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Supplemental Field Investigation for Non-Select Soils

Difficult soils, such as highly compressible organic and soft clay soils, are often encountered in the shallow Florida subsurface, and warrant special attention in design and construction of transportation facilities. These problem soils frequently exist as localized pockets within otherwise suitable sandy soils. Unfortunately, such "problem soil" conditions too often go undetected in conventional geotechnical explorations and then result in costly change orders for differing site conditions when unexpectedly encountered during construction. In other cases, excessive maintenance or reconstruction costs are later realized when problem soils remain undetected during construction but become evident through poor performance. In many cases, frequency and magnitude of these construction or maintenance cost overruns could be substantially reduced through more routine use of continuous alignment geophysical surveys during the project planning and design phases to aid in selection of conventional test boring locations and in the interpretation and interpolation of their results. In an effort to encourage more routine use of supplemental field investigation techniques in conventional roadway geotechnical engineering practice, the Florida Department of Transportation sponsored a research study aimed at identifying and demonstrating the utility of conventional and emerging geophysical methods. The primary objective of this study is to demonstrate the utility and cost effectiveness of several "tools" that can be implemented to enable rapid assessment of subsurface variability and reliable detection of anomalous conditions along extended roadway alignments. Several supplemental investigation methods were evaluated in terms of applicability, practicality, timeliness, utility of results by geophysical non-experts and cost. Surface geophysical methods, including ground penetrating radar, terrain conductivity, direct current and capacitively-coupled resistivity, and seismic methods were selected for testing. During an initial verification testing phase, the applicability of these methods was assessed at a number of sites known to have "problem" subsurface soil conditions. A validation testing phase was then undertaken using selected verified methods at two actual highway project sites in central Florida. During this phase, more than 30 km (nearly 20 mi) of continuous alignment geophysical surveys were performed. This report presents findings from the study, including selection of candidate methods, results of field verification and validation testing phases and recommendations for further study and implementation. Based on the results presented herein, the author is optimistic that more routine use of continuous alignment surface geophysics can provide the advanced notice of potential problem areas that the engineer needs in order to better plan and execute effective geotechnical investigations. The envisioned result is a decline in the number of change orders related to unforeseen problem soil conditions, improved performance, and reduced overall project and maintenance costs.

  • Corporate Authors:

    Ardaman and Associates, Incorporated

    8008 S Orange Avenue
    Orlando, FL  United States  32809

    Florida Department of Transportation

    Structures Research Center, 605 Suwannee Street
    Tallahassee, FL  United States  32399
  • Authors:
    • Werner, Robert J
  • Publication Date: 2008-1-10

Language

  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References;
  • Pagination: 218p

Subject/Index Terms

Filing Info

  • Accession Number: 01088309
  • Record Type: Publication
  • Report/Paper Numbers: File No. 02-198, Project No. BD-498
  • Files: TRIS, STATEDOT
  • Created Date: Feb 15 2008 4:00PM