At the planning stage, the milling mall construction method was selected as an insurance method because there are many wooden piles under the old two lines out of the four lines.
For a while after launching, a small amount of wooden piles and concrete debris were excavated, and it was possible to excavate as usual. However, TBM encountered an unexpected obstacle 1.5m in front of the reception shaft and the cutter locked. So we used a telescopic jack to cut 300mm and was able to pass through obstacles and reach it safely.
As a result, I think we were able to reach it by adopting the milling mall method.