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By Subhash B. Bhide

Deep foundations are affected by the presence of sulphates, chlorides, organic contents and water currents present in the soil. The sulphates in soil and ground water interfere first with setting of concrete. In long term, growing of sulphate crystals in concrete, crevices can spall the concrete. The chlorides mainly affect the steel. The organic content does not allow the concrete to set. It also reduces the compressive strength of concrete. The frequency and methods of sampling and testing for above corrosive elements are discussed. Presently available methods to avoid attack due to these corrosive elements are discussed. The stipulations by various codes are summarised. A method to assess the short term impact is elaborated with results of field studies. A tool developed to study the presence and effects of underground water currents on concrete is also discussed.

Jan 1, 1996

By Kam Ng

For bridges or buildings that may be subjected to large vertical and lateral loads, drilled shafts offer an economic foundation solution. While the current drilled shaft design practice is considered adequate, introducing a performance-based approach to designing the drilled shafts will make their design more cost-effective and produce more dependable response. This concept was examined using analysis of 41 drilled shaft load test data from several states. This process identified the challenge with the lack of information from the Osterberg (O-cell) load test method to characterize the full top load-displacement response. When a typical single O-cell is utilized in a drilled shaft test, depending on the location of the O-cell and the geomaterials present along and beneath the shaft, the load test result typically quantifies either the side resistance or end bearing reaching the ultimate load-displacement curve but not both components. This limitation hinders the determination of a suitable shaft resistance as a function of a target top displacement. To overcome this challenge, an improved procedure is proposed for establishing the full load-displacement curve based on data gathered from one O-cell. The method will be presented in the paper for three different cases (i.e., side resistance reaches the ultimate during the test, end bearing reaches the ultimate during the test, and neither components reach the ultimate values). Because it allows the characterization of the full load-displacement curve, the proposed procedure will allow performance-based design of drilled shafts with due consideration to settlement while satisfying the Load and Resistance Factor Design.

Jan 1, 2013

By Lance A. Roberts

The Federal Highway Administration (FHWA) has mandated the use of the AASHTO Load and Resistance Factor Design (LRFD) specifications for all new federally-funded transportation infrastructure projects beginning in October 2007. This includes the design of all geotechnical-related elements, such as deep foundations, which have historically been excluded from the LRFD requirements. The basis of the LRFD specifications is the application of a probabilistically computed parameter called a resistance factor to the foundation capacity in lieu of the traditional, and often arbitrary, factor of safety. Therefore, the process of computing resistance factors for use in the design of deep foundations is extremely critical to ensure a safe, efficient, and consistent design methodology. In this paper, various methods to calibrate resistance factors for use in the design of deep foundations are examined. The methods that are currently utilized to calibrate the resistance factors reported in the AASHTO LRFD specifications may be classified as the allowable stress design (ASD) method and the reliability theory calibration method using static capacity prediction techniques. These methods are compared to a ?t-z? model design methodology. The current methods focus exclusively on the strength limit state design of deep foundations. The advantage of the ?t-z? model methodology is that it can be utilized for both strength and service limit state design. In addition, the results show that resistance factors vary based on geological setting, construction method, failure criteria and deep foundation type. This variability in the resistance factors should therefore be integrated in the design to ensure that the objectives of the LRFD approach are satisfied.

Jan 1, 2008

By Armin W. Stuedlein, Seth C. Reddy

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

Jan 1, 2013

By H. Mori

Construction of cast-in-place piles with enlarged bases has become popular in the cities in Japan facing to the sea coast, where the subground soil is soft alluvium deposited to depths often exceeding 30 m. The groundwater table is a few meters below the ground surface. Skin friction of piles may become negative due to ground subsidence or reduced due to liquefaction of loose sand during an earthquake. To support highrise buildings, depths of bearing strata to which piles are embedded often exceed 50 m. Due to such geotechnical conditions, methods and equipment to build cast-in-place concrete piles mainly built by the reverse circulation method have been developed since the 1970s. In the first half of this paper, the authors review the cur-rent practise of building cast-in-place piles with enlarged bases. Then they introduce the TFP system developed in recent years, and discuss about the procedures to control and monitor enlarging of bases.

Jan 1, 1989

By Willie M. NeSmith

The use of drilled (screwed) displacement piles is an emerging sector of the United States deep foundation industry. During installation of these systems, a Ko to Kp environment is created in the materials surrounding the pile immediately prior to casting, and this condition results in increased shaft and toe resistance in soils where displacement leads to densification. Current continuous flight auger and drilled shaft design methodologies in the United States assume a Ko to Ka condition in the vicinity of the pile, and are thus an inappropriate starting point for static capacity analysis of drilled displacement piles. This paper examines constructability issues, and the sensitivity of performance to installation, and offers an empirical design methodology for drilled displacement piles. The proposed design process has been based on evaluation of 40 load tests, primarily in granular materials, and in a variety of geologic settings, and includes modification for soil types within the coarse-grained range.

Jan 1, 2002

By George Burke

Of the three projects, particularly the extensive Nimitz II (downtown) project, a single system, which was part of the operation, was used to control the spoil. Spoil control was continuous with the work since a vacuum truck and crew was used to suck up the spoils as they came out of the borehole. So, the whole job was kept clean both during operations and at the end of the shifts. On the Sand Island project, a double system was used. Larger spoil quantities were contained within the shaft limits during the work and the cleanup or disposal of the spoils was performed during excavation.

Feb 10, 2003

By Stefan Dahlin

The laboratory tests indicated low permeability but as I said, as a rule, the permeability in the field has been found to be higher. A high permeability has also been found when doing back calculations of rates of settlements in different cases. But as I also said, there's a need for further studies in this area.

Feb 10, 2003

By Cen Guoji

The foundation of bored pouring concrete pile have been adopted in the bridge engineering of China since early in the sixties. They demonstrated tremendous technical advantage and achieved notable economic benefit. With improvement of bridge technique including construction technique work equipment, design theory, examination in quality and applicable range etc, the pile diameter became bigger and the foundation changed from shallow to deep-water. This paper examples Jiujiang Bridge of Guangdong in China, which is single-tower cable-staged bridge, total length of 1675m, and expouds adopted successfully the foundation of variable section large bored pile (upper part d=3m, central part d=2. 4m and lower part d=2m) on the conditions of complicated technique that the load is tremendous (it require specially to resist 12000 kN ship impact) and the piles have free length 30m. The paper will be to describle design project and construction practice of pile foundation with variable section, and to compare schemes of equal section pile and pile in sinking-well.

Jan 1, 1991

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 Robert Small, Amshu Chappa, Ihab Allam

The Biosolids Digester Facilities Project (BDFP) is located in southeast San Francisco. The jobsite is bounded by active Caltrain and Union Pacific Railroad tracks on the west side and the existing Southeast Treatment Plant (SEP) on the north, south and east sides. The existing SEP was constructed in the 1950s and portions of the facility have reached their operational life. The $2 billion BDFP will replace and relocate the outdated existing solids treatment facilities with more reliable, efficient and modern technologies and facilities. In addition, the nearby Bayview and Hunters Point neighborhoods will benefit from the improved odor control. MWH/Webcor, a joint venture, as the construction manager general con- tractor (CMGC) for the project. As part of an alternate delivery method set forth in the prime contract, the CMGC was permitted to propose the use of a core trade subcontractor partner for the SFPUC's approval to provide precon- struction services. The CMGC identified three major scopes (electrical, mechanical and foundation) where a core trade partner would be able to assist

Jan 1, 2023

By Masaki Kitazume

Five papers were presented orally to the topics of Jet Grouting and Deep Mixing. The session was started with a brief introduction by the moderators. Following the oral presentation, floor discussions were directed by the moderators. A brief introduction of each of the oral presentations is provided before each discussion.

Feb 10, 2003

By R. L. Wei

The disturbing influences of pile driving on the surrounding soil mass, including the induced vibration, pore pressure and displacement of soil, were observed during the construction of pile foundations. It is shown that the effects of pile driving in saturated soft clay are tremendous and ought to be concerned attentively.

Jan 1, 2010

By X. Y. Hou

The design practice of several circular underground projects with large diameter is summarized. By taking the advantages of load-bearing of circular structure, a rational annular tensile bar support system and a new design method are proposed. Calculation for a car park shows that remarkable results are brought in by this design technique.

Jan 1, 2010

By Arash Khosravifar

The seismic design of extended pile shafts for the combined effects of dynamic shaking and liquefaction-induced lateral spreading is investigated using nonlinear dynamic finite element analyses (NDA). Results of NDA parameter studies are used to illustrate how inertia and lateral spreading loads combine during shaking. The NDA results are used to evaluate equivalent static analysis (ESA) methods. Implications for design practice are discussed.

Jan 1, 2010

By Kashyap Chaturvedula, Emad Farouz

The paper presents a discussion on the axial capacity of deep foundation elements bearing in the Yorktown formation in the southeastern region of Virginia. The fossiliferous marine soils of Tertiary age Yorktown formation typically consist of silty/clayey Sand or sandy Silt/Clay with varying amounts of shell fragments. The Yorktown formation is generally divided into Upper and Lower Yorktown layers depending on the shell content and the percent fines. Results of multiple load tests performed by Jacobs Engineering on auger cast piles as part of water and wastewater treatment plant expansion projects in southeastern region of Virginia are presented in this paper. The paper describes the subsurface investigation methods used to study the existing subsurface conditions and the design methodologies followed to estimate the axial capacity of the auger cast piles. The paper provides details regarding installation of test piles, instrumentation, load testing procedure, and interpretation of test results. The paper presents a comparison between the various methods of estimating axial capacity of auger cast piles based on the SPT-N values, the empirical methods for the Yorktown formation and the load test information. The paper distinguishes the side resistance values obtained within the upper and lower Yorktown formations. The paper compares the various design methods to the multiple load test results and recommends a design modification that is closer to the load test results.

By Hannah Lezzoni, Morgan NeSmith

The Augered Cast-in-Place and Drilled Displacement Pile Committee has historically been one of the most active and engaged DFI committees and has performed or spearheaded a number of research projects via the DFI Committee Project Fund (CPF). The authors have had the privilege of being either past or current committee chairs and have been involved in the performance of most of these projects since the fund's inception. The following is a historical overview of the committee's projects and their outcomes.

Nov 1, 2023

By Rob Jameson

"San Francisco is 49 square miles surrounded by reality." So said Paul Kantner of the local '60s icons, Jefferson Airplane, and his words have still held true. The rate, scale and complexity of recent construction in this city has been remarkable, even compared to the Gold Rush or reconstruction after the 1906 earthquake. This article will address developments in soil mixing in San Francisco since 2011, and how the marked settlement of a downtown high rise has influenced this booming construction market.

Jul 1, 2022

By Kyle Murphy, John S. McCartney

This paper focuses on the seasonal thermo-mechanical response of two energy foundations installed at the new Denver Housing Authority Senior Living Facility in Denver, Colorado. The two drilled shaft foundations, which have diameters of 36 inches and depths of 45 ft and are end bearing in the Denver shale formation, include a closedloop series of polyethylene tubes through which fluid is circulated to exchange heat with the surrounding ground. The tubes within the foundations are coupled together with the conventional ground source heat pump system for the building and were installed to evaluate the heat exchange response of the foundations as well as any thermomechanical soil-structure interaction effects. A series of vibrating wire strain gages and thermistors were installed at different depths in the foundation to record the thermomechanical strain and temperature at different depths. Also, pipe-plug thermocouples are used to measure the inlet and outlet temperature of the heat exchanger fluid entering each of the foundations, which is necessary to evaluate the total heat exchange for the foundations and the efficiency of the heat pump. This paper will describe the energy foundation construction processes, the strain distribution and ambient temperature profiles during building construction and the seasonal strain and temperature distributions during heating and cooling of the building. The data indicates that typical heat exchange associated with heating and cooling operations leads to strains which are within acceptable limits, and that the foundations can provide a clear option for absorbing the base heating and cooling load for the building.

Jan 1, 2017

By John S. McCartney

This paper focuses on the seasonal thermo-mechanical response of two energy foundations installed at the new Denver Housing Authority Senior Living Facility in Denver, Colorado. The two drilled shaft foundations, which have diameters of 36 inches and depths of 45 ft and are end bearing in the Denver shale formation, include a closed-loop series of polyethylene tubes through which fluid is circulated to exchange heat with the surrounding ground. The tubes within the foundations are coupled together with the conventional ground source heat pump system for the building and were installed to evaluate the heat exchange response of the foundations as well as any thermo-mechanical soil-structure interaction effects. A series of vibrating wire strain gages and thermistors were installed at different depths in the foundation to record the thermo-mechanical strain and temperature at different depths. Also, pipe-plug thermocouples are used to measure the inlet and outlet temperature of the heat exchanger fluid entering each of the foundations, which is necessary to evaluate the total heat exchange for the foundations and the efficiency of the heat pump. This paper will describe the energy foundation construction processes, the strain distribution and ambient temperature profiles during building construction and the seasonal strain and temperature distributions during heating and cooling of the building. The data indicates that typical heat exchange associated with heating and cooling operations leads to strains which are within acceptable limits, and that the foundations can provide a clear option for absorbing the base heating and cooling load for the building.