Integrated Geophysical Methods for Geotechnical Subsurface Investigations

摘要

This report summarizes the New Hampshire Department of Transportations (NHDOTs) investigation of geophysical techniques to supplement conventional test borings and other explorations on transportation projects. The Departments geotechnical investigations often encounter bedrock or unstable soils at variable depths over short lateral distances. Test borings are point specific and may miss sudden depth changes and variations in the soil and rock properties. Additional borings can be expensive and time consuming and may even result in a more puzzling subsurface interpretation. Site conditions and/or highly conductive soil properties can sometimes limit the use of the NHDOTs ground penetrating radar equipment, but through the implementation of additional geophysical techniques the Department has enhanced its capabilities and helped alleviate some of the uncertainties that arise when making subsurface interpretations based solely on conventional exploration methods. This report presents both successful and less successful case histories utilizing resistivity imaging and seismic refraction in conjunction with test borings and ground penetrating radar to characterize a transportation projects subsurface conditions. The methods employed in using these geophysical techniques, the results of the geophysical investigations, and how these results were calibrated and verified are presented.