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By Mohammad T. Izadi

Piles are, often, used for transferring load from the super structure through soft consolidating strata onto relatively stiff uncompressible soils. Downward movement of the soft soil strata develops negative skin friction and dragload around the pile shaft, with time. Traditionally the induced dragload is considered in determining the pile bearing capacity. On the other hand, field measurements on instrumented piles show that negative skin friction is reduced by the magnitude of applied live load. A method for calculating the pile bearing capacity, driven through soft consolidating strata is presented. In this method, two allowable load-bearing capacities are calculated for each pile, live load plus dead load and dead load. The proposed method, substantially, increases the allowable load bearing capacity of piles compared to calculated values by the traditional methods.

Jan 1, 2001

By Michael W. Neill, O&apos

The performance of foundations that combine the high bearing capacity of rafts (mats) with the settlement reduction capability of piles is described through a summary of 24 case histories. Structures included are high-rise commercial office buildings, governmental buildings, industrial facilities and residential buildings, and subsurface conditions range from soft clay to stiff soil overlying rock. Pile types are bored, augered and driven. Since piled rafts are not commonly used in the United States, most of the case histories are from overseas. In all cases the performance of the foundations was monitored during and after construction. Particular emphasis is placed on measured settlements of the piled-raft foundations, distribution of resistance between piles and raft, and general analysis methods that were used by the designers for various geotechnical circumstances. Finally, patterns of behavior are summarized. In most cases, the piles were not designed to mobilize their full capacities under sustained loading of the foundation; therefore, under long-term loading conditions, the piles typically carried more load than the raft. This paper is the result of a study conducted by ITC-18 (Deep Foundations, Willem Van Impe, Chair) of the International Society for Soil Mechanics and Geotechnical Engineering by a subcommittee chaired by the author.

Jan 1, 2003

By W. H. Craig

Techniques have been developed for installing model piles into beds of soil under high sustained acceleration levels aboard a centrifuge. These piles have been subjected to static and/or cyclic lateral loading in order to assess their performance and provide a data base for assessment of various design techniques for laterally-loaded single piles. From measured bending moment profiles the so-called 'p-y' curves have been deduced using fifth order splines for curve fitting, followed by subsequent differentiation and integration. The results show some divergence from the predictions of the semi-empirical designs, but these latter are generally found to be acceptable.

Jan 1, 2010

By Bengt H. Fellenius

An upgrading and straightening of a highway included building a bridge across a small river. A routine site investigation was initiated to determine the conditions for designing the foundation of the bridge. The proposed bridge was a two-lane highway bridge in one span with a total length of 30 m (100 ft), as indicated in Fig. 1. It was to be placed about 20 m (66 ft) upstreams of the bridge for the existing highway. The site investigation included one boring at each abutment with soil sampling and in-situ vane testing and placed about halfway up the slope from the small river at ground surface elevation + 54 m. Within the investigated maximum depth of 40 m (130 ft), the soils at both borehole locations consisted of a thin clay crust over a thick deposit of soft sensitive clay with a natural water content of about 70 % and a liquid limit of about 60. The undrained shear strength below the crust was about 20 KPa (400 psf) and increased slightly with depth. The sensitivity was high, about 40.

Jan 1, 1987

By Charles R. Conlon, Matthew J. Niermann

This paper presents the underpinning and excavation support systems used for construction at 2100 L Street in Washington, DC. The excavation for the proposed building extended below bedrock, which presented significant challenges for underpinning the historic Stevens School, constructed in the late 1800’s. The Stevens School was underpinned using several techniques consisting of soil mixing below an unreinforced foundation, traditional hand-dug pits to rock, micropiles below rock, and bracket piles. The excavation support system for the remainder of the project consisted of soldier piles and lagging supported laterally by tiebacks and braces. Shotcrete and rock bolts supported the exposed bedrock. This paper will discuss the design, construction and monitoring results.

By D. A. Ponniah

The installation of a pile is considered analogous to the expansion of a cylindrical cavity of a diameter equal to that of the pile. Using Vesic's theory of the expansion of cavities the effect of soil properties on pile installation loads, radial pore and total pressures are evaluated. The theoretical results are compared with load and pressure measurements made in field trials in a stiff clayey glacial till in the U.K.

Jan 1, 1987

By A. Le Kouby

We present in this paper the results of a parametric study carried out in a calibration chamber on instrumented model piles. The aim is to point out group effect on piles within a group through their resulting shaft friction and tip resistance. The methodology relies on the study of the influence of adjacent piles on a "reference" pile. The soil used is a silica sand (Fontainebleau sand). The influence of parameters like pile spacing, number of piles and installation order are evaluated. The results show a positive effect on shaft friction of the group effect and a negative effect on tip resistance. Efficiency factors are defined in order to have a better view on the parameters influencing the response of the pile within a group.

Jan 1, 2006

By Lin Li

A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. In the past effort, a deterministic method using the limiting equilibrium method of slices for determining the global factor of safety of a slope reinforced by a row of drilled shafts was developed using the soil arching concept. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which reduces the driving forces on the down slope side of the drilled shaft. The effect of drilled shafts induced soil arching on the reduction of the driving stresses in the limiting equilibrium slope stability analysis was quantified by the load transfer factor through extensive finite element simulation studies. A semi-empirical equation was also developed for expressing the load transfer factor as a function of the soil properties, including strength parameters and unit weight as well as the slope geometry and soil profile, the location and spacing of the drilled shaft, and the dimension of the drilled shaft. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, a modification of the deterministic method into a probabilistic method is developed in this paper. The Monte Carlo statistical method is used to generate random variables for the soil strength parameters based on the prescribed probability characteristics, including mean, COV, and the probability distribution function. In addition, the modeling error of the load transfer factor is also treated as a random variable in the Monte Carlo simulation method, in which the mean, COV, and probability distribution function for the bias of the semi-empirical equation are used. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Two examples are shown in the paper to illustrate the analysis results of the developed probability approach for determining the reliability of a drilled shaft stabilized slope system.

Jan 1, 2017

By Lin Li

A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. In the past effort, a deterministic method using the limiting equilibrium method of slices for determining the global factor of safety of a slope reinforced by a row of drilled shafts was developed using the soil arching concept. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which reduces the driving forces on the down slope side of the drilled shaft. The effect of drilled shafts induced soil arching on the reduction of the driving stresses in the limiting equilibrium slope stability analysis was quantified by the load transfer factor through extensive finite element simulation studies. A semi-empirical equation was also developed for expressing the load transfer factor as a function of the soil properties, including strength parameters and unit weight as well as the slope geometry and soil profile, the location and spacing of the drilled shaft, and the dimension of the drilled shaft. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, a modification of the deterministic method into a probabilistic method is developed in this paper. The Monte Carlo statistical method is used to generate random variables for the soil strength parameters based on the prescribed probability characteristics, including mean, COV, and the probability distribution function. In addition, the modeling error of the load transfer factor is also treated as a random variable in the Monte Carlo simulation method, in which the mean, COV, and probability distribution function for the bias of the semi-empirical equation are used. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Two examples are shown in the paper to illustrate the analysis results of the developed probability approach for determining the reliability of a drilled shaft stabilized slope system.

"Boston’s Central Artery passes beneath nine active railroad tracks carrying commuter and Amtrak trains into South Station, the City's busiest rail terminal. These railroad operations had to remain in service throughout the construction of the “Big Dig”. The solution was to jack the tunnel under the tracks, rather than build the tunnel by more conventional means.Jacking of utility pipes is fairly common, but jacking boxes as big as a highway had never been done in North America, until the Big Dig came along.Soil freezing was decided upon as a means of stabilizing the soil under the tracks. This allows the tunnels to be jacked into place without soil caving when the soil is excavated at the leading face of the advancing tunnel boxes. Hundreds of pipes were driven into the ground between the tracks. Inside the steel pipes were smaller plastic pipes. A freezing plant near the railroad tracks pumped refrigerated brine into the inner plastic pipes. The brine ran out the bottom of the inner pipe, flowed up to the top inside the outer pipe, and was re-circulated to the freezing plant and back again into the ground. Over several weeks the circulating brine drew the heat out of the soil little by little, and froze the ground outward from the pipes. Soil FreezingThe plan required the construction of jacking pits in which the tunnel boxes could be constructed, and from which they could be jacked forward to their final locations, as described in the accompanying article. Once the jacking pit was built and the tunnel box constructed inside the pit, crews made an opening in the headwall of the pit to allow passage of the tunnel sections, excavated about three feet of the frozen soil, pushed the tunnel box ahead, and repeated the procedure again and again."

Jan 1, 2003

By Mitsuhiro Shibazki

I can't answer that question but I am looking at Andy, my co-author, and he says we didn't measure it. No movement. If I understand it correctly, how do we handle lateral forces in shear? The main columns were designed as pin connections so there wasn't a moment in the shear between the pile cap and the columns the steel reinforcing was used to resist that. I am not aware of how we would have installed those, it is possible to try and submerge them all if the jet grout is still fluid. They were higher than design. You are correct.

Feb 10, 2003

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

Jan 1, 1996

By Peter Deming

"PART 1 OF 2INTRODUCTIONSlurry trenches are the least cost hydraulic barrier available, if the excavated spoils can be recycled into backfill. As such, slurry trenches are constructed where possible, sometimes at high risk. Slurry trenches are also used to install biopolymer drainage trenches, which have a low safety factor because the biopolymer slurry weight is marginally greater than the weight of water. In marginal ground the construction risk falls to both the Owner who designs and asks for the construction, and the Contractor who manages the work and promises to complete the project successfully. This paper discusses design and construction of slurry trench barriers in marginally stable ground and where groundwater chemistry invokes the need for slurry management details to obtain proper backfill placement.As a designer, Mueser Rutledge Consulting Engineers works for both Owners and Contractors. We are usually able to convince Owners of their responsibility for design detailing in order to obtain a working final product and to obtain reasonable bids from Contractors by disclosing construction needs and designing to reduce the contractor’s exposure. We often work for Contractors to produce designs which result in successful construction in projects where the Owner’s engineer places the responsibility of design and construction on the Contractor.This paper is intended to inform both Owner and Contractor audiences of resources which are available to reduce the risks of trench collapse in difficult ground conditions. We hope it serves this purpose.DESIGNSubsurface InvestigationsSubsurface conditions should be defined by borings focused on definition of the soil profile and soil design parameters. After general subsurface conditions are defined, barrier borings should be drilled along the final alignment.Definition of Soil Strength and CompactnessCompactness of sand and gravel strata should be defined with Standard Penetration Test N-values. The shear strength of cohesive materials should be defined by laboratory testing. Silt and fine sand strata with little cohesion should be investigated using mud rotary techniques to prevent disturbance. General strength characterization by soil layer should be used for analysis of trench wall stability."

Jan 1, 2006

By Arturo Ressi di Cervia

"The Construction of the Thrust Pits for Jacking of the I-90 Tunnel for the Central Artery/Tunnel Project (Part of Contract No. C09A4) in Boston MA was nominated for DFI’s 2002 Outstanding Project Award. In the judging, the project and the specialty subcontractor, Treviicos Corporation, was chosen for a Special Recognition Award. INTRODUCTIONBoston’s Big Dig, as the construction of the underground artery became known, is undoubtedly the largest urban construction project of this century.The Central Artery/Tunnel Project, or CA/T, to call it by its proper name, runs approximately eight miles through the heart of Boston, five miles of which are built underground while maintaining traffic on the elevated existing structure, while at its southern end I-90 is extended to Logan airport under active rail lines, Fort Point Channel and Boston Inner Harbor.Since the alignment of the road closely parallels the shoreline as it existed in colonial times, the cut and cover construction had to contend with substantial portions of filled ground, not to mention existing subway lines, live utilities, building foundations and, last but not least, the irritable Boston drivers and litigious adjacent property and business owners.Consequently, while it is impossible to single out the most difficult or challenging contract, the jacking of the tunnels of I-90 under the live rails of Amtrak certainly will rank high on the list.Never before, anywhere in the world, was an attempt made to jack tunnels of this size: the South Bay Interchange consists of three 78 feet (24 m) wide by 38 feet (11.6 m) high tunnels, the shortest of which is 167 feet (51 m) long. TECHNOLOGYIn order to achieve this engineering feat it was necessary to consolidate the soil under the track to prevent it from moving or settling during the jacking process. After a detailed analysis of the geological profile to be traversed it was decided that freezing was the most suitable method, since it could be applied to the full range of soils present on the proposed alignment."

Jan 3, 2003

By Gerald Verbeek

There are certain concepts that seem to invite responses from some, including some in the foundation industry and even some within DFI, that are at best surprising. Business owners and their employees share the desire that their company does well and continues to operate. Maybe company growth is not always realistic but maintaining the current level of activity is in the least what they hope for. In other words, they hope that their company is sustainable, and they are fully behind that notion. But when the concept of sustainability is raised, there is, at least with some, suddenly doubt that that is a good thing. And yet, that concept only aims to achieve at a grander scale what the owners and employees desire for their company. There are many definitions of the term sustainability, but probably the most commonly used description is that framed by the United Nations in 1987. It states that sustainability is the concept of meeting the needs of the present without compromising the ability of future generations to meet their own needs. Arguably that definition is too abstract and does not provide the type of specific goals and targets we are used to. To help with that, to some extent, in 2015 the United Nations formulated 17 Sustainable Development Goals (SDGs), to provide "a shared blueprint for peace and prosperity for people and the planet, now and into the future." And undoubtedly those SDGs are fodder for those that question the concept of sustainability in the foundation industry. How can our industry, they wonder, ensure that there is no poverty or hunger (SDG 1 and 2), and the climate action goal (SDG 13) immediately leads to the hot button topic of global warming. And maybe this is where advocates lose (some of) the sceptics of the sustainability concept, but hopefully they will continue to read this article that lays out why sustainability simply makes sense, also for the foundation industry and especially for DFI.

Nov 1, 2022

By Michael E. Ameel

The vibrated beam method of installing a vertical barrier wall is one of the least applied techniques, yet given certain site conditions and constraints, it is a cost-effective and proven method of controlling lateral groundwater flows. A recent full-scale application of this technique demonstrated its usefulness at an active manufacturing facility located in Northern Wisconsin. At this site, a 3,233 foot long cutoff wall was keyed into an underlying bedrock, which was located an average of 40 feet below the ground surface. Using a slag cement-clay based slurry, a 1E-7 cm/sec or less, nominal 4-inch wide cut-off wall was constructed using the vibrated beam method. Challenges included working around an active manufacturing facility with minimal access to the work area; installing the wall through a very dense glacial till; minimizing soil excavation volumes of potentially impacted soil; and, working around and adjacent to numerous active utility lines without impacting the facility operations. At utility locations, the vibrated beam wall was supplemented with a jet grout panel wall, without the need to bypass or otherwise interrupt any of the plant?s utilities. Quality control consisted of the monitoring and measuring of slurry parameters, survey control, and real-time monitoring and documentation of all critical barrier wall installation parameters. A vibration monitoring plan was also implemented to measure vibrations at utilities and adjacent facility structures. Proper equipment selection, significant up-front planning and close coordination with the facility resulted in a safe and successful project. The work was completed ahead of schedule during the 2009 construction season.

Jan 1, 2010

By Denis Huber

The technical assessment of the final works on the "Stéphany Palace" project at Menton in France's Alpes-Maritimes region shows the importance of daily project monitoring based on the observation method recommended by the European standard Eurocode 7 which applies to Foundations and Geotechnical Engineering. Excavation operations to a depth of 10 m near the France-Italy railway track and adjacent buildings required precise observation of land deformations, regular piezometric monitoring as well as special design arrangements. Temporary active tie-rods were thus placed in phases in order to control deformations in the retaining structures resulting from excavation operations. The Menton region, terminating the Alpine arc of mountains, naturally required the consideration of seismic forces in phase in the lower floors of the building, directly linked to the buried walls. These calculations were carried out in accordance with the PS69/92 rules, calling for an increase in dynamic thrust under the effect of gravity field rotation.

Jan 1, 2002

By Mitsuhiro Shibazaki

Generally, water-soluble polymers are effective in convergence of water jet ejected from a nozzle as they add viscosity to water. However, excessive additional polymers (added to keep water viscous) could increase friction on the contrary. Therefore, we have totally modified the jetting system from every possible aspect, such as the shape and upstream conditions of a nozzle in order to keep the flow spread to the minimum as stated in my presentation.

Feb 10, 2003

By Emad Farouz, Ehab S. Shatnawi, Charles Winter

The increasing demand for small deformations and high-capacity drilled shafts without enlarging drilled-shaft diameters has motivated the development and increased use of a base grouting (BG) technique. This technique has been demonstrated to improve drilled-shaft axial capacity, especially for shafts tipped into loose cohesionless soils. To date, there are a couple of documented design methods for estimating the axial geotechnical resistance of base-grouted shafts. However, there is no or lack of research that addresses the lateral response of such shafts. A base-grouted drilled shaft test program was carried out during the design phase of the Wisconsin I-94 Zoo Interchange reconstruction project. The test program included installing and testing one base-grouted shaft and one ungrouted shaft under both lateral and axial loading. Based on test results, it was concluded that the lateral behavior of the BG drilled shaft is significantly stiffer than conventional drilled shaft . Hypothetical method was developed to account for potential increased, however, the method should be verified with more lateral load test.

By Ting-Wei Wang, Yung-Wen Chen

Artificial ground freezing is commonly used globally during excavation of shield tunnels and for groundwater control. It is a special construction method for temporary ground improvement that involves introducing coolant into underground pipes to freeze water in the soil. The frozen soil is cemented together as a result to form a frozen wall, which provides high strength and low permeability. Once the thickness of the ice wall reaches design requirements, underground excavation can be conducted with the coolant removed afterward to return the soil to its original state. This technique is cost-effective in scenarios where complete groundwater cut-off and excavation support are required; where work is deep underground and faces difficult ground conditions and where access restrictions limit the use of other displacement-type ground improvement techniques. Due to the demand for shield tunnel construction for utilities in Taiwan, ground freezing has become an important soil stabilization method there. In this article, we will share two brine freezing case studies and an in situ liquid nitrogen experiment that was conducted to develop this technique.

Feb 1, 2022