Advantages of Geophysics to Improve Site Characterization and Reliability for Transportation Projects

Abstract

Under the Federal Highway Administration’s innovation development program “Every Day Counts” (EDC-5), the initiative on Advanced Geotechnical Methods in Exploration (A-GaME) aims to improve the knowledge in U.S. practice on existing but underutilized subsurface exploration methods. The A-GaME suite of technologies is a group of proven and effective exploration technologies and practices that, in conjunction with limited conventional exploration methods, mitigate the risks of geotechnical uncertainties and optimize subsurface exploration programs for improved site characterization and reliability over a wider coverage area and maximum return-on-investment. Transportation agencies are becoming more eager to employ alternative exploration methods to supplement their investigations and limit uncertainty emanating from geotechnical subsurface conditions. In this context, Arkansas Department of Transportation, in collaboration with the University of Arkansas, has implemented geophysical methods in subsurface investigation to acquire adequate information in relation to bedrock depth and rippability for new construction and to address slope stability issues along roadways. Different geophysical methods have been employed, including multichannel analysis of surface waves (MASW), electrical resistivity tomography (ERT), and microtremor horizontal to vertical spectral ratio (MHVSR). Two case studies are presented here, one for a proposed and one for an existing transportation project. According to the results of these case histories, the joint application of MASW and MHVSR was determined to be valuable for rock rippability estimates for roadway projects, whereas the combined use of MASW, MHVSR, and ERT produced significant additional subsurface information for landslide assessments and remediation efforts.