In one of many deep shaft sites throughout Singapore, the first of six 6.65-m (21.8-ft) diameter Robbins EPBs is ramping up for a mega construction project. The EPB is one of two that will excavate contract C927, running between Bedok Park and Bedok Reservoir, for contractor CMC di Ravenna of Italy.

Four more Robbins EPBs will excavate contracts C925 and C937 for contractor GS Engineering & Construction of Korea.

The TBMs are part of a massive undertaking for Singapore’s Downtown Line, Phase 3 (DTL3) — a stretch of 21 km (13 miles) with 16 stations utilizing 29 TBMs.  Running almost parallel to the East West Line (EWL) of the metro, the DTL3 will provide a convenient transport link to the Central Business District and Marina Bay areas of Singapore.

The 62 tonne (68 U.S. ton) cutterhead for the first of the two machines was lowered in August and the TBM is scheduled to begin excavation in September 2012. “Assembling the machine was a challenge due to the small shaft opening. 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,” said Robbins site manager Mark Passey.
 
The cutterhead was then lowered through a 14-m (45-ft) 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 (110-U.S. ton) hydraulic jacks.  

The two Robbins EPBs for the C927 contract will bore parallel 1.35-km (0.8-mile) tunnels through alluvium consisting of cemented sandstone and beach rock.  Each of the EPBs was designed with mixed ground cutterheads and cutting tools interchangeable with disc cutters. Flexible additive systems are capable of injecting foam, polymer, Bentonite, or grout depending on the conditions.  A probe drill on each of the machines is capable of drilling through the face and 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 Land Transportation Authority (LTA), will consist of 42 km (26 mi) of new track with 34 stations.  Once complete in 2017, the DTL is estimated to serve half a million commuters daily.

This article was submitted by The Robbins Co., based in Solon, Ohio.