Table 1: Advantages and disadvantages of the spoke type and plate type cutterhead.

Items	Spoke Type Cutterhead	Plate Type Cutterhead
Pressure control of the cutting face	Being almost equal to the earth chamber pressure, the cutting face pressure is easy to be controlled.	On account of the indirect transmission between earth chamber pressure and cutting face pressure, it is a little difficult to perform precise pressure control of the cutting face.
Entry of muck into the excavation chamber	Entry of the excavated materials into cutterhead is smooth on account of the high opening ratio, almost resulting in no clogging of the cutterhead.	Affected by the plate, the entry of the excavated materials is not smooth and the cutterhead is liable to be clogged and jammed by the excavated materials.
Torque of cutterhead	The required torque of the cutterhead is small and the manufacturing price of the equipment is low.	Necessitate high torque of the cutterhead and large capacity of the equipment, as leads to a high construction cost.
Wear of the cutterhead and cutting tools	The high opening ratio of the cutterhead causes the relatively minor wears of the cutterhead and cutting tools.	Because of the small opening ratio of cutterhead, the excessive wear of the cutterhead and cutting tools is a hackneyed phenomon.
Adaptability to the over-sized particles	Over-sized grains or boulders that can’t be extracted from the excavation chamber by the screw conveyor must be handled by manual work.	Kept out of the cutterhead, the over-sized grains or boulders can be broken by disc cutters.
Safety of changing tools	The high opening ratio of the cutterhead to some extent decreases the stability of the cutting face.	The plate is helpful to stability of the cutting face, and a higher construction safety results.
Requirements for shield machine manipulations	The requirements are relatively high.	The requirements are relatively low.