Testing of unknown foundation a case study with comparison of different ndt methods
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Testing of Unknown Foundation: A Case Study with Comparison of Different NDT Methods. Bill X. Yu Assistant Professor, Department of Civil Engineering, Case Western Reserve University, OH, USA, 216-368-6247, [email protected] Present at Ohio Transportation Engineering Conference

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Testing of Unknown Foundation: A Case Study with Comparison of Different NDT Methods

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Testing of Unknown Foundation: A Case Study with Comparison of Different NDT Methods

Bill X. Yu

Assistant Professor, Department of Civil Engineering, Case Western Reserve University, OH, USA, 216-368-6247, [email protected]

Present at Ohio Transportation Engineering Conference

Oct 23-24, 2007


Acknowledgements

  • Jian Fang, Josh Adams, Guoming Lin, WPC, Inc., 2201 Rowland Avenue, Savannah, GA  31404, 912-629-4000

  • Bin Zhang, Case Western Reserve University


Introduction

  • Project Background

    • St. Joseph hospital expansion


NDT Testing Plan

After WPC Inc. Report, 2006


Impact Echo: Testing Schematic


Impact Echo: On-site Photos


Impact Echo: Examples of Analyzed Signals


Parallel Seismic Testing

  • Schematic

    • Borehole

    • SCPT


Parallel Seismic Test: Photo During Test


Parallel Seismic Testing: Ground Conditions by SCPT


Parallel Seismic Testing: Recorded Signal


Parallel Seismic Testing: After Signal Processing


Parallel Seismic Testing: Wave Train Determination


Parallel Seismic Testing: Wave Train


Parallel Seismic Testing: Wave Train Validation


Parallel Seismic: Sensitivity Analyses


Magnetometer Method: Principle


Vertical motion

1 ft

Magnetometer: Validation of Concept


Vertical cyclic motion of rod

Slow vertical motion of rod

Magnetometer: Validation of Concept

At distance of 1 ft


Magnetometer: Validation of Concept


Magnetometer: Validation of Concept


Magnetometer Method: Recorded signal


Magnetometer: Signal Analyses for Pile Length


Design Recommendations Based on Testing Results

50 Ton


Advantages and Pitfalls

Impact Echo

  • Fast, easy

  • Challenge in signal interpretation

    • Influence of internal reflection (due to geometry, crack etc)

    • Signal attenuation with depth

    • Wave modes

  • Source of error: assumption of wave speed


Advantages and Pitfalls (cont.)

Parallel Seismic Method

  • Requires borehole

  • Less influenced by pile integrity

  • Requires careful signal interpretation

    • Wave trains

    • Inflection point


Advantages and Pitfalls (cont.)

Magnetometer Method

  • Fast, easy

  • Requires borehole

  • Can be influenced by soil strata


Summary of Experience

  • Geophysical methods are important tools to supplement engineering decisions

  • Different testing methods can serve

    • Properly applied

    • Properly interpreted

  • Geotechnical complexity needs to be considered


Thank you !


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