Search Documents

By Dan Brown

Improvements in construction equipment and techniques in recent years have made possible the use of drilled shaft foundations in diameters and lengths not previously considered practical or feasible. Many highway bridge and other structures are now routinely founded on drilled shafts which -are 8 to 12 feet in diameter and extending over 200 feet in depth below grade. There are unique challenges associated with constructing such large and deep cast-In-place foundations and engineers should be aware of the special needs associated with site investigation, construction specifications, material requirements, and quality assurance. This paper outlines a number of special considerations for these foundations, along with strategies that may be employed to improve the reliability and quality of large drilled shaft foundations.

May 11, 2007

By Suzanne R. Hess-Brittelle, Sharon L. Schulz, Tyler J. Quick, Amy F. Ebnet

"Abiquiu Dam is a rolled earth fill dam with impermeable core located on the Rio Chama in New Mexico. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. During the 1960’s and 1970’s, the grout curtain was extended 1,000 ft. into both abutments and sections of the foundation beneath the embankment were regrouted. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during multiple phases of supplementary grouting and during verification drilling following the 1970’s grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. The fluid losses in the embankment may be related to seasonal shutdown layers in the embankment or benches in the abutment foundations. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment.INTRODUCTIONAbiquiu Dam is located on the Rio Chama in New Mexico and consists of a rolled earth fill dam with impermeable core, controlled outlet works, and an uncontrolled rock-cut spillway. The dam was authorized for flood control and sediment retention and was designed as a dry dam, holding flood pools for relatively short durations. The foundation is comprised of Permian and Triassic age, interbedded mudstones and sandstones that were deposited in an active braided stream system. Sandstones are moderately fractured and have variable aperture and infilling. Generally speaking, joints are near vertical. Abiquiu has had a history of excessive seepage through the fractured sandstone abutments since water was first impounded in 1963. The foundation was treated with a single row grout curtain in the cutoff trench prior to placement of the embankment. In 1966-1968, the grout curtain was extended 500-ft into the left abutment and the foundation beneath a 560 ft. section of the embankment was re-grouted. In 1978-1980, the grout curtain was extended 1,000 ft. into the right abutment, an additional 500 ft into the left abutment and the foundation beneath the right 520-ft section of the embankment was re-grouted. The alignments of these grout programs are shown in Figure 1. Grouting of the foundation beneath the embankment required drilling through the embankment. Drilling fluid loss or loss of circulation within the impervious core was observed during both phases of supplementary grouting and during verification drilling following the 1978-80 grouting program. It is likely that the drilling methods employed for these grouting and drilling programs caused hydraulic fracturing of the impervious core. In addition, it is likely that the impervious core was fractured from grout pressures during installation of grout pipe through the embankment. This paper provides a summary of the drilling and grouting methods used during these programs and the potential for damage to the embankment."

Jan 1, 2016

By Satyajit A. Vaidya

This paper presents a case-study in the design and construction of deep foundation element supported mats for two residential towers on an18,000-square-foot site in Brooklyn, New York. Based on site sub-surface conditions, conventional mat foundations bearing on medium dense sand, having an allowable bearing capacity of 3 tsf, were originally anticipated for the 16 and 25-story towers. However, when the tower shear walls were relocated to the edges of the mat foundations due to architectural revisions, the significantly increased mat edge contact stresses applied to the soil subgrade resulted in calculated settlements of a magnitude that would adversely impact the proposed structures and the neighboring/bordering lot-line building and rail transit subway structures. To address this issue, deep foundation element supported mats were designed for the towers. The design was performed as an iterative process involving structural SAFE and geotechnical Plaxis finite element computer analysis to develop a coordinated geo-structural model of the foundation system. Initial presumptive design values of 45 pci and 445 kips/inch were used for the modulus of subgrade reaction and minimum deep foundation element stiffness, respectively. The designed foundation system consisted of 40 and 60-inch-thick mat foundations for the 16 and 25 story towers, respectively. Initially, the deep foundation elements were designed as 50-foot-long, 14-inch-diameter elements installed to sustain a maximum individual compressive load of 250 tons. The final deep foundation element design was subsequently refined to consist of a 48-foot-long, drilled and grouted IBO Titan 103/51 element designed to sustain a maximum load of 167 tons. Subsequent field load tests on the deep foundation elements confirmed element stiffness ranging from 1,040 to 1,530 kips/inch, with measured mobilized side shear of about 29 psi. The mat foundation reinforcement was adjusted for the pile stiffness values determined in the field load tests, and the deep foundation supported mats were constructed. The two towers were subsequently constructed, and have performed successfully.

Jan 1, 2010

By Osamu Taki

The innovative Soil-Cement Mixed Wall Technique emerged in Japan and obtained recognition in the engineering and construction communities in the 1980's. This technique was introduced to the United States in 1986. It was accepted as the most credible construction technique by the U.S. Bureau of Reclamation for ground stabilization and cutoff wall work in the Jackson Lake Dam Project, Wyoming in 1987 and 1988. It was also accepted as a remediation technique by U.S. EPA for a Superfund Innovative Technology Evaluation (SITE) demonstration on in-situ solidification/ stabilization. The Soil-Cement Mixed Wall Technique consists of mixing in-place soils with cement grout or other reagent slurries using multiple axis augers and mixing paddles to construct overlapped soil-cement columns. The overlapped column panel is then extended to form an underground continuous soil-cement wall for use as a cutoff wall or a structural diaphragm wall for groundwater control and excavation support. By arranging the column panels in various configurations, the technique becomes a versatile tool for stabilization of soft or liquefiable soils.

Jan 1, 1990

By Andrew Z. Boeckelmann, David S. Graham, Paul J. Axtell

In the last fifteen years, several research studies have evaluated the ability to detect various types of deep foundation concrete integrity flaws with crosshole sonic logging (CSL) and thermal integrity profiling (TIP). This paper synthesizes the findings from the research, focusing on two studies that included CSL and TIP testing of drilled shafts with various types of flaws. The first, a 2016 research study of test shafts for the Wisconsin DOT, included inclusions inside and outside the reinforcing cage, intentional tremie withdrawal during concreting, and soft bottom flaws. The second, a 2021 study of production shafts for the Missouri DOT, included one shaft with and another without soft bottom conditions. After synthesizing the ability of each test method to detect each type of flaw, the paper presents recommendations for improving how CSL and TIP results are evaluated in practice. The recommendations highlight DFI‟s CSL interpretation protocol as well as the importance of evaluating TIP data versus time, not just depth. The paper includes example temperature-versus-time plots for various types of flaws and emphasizes how temperature-versus-time evaluation can be used to distinguish soft bottom conditions from standard bottom-of-shaft temperature roll off.

Oct 1, 2022

By Waddah Akili

At an offshore site along the Red Sea coast of Saudi Arabia, marine structures were supported on tubular steel piles driven into coral and coral contaminated sands and silts. Surprises and disappointments faced during the installation of the piled foundation were, to a large measure, due to inappropriate design methodology and absence of proper soil information. The paper describes the design evolution process, highlights the static pile test program conducted to verify design parameters, and amplifies the need to prepare for worst possible scenario when coral deposits are encountered. Despite corrections made to the design, based on site-specific insitu parameters (skin friction, end bearing) perceived from load tests conducted on site; the final design adopted overestimated capacities in over 50 percent of total piles driven. The paper describes the changes introduced to the design during the execution of the project, highlights the pile test program conducted to verify the design, and compares pile design penetration with actual penetration depth. The unpredictable and erratic pile behavior observed, ascertains the need for more appropriate pile design and installation guidelines for driven piles in coral and coral contaminated formations.

By Min Sunn Ye, Wei Wang, Huawen Xiao, Kai Yao, Fook Hou Lee, Siang Huat Goh

"Previous research have shown that introducing fibers to cement soil mixture is effective in improving the ductility as well as maintaining the strength of cement-treated soil. A good knowledge of stiffness of the improved soil at small strain is essential for realistic predictions of ground movements that may affect adjacent buildings or underlying infrastructure. This paper presents a triaxial system with local strain measurement developed for studying shear modulus degradation of cement treated clay with fibers. Cylinder specimens (70mm diameter by 140mm height) with 50% cement, 100% water, 0% to 1% polypropylene fibers by mass, and 7 days of curing period were used. A local strain measurement system with floating type miniature submersible LVDT is introduced in this paper. Configuration of the mounts including the pin size, length and distance are presented and discussed. Based on the experimental results, a reasonable configuration of the mounts is recommended for fiber reinforced cement treated clay. Results showed that the proposed local strain measurement system is effective for testing the shear modulus degradation of cement treated clay with fibers under both unconfined and confined condition. Comparisons with results from resonant column and bender element tests served to verify the reliability of the local strain measurements using the proposed method.INTRODUCTIONIn many geotechnical engineering problems, the operational strain domain ranges from 10-3% to 10- 1%. A good knowledge of stiffness at small strains is essential for realistic predictions of the ground movements that may affect adjacent buildings or underlying infrastructure. As such, during the last 3 to 4 decades, the importance of using the small strain stiffness of soils for the design of foundation and underground structures has widely been accepted. Triaxial testing has been widely used to study the stress-strain behavior of soil in the laboratory. However, the stiffness obtained from the conventional triaxial apparatus is usually far smaller than those back-calculated from field measurements. This is mainly attributed to the overestimation of axial strains from the external strain measurements, which usually includes compliance effects of the loading and load measuring system as well as sitting, bedding and alignment errors between sample and system (Baldi et al., 1988). The poor resolution of the external strain measurements is another important contribution. Therefore, conventional procedures are inappropriate for small-strain stiffness evaluation due to low accuracy and resolution."

Jan 1, 1900

By Timothy C. Siegel, Derrick Dasenbrock, Rich Lamb, Paul J. Axtell

"The axial resistance provided by deep foundations may be divided into two components: side resistance and tip resistance. The direction that the side resistance acts depends on the relative movement between the deep foundation and the adjacent soil. That is, when the foundation moves downward relative to the soil, then the side resistance is positive and acts upward. Conversely, when the soil moves downward relative to the foundation the side resistance is negative and acts downward. Research supports that both positive side resistance and negative skin friction develop in essentially all deep foundations. The side resistance distribution is a function of the soil strength and stiffness, the applied top loads, and whether the top load is sustained, transient, or a combination of sustained and transient loads. Consideration of drag load and downdrag has become more convoluted with implementation of geotechnical aspects into the AASHTO LRFD Bridge Design Specifications and its use of load and resistance factors. This paper examines the current AASHTO Specifications and presents an alternative design approach for drag load and downdrag using the LRFD framework. The alternative design approach is illustrated by two examples involving drag load and downdrag.IntroductionThe axial resistance provided by deep foundations may be divided into two components: side resistance and tip resistance. The direction that the side resistance acts depends on the relative movement between the deep foundation and the adjacent soil. That is, when the foundation moves downward relative to the soil, then the side resistance is positive and acts upward. Conversely, when the soil moves downward relative to the foundation the side resistance is negative and acts downward. Research supports that both positive side resistance and negative skin friction develop in essentially all deep foundations. The side resistance distribution is a function of the soil strength and stiffness, the applied top load, and whether the top load is sustained, transient, or a combination of sustained and transient.Consideration of drag load and downdrag has become more convoluted with implementation of geotechnical aspects into the LRFD Bridge Design Specifications and its use of load and resistance factors. This paper examines current LRFD design specifications and presents an alternative design approach for drag load and alternative design approach is applied to several examples where drag load and/or downdrag may control design."

Jan 1, 2015

By Dan Yang

Pile foundation designs are performed routinely based on geotechnical information available at the time of design, often with due consideration of large uncertainties inherent to soils and site conditions. These uncertainties frequently are the causes of piles being installed not the same as those designed, especially by factors beyond quality assurance and quality control. With a variety of both satisfactory and unsatisfactory pile test results from these nonconforming piles, the design engineers are required to examine the foundation performance as a whole against the project design requirements before signing off on them or calling for potentially costly remediation. Over the years, as-built analysis has been a consistent way of dealing with pile non-conformity and damage in our practice, avoiding many construction delays and it is an integral part of our pile foundation design. In this paper, the key elements of an as-built analysis along with several major bridge projects are presented.

Jan 1, 2010

By Nils Schneider, Marc Peters, Stefan Frey, Andrea Fluck

Due to the worldwide population growth, the development of sustainable infrastructure and the exploration of renewable energies plays a key role to handle the rising megacity trends and to limit carbon footprint. Herrenknecht AG is a leading manufacturer of Tunnel Boring machines and has constantly endeavored through its extensive Research and Development programs to address limitations faced by the civil engineering industry as regards to construction equipment capabilities. New mechanized technologies, mainly coming from the tunnelling industry, have been developed by Herrenknecht AG as an efficient alternative to conventional civil engineering, where tailor-made concepts are required to comply with restricted conditions onsite. Very often this innovation led technology capability has meant making construction processes safer due to minimal human intervention and also far more productive due to higher performance as compared to other latest or conventional methods of construction. The rising need for even higher building structures and large-capacity bridges involve the development of innovative deep foundation technologies for on- and offshore operation. Conventional methods like bore piles reach their technical and economic limits under certain conditions. For building shafts and foundations, the mechanized Vertical Shaft Sinking Machine technology (VSM) from Herrenknecht AG is a proven innovation and has now been used in various onshore infrastructure projects worldwide to construct a total of 94 circular shafts in depths of up to 115 meters. It operates below the groundwater level, completely remote-controlled from the surface in a diameter range from 4.5 to 18 meters. Subsequently Herrenknecht noted that Offshore foundations, especially in non-drivable ground conditions such as soft and hard rock (e.g. limestone, sandstone, mudstone, granite etc. or soft soil with high density) and shallow continental shelf (water depth approx. 20-60m), presented construction challenges and equally an opportunity for building high performance equipment. The latter construction conditions usually requires drilled installation methods for applications such as harbor enlargements, bridge foundations and foundations for offshore wind turbines. The Offshore Foundation Drilling technology (OFD®) is Herrenknecht’s latest innovation, incorporating our learnings from the VSM and full-face Tunnel Boring machines, and the OFD® enables a rapid and economical offshore installation in such variable ground and rock conditions. This paper will discuss the technology behind the new mechanized technology of VSM and Herrenknecht’s latest innovation of the OFD® along with their respective application fields in foundations construction. The paper will further present in details, their range of benefits to the construction industry.

Nov 1, 2022