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By Ganesh Kumar S.

"Soil reinforcement using stone columns is one of the well-developed ground improvement techniques for soft clay deposits. The load carrying capacity can be further improved by encasing it with geosynthetic material around the column which offers effective lateral confinement, prevents column contamination with improved drainage and strength characteristics. Improvement of undrained shear strength using vacuum consolidation is a type of hydraulic modification technique in which negative pore pressure will be developed which increases the effective stresses in soil without changing the total stress. The improvement in effective stress resulted in improved undrained shear strength of surrounding soil. In this research work, combined geosynthetic encased stone column and vacuum treatment method is examined for improving of extremely soft clay soils. The improvement in the time rate of consolidation and load carrying capacity of stone columns after vacuum treatment was studied using experimental investigations. It was observed that both load carrying capacity and stiffness of the encased stone column increased significantly with vacuum application. Also, application of vacuum accelerates rate of primary consolidation settlements. With this reduction in time, the construction activity can be accelerated which makes the project economically beneficial.INTRODUCTIONThe rising demand for the land for country’s infra-structure compels the engineers to work with even soft clay deposits which are not suitable for construction activities. As these soils have low bearing capacity and excessive settlement characteristics, ground improvement methods will be required before commencing construction. Among all available treatment methods, soil reinforcement and hydraulic modification technique are well-known popular techniques for its reduction in time required for consolidation settlement with improvement in load carrying capacity. When stone columns are used as a reinforcing member, it creates drainage with improves bearing capacity (Greenwood, 1970; Mitchell & Huber, 1983). However, the limitation includes lack of lateral confinement in very soft clay deposits, possibility of contamination, reduction in drainage path all which leads to the failure of stone columns (Mckenna et al, 1975). To overcome these limitations, encasement using geosynthetic material was adopted around the column which offers better lateral confinement, prevents intrusion of finer clay particle inside the column and provides effective drainage path with improved load bearing capacity characteristics (Van Impe, 1986; Raithel et al. 2005; Short et al. 2005; Borkemper et al. 2006; Murugesan & Rajagopal 2010; Kumar et al. 2014)"

Jan 1, 2017

By R. T. Stain

Dynamic methods of load testing piles using a drop hammer to generate the input force have been in use for many years. These systems are based on the wave equations developed at the Case Institute of Technology, Cleveland, Ohio in the late 1960's and are well documented. Such tests are generally restricted to preformed driven piles, the driving hammer being a convenient means of generating large input forces. In 1979 the CEBTP (France) was sponsored by the FNTP (Fédération Nationale des Travaux Publics) to undertake research into existing classical methods and to develop a test that would be equally applicable to bored cast in place piles. The result of this research programme is a methodology known as SIMBAT, and which was included in a series of class A prediction trials in Belgium in 1987 (Refs 1 & 2, Paquet 1987, 1988). The purpose of this paper is: a) to examine the type of 'dynamic'/'static? load test correlations that can be obtained. b) to highlight the differences between the classical' methods and the 'SIMBAT' technique.

Jan 1, 1989

By David R. Beadman

The Fleming method is widely used for the analysis and prediction of single pile behaviour under maintained loading. The method does not distinguish between bored and driven piles. Driven piling avoids the need to dispose of spoil from the pile installation and is therefore becoming increasingly attractive. This paper considers the theoretical effects of the possible preload at the base of a driven pile after installation, using the hyperbolic functions as defined by Fleming. The Fleming method is reviewed and the equations and analyses are adapted, using spreadsheets, to allow for a possible preload. The simplifying assumption of the effect of the elastic compression of the pile is also reviewed and a more analytical method adopted to assess the elastic compression. Some driven pile test data is analysed to consider the possible effects of the preload on the performance of a driven pile and to test the theoretical relationships that are developed in the paper.

Jan 1, 2006

By Geoffrey C. Hebner

Augered, cast-in-place piles (ACIP) have become a very common foundation type in Atlanta and the Southern Piedmont Province as well as much of the United States in the past 20 years. Prior to the introduction of ACIP foundations in Atlanta, the most common deep foundation type was Raymond piles. Raymond piles are basically a driven, thin-walled step-tapered steel pile filled with concrete. Drilled piers were also relatively common and continue to be used, particularly in shallow bedrock or high column load situations. Driven piles, including pipes, H-sections, and timber piles were previously common with working loads typically in the 30 to 50-ton range. Initially, ACIP foundations had similar allowable capacities, however, over time improvements in installation techniques and equipment have resulted in an increase in allowable ACIP capacities. Correspondingly, they have become a more cost-effective and trusted foundation for geotechnical and structural engineers. Over the next several decades many other deep foundation alternatives began to lose popularity. ACIP are one of the predominant deep foundations in Atlanta and the Southern Piedmont today. Although ACIP foundations have widespread popularity in the private sector, they have not been readily accepted currently by government transportation agencies. ACIP may be used by some of the smaller municipalities, but to the author's knowledge, have not been used with regularity by larger, state agencies.

Jan 1, 2003

By Rick Deschamps

The Block 76 project includes the demolition and redevelopment of an entire city block for mixed use retail, office and residential properties directly adjacent to Historic Temple Square in Salt Lake City, Utah. Excavation was carried out 65 ft below street grade and by as much as 50 ft directly below adjacent buildings supported by shallow foundations. Movements of the earth retention system and adjacent buildings were monitored in real time using automated equipment which complemented traditional geotechnical instrumentation. In the areas immediately adjacent to the existing buildings 9 stories or greater, anchored diaphragm walls were employed. Areas of the site not supported by diaphragm walls employed a soil nail wall system. Jet grouting was used for water cutoff in lieu of dewatering along the north and east sides of project. In total, the earth retention scope included 45,000 sq. ft of diaphragm wall, 104,000 sq. ft of soil nail wall, and micropile underpinning of 3 buildings. This paper provides an overall description of the Block 76 project. A detailed account is provided of the technical and commercial lessons learned. The project provided a unique example of how an owner can receive best overall value by acceptance of some technical risk up front. Benefit was gained by allowing the contractor to reduce contingencies within the bid from unknowns on a fast-track project.

Jan 1, 2009

By David S. Yang

The construction of Oakland Airport Roadway Project for the airport expansion requires stabilization of subsurface soils for the construction of three grade separation structures at two roadway interchanges and the intersection of a roadway and taxiway serving the airport. Loose sandy fills and soft Bay Mud were improved by Cement Deep Soil Mixing (CDSM) for the construction of a soil-cement foundation under the MSE (Mechanically Stabilized Earth) walls of a roadway overcrossing and a soil-cement gravity retaining wall to maintain stability of a roadway undercrossing during and after a major earthquake. CDSM was also used to construct two cutoff walls for groundwater control. A test section was carried out prior to full production to verify that the CDSM equipment, installation procedures, and mix designs could produce the soil-cement with required strength, uniformity, and permeability to meet the design intent. Additional test sections were performed for the confirmation or modification of the mix design and installation procedure to cope with the complex subsurface conditions resulting from the historical development of the site. The test section revealed that the CDSM cutoff walls, retaining wall, and foundation improvements could be constructed to satisfy the design requirements and that the intermittent test sections alleviate the impact of the varying subsurface conditions. Based on the data obtained from the test sections, one CDSM cutoff wall was completed in July 2000. Full production of the CDSM retaining wall, cutoff wall, and foundation began in March 2001 and is expected to be complete in November 2001.

Jan 1, 2001

By Mohab Sabry

Pile foundations are used extensively around the world to support both inland and offshore structures, including important structures such as nuclear plants and oil drilling platforms. The limit of the pile depth is currently predicted during the pile deriving process, given no chance for the designer to predict accurately the capacity of these piles prior installation. Furthermore, after pile installation, designer may not be able to modify the pile group design by increasing the number of piles and or changing the geometry of the pile group. This paper presents a numerical model for the case of single piles driven in homogenous sand using finite element technique and the theory of cavity expansion. The model is capable of simulating all the construction stages of concrete piles up to the maximum depth, which can be driven in sand and accordingly the capacity, which can be attained by these piles. The program "PLAXIS" is used to perform the proposed analysis. This model simulates the process of pile driving in terms of the changes in the earth pressure and the overconsolidation ratio acting along the pile's shaft. Based on the results of the present investigation, these depths can be predicted based on the pile geometry and the sand properties. Charts are given to provide these depths for given pile/soil conditions.

Jan 1, 2006

By Bill Starke

The acceptance of AugerCast piles in Canada has been limited. Many engineers are apprehensive about the quality of the piles produced by this method. However, advances in the sensing instruments and computer technology can now provide satisfactory levels of quality assurance. Post construction tests such as the sonic echo method can give an indication of pile shaft integrity. Computerized monitoring of the pile installation process is an immediate and more positive method of quality assurance. The computer continuously measures and records the parameters which indicate the quality of the pile. If these parameters do not indicate a satisfactory pile, it is replaced before the concrete hardens. Computerized monitoring of the installation process is another tool available to the engineer. The data from this system analyzed with soil borings, site inspections, and possibly sonic tests can provide the engineer with enough information for pile certification.

Jan 1, 1997

By Sangseom Jeong, Kyoungyul Kim, Jaeyeon Cho

"Abstract The lateral earth pressure of vertical circular shaft is investigated by using experimental tests and a theoretical analysis. The emphasis was quantifying on the magnitude and distribution of a lateral earth pressure measured by three-dimensional arching effect. A framework for determining the earth pressure distribution on the basis of both centrifuge model and full-scale field test results is introduced. Through these studies, it is found that the lateral earth pressure decreases within active displacement (dh/H: 0.2×10-2, dh: horizontal displacement, H: Height of vertical shaft) of wall at deep excavation and the arching effect is more significant for deep excavation than for shallow excavation. It is also found that the lateral earth pressure acting on a vertical circular shaft considering arching effect is 70% smaller than that calculated by Rankine theory, and thus represents a significant improvement in the prediction of realistic earth pressure for vertical circular shaft subjected to arching pressure.INTRODUCTIONIn South Korea, an increasing need for underground excavation and the application of the vertical circular wall (i.e. vertical shaft) is becoming an important issue in engineering practice. Here the vertical circular wall is generally embedded in soft or hard rocks through weathered soil varying thicknesses ranging up to 15 m. Since 1980, a number of huge excavation projects such as underground space for constructing power stations, subways, high-speed railways, and many lifeline constructions have been performed in urban areas (Jeong and Seo, 2004). Although there have been considerable advancements in construction techniques involving vertical circular wall, it is still very important for tunnel engineers to control the lateral earth pressure. Additionally, Proper estimation of earth pressures is a key factor in design of vertical circular wall. Because of three dimensional arching effects, i.e. convex arching and/or inverted arching, the earth pressure acting on a circular type of wall is less than other types. Thus, the vertical circular wall is generally used."

Jan 1, 2014

By Maurizio Siepi

The realisation of most of the civil engineering works is subordinate to the execution of consolidation works, in order to improve the soil physical-mechanics characteristics. The works classifiable with the term "Soil Improvement" can be realised using several technologies, among which the Deep Mixing Method is distinguished for his remarkable flexibility and productivity characteristics. The Deep Mixing Method is a process whereby a rotary drilling machine mechanically drills a constant diameter hole while cement slurry is injected into the soil at high pressure. The process combines state of the art construction techniques merging mechanical and hydraulic mixing energies at the tool bit. The result is a soil-cement column of engineered strength, consistency and dimension. Whereby the soil cement column formation process is controlled by a computerised device, the result is a speedy installation, thorough mixing, and a high degree of control, repeatability and documentation.

Jan 1, 2002

By Eric M. Klein

As part of the Woodrow Wilson Replacement Bridge project several damaged wetland and environmental areas were to be mitigated. One of the mitigation projects consisted of constructing a Denil fish ladder around Peirce Mill Dam in Rock Creek National Park, Washington, D.C. The dam is a historic structure operated by the National Park Service. The fish ladder is located between the east abutment of the dam and Beach Drive, a major collector road. Construction of the fish ladder required removal of a portion of the east abutment and an excavation that extended about 22-ft below the pavement of Beach Ave. It was not possible to close Beach Drive except for very brief intervals or at night; therefore, a support of excavation system that would minimize disruption to the public was required. The high groundwater required that the groundwater be cut off prior to excavation; the random rubble and soil fill, and shallow but erratic rock surface precluded driving sheet piling. A jet grout system was selected because the grout probe could penetrate the rubble fill, stabilize a variety of soil conditions, and cut off the ground water prior to excavation. It was not possible to construct a stable wall without tiebacks or soil nails. Given the schedule and tight working conditions it was decided that soil nails through the jet grout wall facing would be the most cost effective method, as it did not reduce the working space as rakers would and would be more cost effective than prestressed tiebacks.

Jan 1, 2006

By Wolfgang G. Brunner

The closing of the gap in the European waterway- net is one of the big and challenging traffic projects following the German reunification. The water canals in the North German plain connect the Rhine river, the border between Germany and France, with the Oder, the German border river to Poland. As early as in the 30's of the 19th century the planning and construction of a ship- lift and a canal bridge started, in order to close this last big gap in the system between the Mittelland Canal and the Elbe- Havel Canal near Magdeburg. This main waterway connects the West of Germany, known for its coal mines and steel mills, with the capital Berlin, and from there it goes on into Poland. The building activities started in 1934 but came to a complete stop in 1942 because of the war. The communist government in East Germany was not interested in continuing this huge project, including the ship lock Rothensee, the canal bridge crossing the river Elbe, the former border river between West and East Germany, and the lock Hohenwarthe due to lack of political backing along with low construction capacity. Now this important project is in progress and this report describes the special foundation techniques used on the great ship lock Hohenwarthe. Hohenwarthe is a double- bay ship lock of considerable scale, which is notable for recirculating water rather than letting it flow. It includes 44 800 m2 ( 481 720 sq. ft) of up to 55 m ( 180 ft) deep cut- off walls, ground water control, 1248 bored piles with a depth of 22 m ( 72 ft ) serving as foundation and 28 000 m ( 91 864 ft) of soil densification with vibroflotation equipment for ground improvement. In the year 2003 the project shall be completed and all ships can travel from the West to the East through Germany without expensive and time- consuming detours through other canals and locks.

Jan 1, 2000

By J. M. Mitchell

Kuala Lumpur, Malaysia is underlain by karstic limestone. Firm clays, mudstones and siltstoncs of the Kenny Hill Formation overlie the limestone for about two thirds of the city. The remaining third has deep deposits of very soft alluvium, or tin mining slimes, overlying the limestone. It is only recently that large buildings have been constructed in the area. Arup Jururunding have been concerned with several projects located on the limestone, although space here only permits the description of four sites in detail. The experience has allowed the development of a design approach for the foundations. The aim is to make the architectural scheme compatible with the geology. This is not always possible, and examples are given of both situations. The case histories give examples of compensated foundations, and piled foundations include steel H-piles, precast concrete piles, micropiles, bored piles with rock sockets, and barrettes up to 90m deep.

Jan 1, 2010

By D. Michael Holloway

The California Department of Transportation (CALTRANS) evaluated several pile foundation schemes for supporting the structures along the realignment of Interstate 880. The project replaces the double-decked (Cypress) viaduct collapsed in Oakland, California during the 1989 Loma Prieta Earthquake. Structural support demands led to the selection of steel pipe piles (16-, 24-, and 42-inch-(406-, 610- and 1067-mm-)diameter), filled with concrete and steel reinforcement. Deep penetrations required through layers of very dense/cemented sands in some locations, caused serious drivability and pile integrity concerns. The need for large pile driving hammers and large diameter steel pipe piles pushed the engineers well beyond local experience. Such questions as the feasibility of driving the pipes closed-ended through dense upper strata and quantifying the effects of installation on the long-term capacities of the piles led Caltrans to develop a comprehensive pile test program to address the design and construction issues effectively. The results were furnished to prospective bidders on the production stages of the ensuing contracts.

Jan 1, 1995

By Graeme McWhirter

This paper discusses the Installation of a Vibwall for the Cardiff Bay Barrage Project Wales, UK, by Kvaerner Cementation Foundations. Only the second use of the technique in the UK the wall was successfully placed to a depth in excess of 20 metres, in unique and challenging conditions. The installation of the Vibwall was a technical success, but not a financial one. The use of the technique was at its "limits" and this paper recommends some of the controls essential in the carrying out of such work in the future.

Jan 1, 2000

By Jeffrey A. Schaefer

The Olmsted Locks and Dam project is located on the Ohio River approximately 16.5 miles upstream of its confluence with the Mississippi River. It consists of twin 1200 ft. locks with floating and fixed approach walls, five 110 ft. wide tainter gate bays, a 1400 ft. wide navigable pass boat operated wicket gate section, and a 400-ft. section of fixed weir (Fig. 1). The project will have a total cost over 1.0 billion dollars, and as such is one of the largest civil works project underway in the Corps of Engineers.

Jan 1, 2001

By Bengt H. Fellenius

The bearing capacity equation?"the triple N formula"? is now about 50 years old. It was developed from theory of plastic resistance of metal to a cone being pressed into the surface of the metal, superpositioned by resistance due to shear in an interparticulate medium (soil; note, we are not dealing with metallurgy), and tempered by work necessary to move the footing into the medium. The equation (and its coefficients) was "confirmed" by tests on small footings placed at or near the surface of the soil. The equation is a basic tenet of every geotechnical textbook, manual, and code. Over the years, innumerable variations of the N-coefficients and adjustments to the equation have been published. The main assumption behind the bearing capacity equation is that a shear plane develops between two essentially otherwise unaffected bodies: the main soil body and a body comprised of the footing with some soil. Moreover, the notion is that a model footing placed at or near the surface of a soil would behave proportionally or similarly to a full-scale footing, or to even a same size footing (pile toe) placed at some depth in the ground. This is not in agreement with factual observations. It is suggested that the behavior of a small or large diameter footing as well as a pile toe is governed by compression of the soil below the footing or pile toe and not by "bearing capacity".

Jan 1, 1999

By Walter Ensinger

Working safely means working cost-effectively. Every "dangerous occurrence" and - even more so - every industrial accident causes disruptions in the planned course of construction. Besides moral and legal obligations, economic aspects are therefore also factors motivating increased efforts towards optimal prevention: improvements in work safety and protection of health are wise investments! Ever since its earliest days, the European Federation of Foundation Contractors (EFFC) has made this subject one of its key objectives and therefore set up a Safety + Environmental Working Group, in which experts from the member organisations exchange national experience and develop proposals for "best practices". The paper presents current developments and results from the work of the S+E WG with particular reference to the project "Ideas for Safety Improvement".

Jan 1, 2006

By Jay A. Berger

Nondestructive testing of deep foundations for integrity problems made great strides in the late 1980's. Inexpensive portable computers have allowed the immediate and rapid processing of field measured acceleration records which can provide insight into the relative structural integrity of a previously installed foundation member. Although the gathering, processing and displaying of the data is now straightforward, interpretation remains at times rather challenging. This paper provides a brief introduction into the theoretical basis for data interpretation and the hardware necessary for data acquisition. Five case studies are discussed which demonstrate the varied applications of low strain integrity testing of deep foundations and the efficiency at which they are completed. BACKGROUND One dimensional wave mechanics, when applied to a linear elastic pile with a length that is an order of magnitude greater than its width, provides a straightforward basis for the interpretation of motion measurements made at a pile top. When impacted, a stress wave travels through the pile at a wave speed, c, which is a function of the elastic modulus, E, and mass density p (i.e., E=pc2). The applied load F, and particle velocity v, at a point are related by the equation F=Zv. For a cross-sectional area A, the proportionality constant Z is equal to EA/c. Because Z is a measure of the pile's resistance to change in velocity it is called the pile impedance.

Jan 1, 1990

By Dennis J. Riley

A. This outline addresses what a sub-contractor, or a subsub-contractor should do to get paid in the event the general contractor or building owner files for bankruptcy. B. Negotiating payment terms. Progress payments vs. "pay when paid". How a sub or subsub can avoid financing the contract. C. Court interpretation of "pay when paid" clauses allow postponement not excusal of payment. See, e.g., Seal Tite Corporation v. Ehret. Inc., 589 F. Supp. 701 (D.N.J. 1984) (where the court held that the general contractor could not delay payment indefinitely to the subcontractor in the event of non-payment from the owner); United Plate Glass Co. v. Metal Industries. Inc., 525 A.2d 468 (Commw. Ct. Pa. 1987) (where the court held that payment from owner was not a condition precedent to paying subcontractor but instead a timing mechanism indicating when payment should be made); But see. Straham v. Landis Construction Co., 499 So. 2d 417 (La. App. 4 Cir. 1986) (where the court strictly interpreted the "pay when paid" clause).

Jan 1, 1991