Abstract: To improve the applicability of tunnel boring machine (TBM) excavation in the weak surrounding rock and fault fracture zone and effectively cope with the problems caused by the convergence and deformation of the surrounding rock, such as beyondlimit deformation and TBM jamming, five targeted overcutting designs, namely, hydraulic over cutter, outward movement of gauge disc cutter, reserved over cutter housing, main drive eccentricity design, and changing cutterhead side block are compared based on the application of TBMs in Qinling Tunnel, DaliRuili Railway and other projects, and the application characteristics, and applicable TBM types of different overcutting methods are concluded. It is concluded from the above research that: (1) the hydraulic over cutter can be used alone and is suitable for shortdistance overcutting, whereas the other four methods are all suitable for longdistance overcutting; (2) when the overcutting volume needs to be greater than 50 mm in the radial direction, both the outward movement of gauge disc cutter and the lifting of cutterhead must be conducted simultaneously; (3) the maximum overcutting volume in the radial direction shall not exceed 100 mm, and a larger overcutting volume must be achieved by changing cutterhead side blocks; and (4) with the development of TBM technology, the easier overcutting method with an overcutting volume of more than 100 mm in the radius direction should be further studied in the future.

Key words:  , tunnel boring machine, overcutting method, hydraulic over cutter, main drive eccentricity, over cutter housing