testing of unknown foundation: a case study with comparison of different ndt methods
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Testing of Unknown Foundation: A Case Study with Comparison of Different NDT Methods
Present at Ohio Transportation Engineering Conference
Oct 23-24, 2007
Bill X. Yu Assistant Professor, Department of Civil Engineering, Case Western Reserve University, OH, USA,
216-368-6247, [email protected]
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
Magnetometer: Validation of Concept
1 ft
Vertical motion
Magnetometer: Validation of Concept
Vertical cyclic motion of rod Slow vertical motion of rod
At distance of 1 ft
Magnetometer: Validation of Concept
0
10
20
30
40
50
60
0 10 20 30 40 50 60
Distance (in)
Sig
nal
(m
illi-G
auss
)
Magnetometer: Validation of Concept
-450
-400
-350
-300
-250
-200
-150
-100
-50
0
0 20 40 60 80 100 120
Distance (inch)
Vert
ical M
agnetic F
ield
(m
ili-G
auss)
Column 1
Column 2
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 !