Herrenknecht Breakthrough on Circle Line Stage 3 in SingaporeOn 25th August, 2005, a Herrenknecht TBM brought down an 80 cm-thick retaining wall, into the tunnel at Lorong Chuan station on Stage 3 of the Circle Line in Singapore. The TBM has come through from Serangoon station. Over the next months, it will do the same thing from the opposite direction, from Bishan station to Lorong Chuan (see alignment map).A 5.7 km section, the SGD1.2 billion Stage 3 of the Circle Line has five stations (Bartley, Serangoon, Lorong Chuan, Bishan and Marymount). It will intersect with the North-South Line at Bishan and the North-East Line at Serangoon. The Land Transport Authority announced that Stage 3 is on schedule. For stages 4 and 5 the first contracts are out and starting work soon. With this, the Circle Line should be open by 2010. Visit www.lta.gov.sg/projects/index_proj_ccl.htmStage 3 mainly includes contracts 852 and 853. Contract 852 is for the construction of the Serangoon interchange station, the interconnecting tunnels between Serangoon station and Lorong Chuan station, and between Serangoon station and Bartley station. The contract also includes modification works on the existing Serangoon station along the North East Line. In terms of geology, there is fluvial sand and clay, as well as old alluvium developing into mass old alluvium.Two EPB shields, manufactured by Herrenknecht, have been used for this contract. The excavated diameter is 6.6 metres and the internal tunnel diameter is 5.8 metres. Currently, 70% of the station excavation works is finished and 35% of the base slab. The interconnecting tunnels between Serangoon station and Lorong Chuan station are 700 m long each, while those between Serangoon station and Bartley station span 1,200 m each. Breakthrough for the outer tunnel took place on 11th May, 2005 and on 25th August, 2005 for the inner tunnel. Currently, the launch shaft support infrastructure is being installed. The TBM that broke through in May is currently being maintained before reassembly, while preparation works are being carried out to remove the other TBM from the shaft. Contract 852 is built by Woh Hup, Shanghai Tunnel Engineering Co. (STEC) and Alpine Mayreder. Visit www.herrenknecht.comContract 853 is for the construction of Marymount station and the interconnecting tunnels between Marymount station and Bishan station. Two slurry shields are used for the tunnels between Marymount station and Bishan station, while two EPB machines are used for those between Bishan station and Lorong Chuan station. These four machines are manufactured by Kawasaki Heavy Industries. In terms of geology, between Marymount station and Bishan station, there is moderately weathered to completely weathered granite of the Bukit Timah granite formation. Between Bishan station and Lorong Chuan station, there is mainly old alluvium and some marine clay. To date, 70% of the station excavation works is completed. The interconnecting tunnels between Marymount station and Bishan station are 1,300 metres long each. The excavated diameter for the tunnels from Marymount station to Bishan station is 6.63 m, while that from Bishan station to Lorong Chuan station is 6.61 m. The internal diameter for these tunnels is 5.8 m. Currently, about 17% of the inner tunnel is completed and less than 1% of the outer tunnel between Marymount station and Bishan station. The TBM for the outer tunnel was commissioned very recently on 2nd September, 2005. As for the tunnels between Bishan station and Lorong Chuan station, nearly 62% of the inner tunnel is completed while progress on the outer tunnel has reached nearly 50%. Contract C853 has been awarded to Taisei. Visit www.khi.co.jp/tekkou/en/index_e.htmlSo far, 13% of the excavation works is completed at Bartley station (contract 851A) and 40% at the Bishan interchange station (contract 853A). Click sg/15. 38/05. Click to enlarge