Equipment: 

HK and CREG  with Diameter 15.03m, Atmospheric pressure slurry TBM

Geological Condition:  

Most of the strata are sand beds, and in the middle there are several sections of bedrock bulges of breezed granite (120-150MPa).

The main existing problems:

1) The advance speed of bedrock section is slow;

2) the disc cutter ring is easy to collapse and fracture when the disc cutter passes through the bedrock.

Damage form

Solution improvement measures

•The original cutting edge width was 25.4mm, which was gradually optimized into a 22mm rounding top. 

•Standard smooth-faced cutter ring with hardness of HRC 57-59 is adjusted to gradient cutter ring with hardness of HRC55-57 on the blade. 

•The cutter ring is cryogenically treated.

Improved effect

1. After the blade is optimized, the tunneling efficiency increases, and the hardness optimization reduces the break of the cutter ring and increases the cutters' tunneling distance. 

2. The optimization of the propulsion parameters reduced the cutter consumption of the western route by 20% compared with the eastern route. 

3. Gradient hardness cutter ring outside hard and inside soft form greatly reduces the probability of cutter ring rupture by impact, most of the cutter ring is normal wear replacement.