Abstract
A big problem occurred during tunnel construction is unexpected increase of construction cost caused by discrepancy of formation rock conditions between those predicted by the geological investigations before the construction and those found at the actual excavation. One of the reasons of the discrepancy is uncertainty in evaluating formation rock conditions at the investigation stage. Although the uncertainty may be caused by insufficient geological investigations due to limited budget, the investigation budget tends to be cut, recently, as well as construction budget reduction. This situation may be caused by the reason that one cannot explain well how much uncertainty is expected in the geological investigations.
In order to increase the value of geological investigations, it is important to consider evaluation of financial risk for unexpected cost increase due to the geological condition discrepancy. In this paper, the authors study and discuss on evaluating uncertainty in seismic refraction survey, which is one of the geophysical exploration methods usually used for the tunnel investigations especially in mountainous area.
