Shield tunnels of various cross sections can be constructed.
|| Flexible cross section
Rectangular shield tunnels can be constructed
using a simple excavation mechanism.
|| Compact shield tunneling machine
The weight and length of the shield tunneling machine, and the cost
of excavation can be reduced by using hydraulic jacks.
The lining of the rectangular shield tunnel has
an effective sandwiched structure. The outside of the tunnel has
a steel-concrete composite structure composed of steel shells that
are used as main tension members. The inside has a reinforced concrete
|| Structure of lining of rectangular
Using steel shells not only for temporary linings during temporary
work but also for the main tunnel upon completion of tunnel linings
leads to the reduction of construction cost.
Cutters are expanded and contracted like pistons by hydraulic jacks.
Thus, the structure is mechanically simple and the weight and length
of the tunneling machine can be reduced.
The rotation of cutters and the expansion and
contraction of overcutters are automatically controlled to enable
accurate excavation of corners of the cutting face.
Long stroke cutters essential to the non-circular
wagging cutter shield method are required to have higher durability
and reliability than ordinary cutters.
The newly developed high-performance "spike" bit is capable
of penetrating and cutting the earth when the overcutter is expanded
or contracted, and before and after the cutterhead is wagged.