Search Documents

By C. Michael Morgano

Static tests are costly and time consuming, so they are not always the best answer [ ]

Jan 1, 2005

By Andrew Budek

"Analytical and experimental work has shown that achieving the full inelastic lateral capacity of a pile may require the formation of a plastic hinge below ground level, in the pile shaft. The confining action of soil about the pile shaft was further been shown to greatly enhance the ductility capacity of the pile. An experimental program was therefore undertaken to build in the effect of external confinement through the addition of a GFRP jacket to the subgrade plastic hinge region. Two piles were thus modified, and compared to an unjacketed pile in a test rig which simulated a subgrade moment pattern and soil confinement. The ductility achieved by the jacketed piles was found to be substantially lower than an unjacketed control specimen. Failure mode of the jacketed specimens was also undesirable, involving complete tendon rupture and sudden loss in capacity IntroductionSeismic loading of concrete pile shafts can result in a demand for inelastic response. In the case of a superstructure supported by a single pile (i.e., a pile-column forming a single-column bridge pier, in which there is no rotational restraint at the top of the pile}, a plastic hinge will form below grade, at a depth which varies with soil properties and above-grade height of the center of seismic mass.In the case of a superstructure supported by multiple piles, there is rotational restraint, and the connection will experience inelastic action first. However, development of the full lateral inelastic capacity of the pile may call for the formation of a second, subgrade plastic hinge (fig. 1 )."

Jan 1, 2005

By Stephan A. Jefferis, Adrian H. Bath

"This paper draws together some themes on the durability of barrier systems, and particularly cementitious systems. For contaminated land and water retaining structures, durability can be poorly addressed at all stages of a project, from specification, to barrier material selection, barrier design including toe-in and through to performance assessment in operation. Permeability (hydraulic conductivity) is a dynamic property which will vary over time as reaction processes propagate through a barrier. However, laboratory testing, when undertaken, tends to be focused on short term tests with aggressive chemicals so that the effects of longer-term processes such as carbonation and leaching by permeating water are missed. For water retaining structures, carbonation and leaching actually may be the most significant processes affecting barrier performance as the groundwater adjacent to many water bodies can be otherwise rather benign (as regards bentonite and cementitious systems). These and other reaction processes have been modelled in the arena of nuclear waste repositories and procedures are well recognised. However, such procedures have yet to be widely adopted for the assessment of other barrier systems.INTRODUCTIONOver the last few decades there has been an enormous amount of laboratory research on the durability of barrier materials or more specifically papers reporting the results of permeability tests. Unfortunately there is a much smaller literature on scaling test results to barrier dimensions in the field or to required design lives. Although in the geotechnical industry durability research has been largely laboratory based, in the nuclear industry where relevant timescales are multi-millennia rather than decades, research has been heavily underpinned by geochemical modelling. A significant purpose of this paper is to examine the tools that may be used to analyse the results of tests on barrier materials used in geotechnical engineering, for example, for water retaining structures and contaminated land and draw the attention of the construction industry to the potential of the modelling procedures developed for nuclear repository assessments. Modelling can help to identify underlying processes and so augment information from laboratory testing focused on changes of physical properties such as permeability and strength."

Jan 1, 2016

By Annika Gram, Teddy Johansson, Lutfi Ay

Micropiles transfer tension or compression forces as well as cyclic loads into the ground via skin friction. The Self Drilling Micropiles (SDM) can be utilized for permanent applications. The hollow bar simultaneously acts, as drilling rod, injection tube and reinforcement for the micropile. The SDM system can be used in any type of soil, including unstable soils, without the need for temporary casing. Injecting a cement grout through the hollow steel tendon ensures that the borehole is filled from the bottom to the top. The system is fast, simple, and flexible. The installation minimises noise, vibration, and spoil. There are many potential applications, including foundations, underpinning, resisting uplift, dynamic/cyclic load applications and geothermal installations. The SDM technology were introduced to India first time in the Indian history and utilised in the 4G and 5G network projects. The SDM challenge the traditional cast-in-situ piles in the 4G project and raft foundations in the 5G project. Utilisations of the tensile and the compressive strength capacity of SDM with smart solutions results in noticeably big costs, 17-38 % depending on the soil conditions and time savings. The cost of the SDM solutions was about 40% less than the cast-in-situ piles and raft foundations in an ongoing 5G project. The SDM were used successfully in the liquefiable soil types as well.

Nov 1, 2022

By Peter Faust, Peter Hubbard, Kenichi Soga

The European Federation of Foundation Contractors (EFFC) and The Deep Foundations Institute (DFI) have set up a task group to compile a Guide for Working Platforms. The first edition of this Guide has been published in January 2020. The aim of the Guide is to provide reliable methods for design, testing and verification of working platforms for construction equipment, especially in the deep foundation industry where track loads can be excessive due to the nature of its operations. The Guide has identified areas where knowledge is limited. Actual track pressure and its distribution along the length of the tracks is still not well researched. Current recommendation provided in EN 16228-1 are believed to be overly simplified and may lead to conservative requirements for working platform thickness. This paper presents results of a series of field tests where the actual track pressure of a large drilling rig during operation was measured in real time together with the deformation of the working platform. Embedded, distributed fiber optic sensing (DFOS) at different depths throughout the platform allowed for a three-dimensional evaluation of the platform deformation throughout the entire operation. Results will help to develop more reliable recommendations for future safety requirements of working platforms for deep foundation equipment.

May 1, 2022

By Braxton P. Erbe, Douglas C. Brunot

A variety of systems and techniques exist to support deep excavations where sloping is not feasible. This paper will explore an example project involving the use of pre-engineered hydraulic bracing systems to support sheet pile walls. Challenges on site that drove the final design include a high water table, irregular excavation geometry, and underground obstructions. The hydraulic system, connected by pins and not requiring welds, allowed for quick deployment and the modularity to change as required due to unforeseen site conditions.

By Ronald Damen, Dion Denes

"Friction fatigue is the loss of soil-pile friction around the shaft area of the pile. It has been observed during impact driving of piles, and has been modelled to a limited degree using physical scale models. This paper proposes the use of high strain dynamic pile testing to assess and quantify friction fatigue in impact driven piles. The method is applied to two case studies: one on a project off the north-west coast of Australia and one on a South Pacific Island. On both sites calcareous sand layers are present. Pile Driving Analyzer (PDA) monitoring has been conducted during impact driving of steel piles, which allowed for assessment of shaft resistance development both with depth and with progressive driving, by use of wave equation signal matching. Lessons are drawn from the case studies to improve future observations.INTRODUCTIONFriction fatigue is the loss of soil-pile friction around the shaft area of the pile, under cyclic loading or during pile driving. The phenomenon has been frequently observed in some non-silica sands, such as pumice sands and calcareous sands and has been the subject of academic study.The occurrence of friction fatigue impacts the driving behaviour of piles and the shaft friction component of the ultimate geotechnical strength (Rd,ug). If potential friction fatigue is not recognised in the design phase of a project, required pile toe levels can be significantly underestimated. This could lead to extra cost and delays, or, if no adequate pile verification is conducted, to geotechnical failure or underperformance of piles. This is especially true in remote locations, such as Pacific islands, where calcareous material is often present.A better understanding of the phenomenon would aid both pile design and driveability assessment. This paper proposes the use of high strain dynamic pile testing to assess and quantify the effect of friction fatigue from impact driving. Two case studies are presented in which high strain dynamic testing has been conducted on driven piles in calcareous sands to illustrate the method.BACKGROUNDFriction fatigueThe geotechnical strength of piles is composed of the resistance to static loading by the base of the pile and the shear resistance between the shaft of the pile and the adjacent soil. The latter is often referred to as the shaft resistance or shaft friction.During impact pile driving, a decrease in shaft resistance is often observed. Although this phenomenon is also observed during vibratory pile installation, this paper deals predominantly with impact driving. This decrease in material strength from the tip of the pile influences the shaft resistance and may be either temporary or permanent. Temporary reduction in shaft resistance is common in cohesive soils and is thought to be caused by excess pore water pressure, which has insufficient time to dissipate. This phenomenon, commonly referred to as set up, is observed to a significantly lesser extent in non-cohesive materials such as clean sands (Rausche et al., 2004)."

Jan 1, 1900

By Chris L. Powell, Russell J. Denny

"The remotely located Cockatoo Island iron ore mine off the Kimberley coast in the northwest of Western Australia has been in operation since 1951. The mine was recently expanded up to about 50 m (165 ft) below sea level using staged construction to create a rockfill seawall around the open cut mining operation. Late in 2013, to allow expansion of subsea iron ore mining operations, Wagstaff Piling was engaged to install a seepage barrier through the rockfill seawall and into the underlying seabed sediments.Earlier stages of seawall construction had used a variety of different construction techniques with varied success, and the history of subsea mining on the island had been plagued with failures, including failures in the slope of the seawall itself, hanging wall failure underneath and inside the seawall, and footwall failures as the ore was mined leaving the rock face inclined at 55 degrees, parallel to the bedding. The current expansion, known as the Stage 4 expansion, was more tightly constrained by the pit geometry and available materials than previous seawall expansions that adopted clay core and sheet pile seepage barrier solutions. In Stage 4, an innovative seepage barrier solution using a grout curtain was selected to provide the necessary cutoff to allow access to high-grade ore, while protecting the mine from inundation by the sea.Seawall ConceptThe open cut subsea mining operation consisted of a 3 km (1.9 mi) long narrow pit along the south side of Cockatoo Island that extended to depths of about 50 m (165 ft) below sea level, and were exposed to the open sea on the south side of the pit. Massive tidal variations of more than 10.5 m (34.5 ft) required a seawall founded on the seabed, extending upwards to RL+13, to safely protect the pit from the high tide level rising to above RL+10."

Jan 1, 2017

By Chris L. Powell, Russell J. Denny

"The remotely located Cockatoo Island iron ore mine off the Kimberley coast in the northwest of Western Australia has been in operation since 1951. The mine was recently expanded up to about 50 m (165 ft) below sea level using staged construction to create a rockfill seawall around the open cut mining operation. Late in 2013, to allow expansion of subsea iron ore mining operations, Wagstaff Piling was engaged to install a seepage barrier through the rockfill seawall and into the underlying seabed sediments.Earlier stages of seawall construction had used a variety of different construction techniques with varied success, and the history of subsea mining on the island had been plagued with failures, including failures in the slope of the seawall itself, hanging wall failure underneath and inside the seawall, and footwall failures as the ore was mined leaving the rock face inclined at 55 degrees, parallel to the bedding. The current expansion, known as the Stage 4 expansion, was more tightly constrained by the pit geometry and available materials than previous seawall expansions that adopted clay core and sheet pile seepage barrier solutions. In Stage 4, an innovative seepage barrier solution using a grout curtain was selected to provide the necessary cutoff to allow access to highgrade ore, while protecting the mine from inundation by the sea.Seawall ConceptThe open cut subsea mining operation consisted of a 3 km (1.9 mi) long narrow pit along the south side of Cockatoo Island that extended to depths of about 50 m (165 ft) below sea level, and were exposed to the open sea on the south side of the pit. Massive tidal variations of more than 10.5 m (34.5 ft) required a seawall founded on the seabed, extending upwards to RL+13, to safely protect the pit from the high tide level rising to above RL+10."

Jan 1, 2017

By Heman Manchanda, Sandeep Sharma

Several infrastructure projects are in various stages of construction and planning in India and almost all of them involves open ground excavation extending to varying depths. These structures are generally multipurpose and fulfil several needs of the society, their failure can be catastrophic. The design and construction of deep open excavations is generally associated with a high level of risks due to a whole series of uncertainties involved, and the success of such projects depends on various factors including appropriate evaluation of ground behavior and response to excavation stages, correct choice and analysis of construction supports, control of ground water flow during excavation, etc. One of the most critical amongst all these is ground water flow during construction and stability of underground excavation depends to a large extent on ground water control. This paper uses numerical studies for the assessment of the potential impact of ground water and ground water movement for the design of underground deep structures. The studies are being conducted using PLAXIS 2D finite element software and analysis all construction stages to which an open underground excavation shall be subjected. The paper discussed in detail the impact of water table fluctuations and comparative evaluation of different water flow conditions – a) Different Stages of excavation in line with the construction sequence (Phreatic), b) Coupled flow analysis (Transient- 1 year and 2-year duration) and c) Steady state flow conditions. The paper also covers seepage calculation and design of dewatering system.

Sep 1, 2022

By Darren S. Diehm

"Construction for the restoration and expansion of 102-year-old Wrigley Field in Chicago, Illinois began at the conclusion of the 2014 baseball season. This six year project involves structural upgrades to the Stadium, improvements to the facade, infrastructure, restrooms, concourses, suites, press box, and bullpens, as well as the addition of restaurants, patio areas, batting tunnels, video boards, an adjacent Office-retail Tower and a new Hotel. The Bleachers were demolished and replaced, and a new underground Clubhouse was constructed for the Chicago Cubs beneath a new open-air Plaza. The 1060 Project is privately funded, projected at $750 million (US). The work will be completed in phases during consecutive off-seasons, each with a maximum 23-week duration extending through the Chicago winter. Ownership mandated that on-going construction cause no disruption to the Major League Baseball season, have no impact on hosting concerts and other special events, and it should not adversely affect seating capacity, or diminish the fan experience.The 1060 ProjectAfter purchasing the Chicago Cubs baseball team in 2009 from the Tribune Company, the Ricketts family began planning the renovation and improvement of Wrigley Field and its near neighborhood surroundings in Chicago, Illinois. What came to be known as the 1060 Project was officially announced at the annual Cubs Convention in 2013. Construction began on the $750M privately funded project in October 2014 at the conclusion of the Major League Baseball season. In their vision, the Ricketts committed the 1060 Project to three primary goals. First and foremost as a MLB franchise, the work should provide a meaningful contribution toward winning the World Series and ending the championship drought which stretched to the last win in 1908. Second, the project should be focused on preserving and improving Wrigley Field. Finally, the project should be committed to outcomes that enable the team to be a good neighbor and provide economic and social benefit to the local community.Constructed as Weeghman Park in 1914 for an estimated total cost of $250,000, the stadium provided seating for 18,000 fans and a home for the Chi-Feds and Whales of the National Federal League. The Chicago Cubs were enticed to move from the West Side Grounds in 1915. In the next 100 years, the Wrigley Field would be sliced apart and expanded, double its seating capacity with the addition of double deck grandstands, be enclosed by bleachers (and an ivy covered wall), and, in 1988, experience its first nighttime baseball game with the addition of lighting.The 1060 Project has a total budget of $750M, with an expected construction value of $350M. It is projected to add over 2,100 jobs to the economy and be completed before the 2020 baseball season. The work will be completed in phases during consecutive off-seasons, each with a maximum 23-week duration extending through the Chicago winter. Ownership mandated that on-going construction cause no disruption to the Major League Baseball season, have no impact on hosting concerts and other special events, and it should not adversely affect seating capacity, or diminish the fan experience."

Jan 1, 1900

By Peter J. Nicholson

"IntroductionDuring my more than 40 years in the practice of underground construction and engineering, the industry has seen progress from the dig down to rock or hardpan or alternatively drive concrete or steel into the ground and count the blows; then you can be sure of you have a solid foundation; to the modern day, I’m willing to try anything to save money. Of course these are both exaggerations, but not gross ones. After getting bored being supervision on jobs counting blows, I struck out into the new field of “tie-backs” as they were called in the United States, or “ground anchors” as they were then termed in the United Kingdom. After installing some of the first permanent ground anchors for the Corps of Engineers on Lake Michigan as well as the highest loaded rock anchors of the time at two dams on the Ohio River, we were at the top of our game in the 1970’s. Subsequently in the 1980’s when my view of the future of ground anchors saw their installation becoming a commodity item, we branched out into “Pin Piles” now known as Micro Piles, high capacity, steel tube encased, small diameter (5-12” or so), high capacity (100-500 tons) piling. Next came soil nailing, both temporary and permanent retaining walls, as at Cumberland Gap Kentucky. My next morph was into “Cement Deep Soil Mixing” earlier on, known simply as “soil mixing”. For this education I traveled to Japan several times and established a long-term, Joint Venture, relationship with one of the better known Japanese specialty ground modification companies. In Boston at the “Big Dig” we established the then record size soil mixing project, 500,000 or so cubic meters of CDSM concluding in the year 2000. Since then I’ve been involved as a consultant mainly for dams and levees. Below is the story of how I came to be at this place in the road to innovation in Geotechnical processes."

Jan 1, 2017

By Peter J. Nicholson

During my more than 40 years in the practice of underground construction and engineering, the industry has seen progress from the dig down to rock or hardpan or alternatively drive concrete or steel into the ground and count the blows; then you can be sure of you have a solid foundation; to the modern day, I?m willing to try anything to save money. Of course these are both exaggerations, but not gross ones. After getting bored being supervision on jobs counting blows, I struck out into the new field of ?tie-backs? as they were called in the United States, or ?ground anchors? as they were then termed in the United Kingdom. After installing some of the first permanent ground anchors for the Corps of Engineers on Lake Michigan as well as the highest loaded rock anchors of the time at two dams on the Ohio River, we were at the top of our game in the 1970?s. Subsequently in the 1980?s when my view of the future of ground anchors saw their installation becoming a commodity item, we branched out into ?Pin Piles? now known as Micro Piles, high capacity, steel tube encased, small diameter (5-12? or so), high capacity (100-500 tons) piling. Next came soil nailing, both temporary and permanent retaining walls, as at Cumberland Gap Kentucky. My next morph was into ?Cement Deep Soil Mixing? earlier on, known simply as ?soil mixing?. For this education I traveled to Japan several times and established a long-term, Joint Venture, relationship with one of the better known Japanese specialty ground modification companies. In Boston at the ?Big Dig? we established the then record size soil mixing project, 500,000 or so cubic meters of CDSM concluding in the year 2000. Since then I?ve been involved as a consultant mainly for dams and levees. Below is the story of how I came to be at this place in the road to innovation in Geotechnical processes.

By Stuart Hardy, Xiangbo Qiu

The South Bank Place project comprised the redevelopment of the iconic Shell Corporation headquarters in Waterloo, located on the Southbank of the River Thames in central London. The site was originally developed in the 1950’s and due to the monitoring of the underlying Bakerloo Line tunnels by the Building Research Station it has become a seminal case history for the long term swelling behaviour of London Clay. The redevelopment, undertaken by a joint venture of Canary Wharf Group and Qatari Diar, included demolition of the existing building (with the exception of the main towers) retention of the existing basement structure and the construction of eight new mixed use buildings, up to 31 storeys in height. The foundations for the new buildings varied according to the building height and the below ground constraints. Two of the buildings are partially founded in reused under reamed piles that were installed as part of the original 1950’s development. The paper describes the novel methodology developed to assess the re-use of the under reamed piles which builds on the guidance published by CIRIA and the BRE for straight shafted piles. The paper also describes the physical investigations and numerical analyses undertaken as part of the assurance process and the procurement of latent defect insurance by the client.

May 1, 2022

By Ahmad Mahboubi

The damage caused by catastrophic earthquakes has always been an incentive towards more sophisticated building codes and requirements. In parallel to computer technology development, the engineers? attitude towards acquisition of more accurate results is increasing. This approach leads to designation of structural elements with more elaboration considering different aspects of their behavior. In addition, less simplified methods will be considered as satisfactory for analyzing such problems. The problem of soil-pile-structure interaction is one of the phenomena that can be included in this category. In general, there are two methods by which the study of soil-pile interaction phenomenon is studied. These include direct and sub-structuring methods. The sub-structuring approach relies on the linear or slightly non-linear behavior of soil since it employs the results of kinematic interaction analyses for inertial interaction studies. In the past, the kinematic interaction between pile-soil was considered as negligible. This was due to the softer nature of the surrounding soil that increased the time period of vibrations. However, more research revealed that although this approach was consistent in many cases, there were some sites where the time period decreased. This was due to the material properties of the foundation and the soil, in a way that caused the frequency of vibration meet natural frequency of the system. The second type of interaction is the inertial interaction which reflects the effect a structure on top exerts on the oscillation experienced by the foundation. This paper examines the impact of vertical load on the inertial interaction by virtue of impedance functions. Three different load cases for the structure at the top of a pile foundation were considered for the analyses conducted in this study. The changes in the stiffness and damping of the system by frequency are studied and finally, the results are presented.

Jan 1, 2010

By David P. Sauls

Design-build contract delivery provides unique opportunities for efficiencies in pile foundation design and installation. The Louisiana Department of Transportation and Development (LADOTD) US Highway 90 at Louisiana State Highway 85 (US90/LA85) intersection was contracted under the design-build delivery system, in part to take advantage of these efficiencies. As one of five projects recognized by the Design Build Institute of America (DBIA) when it honored LADOTD as its 2011 Transportation Owner of the Year in the highway/bridges category, the design-build method provided a way for this project to be ?shovel-ready?, which enabled the LADOTD to secure American Recovery and Reinvestment Act (ARRA) funding. This paper describes the benefits this project gleaned from the design-build process, which included synergy, schedule, design and construction efficiencies, and team building. Interlaced with design and construction of precast prestressed concrete (PPC) piling in compressible southern Louisiana soils, the design-build process rapidly translated computations to cost and schedule savings. A robust quality assurance program using Pile Driving Analyzer (PDA) equipment to evaluate pile set-up provided expedited acceptance of bridge bents and advanced construction schedule. Data evaluation includes analyses of PDA data obtained from 1-hour, 24-hour, 7-day, 14-day and 6-month restrikes of the project test pile.

By Richard D. Luark, Fernanda S. Madrona

Deep foundation construction in highly developed urban settings pose unique challenges of working with deep excavations in a relatively confined area while preserving the integrity of nearby structures. For construction of the below grade parking for two, 40-story residential high-rise towers, shoring walls were required to support the maximum 70-foot-deep vertical excavation in downtown Seattle, Washington. The design of the excavation support system consisted of soil nails combined with closely spaced vertical elements to allow the top row of soil nails to be installed up to 10 feet below the ground surface avoiding conflicts with adjacent underground utilities. To limit deflections next to a seven-story building, the upper rows of soil nails were post tensioned. An instrumentation program was implemented to monitor the deflections in the shoring walls by means of vertical inclinometers and optical survey monitoring. The shoring wall performance, designed to limit deflection to less than 1-inch to meet the City of Seattle requirements, was validated by the instrumentation program. This paper provides a discussion of the design and construction of the shoring walls as well as the monitoring data collected from the instrumentation system. PROJECT INFORMATION The project consisted of two residential high-rise towers, with five levels of below grade parking, located at 707 Terry Avenue Seattle, Washington. The project site covers a half city block, approximately 120 feet by 240 feet, and is bounded by Terry Avenue to the east, Columbia Street to the north, Cherry Street to the south, and an alley to the West. Prior to the development, site was occupied by surface parking. A 7-story concrete building with two stories of below grade parking, owned by the Archdiocese of Seattle is located just west of the 16-foot-wide alley. Numerous below grade utilities consisting of electrical, telecommunications, gas, water, sanitary sewer, steam, and storm drains, surround the project. The perimeter below grade parking walls extended within inches of the property boundaries. Topographic relief across the site was on the order of 8 feet. Figure 1 illustrates the site plan view.

Jan 1, 2019

By Gilbert R. Tallard

"Pouring deep foundations by the tremie pipe method is nowadays such a common process that it has becomes an unspecified practice. Means and methods are almost entirely at the contactor’s discretion. A variety of practices are permitted and seldom associated with the discovery of abnormalities and areas of random defects in concrete. This writer wishes to call the attention of stakeholders to the initiation details of the tremie pour operation.KEYWORDSINTRODUCTIONThe advent of slurry as a means of shoring an excavation of relatively small cross section but of possibly great depth has become part of state of the art in foundations construction, with the substitution of said slurry by concrete to provide the structural end product element through the use of tremie pipes. In appearance, there is nothing more simple than pouring concrete into a tremie pipe through a hopper after the basic work has been done i.e. the excavation or drilling, the cleaning of the slurry, the placement of the reinforcing cage, then the tremie concrete pour is almost a reward for a successful achievement. Force of habit has removed the awareness on the process fundamentals for initiating the pour; a variety of practices used call for a review and a reassessment as a means of reducing construction defects that may result from flawed practices, and and especially we are pouring deeper holes. This writer intends to address this issue focusing both on the drilled shaft and the diaphragm wall industries.TREMIE PIPES AND HOPPERSA tremie pipe diameter needs to be sufficiently large to allow the rapid descent of concrete with a minimum of friction loss and avoiding possible bridging in relation to aggregate size. Impervious joints between pipe sections are essential to prevent slurry “raining” over the concrete which can cause concrete segregation pockets and possibly plug the pipe with damaging consequences. That tremie pipes be long enough to reach the bottom may be self-evident but poorly written specifications can be erratic on that subject and seldom specific in terms of inches. A standard pipe of 10 inches is well accepted throughout the foundations industry; double O rings and spline joints are common and function well if properly maintained. However the practice to cover the joint with the ineffable duct tape indicates that all is not always well with this detail. Also, spline cables may shear in case of very long tremie pipes causing the separation of the tremie pipe requiring a restart in midstream with another probable source of inter mixing of concrete and slurry with subsequent defects."

Jan 1, 2017

By Seyyed Mehdi Radeghi Mehrjou

The current work investigates the behavior of inclined micropiles under seismic loads. The dynamic finite element method (FEM) was employed. Rayleigh damping was applied to the soil, and elastic beam elements were employed to model the micropiles. The micropile structure was assumed to have one degree of freedom as a column with concentrated mass. The numerical modeling of micropiles was performed to explore the effects of their inclination on their seismic performance within homogeneous soils with uniform stiffness. In addition, the effect of soil stiffness was studied by considering various stiffness in soil depth. The results from the studies have shown significant effects on the dynamic amplification and internal seismic-induced loads of inclined micropiles.

Sep 1, 2022

By Dzianis Proshchanka, Yoshi Izumi, Koji Mitani, Ayuna Kitaura

"A new pile driving and drilling navigation system has been developed. It utilizes the commonly used surveying total station, combined with an innovative reticle. Conventional crosshairs have been replaced by a concentrically circular reticle called Baum. It allows for easily performed measurements of central axes of cylindrical objects such as piles, chimneys, electricity poles, etc. This provides several significant advantages compared to other existing systems. It is cost-effective as only one operator is required to control deviations in positioning and inclination. Furthermore, repetitive reinstallation of the instrument is not required for every pile driven or hole drilled. It is also a safer method, as workers have no need to be near a pile driver or drilling machine to perform the measurements. With Baum Station, necessary measurements can be performed away from the actual work area. Moreover, it is highly accurate with real-time solutions, as three-dimensional orientation information for the pile/drill is obtained simultaneously with the pile being driven or the hole being drilled. This allows for the highest levels of precision-control and correction to minimize eccentricity of the intended center positioning.INTRODUCTIONBackgroundIn foundation construction for structures, pile foundations are widely used for deep bearing strata. There are two patterns to driving piles: vertically or obliquely to the ground. The shapes of the piles are normally cylindrical. Vertical pile foundations are employed as the foundations of many structures due to their high workability. There is a problem however, which is that this method does not bear measurement data as construction accuracy is visually checked. On the other hand, tilted pile foundations are rarely employed because it is too difficult to ensure construction accuracy. In addition, commonly used percussion methods create noise and vibrations when the piles are hit, while there are advantages that thinner piles are available, ensuring earthquake-resistance, as tilted piles curb horizontal displacements of structures, which may be caused by earthquake ground motion. However, current requirements of cost reduction bring professional attention to tilted pile foundations, which can be driven reasonably and economically with much research of tilted piles having been carried out to improve their capacity. Also, a method of screwing piling has been developed, which produces small amounts of noise and vibrations. This method has solved tasks of workability and environmental burdens, and is becoming more and more common. However, there is a necessity to develop a method to accurately measure angles of piles’ axes in order to drive piles into the ground with appropriate angles. It is also expected to find out a way to control construction information, such as correction amount and driving record."

Jan 1, 2017