Nondestructive Evaluation of Existing Deep Foundations

Davis, Allen G.

doi:10.1061/(asce)0887-3828(1995)9:1(57)

Cited by 46 publications

(13 citation statements)

References 2 publications

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“…Resonant Frequencies: The harmonic frequency spacings between resonant peaks on the mobility-frequency plot are directly related to the shaft length, as well as to the depth to any changes in geometric and material properties in the shaft, such as concrete density and shaft cross section. In a simple case where the shaft is straight-sided with no changes in concrete quality, the shaft length, 1 is given by: l=v/2df (1) where: v is the stress wave velocity in the concrete (a function of density and modulus), df is the frequency increment between resonant peaks on the mobility plot.…”

Section: Impulse Response Test Methodsmentioning

confidence: 99%

<title>Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers</title>

Davis¹,

Kennedy

1998

SPIE Proceedings

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Alkali-aggregate reaction (AAR) has affected the concrete in drilled shafts (cast in place piles) beneath electricity transmission towers along a 42-mile (67 km) section of transmission line in Southern California. In order to prioritize the maintenance program for these shafts, a nondestructive test methodology was sought to quantify the severity of the AAR with depth in each shaft. Shaft diameters of 19, 30, 36, 42 and 54 inches (475, 760, 910, 1067 and 1660 mm) were present, with shaft lengths between 10 and 30 feet (3 and 6 m). Over the last thirty years, Impulse-Response (I-R) testing has been successfully used to evaluate the integrity of drilled shafts, and computer simulation programs have also been developed for matching I-R test responses with theoretical shaft shapes and concrete quality. A program to test as many shafts as could be accessed in the difficult, mountainous terrain along this transmission line included mobilization of equipment and testing personnel by helicopter. 210 shafts were tested along the line in five days. Matching of test response mobility-frequency plots in computer simulation was achieved by varying the simulated concrete modulus and density, as well as the shaft cross section area. Up to three grades of concrete quality were identified in each shaft, representing the decreasing degree of AAR with depth. The tested shafts were then rated for increasing AAR severity, in order to select shafts for repair or replacement.

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Section: Impulse Response Test Methodsmentioning

confidence: 99%

<title>Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers</title>

Davis¹,

Kennedy

1998

SPIE Proceedings

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“…One of the original papers seems to be the work of Paquet (1968). The following names and references appear to be particularly relevant: Briard (1970), Davis and Dunn (1974), Koten and Middendorp (1981), Hearne et al (1981), Olson and Thompson (1985), Rausche et al (1988), Paquet (1991), Hertlein (1992), Baker et al (1993), Davis (1995), Samman and O'Neill (1997), Finno and Gassman (1998). One can also get much information from the proceedings of the five international conferences on the application of stress wave theory to piles held in Stockholm (1980Stockholm ( , 1984, Ottawa (1988), The Hague (1992), and Orlando (1996).…”

Section: Defect Detection Methods Usedmentioning

confidence: 99%

Defect and Length Predictions by NDT Methods for Nine Bored Piles

Briaud

Ballouz

Nasr

2002

Deep Foundations 2002

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Nine bored piles were built at the National Geotechnical Experimentation Sites at Texas A&M University: five at the sand site and four at the clay site. The piles had a nominal diameter of 0.915 m and varied in length from 10.7 m to 24.1 m. Various defects were intentionally placed in the piles including necking, bulging, soft bottom, tremie displacement, mud cake, and inclusion. Five companies were invited to make class A predictions of the length of the piles and of the defects size and location. They used small strain dynamic methods including sonic echo, impulse response, impedance logging, and sonic logging. The results are an indication of how reliable these methods are for predicting length and defects.

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“…The methods differ from one another in the way the force and acceleration time histories are processed. The most commonly used methods in the United States are (a) acoustic wave reflection, pulse echo, or sonic echo and (b) impulse response or sonic mobility (4).…”

Section: Surface Techniquesmentioning

confidence: 99%

“…Next, velocity (integrated from acceleration) is normalized by force and plotted against frequency to obtain a mobility plot. Shaft length, diameter, stiffness, and depth of defects theoretically can be deduced from the mobility plot (5,4). One recent development in impulse response testing is the use of multiple geophones at the pile top, to improve the reliability of the technique (6).…”

Section: Surface Techniquesmentioning

confidence: 99%

Class-A Prediction of Construction Defects in Drilled Shafts

Iskander¹,

Roy²,

Ealy

et al. 2001

Transportation Research Record: Journal of the Transportation R

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The results of a blind Class-A prediction symposium of construction defects in drilled shafts are presented. Six drilled shafts were constructed at the National Geotechnical Experimentation Site in Amherst, Massachusetts. Several types of defects were integrated into the shafts, including necking, voids, caving, and soft bottoms. Seven organizations participated in a blind defect prediction symposium and used a variety of nondestructive testing techniques, including down-hole techniques, such as cross-hole sonic logging, single-hole sonic logging, and cross-hole tomography, and surface techniques, such as pulse echo and sonic mobility. Most participants found defects that were larger than 10 percent of the cross-sectional area. However, false positives and an inability to locate smaller defects and multiple defects in the same shaft were encountered.

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Nondestructive Evaluation of Existing Deep Foundations

Cited by 46 publications

References 2 publications

<title>Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers</title>

<title>Impulse-response testing to evaluate the degree of alkali-aggregate reaction in concrete drilled-shaft foundations for electricity transmission towers</title>

Defect and Length Predictions by NDT Methods for Nine Bored Piles

Class-A Prediction of Construction Defects in Drilled Shafts

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