Design of Geophysical Surveys in Transportation

Designing geophysical investigations for transportation related projects requires special attention to the constraints imposed by right-of-way, irregular topography, noise from traffic, and the need to avoid the interruption of traffic flow. A geophysical engineer needs to be prepared to consider these design issues that are not addressed in a standard procedure such as ASTM D-5777. The author presents design strategies that address these issues, and illustrates the concepts with case histories taken from bridge and highway projects. Beam steering, broadside shooting, and non-traditional designs that preserve alternative analysis options are presented. Transportation engineers who augment traditional subsurface geotechnical surveys with engineering geophysics are better prepared to avoid costly delays and redesign of projects due to differing site conditions. INTRODUCTION Application of geophysical methods to transportation projects falls into three general areas. First, there is the area of subsurface characterization and mapping. The goal is to avoid problems associated with unknown geological conditions which may require costly redesign measures and delays in project completion. Second, there is the location of buried utilities and other man made objects. This area is also known as subsurface utility engineering. Third, there is the field of non-destructive testing of roadways, bridges, and other transportation facilities. This paper will be limited in scope, and focus only on the first area, characterization of the shallow subsurface geology. Further, it will be limited to seismic methods. The principals discussed will be illustrated by reference to case histories on the design of bridge foundations and the problems of slope stability above a roadway. 1Associate Professor, Boise State University, 1910 University Drive, Boise, Idaho 83725 . 1832 This is an author-produced, peer-reviewed version of this article. The final, definitive version of this document can be found online at Geotechnical Engineering for Transportation Projects (GSP 126), published by the American Society of Civil Engineers. Copyright restrictions may apply. doi: 10.1061/40744(154)177