The National Academies Press

Currently Skimming:

Pages 21-37

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 21... ... 21 A survey was distributed electronically to 55 agencies, including state transportation agencies for all 50 states, Puerto Rico, and the District of Columbia as well as three offices of the Federal Lands Highway Division of FHWA. The complete survey questionnaire is provided in Appendix A, and complete survey results are presented in Appendix B Read the entire page →
From page 22... ... 22 Advancements in Use of Geophysical Methods for Transportation Projects Forty-three of the 48 agencies (90%) that responded to the survey reported experience with geophysical methods as defined in the survey. Read the entire page →
From page 23... ... Survey Results 23 CA AZ CO NM TX OK AR LA MO KY AL GA FL VA OH MI VTAK MT NV ME WA OR UT KS ID WY ND SD MN NE WI IA IL IN MS TN SC NC WV PA NY CT NJ DE MD MA NH PR HI RI LEGEND Geophysical Methods Experience No Geophysical Methods Experience No Response Figure 14. Agency experience with geophysical methods. Read the entire page →
From page 24... ... 24 Advancements in Use of Geophysical Methods for Transportation Projects The 2006 survey by Sirles inquired about motivations for geophysical methods in a different manner, by asking respondents to select the greatest value provided by geophysical methods. The speed of data acquisition, cost benefits, better subsurface characterization, and ability to perform two- and three-dimensional assessments were all selected by between 15% and 21% of respondents. Read the entire page →
From page 25... ... Survey Results 25 Frequency of Application of Geophysical Methods and Agency Spending on Geophysical Methods The 43 respondents who indicated agency use of geophysical methods were asked how frequently their agency had used geophysical methods over the past 5 years. Respondents were asked to select among the ranges shown in Figure 17. Read the entire page →
From page 26... ... 26 Advancements in Use of Geophysical Methods for Transportation Projects previous 5 years. Respondents were asked to select among the ranges shown in Figure 19, which presents responses to the question. Read the entire page →
From page 27... ... Survey Results 27 Geophysical Method Number Percent Seismic methods: Seismic refraction 33 85 Seismic reflection 10 26 Seismic tomography 9 23 H/V spectral ratio 2 5 Full waveform inversion 3 8 Active source surface wave techniques (e.g., SASW, MASW) 19 49 Passive surface wave techniques (e.g., ReMi) Read the entire page →
From page 28... ... 28 Advancements in Use of Geophysical Methods for Transportation Projects The most commonly used methods are ground-penetrating radar and seismic refraction, with 34 and 33 respondents, respectively (87% and 85%) Read the entire page →
From page 29... ... Survey Results 29 a relatively wide variety of applications, with some applications more common than others but none dominating. The most common applications were evaluation of roadway subsidence (28 respondents, 65%) Read the entire page →
From page 30... ... 30 Advancements in Use of Geophysical Methods for Transportation Projects The geologic investigation objective results presented in Table 4 indicate the objectives are largely the same as indicated by the 2006 survey by Sirles. Both surveys indicated evaluating the depth to bedrock is most common, while mapping soil lithology and potential voids were also common objectives. Read the entire page →
From page 31... ... Agency Description of Agency Documentation of Geophysical Methods Caltrans Caltrans's Geophysics and Geology Branch of the Division of Engineering Services has a quality management plan that documents agency objectives and practices for quality assurance related to geophysical method testing and data. In addition to administrative information, the document lists and briefly describes the ASTM standards used by the branch and provides a bibliography of useful resources. Read the entire page →
From page 32... ... 32 Advancements in Use of Geophysical Methods for Transportation Projects Just more than half of the respondents, 19 (51%) , have used lump sum or firm-fixed-price contracts. Read the entire page →
From page 33... ... Survey Results 33 not. For the 33 agencies that fund subsurface investigations through other sources, those sources are summarized in Figure 24. Read the entire page →
From page 34... ... 34 Advancements in Use of Geophysical Methods for Transportation Projects Figure 25. Agency use of various training resources related to geophysical methods (48 responses) Read the entire page →
From page 35... ... Survey Results 35 The final survey question asked respondents to indicate the perceived usefulness of five content areas for new training resources on geophysical methods. The five content areas and the perceived usefulness of each are presented in Figure 27. Read the entire page →
From page 36... ... 36 Advancements in Use of Geophysical Methods for Transportation Projects agency engineers were unfamiliar with geophysical methods, and four of five (80%) indicated that agency engineers did not know how to interpret geophysical results. Read the entire page →
From page 37... ... Survey Results 37 • The most common source of funding for geophysical investigations is project design funds, with 30 of 33 respondents indicating such funds had been used. Project construction funds were also used by more than half the respondents. Read the entire page →

From page 21...

... 21 A survey was distributed electronically to 55 agencies, including state transportation agencies for all 50 states, Puerto Rico, and the District of Columbia as well as three offices of the Federal Lands Highway Division of FHWA. The complete survey questionnaire is provided in Appendix A, and complete survey results are presented in Appendix B