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 beyondlimit 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, DaliRuili
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 shortdistance overcutting, whereas the
other four methods are all suitable for longdistance
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.
