First TBM launched for construction of Patna Metro underground section

Patna, India (Metro Rail Today): The engineers of Larsen & Toubro Ltd (L&T) have successfully lowered the First of four Tunnel Boring Machines (TBM) of Patna Metro Rail Project at Moin-Ul-Haq Station of Patna Metro Rail project on the evening of 20th March 2023. The TBM nicknamed “Mahavir”  bearing serial number DZ1090 weighs around approx. 420MT lowered with a drive length of 1494m for tunneling works towards Patna University station. 

The underground tunnelling work in Patna Metro Project will be done with the TBM machine. The lowering of the TBM is first step of tunnelling for Patna Metro which has commenced at Moin-Ul-Haq Stadium. Other parts of the TBM which will be assisting in muck disposable, feeding of the tunnels segments shall be done subsequently that is after lowering of the main part of the TBM the process of complete assembling of the TBM takes about 2 to 3 weeks’ time. Once TBM is assembled in totality the drive will start.

TBM assembly was lifted with the cradle using strand jacks with capacity of 325 Metric Ton each. Four strand jacks are being used to lower the TBM at MUH. The Mega lift will lift the cradle and then push it up to TBM lowering position (Launching Shaft). Then TBM will be lowered into the shaft which is approx. 16m below the ground level after skidding.

The TBM Mahavir will be part of Patna Metro's 8 km underground tunneling Package PC-03 of 14.05 km Corridor 2 (Patna Railway Junction to New ISBT) of Patna Metro connecting Rajendra Nagar – Patna Junction Railway Station.

Patna is located on the south bank of the Ganges River in eastern India which has alluvial soil. The ground water level is also very high. As per the soil strata, soft soil Earth Pressure Balance (EPB) TBMs has been designed and manufactured for Patna Metro by CRCHI (China Railway Construction Heavy Industry Corporation Ltd.) The TBM shall first be launch from Moin Ul Haq Station towards Patna University station.

The Earth Pressure Balance (EPB), Tunnel Boring Machine (TBM) comprises of a cutter head, front shield, middle shield, tail shield along with the backup gantries. The main body length of the TBM is approx. 9m with EPB full length of 95m approx. The excavation diameter is 6650mm, with the precast ring lining with an outer diameter of 6350mm and inner diameter of 5800mm. An approximate of 49cum of earth will be mined for every ring installed. Grouting behind the segmental lining shall be carried to ensure that full and immediate support is given to the rings as they emerge from the rear of the TBM. Thus, a continuous process of mining, grouting, ring building , with ground monitoring information analysis will be applied during operation of the TBM.

In December 2021, Delhi Metro Rail Corporation Ltd awarded a contract worth Rs 1,989 crore to Larsen & Toubro Ltd (L&T) for Design and Construction of Twin Tunnel by Shield TBM, Tunnel by Cut & Cover, Underground Ramp at Rajendra Nagar and Six Underground metro stations viz. Rajendra Nagar, Moin Ul Haq Stadium, University, PMCH, Gandhi Maidan & Akashvani with Entry/Exits & Connecting subway including Architectural Finishing, Water Supply, Sanitary Installation & Drainage works on New ISBT to Patna Station of corridor 2 of Phase I of Patna Metro Rail Project.

The 14.05 km Corridor 2 of Patna Metro will connect Patna Railway Junction to New Inter State Bus Terminal with 12 stations at Patna Junction (interchange with Corridor 1), Akashvani (formerly Dak Bungalow), Gandhi Maidan, PMCH, Patna University, Moin Ul Haq Stadium, Rajendra Nagar, Malahi Pakri, Khemni Chak (interchange), Bhoothnath, Zero Mile and New ISBT. Out of, 6 kilometres section with 5 stations will be elavated and remaining 8 kilometres with 7 stations will be underground.

For more details, please explore the Patna Metro page of Metro Rail Today.