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TBM RECORDER EPBMs managing mixed ground in Nanjing May 2012
Desiree Willis, Technical Writer, The Robbins Company
Soft soils, silty sand, pebbles, sandstone and manmade fill materials are all being mastered by four Robbins EPBMs working on new lengths of the Nanjing Metro line in China. The 6.5m diameter machines are fitted with mixed ground cutterheads and working in two pairs on Line 3 Lot 11 and Line 10 Lot 5, for the China Railway Construction Corporation (CRCC) 13th Engineering Bureau and 23rd Engineering Bureau, respectively.

Robbins contribution to Nanjing metro expansion

Launched in December 2011 and February 2012 for Line 10 and in January and March of 2012 for Line 3, the machines are making firm progress through the mixed ground conditions. "We used a Robbins TBM previously in Chengdu," said Li QuanShe, Nanjing Line 3 Project Manager for CRCC Bureau 23, "and there was very good performance at on that project. The machine achieved a project record of 129m in one week through mixed ground on that project and the same quality is here on these new machines."
Shallow cover of 8m to 10m beneath a sensitive urban environment for which strict settlement limits of less than 10mm to 20mm are applied are requiring customised excavation methods. "The earth is quite soft so we are keeping the thrust force low at 6,000 to 9,000kN," said Jason Xiao, the Robbins Project Manager for the four Nanjing machines. "The operator is also employing continuous monitoring to maintain the proper alignment and earth pressure. Foam additive is applied to make the ground less sticky and reduce the cutterhead torque required to excavate the material."
  • Robbins contribution to Nanjing metro expansion

    Robbins contribution to Nanjing metro expansion

  • Ring building behind a Line 10 Robbins EPBM

As of early May 2012, the Line 10 EPBMs have excavated more than 600m and 500m and have recorded advance rates of 40mm/min and settlement readings well within limits. On Line 3, the two machines have excavated more than 500m and 100m with advances exceeding 60mm/min.
Fabrication of the first Robbins EPBM for Nanjing delivery

Fabrication of the first Robbins EPBM for Nanjing delivery

Construction of the 40.2km long Metro Line 3 and the 41.4km long Metro Line 10 is well underway for owner Nanjing Metro Company. The new underground lines are part of the municipal government's extensive plans to improve access across the Yangtze River Basin by building and operating up to 17 rail routes totaling a network of some 600km by 2030.
Nearly 750,000 people currently ride the rails daily on the two existing metro lines in the state capital city of Jiangsu Province and that number is expected to increase dramatically with the construction of several new metro lines. These new metro extensions have employed 40 TBMs from different manufacturers, including four Robbins EPBs. The rail routes have a firm completion deadline of 2014, when they will need to be ready for up to 40,000 visitors attending the Youth Olympic Games in Nanjing.
References
Robbins consolidates presence in China - TunnelTalk, March 2011
First Robbins slurry TBM set for launch in China - TunnelTalk, August 2011
Record-setting headway under high overburden - TunnelTalk, July 2011

           

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