Abstract: The geotechnical investigation for the special construction methods is an important part of the geotechnical engineering practice. This paper presents two case histories of geotechnical investigations for a highway tunnel to be excavated by the Tunnel Boring Machine (TBM) method and a proposed highway box culvert under cross a railway by horizontal jacking method. The geotechnical investigation aspects of TBM excavation in hard rock and horizontal jacking of highway box culvert in soft soil are introduced in the paper. The characteristics of the geotechnical investigation for the special construction methods are evaluated. The engineering practices indicate that in the highway construction projects, the special investigation has wide applications and is also important.

Key words: geotechnical investigation for the special construction methods, geotechnical investigation for highway project, tunnel boring machine excavation method, highway box culvert jacking