Investigation of pile length variability between design and construction

Keywords

Piling (Civil engineering)

Abstract

Mankind has been using pile foundations for more than 2000 years. Engineers design piles to support many types of structures. The use of piles is important to ensure structural performance and safety. Due to soil variability, uncertainties during in-situ testing, test data interpretation, and different pile installation methods, selecting the type of pile and estimating its necessary length are difficult tasks. The objective of this thesis is to investigate the variation between the estimated geotechnical pile lengths with the actual driven pile length. Determining

the pile length is an important factor in pile design to provide the required capacity and ensure structural safety. The length of a pile depends on many factors including: soil type, soil strength, the applied load, pile size, subsurface conditions, construct ability, reliability, and cost. The approximate piles lengths are based on theoretical or empirical engineering design, the final pile length is determined when the pile is driven and may vary significantly from design lengths. Under designed piles may fail to support the loads transferred by the structure which would result in compromising safety and functionality. Whereas, over-designed piles would result in an overly safe design and an extra unjustified cost. Therefore, predicting the required length with a fair degree of accuracy is essential. Geotechnical engineers have developed analytical and empirical methods utilizing laboratory tests, field investigation results, and computer modeling in order to optimize their pile design. The results of these analyses are usually presented as design charts of pile capacity and depth.

Nine pile projects in central Florida were studied and analyzed in this thesis to evaluate the estiffiated pile length versus the actual constructed pile length. Results of the evaluation indicated that estimating pile length using standard penetration test results (SPT) in combination with the FOOT pile design programs generally overestimate the length. The increased cost for the overestimated pile length ranged from 15% to 97%. The total design pile lengths that were shorter than the actual driven pile length ranged from 141 to 1514m. The amount of insufficient required pile lengths for all the projects ranged as much as 3% to 52%. The study also showed that the use of pile driving test instrument with Pile Driving Analyzer (PDA) provides a great assistance in evaluating construction problems, confirms the evaluation of the load capacity and better predict the estimated length. The new design lengths from the PDA testing reduced the total overestimated piles length and the cost to a lower range of 9% to 22%. The PDA design recommendations did provide improvements to the geotechnical design of the underestimated piles. The new design method increased the piles lengths, and decrease the amount of insufficient to a lower range of 0% to 7%.

Notes

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Graduation Date

2003

Advisor

Chopra, Manoj B.

Degree

Master of Science (M.S.)

College

College of Engineering

Department

Civil and Environmental Engineering

Format

PDF

Pages

330 p.

Language

English

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Identifier

DP0029127

Subjects

Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic

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