Following an impressive monthly record of 1226m in May 2016 and then a successful passing through 7km of limestone karst area in late June, the gripper TBM "Yongji" by CREG achieved a monthly advance of 1024.8m in July while boring through stratum consisting of diorite. A new record of 37.1m per shift (10 hours) has been set ever since its launching for Jilin Yinsong Water Supply Project.

Compared to the previous formation of carbonaceous slate and limestone karst coves, the diorite section poses brand new challenges for the machine. Due to the higher strength of diorite, the abrasion of cutters increases accordingly and the time interval of cutter replacement shortens as a result. As many as 150 pieces of cutters have been replaced in July alone.
 

The heat wave that overwhelms the northeastern city in July makes it rather difficult to carry out cutter replacement in the chamber. Yet despite all the adverse conditions, CREG technical staff on jobsite accomplished their duties with extraordinary craftsmanship and thus ensures the smooth advancing of "Yongji". 

The machine is ready to bore through hard rock stratum in the next phase. To guarantee its satisfactory performance as always, the project team is working on a thorough geological analysis to figure out the best solution to possible challenges.