Article

Selecting surface geophysical methods for geological, hydrological, geotechnical, and environmental investigations: The rationale for the ASTM Provisional Guide

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Abstract

The ASTM Provisional Guide (PS 78-97) for Selecting Surface Geophysical Methods was developed as a guide for project managers, contractors, geologists, and geophysicists to assist in selecting the most likely geophysical method or methods to conduct specific subsurface investigations. Numerous surface geophysical methods and techniques exist that can be used to determine subsurface soil and rock properties and their distribution. These same methods are also widely used to investigate and locate manmade structures such as buried objects and landfills. This paper discusses the general uses of surface geophysics and the use of the provisional guide. This paper is not intended to be used as the guide. The ASTM Provisional Guide provides direction in selecting the most appropriate geophysical method or methods for a specific application under general site conditions. Secondary methods are also proposed that, under general circumstances, should be evaluated before a final selection is made. Some typical conditions under which a primary or secondary method might or might not provide satisfactory results are given in the provisional guide. References for further information about selected methods and to method-specific ASTM guides are also provided. Secondary methods usually have less than desired performance, higher cost, or greater labor requirements as compared to the primary methods.

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Chapter
We now have a work plan that is based upon regional and local existing data and possibly some site-specific data. A conceptual model has been developed and focuses our attention on what we know, what we need to know and what we might expect on site. As we begin to acquire on-site data using surface geophysical methods, we will begin to test the conceptual model. Their primary benefit is that of greatly increasing the data density over the site, which improves the definition of background and anomalous conditions. These measurements allow us to more accurately locate invasive measurements based upon data rather than guesses thereby improving the chances of accurately defining geologic conditions. This section provides an introduction to the many surface geophysical methods. We have focused on considerations for their use and how to select methods rather than how to make the measurements. In addition, a large number of examples showing their application are provided to show how these methods can be used in a site characterization effort.
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