. Each approach pier consists of a two-column bent with each column supported on a rock-socketed drilled shaft. A rendering of the Main Bridge crossing the Arthur Kill is shown in Fig. 1."

Jan 1, 2016

By Charbel Khoury, Kwabena Ofori-Awuah, Kofi B. Acheampong

"Following heavy rains in spring of 2014, Prince George’s County officials issued a mandatory evacuation for homes in the Piscataway Hills subdivision of Fort Washington, Maryland where a landslide along a 1700-foot hillside destabilized homes, collapsed the single access road, and resulted in water and sewer mains break. Forensic investigations, including geologic assessments, test borings and in-situ Cone Penetrometer and Dilatometer soundings, were performed to evaluate subsurface conditions and provide stabilization options for the roadway and slopes. Post-failure ground movements were monitored using inclinometers. Critical failure planes were identified within the underlying 30-foot thick Marlboro Clay formation, a known geologic hazard with historic occurrences of landslides and slope failures.This paper discusses the remedial design for stabilizing the landslide and 60-foot hillside slope failure, and protecting the roadway. Amongst several feasible options, driven piles were selected in consultation with the County and retained contractor based on cost, environmental impacts and site constraints. Constraints included private ownership of hillside slope, upslope buildings safety; deep-seated failure, relocation of underground water and sewer mains, and accelerated construction schedule.Pile design included global slope stability analyses and lateral pile analyses using several loading configurations to optimize pile geometry and spacing, and determine a value-engineered design satisfying both serviceability and strength limit states to achieve long-term stability with factor of safety of 1.3. Soils within the active landslide plane were assumed to provide no resistance, while soils below the failure plane provided lateral resistance. This stabilization scheme, which extended along the 1700-foot roadway section and toe of hillside slope area, consisted of 410 steel HP16x141 piles in two to three rows driven to depths between 60 and 70 feet below the Marlboro Clay stratum at 5 to 7-foot spacing."

Jan 1, 2017

By Ramin Motamed, Farshid Ghazavi, Joseph A. W. Toth

"Post-disaster reconnaissance of areas affected by earthquakes has documented extensive damage to buildings with shallow foundations located in liquefaction-prone areas. Currently, estimation of liquefaction settlement is based on empirical correlations that evaluate settlement in the free-field environment and are based on one-dimensional consolidation. However, observations have shown that liquefaction settlement under buildings can be considerably greater. This research is based on a series of 1- g shake table experiments using a transparent soil box to reproduce liquefaction-induced building settlement. Building settlements were evaluated using a scaled model of a building foundation representing a 1-2 story building. Comprehensive parametric study was carried out to establish the effects of several parameters on free-field and building settlements such as building width and thickness of liquefiable soil layer. The experiments utilized accelerometers and pore-water pressure sensors to monitor ground accelerations and buildup of pore-water pressures in both the free-field and model building footprint. Results of these experiments are compared to available centrifuge tests and field observations and conclusions are drawn with respect to the potential scaling effects. Lastly, this paper discusses the feasibility of installing helical piles as a mitigation strategy to reduce the building settlements by presenting some of the exploratory experimental data obtained from this series of 1-g shake table tests.INTRODUCTIONThe 2010-2011 Canterbury earthquake sequence and the 2011 Great Tohoku earthquake are some of the most recent examples where large numbers of low-story structures sustained damage resulting from liquefaction-induced settlements. This damage has commonly been observed in residential and commercial areas developed over loose, unconsolidated and saturated coarse grained soils resulting from both natural and man-made deposits. Damages incurred from the 2010-2011 Canterbury earthquake sequence occurred in the largely unconsolidated fluvial environment bordering the Avon River in Christchurch (Henderson 2013). Similar damage was also incurred during the 2011 Great Tohoku earthquake where liquefaction of soils occurred in both young alluvial deposits and fill materials (Ashford et al. 2011). Figure 1 presents typical modes of failure to structures resulting from the effects of liquefaction. Current practices in evaluation of liquefaction settlement rely on empirical correlations (Tokimatsu et al. 1987; Ishihara et al. 1992) developed for liquefiable soils in the freefield environment (Dashti et al. 2010a). However, recent observations of the performance of foundations suggest that settlement of rigid shallow foundations in liquefiable soils are commonly greater than those predicted in the free-field. Therefore, new correlations should be developed to better predict the degree of settlement of shallow foundations in liquefiable soils. Current research is beginning to focus on the mechanisms of settlement during liquefaction in regards to confining stress, pore-water pressure and shear stress induced from foundations (Dashti et al. 2010b)."

Jan 1, 2016

By Armin W. Stuedlein, Seth C. Reddy

In this study, factors affecting the reliability of augered cast-in-place (ACIP) piles under axial compression at the serviceability limit state are addressed using a simple probabilistic hyperbolic model and a database of load tests on ACIP piles in cohesion less soils. The aleatory and model uncertainty in a selected load-displacement model is statistically characterized, and is used to simulate representative random samples from the bivariate random vector of model parameters. A first-order reliability method (FORM) was used to determine the effect of sample size on the stability and uncertainty of the reliability index. Sample sizes greater than about 40 provided relatively consistent estimates of the reliability index; however, its uncertainty continued to decrease with increasing sample sizes. Additionally, the effect of slenderness ratio on the reliability of the serviceability limit state design was characterized and found to exhibit a significant effect on the probability of exceeding a specified displacement.

Jan 1, 2013

By David Chadwick, Paul Marsden, Chris Hughes, Mathias Delapille

"Following damage caused by the 2011 Christchurch earthquakes, the NZ$127.5million Christchurch Town Hall Restoration project is due for completion in 2018. The building is undergoing extensive repairs and a strengthening regime to meet New Zealand’s New Building Standard. One major aspect of the project is the stabilisation of the soil directly beneath the building using interconnected jetgrouting columns installed a cellular configuration, the purpose of this being to decrease the likelihood and severity of foundation movements caused by earthquake-induced soil liquefaction and lateral spreading. The soils encountered on the site ranged from cobbles and gravels through to sandy silts with a significant quantity of timber and rootlets. This wide variation of soil types presented a number of challenges with regard to effective and consistent treatment by jet grouting. The paper presents an overview of the quality assurance practices and also the testing regime adopted on this project.INTRODUCTIONMost of the deformation experienced by the Christchurch Town Hall structure over the course of the Canterbury earthquakes was caused by movement of the underlying ground. Two primary mechanisms of ground deformation were observed:- Liquefaction of the soils underlying the building foundation- Lateral spread of surface soils towards the free face at the river edge which runs 20 metres from the building. This mechanism also resulted in additional vertical settlement of the building foundations.The overall foundation design philosophy adopted by the project team for the Christchurch Town Hall Conservation Project has been to improve the ground directly beneath the structure to mitigate against these two mechanisms of ground movement. Additionally, a robust raft slab is proposed to distribute the foundation loading more evenly and increase the ability of the structure to resist lateral stretch of the underlying ground.The ground improvement system proposed by the Client’s geotechnical consultants, Tonkin &Taylor, comprised a cellular arrangement of interlocking jet grout columns, this arrangement would effectively encapsulate the soil within the cells preventing lateral spread.In total 1,097 interlocking jet grout columns, extending over the entire floor plan of the structure, were required to satisfy the design requirements."

Jan 1, 1900

By Donald A. Bruce

"The Deep Mixing Methods (DMM), in their current forms, have been employed in the United States since 1986, although an earlier version had seen service from 1954. The earlier developments were strongly influenced by practices in the Nordic countries and Japan, while by the late 1980’s several DMM systems had been developed in the U.S. itself. Since then, DMM has continued its evolution, principally via the challenges of a series of large, landmark projects, but also via distinct, significant technological advances. This paper highlights the key points in the history of DMM in the U.S., and provides an overview of the different methods currently in use.IN THE BEGINNINGIt is a common misconception that the history of applications of the Deep Mixing Methods (DMM) in the United States dates from 1986 when SMW Seiko Inc. — a subsidiary of Japan’s Seiko Kogyo Company — was established in the Bay Area. However, the author believes that Intrusion Prepakt Co.’s patented MIP (Mixed in Place) system had been used, albeit sporadically (about 30 projects are recorded), since 1954 (FHWA 2000, 2001). Ironically, by 1961 this single auger method had been extensively used under license in Japan for excavation support and groundwater control — by the Seiko Kogyo Company. By 1972, the original MIP technique had been succeeded by more advanced Japanese methods, involving multiple augers. Intrusion Prepakt have long since become defunct.The first systematic studies of contemporary Deep Mixing Methods in Japan began in 1967 when the Port and Harbor Research Institute of the Ministry of Transportation began laboratory testing using granular and powdered lime for treating soft marine soils. Fundamental studies continued through the early 1970’s, by which time the development of industrial scale equipment was well advanced, having its first application on a marine trial near Haneda Airport. Coincidentally, laboratory and field research also began in 1967 in Sweden (“Swedish Lime Column Method”) for treating soft clays using unslaked lime. Reportedly the progenitor was a Norwegian, Kjeld Paus, who had made observations on fluid lime columns in the U.S. It would seem that developments in Japan and the Nordic countries proceeded independently until 1975 when the technology leaders from each group (Broms and Boman; and Okumura and Terashi, respectively) presented their — very similar — findings at a conference in Bangalore, India. Limited technical exchanges ensued thereafter.Whereas the Nordic developments continued to focus on the use of dry reagents (cement and lime) and relatively light equipment compatible with operating on and in very soft clays and organics, the Japanese progressed into the use of fluid reagents (cement-based grouts) and heavier equipment for both marine and land-based projects. Thus, by 1986, there were a large number of proprietary (wet and dry) DMM systems in Japan, and a rapidly growing market already by then accounting for over 12,000,000 m3 of ground treatment."

Jan 1, 2015

By William H. Walton, Joel Dellaria, Jeffrey R. Hill

The City of Chicago has a world-renowned skyline and is known for its provocative architecture. The subsurface conditions in the city have allowed for construction of these significant structures. The skyline is supported on caissons as they are called in Chicago or drilled shafts in other locations. Despite the significant strides the industry has made in advancing the drilled shaft, the use of other specialty geotechnical construction techniques like micropiles has not been overlooked in Chicago and the surrounding areas. Micropiles have been utilized to underpin famous existing historic structures like Orchestra Hall any many others. Engineers have used 200 to 600 kip micropiles to underpin compromised, inadequate, or damaged caissons. The paper will discuss the use of drilled shafts, micropiles, and ground improvement over the last 30 years in Chicago using a curated collection of case histories. It will also examine advancing the industry beyond its current technical limitations using these techniques. INTRODUCTION 20,000 years ago, glaciers from the Chicago region left behind sheets of glacial clay till underlain by dense, over consolidated glacial till below: limestone bedrock, found about 100 ft below street level. An unusual feature in this profile is the soft Chicago Blue Clay. Chicago has been called the birthplace of the Skyscraper and drilled shaft foundation, both of which came about in the 19th century. After the Great Fire of 1871, tall new structures were built rapidly and designing a successful foundation was trial and error. The first deep driven wood pile and caisson foundations bypassed the problem layer and found solid support on hardpan till or bedrock below (Schock and Risberg 2013). Once the drilled shaft foundation became acceptable to the Chicago engineering and construction community, building heights and complexity grew dramatically. As the city grew, building foundations were being repurposed. There was also the need to underpin structures for additional loads and shallow foundations for adjacent construction. Hand-dug drilled shafts were an option for some of these restricted access and low headroom sites but a new technique, micropiles, would prove to be the future of retrofit and hard to construct foundations. Micropiles were introduced on a limited basis to the United States market in the 1970s and 80s. In the early 1990s, the Chicago market began to latch onto micropiles and their use has grown significantly as a solution to the most complex foundation problems a maturing skyline has to offer.

Jan 1, 2019

By John Dunn, Matt Hawley, Kashif Butt, Nicholas Gura

"This paper presents the results of a static load testing program completed on helical pile foundations for the replacement of high voltage transmission line tower structures. The foundations were part of the Northeast Grid Reliability Project (NGRP) for the Public Service Electric & Gas Company (PSE&G) near Newark, New Jersey. Structure foundations “anchor bolts down” was a design build contract model with the superstructure as bid-build.The soil stratigraphy along the alignment generally consisted of fill over about 10 ft of organic deposits underlain by up to 260 ft of normally consolidated glacial lake clays and silts. Additional project challenges included working under/adjacent the existing live high voltage lines, narrow site access due to environmental permits, foundations in a tidally influenced area, and pile projections in the order of 10 feet to meet the 10 year flood level requirements.The helical piles were constructed of 12.75 inch diameter open ended pipe piles with 36 to 40 inch diameter helices. A total of seven static load tests (compression and tension) were completed on 60 ft and 90 ft long piles, using both welded and mechanical pile splices. To evaluate pile-soil setup in the sensitive fine grained soil and determine representative longer term installation torque factors (Kt) for the production piles, the static load tests were performed 7 to 49 days after pile installation.Helical piles were found to be the most cost effective foundation alternative for this project. The required length of helical piles was less than other alternatives for similar allowable axial capacity. Helical piles with mechanical splices were installed for the varying structure foundations including tangent and heavy deadend, to a deadend monopole. Installation of 448 production piles (34,320 linear ft) was completed in three months. The installation timeline was critical to meeting the semi-annual PSEG outage for switching the old and new structures. Helical piles employing a mechanical splice resulted in an efficient and effective foundation solution for the conditions encountered on the project."

Jan 1, 2017

By Paul J. Sabatini

Between 2008 and 2009, more than 6,000, 23-m long deep mixing method (DMM) elements were constructed to support 124 concrete mats comprising the foundations for the process trains for an LNG facility. The Owner requested first-of-its-kind analyses and assessments to confirm the quality and reliability of the DMM foundation. This paper provides information on these assessments and the procedures used to ultimately conclude that a fit-for-purpose foundation system was constructed. During early phases of construction, several DMM test cores revealed nodules of unmixed clay in upper core samples. A comprehensive review of available DMM core information was undertaken. It was concluded that the amount of coring being conducted as part of the contractor?s QA/QC program should be increased to achieve a foundation system with the required level of reliability. Three-dimensional finite element analyses were completed considering various distributions of defects in the DMM elements and the effects of potential downdrag on DMM elements. Calculated mat settlements and mat stresses were compared to cases without defects in the DMM elements. Various distributions of loaded and unloaded mat areas and number and position (both in the subsurface and laterally) of defects were considered. Four (of the 124) mats were identified as potentially ?at-risk?. The settlement performance of these mats is currently being monitored and, to date, performance has been acceptable.

By Gerald Verbeek, Erick Baziw

Cone penetration testing (CPT) is a popular and cost effective tool for geotechnical site characterization. CPT consists of pushing at a constant rate an electronic penetrometer into penetrable soils and recording cone bearing (qm), sleeve friction (fs) and dynamic pore pressure (u) with depth. The measured qm, fs and u values are utilized to estimate soil type and associated properties based predominantly on empirical correlations. The cone bearing measurements are highly susceptible to additive measurement noise for sandy, silty and gravelly soils. This measurement noise results in high peaks due to interbedded gravels and stones and low peaks due to softer materials or local pore pressure build-up. To date there has been little progress in filtering this additive noise aside from ad hoc techniques, which include discarding qm measurements and smoothing/averaging qm measurements. This paper outlines a qm filtering technique which attempts to put structure into the estimation problem. In this case, the dynamics of the cone bearing measurements are modelled within a state-space mathematical formulation and a Kalman filter (KF) is then utilized to obtain optimal estimates of qm. The mathematical details of the qm KF algorithm are outlined in this paper along with the results from a challenging test bed simulation.

Sep 8, 2021

By Gerald Verbeek, Erick Baziw

Cone penetration testing (CPT) is a popular and cost effective tool for geotechnical site characterization. CPT consists of pushing at a constant rate an electronic penetrometer into penetrable soils and recording cone bearing (qm), sleeve friction (fs) and dynamic pore pressure (u) with depth. The measured qm, fs and u values are utilized to estimate soil type and associated properties based predominantly on empirical correlations. The cone bearing measurements are highly susceptible to additive measurement noise for sandy, silty and gravelly soils. This measurement noise results in high peaks due to interbedded gravels and stones and low peaks due to softer materials or local pore pressure build-up. To date there has been little progress in filtering this additive noise aside from ad hoc techniques, which include discarding qm measurements and smoothing/averaging qm measurements. This paper outlines a qm filtering technique which attempts to put structure into the estimation problem. In this case, the dynamics of the cone bearing measurements are modelled within a state-space mathematical formulation and a Kalman filter (KF) is then utilized to obtain optimal estimates of qm. The mathematical details of the qm KF algorithm are outlined in this paper along with the results from a challenging test bed simulation.

Oct 1, 2021

"Premissas BásicasCaracterísticas do concreto centrifugado(Spun concrete characteristics)Aplicação em obras de engenharia de fundações(Application engineering works foundations)Logística de fabricação e transporte(Manufacturing logistics and transportation)Emendas x uso de aplicação(Amendments x use application)Geologia brasileira, da região costeira a presença de grandes bolsões de argila mole(Brazilian geology, coastal region the presence of large pockets of soft clay)Influencia do sistema de cravação(Influence of driving system)Transferência da Energia Aplicada(Applied Energy Transfer)Estacas longas(long piles)Controles executivos (diagrama de golpes, nega, repique elástico, ensaios de carregamentodinâmico, provas de carga).(Executive Controls (blows diagram, sets, elastic rebound, dynamic load tests, load tests).)ECD – aplicação da metodologia do DIETECD - application of the methodology DIETBrazil has a highly variable geology all along its coast that directly influence the choose of foundation type, being too employed the use of reinforced spun concrete piles initially ranged in diameter from 60 to 80 cm. Over the past 10 years with the advent of investment in marine works projects began to demand a new range of piles with diameters greater than 100 cm and in the absence of amendments.On land is also very remarkable the presence of regions with large layers of soft clay, in prime areas that have been explored. A classic example is the Barra da Tijuca in Rio de Janeiro that has suffered from the housing boom growing toward these regions. In these regions it has been very common driven lengths of about 40.0 meters, which basically go through thick layers of soft material or unconsolidated and they will find strength in depth with residual soil layers or even the bedrock.The spun concrete has great qualities for application in deep cuttings resulting from the production process, which gives a redistribution of fresh concrete mass collaborating with the particle size distribution effective loss of water that is thrown to the center stake being subsequently discarded. Consequently this contributes to a reduction in the factor a/c that is directly connected to increase strength.The fact that there is a sort of concrete helps to reduce voids in the mixture, which increases the durability characteristics. This condition made it possible to employ the spin technique on poles, which are directly linked to aggressive media in large urban centers.Another very attractive feature is that the centrifuge process can work with concrete with the lowest percentage of mortar and more gravel. This concrete mix directly contributes to increasing the specific modulus of elasticity, thus allowing a greater capacity to absorb the energy of the blows transferred with less deformation.Despite the great potential of land application of prefabricated spun concrete stakes there are only three factories and its limitation is the cost of transporting manufactured for the various regions, since all transportation is done by road.For its transportation is carried out exclusively by trucks, this limits the size of cuttings being produced commonly in length from 11.0 to 12.0 meters in length and smaller compositions. For use in long piles of works is resorted to amendments in the form of metal rings, concreted near the ends of the stakes, with the transfer through steel bars in CA-50 welded to the ring. Usually run in steel ASTM A-36. Later in the work these rings are welded with coated electrode.In the case of maritime stakes are very used to drowned splicing technique, which basically consists during the spin process leave one end with the armor of the apparent stake and work together two elements and make specific, with superior resistance to the prefabricated stake.This study in addition to briefly introduce the process of manufacturing, design and logistics presents a detailed study of applicat"

Jan 1, 2015