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TBM RECORDER First of six Robbins EPBMs set in Singapore Sep 2012
Desiree Willis, Technical Writer, The Robbins Company
In one of many access shaft sites throughout Singapore, the first of six 6.65m diameter Robbins EPBMs is ramping up for a mega construction project. The machine is one of two that will excavate the running tunnels on Contract C927, between Bedok Park and Bedok Reservoir, for engaged contractor CMC di Ravenna of Italy. Four further Robbins EPBMs will excavate the running tunnels for Contracts C925 and C937 for Korean contractor, GS Engineering & Construction.

Bringing the components of the EPBM together under the watchful eye and supervision of Robbins Site Supervisor Leif Schmidt (right) and Robbins Field Technician Paul Wilson (left)

The TBMs are part of a massive underground undertaking for Singapore's Downtown Line Phase 3 (DTL3), which comprises a stretch of 21km of twin running tunnels with 16 stations and on which 29 TBMs will be deployed. Running almost parallel to the East West Line of the metro, DTL3 will provide a convenient transport link to the Central Business District and Marina Bay areas of Singapore.
Singapore's DLT project (in dark blue) will see application of up to 50 TBMs for its total 42km underground length

Singapore's DLT project (in dark blue) will see application of up to 50 TBMs for its total 42km underground length

The 62 tonne cutterhead for the first of the two Robbins machines was lowered in August and the TBM is scheduled to begin excavation in September. "Assembling the machine was a challenge due to the small shaft opening," said Mark Passey, Robbins Site Manager. "This required assembling the shield in smaller sections than usual, and required the use of a purpose-built lifting adaptor to lower the cutterhead support and forward shield separately." The cutterhead was then lowered through a 14m opening through the shaft cross bracing. The small launch area required shunting of components forward and backward on the launch cradle using two 100 tonne hydraulic jacks.
The two Robbins EPBMs for the C927 contract will excavate their parallel 1.35km drives through alluvium consisting of cemented sandstone and beach rock. Each of the EPBs was designed with mixed ground cutterheads and cutting tools that are interchangeable with disc cutters. Flexible additive systems are capable of injecting foam, polymer, bentonite, or grout, depending on prevailing ground conditions. A probe drill on each of the machines is capable of drilling through the face and through ports around the periphery of the shield, enabling quick and efficient excavation if any changeable ground conditions are encountered.
The entire Downtown Line, including Phases 1 and 2, for Singapore's LTA (Land Transportation Authority), will consist of 42km of new track with 34 stations. Once complete in 2017, the DTL is estimated to serve half a million commuters daily.

           

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