Long distance pipe-jacking cases using long life cutter bits in the big boulder and hard rock ground

Mechanical pipe jacking methods are adopted for no-dig infrastructure-constructions because of reliability and safety. In especially, high density mud slurry pipe jacking method had much actual results under unique works. Nowadays these methods are desired any diversification under working surrounding. That is, "Direct- Arrival-Method to the existing underground structure", "Sharp radical curve pipe jacking works, for example ,U.L turning curved pipe lines", "Recovery function for un-expectation objects in the ground", and "Rectangular (Box Culvert) pipe jacking method" are demanded. On the other hands, the works in big cobble and hard rock layer are increasing. Under these conditions, the long life inspection of cutting bits is the most important problem. In generality, at life-time over, cutter bits are exchanged in the shield machine or outside pit with bad conditions. However, there are some troubles in these conditions. This report shows the works with long distance pipe line construction through the big cobble and hard-rock layer without replacing cutting bits.