Application of drilling survey system for soft rock

In tunnel constructions, heterogeneity of rock bodies such as faults and related fracture zones can be serious problem for safety management, construction planning and excavation costs. Thus, the estimate of geological conditions and rock properties ahead of the tunnel faces is strongly required and several methods of such fore survey have been proposed by many researchers. For this purpose, we have developed "DRISS", the Drilling Survey System, for fore surveys at tunnel faces with higher accuracy, and report here the application of this system to tunnel construction sites. In this paper, we outline our fore survey system, and show the successful fore survey results including the improvement in drilling techniques at the tunnel construction site with soft rocks.