Application Of Geotomography To Rock Investigations

Three types of geotomography, namely, seismic, radar and resistivity tomographies were<br>developed and applied to investigating the rock foundation for a planned bridge pier.<br>These techniques made it possible to reconstruct distribution images of seismic wave velocity,<br>electromagnetic ( EM ) wave velocity and resistivity, respectively. Therefore, if we want to<br>know the rock conditions totally, it is very effective to apply these three kinds of geotomography<br>jointly, and to interpret the results consistently.<br>In this paper, the methods of these tomography techniques developed by the authors were<br>reviewed briefly and a field example of applications of these techniques to site investigations<br>was demonstrated. We obtained three kinds of tomograms and identified fracture zones as<br>the low seismic velocity, low EM wave velocity and low resistivity zones. In addition, from<br>the interpretation results of these tomograms, we could not only map the fracture zones, but<br>could also estimate the rock conditions in detail. The results were confirmed by geological and<br>geotechnical investigations conducted after the excavation for the construction of the bridge pier.