Cost Effective Geophysical Approaches for Various Geotechnical Problems

A well conceived and executed geophysical program can lead to overall project cost savings by providing information about local geologic / hydrogeologic conditions, buried utilities and structures, groundwater conditions and other subsurface conditions which allows for more efficient planning of engineering activities and more cost effective deployment of construction equipment. This information ultimately leads to more complete bid packages with less uncertainty in cost estimation and, subsequently, fewer change orders, and surprises in the field. Geophysical programs combine multiple technical and scientific disciplines required to accurately, efficiently and non-destructively detect, locate, and characterize subsurface conditions. Knowledge of these conditions reduces cost and risk. Typical geophysical investigations require extensive experience and expertise in multiple disciplines. There are three keys to a successful geophysical assessment, including: (1) A comprehensive understanding of the site activities, geologic / hydrogeologic conditions, topography and weather; (2) Experience in the review of archive search reports and historic site information, as well as local political and regulatory issues; (3) An in depth understanding of geophysical sensors, navigation technologies, surveying deployment methodologies, and advanced data analysis methods. In order to meet specific project objectives to map the subsurface accurately and efficiently, the following "expedited geophysical approach" has been developed: Fully understand the challenge; Define a suite of geophysical instruments required to efficiently map the target objects; Decide on survey control; Design an appropriate and efficient instrument deployment system; Develop an efficient data processing approach. This paper uses case histories to demonstrate the cost effectiveness and technical approaches typical of geophysical characterization projects related to solving common geotechnical problems.