The Thrust Reducer is designed to achieve long distance
jacking of up to 1000 meters. The system is comprised
of a Top Reducer, which is attached to the back of
the shield machine for the purpose of reducing skin friction
force. Other components include the Sub-Reducers (additional
reducers at various intermediate locations) for the purpose of
further reducing skin friction force during jacking operations.
Also included are an auto-flow meter, control panel, and a
pump and mixing plant for grouting.
The principle of this system is to mix surrounding
ground (approximately 2 to 3 cm) in the grouting mix pan while
at the same time lubricants (e.g. RASA BIOS™) are being
injected automatically in relation to the jacking speed. The
amount can be reduced by about 1/3 to 1/2 as compared to conventional intermediate jacking systems.