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In 1987 the Robbins-Markham Joint Venture (RMJV) was awarded a
£15m contract to supply two machines for the Marine Rail tunnels driving some
22km towards France.
Bennett Associates was awarded a contract by RMJV to design and
produce detail manufacturing drawings for the 235m long back-up system to the
Tunnel Boring Machine (TBM) and a contract from the Robbins Company, USA to
carry out a full Finite Element Stress Analysis of the Tunnel Borning Machine
which they were designing.
Design of the TBM back-up system
The back-up system consisting of thirteen articulated gantries,
running on temporary rails, performs the following functions:
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Offloads, transports and places 1.5m wide
precast concrete segments in position to form to form the tunnelling lining. The
45 ton segment ring in nine pieces has to be built in 15 minutes. |
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Transport muck from the cutterhead on conveyors at a peak
rate of 1,500 and normal rate of 1000 tonnes per hour. |
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Supports the TBM with all services paid out continuously as
the machine advances. The power supply is 2,300kw at 11,000 volt, clean water in
by 4" dia hose reel, dirty water out by 6" diahose reel, inrush water out 12"
dia x 2 telescopic pipes, fresh air in by 2m dia flexible duct plus radio
telephone and computer data links. |
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Performs and supports a high pressure grouting system,
filling voids between pre-cast lining and the ground. |
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Provides air extraction and cleans by filtration
and wet scrubbing prior to discharge. |
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Provides compressed air, fire fighting systems, emergency
power and workshop/messroom facility. |
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Houses the TBM and back-up system air conditioned sound
proof control room and hydraulic powerpacks and electrical control gear. |
Some 800 drawings were produced, mainly using AutoCad, over a ten
month period. Qualified engineers were on site during the tunnelling period,
assisting with machine operation and modification to suit changing ground
conditions.
Stress analysis of TBM
The 12m long TBM weighing some 800 tonnes was designed to
withstand the full hydrostatic head of sea pressure of 12 bar, exerting a force
of 6,600 tonnes on the front of the TBM.
The machine is propelled forwards by hydraulic rams able to
provide 4220 tonnes of thrust reacted by gripper pads thrust out against the
tunnel bore.
Bennett Associates was responsible for carrying out a full stress
analysis of the cutterhead support, TBM structure and gripper body and pads
which was done by Finite Element analysis using ANSYS software solid modelling
elements.
The analysis was used interactively by the Robbins designers in
Seattle USA. Close co-operation was maintained by visits to Seattle and exchange
of AutoCad drawings on disk to ensure that the complex interface between TBM and
its back-up system was correctly engineered.
For more information, contact us on 01709-373782 |
