Advancing Subsurface Investigations Beyond The Borehole With Passive Seismic Horizontal-To-Vertical Spectral Ratio And Electromagnetic Geophysical Methods At Transportation Infrastructure Sites In New Hampshire

The U.S. Geological Survey (USGS), in cooperation with the New Hampshire Department of Transportation (NHDOT), surveyed transportation infrastructure sites using rapidly deployable geophysical methods to assess benefits added to a comprehensive site characterization with traditional geotechnical techniques. Horizontal-to-vertical spectral-ratio (HVSR) passive-seismic and electromagnetic-induction (EMI) methods were applied at four sites including a roadway-stream crossing, roadway-bridge rail-trail crossing, commuter-parking expansion, and a railroad-adjacent river-cutbank slope-failure site. Additionally, ground penetrating radar (GPR) was used at the slope-failure site. Typically, at transportation projects, subsurface geotechnical properties are determined from boring data; however, borings are often spaced hundreds of feet apart, potentially missing important spatial variability between boreholes. Geotechnical site characterization including geophysical surveys helped provide a more accurate characterization by using continuous or near continuous profiling. Three-component ambient noise measured with the HVSR method was used to determine site resonance frequency for estimating sediment thickness. The method works best when there is a strong shear-wave acoustic impedance contrast (> 2:1) between sediment and bedrock. Sediment thickness estimates from HVSR measurements were combined with boring data to make detailed maps of the bedrock surface elevation. The bulk electrical conductivity of the subsurface was indirectly measured with EMI methods and was used to identify lithologic variations, shallow bedrock, and conductive groundwater. Ground penetrating radar, which transmits pulses of electromagnetic energy into the subsurface and records the amplitude and timing of reflected signals, was used to identify bedding and changes in lithology or water content. By combining geophysical and boring data analyses, transportation projects produced more spatially comprehensive representations of geotechnical subsurface conditions than would be determined using conventional borings alone.

• Record URL:
  https://www.highwaygeologysymposium.org/wp-content/uploads/72nd-HGS-Tacoma-WA-2023-Proceedings_.pdf
• Supplemental Notes:
  • Copyright © 2023 Highway Geology Symposium (HGS).
• Corporate Authors:

  Highway Geology Symposium

  ,   United States 
• Authors:
  • Degnan, James
  • Pelham, Krystle
  • Terry, Neil
  • Welch, Sydney
  • Johnson, Carole
• Conference:
  • 72nd Highway Geology Symposium (HGS 2023)
  • Location: Tacoma Washington, United States
  • Date: 2023-8-14 to 2023-8-17
• Publication Date: 2023

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Maps; Photos; References; Tables;
• Pagination: 24p
• Monograph Title: Proceedings of the 72nd Highway Geology Symposium (HGS 2023)

Subject/Index Terms

• TRT Terms: Geological surveying; Geotechnical engineering; Infrastructure; Roads; Seismic prospecting; Surveying
• Geographic Terms: New Hampshire
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 01895166
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 3 2023 1:53PM