Advancements in Use of Geophysical Methods for Transportation Projects (2020) / Chapter Skim
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6 The literature review presented in this chapter covers three topic areas. First, a summary of relevant findings from the 2006 NCHRP Synthesis 357: Use of Geophysics for Transportation Projects is presented (Sirles)
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Literature Review 7 Perceived Benefits of Geophysics and Deterrent to Use When agencies were asked what they considered the greatest benefits of geophysics in transportation projects, their top three answers were as follows: data acquisition speed (21%) , cost benefit (19%)
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8 Advancements in Use of Geophysical Methods for Transportation Projects Figure 3. Greatest deterrents to use of geophysics in agency transportation projects as reported in 2006 synthesis (Sirles 2006)
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Literature Review 9 Budgeting and Cost The 2006 survey results indicated that the fiscal budgets of most transportation agencies (67%) do not include geophysics.
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10 Advancements in Use of Geophysical Methods for Transportation Projects Surface Geophysical Measurements Surface geophysical methods are defined as methods that are performed without the need for penetration into the subsurface through use of a borehole or penetrometer. All sources and receivers used in the measurement are placed on or above the surface of the earth.
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Literature Review 11 variability. An example of seismic tomography for imaging lateral variability between boreholes using borehole-to-surface tomography is presented in Figure 39 (in Chapter 4)
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12 Advancements in Use of Geophysical Methods for Transportation Projects the geophone recordings, and a dispersion curve that relates phase velocity to frequency is developed. The shear wave velocity profile that produces a matching dispersion curve is determined through an inversion process.
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Literature Review 13 Resistivity. Electrical resistivity (ER)
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14 Advancements in Use of Geophysical Methods for Transportation Projects electrode and one mobile electrode that is moved around the survey location. In engineering applications, the SP method is used primarily to map the flow of groundwater, including flow conditions in karst terrain (Bumpus and Kruse 2014)
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Literature Review 15 Frequency-Domain EM. In the frequency-domain EM (FDEM)
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16 Advancements in Use of Geophysical Methods for Transportation Projects Seismic Methods Seismic borehole methods involve exciting body wave (p-wave and s-wave) energy and detecting the waves' arrival to determine the propagation velocity in the soil or rock.
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Literature Review 17 background levels of radiation and can be used for lithology, for correlation of strata, and to infer permeability. Active methods such as gamma-gamma logging and neutron logging introduce small levels of radiation and measure backscatter from the soil and rock.
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18 Advancements in Use of Geophysical Methods for Transportation Projects Application Surface Methods Borehole Methods R ef ra ct io n R ef le ct io n R ef ra ct io n T om og ra p h y H V S R FW I S u rf ac e W av e R es is ti vi ty IP S P G P R FD E M T D E M M ag n et ic G ra vi ty D ow n h ol e C ro ss h ol e P S L og ge r R ad ar In d u ct io n N u cl ea r R es is ti vi ty /S P O p ti ca l T el e.
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Literature Review 19 Educational and Training Resources A variety of educational and training resources are available to geotechnical engineers and other users of geophysical methods. This portion of the literature review provides a summary of current educational and training resources regarding (1)
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20 Advancements in Use of Geophysical Methods for Transportation Projects Fundamentals of Geophysical Measurements In some cases, practicing engineers either need or want a deeper understanding of geophysical methods. Training and education for this audience help users grasp the principles of geophysical measurements and understand the offerings of geophysical contractors.
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