UK machines at home and abroad Oct 2009
- UK machine manufacturer Dosco Overseas Engineering is celebrating achievements in the UK and across the seas in the Dominican Republic.
- To the Dominican Republic, the roadheader and TBM supplier has delivered a second MK3A roadheader to the Santa Domingo Metro project. The new machine was ordered after the first Dosco roadheader, launched on the project in 2006, had completed successfully several running tunnel drives between stations.
Dosco MK3A breaking ground in the
- The 104 tonne MK3A Dosco roadheader with its 270kW boom was chosen for its high speed cutting capability in the generally soft to medium strata encountered on the 6.25m high x 8.25m wide tunnel alignments and through the harder ground found on certain sections. The versatility of the machine also enables its use at intersections where the tunnel cross-section is more than double the running tunnel width.
- Advance rates of 1m/h are the general rule, and a best of up to 20m in a 12h shift has been achieved.
- On the home front, a Dosco SB400U boom-in-shield machine has completed a new baggage-handling tunnel for Terminal 5 at London's Heathrow Airport. The TBM, named Beatriz, was the machine of choice for Spanish contractor Ferrovial Aggroman, for the 2.2km long x 5.5m diameter drive through London Clay.
- The machine was built and tested at the Dosco factory in Tuxford, Nottinghamshire before being transported to site. The segmental shield was stripped into transportable sections and assembled on site using a 40 tonne capacity gantry crane.
Dosco boom shield ready to go at Heathrow
- Dosco supplied a team of engineers to supervise and train site personnel in the assembly and operation of the machine. Final commissioning of the TBM was completed in three weeks.
- The 142kW boom with its purpose-designed clay cutting head, coupled with the ability to cut the face and build the segmental lining simultaneously facilitated positive advance rates. A semi-rotary ring vacuum erector and hydraulic build bars allowed safe and efficient placement of the segments directly against the clay of the excavated tunnel.
- Steering of the TBM via 17 proportionally controlled thrust cylinders, each with a thrust of 890kN, was precise and easily accomplished for navigating through the various curves and grades of the tunnel drive.
- A three-stage conveyor system comprising a chain primary belt and two cross belt conveyors, provided a muck discharge capacity of 600 tonne/h across the eight back-up trailers and onto the continuous muck-haulage belt conveyor.
- During the drive the TBM achieved a best rate of 52, 1m long rings of segmental lining built in a 24h period, easily achieving its target performance.
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