Top down TBM escalator drives
Feb 2009
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Finish of the first escalator access drive
LOVAT EPBM ready to head to Moscow
- It has been done. The first ever large diameter, top down TBM drive to create an escalator access shaft for a metro system has been completed by a LOVAT EPBM used by OAO Mosmetrostroy in Moscow.
- The 11m diameter mixed ground machine named ‘Victoria’ broke through in January after it had excavated, mucked out and erected the precast concrete lining in the 150m long x 30° declined escalator access drive. This is the first of several top down escalator drives that Mosmetrostroy will complete for the Moscow Metro system using the LOVAT RME430SE Series 23400 EPBM.
- The steep 30° decline of the drive posed unprecedented design challenges. These included in particular, stabilizing the TBM’s centre of gravity. To overcome this challenge, modifications were made to the cutting head overcut diameter such that the mounting of the main drive was offset upwards in a vertical direction. This development eliminated a gap between the TBM outer shield and the ground at the invert, which in turn kept the TBM from sinking at the invert.
- Additional modifications allowed the TBM to operate within the confines of the designed tunnel axis tolerances. Using twin articulation joints (passive and active) and a cyclical copy cutter, the machine is capable of negotiating a 100m radius vertical curve.
- A main design concern was delivery of the 7.25 tonne concrete segments down the 30° tunnel. A cable winch hoist of the type used in the mining industry was implemented to deliver materials from the tunnel portal to the TBM’s backup system. A large segment car custom designed to handle the large segments and other materials was lowered by cable into the tunnel. This ensured the safety of the personnel working in the TBM.
- Mixed ground conditions were encountered during excavation. These comprised dolomite, limestone and soils including clay, marl, loam and sand. The TBM is equipped with a mixed face cutterhead powered by a variable frequency electric drive. The cutterhead is faced with abrasion resistant plating and dressed with a combination of LOVAT ripper teeth that are interchangeable with disc cutters, and LOVAT scraper teeth. It also has six independent ports for the injection of ground conditioning agents.
11m diameter drive on a 30° decline
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The 11m diameter LOVAT EPBM
- The alignment of the first drive passed through three ground water aquifers at different elevations. Maximum ground and water pressure on the maximum 80m deep tunnel was 4.5 bar. As well as equipment to generating and injection ground conditioning agents, the TBM is fitter with a state of the art guidance system and a through-the-tailskin annular grouting system.
- Due to the steep decline and the pressurized requirements of the face, a double screw conveyor and a pumping system was fitted as the most viable method for mucking out. The final design was a primary and secondary screw conveyor with an advanced muck pumping system developed specifically for the application. The coupling of the primary and secondary screw conveyors and the connection to the muck pumping system classifies as an important technological advancement on LOVAT TBMs.
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View down the steep escalator access decline
- LOVAT technicians were on hand to provide full support and ensure successful completion of the initial drive and will continue to provide assistance for the remainder of this special tunneling project.
- Contractors OAO Mosmetrostroy of Moscow, ordered the 800 tonne, 11m diameter EPBM from LOVAT in September 2006. Following successful construction and factory performance testing, the machine was accepted for delivery by Mosmetrostroy specialists Vladimir Bogdanov, Mikhail Maslov, Sergey Matrosov, Alexander Shirokov, and Evgeny Sokolov. It was shipped from the LOVAT factory in Toronto in late 2007 and arrived in Moscow for assembly and launch on the first drive in early 2008
- With that first drive now complete, the 11m diameter TBM is being disassembled leaving the shield behind and retracting the internal components back through the tunnel to the surface.
- This cutting edge project represents a significant technological advancement for the tunneling industry and is an example of LOVAT’s continuous search for new ways to expand the boundaries of TBM technology.
