Using Seismic Tomography and Holography Ground Imaging to Investigate Ground Conditions

摘要

Unforeseen, variable subsurface ground conditions present the greatest challenge to the heavy construction and civil engineering industry in the design, construction, and maintenance of large projects. A detailed, accurate site investigation will reduce project risk, improve construction performance and safety, prolong the life of the tunnel or structure,and prevent waste in over - design. Presently, site characterization and geotechnical engineering are limited by the inability to adequately describe these subsurface ground conditions.NSA Geotechnical Services has successfully applied seismic tomography and holography ground imaging technologies on tunneling and heavy civil excavations worldwide. Seismic signal waveforms traveling through a complex medium consist of various arrivals from refractions, reflections, scattering, and dispersion. Tomography and holography are proven inversion technologies for estimating location and extent of material property variations causing changes in signal waveforms.ent attenuation rates and velocities. Seismic waves will travel faster through competent material and be generally less attenuated than through broken/fractured ground or voids.encounters an interface between ground zones possessing different seismic properties. Most geologic structures, anomalies,and changes in lithology provide detectable seismic reflections if they are within a reasonable distance of the seismic source.This paper will present various applications of these technologies, illustrating how seismic imaging can provide accurate information regarding ground conditions associated with tunneling projects. With this information, engineers can complete projects safely, within time and budget constraints.