【Domestic News】Mawan Tunnel - The Largest Diameter Underwater TBM

At 5:36 on August 15, the largest diameter underwater Mawan TBM advanced to one hundred meters which achieved the first milestone from its launch on July 15.

The TBM part of Mawan Underwater Channel Project is 2,063m long. There are 50% uneven rock stratum in the whole line, and the full section of hard rock exceeds 34%. TBM single heading in the mix stratum for a long distance, the variability of stratum would cause abnormal wear of cutter head and cutting tools, weaken cutting capacity and decrease advancing speed, which indirectly leads to TBM jamming, clogging and so on.

Mawan air cushion slurry balance TBM is independently designed and manufactured by CREC. The diameter is 15.53m and the height is more than 5 floors. The main components are 140 meters long and 4,650 tons weight, and the excavation section is six times as big as regular metro TBM.

In order to ensure the safety of advancing, the project staff has planned ahead since the TBM was launched, and invited experts to optimize the construction scheme for many times. The project staff continuously strengthen monitoring work and feedback the monitoring data of the surface and tunnel in real time, pay attention to parameters of TBM to ensure the safety of advancing.

Increase the specific gravity and viscosity of the slurry to increase the thickness of the mud film of the tunnel face to stabilize the formation, and adjust the mix design of synchronous grouting to shorten the mortar setting time. The shield tail seal keeps the pressure by supplementing the shield tail grease to avoid the risk of water and sand gushing.

Now all driving parameters of Mawan TBM are normal and tunnelling is advancing smoothly according to the scheme plan.