Herrenknecht TBM achieves breakthrough on Singapore project

Herrenknecht has reported that the contractors working on the Deep Tunnel Sewerage System (DTSS) project in Singapore have completed tunnelling works for the second construction phase using a Herrenknecht Vertical Shaft Sinking Machine (VSM).

In the second phase of the project, 18 of Herrenknecht’s Mixshields and one EPB Shield (Earth Pressure Balance Shield) with diameters between 4.50 and 7.56 metres were chosen to bore the sewage collectors and line them with segments.

Herrenknecht also supplied 12 separation plants for the Mixshield drives and provided support services throughout the entire project. This included remote access to individual machines, enabling them to be monitored and controlled remotely.

During the project, the teams faced challenges with the grounds complex geology. The ‘Jurong Formation’ consists of sandstone, siltstone, mudstone, limestone, dolomite, and conglomerate. These rock types have been folded extensively due to tectonic plate movements.

As a result, diverse rock types with different weathering grades often alternate along a tunnel alignment and even in the cross section of a tunnel.

“In close cooperation with the customers, we adapted the design of the TBM to the complex geological conditions,” said Dirk Schrader, Herrenknecht’s general manager of Asia Pacific.

Special solutions were also required for construction of five of the 24 shafts in Tunnel Contract T-11 with diameters between 10 and 12 metres. Herrenknecht says that, in this particular section, with depths of up to 60 metres there was high water pressure the shafts constantly had to withstand.

“For this reason, for the first time in the Asia-Pacific region, a Vertical Shaft Sinking Machine (VSM) from Herrenknecht was used for sinking the shafts,” added Schrader.