4. A Survey of Elastic and Electromagnetic Properties of Near-Surface Soils

Abstract

The near-surface is covered with soil in most onshore and offshore locations. Soil characterization by sampling and in-situ testing techniques (e.g., cone penetration and pressure meters) faces unavoidable perturbation effects. On the other hand, low-power geophysical techniques cause no appreciable perturbation and provide an effective alternative for site assessment. In particular, near-surface site characterization using elastic and electromagnetic perturbations yields important information related to the soil mass, including the spatial distribution of materials, smallstrain elastic properties and electromagnetic characteristics. In turn, geophysical measurements can be associated with soil parameters relevant to geotechnical engineering analysis and design. This chapter presents information about elastic (smallstrain) and electromagnetic properties of soils and their relations to soil parameters. The goal is to explain physical links between geophysical measurements and soil properties, emphasize global trends, and highlight variables that exert first-order effects. The chapter includes simple, yet robust, concepts and relations that can be readily used in designing measurement procedures and in data interpretation. The information in this chapter is structured resembling Chapter 3 of this volume by Knight and Endres. Comprehensive coverage of equations, trends, and behavior discussed herein can be found in Santamarina et al. (2001).