Use of Geophysics for Transportation Projects (2006) / Chapter Skim
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Appendix D - Case Histories
Appendix D - Case Histories
Pages 99-107
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From page 99... ...
As the authors indicate, poor application, instrumentation, or data interpretation software may often be the reason a geophysical investigation does not meet the objectives. CASE HISTORY 1 How not to do it -- A summary of a reflection seismic project to delineate potential faulting across structures proposed for a major Interstate project in southern California An Unsuccessful Geophysics Project William Owen, Chief, Geophysics and Geology Branch, California Department of Transportation Objective and Purpose In the summer of 2002, a staff geophysicist was consulted to propose investigations for Interstate improvements in the San Bernardino Valley in southern California.
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From page 100... ...
. In the opinion of the consulting geophysicist, the interpretation of the deep seismic sections included geologic structures that were not plausible given available knowledge of faulting and geology in the area.
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From page 101... ...
The follow-up shear-wave survey was not carried out and, in this case, the client's negative experience makes that follow-up unlikely. CASE HISTORY 2 Application of Ground Penetrating Radar at the Stony Rapids Airfield in a remote area of northern Saskatchewan A Successful Geophysics Project Saskatchewan Department of Highways and Transportation (SDHT)
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From page 102... ...
The source of the moisture could not be determined because surface FIGURE D3 Truck-mounted GPR at Stony Rapids Airfield. FIGURE D4 Ground penetrating radar scan pass 1A.
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From page 103... ...
Bedrock in the area consists of alternating layers of Permian age limestone and shales. Kansas River alluvium typically consists of quartz sand with lenses of clay and silt; the alluvium is less FIGURE D5 Stony Rapids Airfield wetted up subgrade contours.
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From page 104... ...
We finally decided to try both the seismic and electrical methods and learn for ourselves. KDOT has a standing contract for drilling services with a consulting firm that also performs geophysical investigations.
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From page 105... ...
Lessons Learned Companies specializing in seismic refraction and resistivity on this scale are not common in the central plains. KDOT Geology assumed that, given the planer geology and existing FIGURE D7 Conception geologic model of K-18 site.
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From page 106... ...
An old city landfill, with little to no historical data on the nature and extent of filling, occupies a preexisting ravine on the property that extends beneath the limits of construction of the proposed Birch Street intersection. A geophysical investigation was conducted at the property in December 2002 to estimate the horizontal extent of landfilling within the proposed limits of construction and to focus future geotechnical and environmental work at the site.
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From page 107... ...
Interpretations of the extent of landfilling at the site were developed using both the EM31 image maps and GPR profile data. Reasons for Success and Lessons Learned Overall, these two geophysical methods worked well to identify both the horizontal extent of filling and the location of high conductive fill material within the preexisting ravine.
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