Federal Highways Administration- Geophysical Imaging Resource Site
Federal Lands Highway Program
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Evaluation of Appropriate Geophysical Methods...

This website presents a summary of the state-of-practice of geophysical imaging and NDT methods appropriate for a wide range of transportation problems.  Advancements in computing capabilities, analysis software, graphic software, and survey methodology have contributed to significant gains in the value of geophysical and NDT methods, and have produced results that are more accurate and reliable than traditional approaches.  Therefore, there is a need to provide geotechnical engineers with suitable geophysical tools to assist in the rational development of the survey methodology as well as in the selection of the appropriate methods, and interpretations.

Table 1 is prepared to provide an overview of suggested geophysical imaging and NDT methods used for highway geotechnical investigations, as described in Part I.  These methods are listed in terms of engineering problems and applications of these technologies to highway design, construction, repair, and maintenance.  The table is designed as a "Solution Matrix" that guides the user, without reading the entire web manual, to obtain an answer during the initial design phase of the survey.  For more complex highway engineering problem, it is recommended that the user review specific sections to assess the most appropriate method(s) for solving highway engineering problems.  Finally, the table has been organized in order of the subject material presented in the web manual

Table 1

Engineering Problem

Application

Geophysical/NDT Solutions

 

BRIDGE SYSTEM SUBSTRUCTURE

Unknown Depth of Foundations

Sonic Echo/Impulse Response, Bending wave, Ultraseismic, Seismic Wave Reflection, Transient Force Vibration, Parallel Seismic, Induction Field, Borehole logging, Dynamic Foundation Response, Borehole Radar, Borehole Seismic

Integrity Testing of Foundations and Structures

Crosshole Sonic Logging, Crosshole Sonic Logging Tomography, Gamma-Gamma Density Logging, Singlehole Sonic Logging, Sonic Echo/Impulse Response, Ultraseismic Profiling, Ultrasonic Pulse Velocity, Impact Echo, Ground Penetrating Radar, Spectral Analysis of Surface Waves, Acoustic Emissions, Radiography

Rebar Quality and Bonding

Half-cell Potential, Linear Polarization Resistance, Galvanostatic Pulse Technique, Electrochemical Noise, Acoustic Emissions, Magnetic Field Disturbance

Foundation Scour

Time Domain Reflectometry, Parallel Seismic, Ground Penetrating Radar, Continuous Seismic Reflection Profiling, Fathometer

 

BRIDGE SYSTEM SUPERSTRUCTURE

Bridge Deck Stability

Vibration Monitoring, Ground Penetrating Radar, Electromagnetic, Impact Echo, Spectral Analysis of Surface Waves and Ultrasonic Surface Waves Methods, Half-Cell Corrosion Potential Mapping, Infrared Thermography

New Decks

Baseline Assessment

Existing Decks

 

PAVEMENTS

QA/QC Of New Pavements

GPR, Impact Echo, Spectral Analysis of Surface Waves, Ultra Sonic Surface Wave (USW), Multichannel Analysis of Surface Waves (MASW)

Existing Pavements

Transportation / Geotechnical Methods

 

ROADWAY SUBSIDENCE

Mapping Voids, Sinkholes, Abandoned Mines, and Other Cavities

 

Gravity, GPR, Resistivity , Seismic Refraction, Seismic Reflection, Rayleigh Waves Recorded with a Common Offset Array, Cross-borehole Seismic Tomography

Roadbed Clay Problems

Conductivity Measurements, Resistivity Measurements, Time Domain Electromagnetic Soundings, Induced Polarization

 

SUBSURFACE CHARATERIZATION

Mapping Bedrock, Lithologies, Sand & Gravel Deposits, Groundwater Surface, and Flow

Ground Penetrating Radar, Seismic Refraction, Compressional and Shear Wave Reflection, Resistivity, Time Domain Electromagnetic, Conductivity Measurements, Spectral Analysis of Surface Waves, Gravity, Very Low Frequency Electromagnetic, Borehole Televiewer, Induced Polarization, Borehole Gamma and HydroPhysical Logging, Nuclear Magnetic Resonance, Self Potential, Electroseismic

Determining Engineering Properties and Rippability of Soil and Rock

Seismic Refraction, Nuclear Magnetic Resonance, Ground Penetrating Radar, Spectral Analysis of Surface Waves, Suspension Logging, Full Waveform Sonic Logging, Crosshole Shear

Utility Locator, Detecting Underground Storage Tank, UXO and Contaminant Plums

Magnetic, Electromagnetic, Ground Penetrating Radar, Acoustic Pipe Tracer, Metal Detectors, resistivity, Induced Polarization, Refraction

 VIBRATION MEASUREMENTS

Vibration Caused By Traffic, Construction, and Blasting

Vibration Monitoring