With piling works coming to an end, last week workers from the CEC-CICI JV began excavating soil for a crucial mid-shaft for package CC-04 of Delhi Metro’s 58.596 km Pink Line to facilitate the retrieval of 4 tunnel boring machines (TBMs) in north Delhi’s Rameshwar Nagar!
In some circles, this mid-shaft is also known as the ‘Gurudwara Shaft’ as it’s just down the road from Model Town’s R Block Gurudwara. It wasn’t part of the original construction plan, but had to be constructed as two TBMs commissioned from Azadpur station towards Majlis Park, tasked with tunneling 1100m, got stuck mid-way in 2014. Here’s a excerpt on the issue from the Tunnels and Tunneling magazine with a brief history of the difficulties faced and what CEC-CICI tried to do to resolve:
Both TBMs met with a large mass of intact rock which infringed the lower portion of the tunnel face and extended for approximately 30m. The TBMs used were both soft ground machines which have been used on a previous phase of the metro, and experienced high torque and overheating when attempting to cut through the rock zone. An attempt was made to break up the rock ahead of the cutter face by drilling and placing an expanding chemical to burst the rock and allow the cutter head to rotate and advance one ring at a time. The space within the chamber available to manage this exercise was very limited and matters were made worse by the presence of wet running sand above the rock zone which dictated working under compressed air.
In 2015, the CEC-CICI team secured a deal with HCC-Samsung (CC-34 project on Magenta Line) to lease 2 TBMs which they commissioned from the Majlis Park side in March & April 2016. View details & images:
- Last TBM Commissioned for Delhi Metro’s Pink Line at Majlis Park
Three TBMs are sitting on either side of the shaft right now. This includes the original 2 TBMs on the south-side and the 1st ‘rescue’ TBM on the north-side. The 2nd ‘rescue’ TBM is expected to arrive here in early July. Once the entire shaft is excavated in about 45 days, then workers will descend into it and begin core cutting activities to push, dismantle & retrieve the 4 TBMs one by one.
For more updates, check out Delhi section of The Metro Rail Guy!