“Differing site conditions” is one of the top five root causes of delay to highway construction (1), by triggering costly construction claims and time-consuming change orders. Incomplete characterization of subsurface factors, such as relict or current infrastructure, underground storage tanks or utilities, hazardous waste, and soils or geologic strata, is generally to blame. Geophysical methods are increasingly recommended to non-invasively explore subsurface conditions, to identify potential problems during the planning and design phase, rather than in the course of construction (2-7) to avoid untimely project completion, reduce design errors and change orders, and accelerate project delivery.
Recognizing the potential of the EM3, Argus was selected by the National Academies of Science to participate in the IDEA program, Innovations Deserving Exploratory Analysis, which is managed by the Transportation Research Board (8, 9).
This IDEA project assessed a specialized application of the EM3 for conducting non-destructive preliminary surveys for highway construction. The EM3 provides fundamental information regarding the consistency or variability of subsurface materials, the presence or absence of buried objects, and lateral trends in soils and rock. This information is important because unknown subsurface factors such as relict or current transportation infrastructure, underground storage tanks or utilities, and unpredicted changes in soils or geologic strata complicate excavation work and trigger highway construction delays.
Studies of the near surface using older hand-held or invasive geophysical instruments are generally cumbersome (requiring grid setup), time consuming (data acquired at a walking pace or slower), and consequently expensive, not to mention data-sparse. Thus, such studies, despite their advantages, are often overlooked in site reconnaissance in favor of an extensive drilling effort. Their application to civil engineering and environmental problems however, is becoming more widely accepted with developments of digital methods for recording, processing, and presenting data, along with significant technological advancements in geophysical instrumentation (10). Finally, during the project study and design phase, the technology will be useful for addressing issues of constructability in Value Analysis/Value Engineering on the state and national levels.
- H.R. Thomas and R.D. Ellis. (2001) Avoiding Delays during the Construction Phase of Highway Projects. Report 20-24(12), National Cooperative Highway Research Program.
- Application of Geophysical Methods to Highway Related Problems Blackhawk GeoServices & CFLHD (2003).
- Anderson N., et. al., Geophysical Methods Commonly Employed for Geotechnical Site Characterization. Transportation Research Board, July 2008.
- Rutlege, F.A., M. Mauldon, and C.J. Smith (2005) Geophysical Primer for Geotechnical Engineers. Center for Geotechnical Practice and Research at Virginia Tech, 123pp.
- Neil Anderson, Neil Croxton, Rick Hoover, and Phil Sirles. Geophysical Methods Commonly Employed for Geotechnical Site Characterization. Transportation Research Circular No. E-C130, for the Transportation Research Board of the National Academies, Oct. 2008.
- U.S. Army Corps of Engineers. EM 1110-1-1802 Geophysical Exploration for Engineering and Environmental Applications. Department of the Army, 1995.
- Sirles, Phil (2006) Use of Geophysics for Transportation Projects: A Synthesis of Highway Practice. NCHRP Synthesis 357. National Cooperative Highway Research Program, Transportation Research Board of the National Academies
- Mobile Geophysical Technology: A Subsurface Scoping Tool for Reducing Unforeseen Roadblocks in Project Delivery (NCHRP-IDEA Project 107) in: NCHRP Highway. Annual Progress Report: New IDEAs for Highway Systems, Transportation Research Board of the National Academies. January 2005. Regional Panel of Experts: Brent Felker, W. Region Transportation Director and Senior Vice President, HDR Engineering, Inc.; Susan Greenwood, Assoc. Environ. Planner, Central Region Hazardous Waste and Paleontology Unit; Ali Kiani, Caltrans Division of Program/Project Management, Summit Rehabilitation Project; Wes Lum, Caltrans Division of Research and Innovation; Bill Owen, Branch Chief, Geophysics and Geology Caltrans Office of Geotechnical Support; Habib Sabzehzar, Caltrans Central Region Value Analysis Coordinator; Eric Wong, Design Senior, Caltrans Division of Design
- New Ideas: What Lies Beneath in: Ignition, News from the Transportation Research Board's IDEA Programs. Issue 8, Winter 2005.
- P.W. McDowell, et al. (2002). Geophysics in Engineering Investigations. Construction Industry Research and Information Association, London.