There are two types of Hybrid TBMs.
Type one: EPB - gripper/open TBM
This TBM not only has function of maintaining earth pressure balance on working face, but also possesses features of open hard rock cutterhead which discharges mucks via belt conveyor machine. It adapts to complex geological conditions such as soft rock, hard rock and transitional mixed formations. When geological variations are encountered, the boring modes and mucking manners can be changed for good adaptations; construction interferences and risks are therefore effectively minimized.
Type two: EPB - slurry TBM
The TBM mode will be put to work when countering a tunnel face with poor stability or moisture-rich soft soil, soft rock, sandy gravel and mixed strata in order that excavated mucks could receive liquidity and impermeability. When the cut face is rich in water or sandy gravels, the slurry pressure balance mode can be launched to bore. Inexpensive and economical, this equipment is able to meet construction needs flexibly.