Evaluation of Inaccessible Drilled Shafts Using the Impulse Response Method

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EVALUATION OF INACCESSIBLE DRILLED SHAFTS USING THE IMPULSE RESPONSE METHOD

by Richard J. Finno and Peter J. Prommer
Northwestern University
September 1994

Based on Prommer's Thesis (M.S.) in Civil Engineering, Northwestern University, 1994.

ITI technical report no. 3

Abstract
Acknowledgments
Chapter 1. Introduction
Chapter 2. Non-destructive deep foundation integrity tests
Chapter 3. Impulse response testing
Chapter 4. Impulse response field testing study
Chapter 5. Summary and conclusions
References
Appendix
Subject index terms and Author contact information

ABSTRACT

The sonic echo, impulse response, parallel seismic and sonic logging methods of non-destructive evaluation for deep foundations are presented. The impulse response method is discussed in more detail. It is a surface reflection method typically used for evaluating drilled shafts in a free-head condition. By studying the effectiveness of the impulse response on inaccessible shafts, the method can possibly be expanded to help solve the problem of unknown bridge foundation types without the need for costly access tubes required for the parallel seismic and sonic logging methods. The testing equipment and software required for impulse response testing are described in detail. The applicability of the impulse response method in determining the integrity of inaccessible drilled shafts is evaluated by means of a field testing study and shaft response simulations. The testing program consisted of evaluating several drilled shafts that had concrete grade beams connected to the shaft heads. Based on the field testing study, it was found that more rigidly held shaft heads (due to larger or several grade beam connections) exhibited greater signal attenuation and became more difficult to evaluate. Shaft integrity could be determined for cases where as many as three grade beams were attached to the shaft head. The ability to determine shaft integrity for the accessible shafts depended mostly on the configuration of the grade beams and the length/diameter ratio of the shafts.

ACKNOWLEDGMENTS

Special thanks is expressed to the Infrastructure Technology Institute of Northwestern University for their support of the Bridge Management research work. The authors are indebted to Dr. Allen Davis and Bernie Hertlein of STS Consultants, Ltd. for their expertise, patience, and willingness to advance the field of non-destructive testing. Thanks is also extended to others on the staff of STS Consultants including: Deon Thelwell, Clyde McComb, Guiliano Alciomani, Matt Johnson, and Ron Palmieri.

Chapter 1. Introduction ( PDF)

Chapter 2. Non-Destructive Deep Foundation Integrity Tests ( PDF)

Chapter 3. Impulse Response Testing Equipment ( PDF)

Chapter 4. Impulse Response Field Testing Study ( PDF)

Chapter 5. Summary and Conclusions ( PDF)

References ( PDF)

Appendix

Subject index terms

Bridge foundations Impulse response method Parallel seismic method
Sonic logging method

Author contact information