Slurry balanced CREG TBM equipped with 19-inch cutters was used in the project. The formation is weakly weathered granite with the UCS of 120-190MPa.
The UCS is high, leading to high abnormal damage rate of the disc cutters.
Measures and effects:
After comparing the products from several manufacturers and through strict data filtering, the customer selected our cutters due to our most stable quality and lowest abnormal damage rate.
Project: Interval from Xixincheng Station to the Air Shaft of Fuzhou Metro Line 5 Bid No.1
Formation conditions: The tunnel formation mainly consists of soft and hard soil section, upper-soft lower-hard formation and full face rock formation. The rock formation mainly is completely ~ weakly weathered granite, of which the UCS of moderately weathered granite is 15.2-90MPa and of weakly weathered granite reaches 208MPa at the highest.
Use condition: At first, our common cutters with gradient hardness were provided for the whole cutterhead: 4 17-inch centric duplex cutters and 37 19-inch single-blade cutters. For the first replacement, the distance of 560 meters was bored of which the first 400 meters is silty clay and silty sand formation. Later, 355 meters were bored in one time through the Minjiang Section including 40 meters of (moderately weathered granite) uneven formation. After then, an inspection was done at the full face formation and all cutters were normally worn.
In full face hard rocks, the edge cutters were replaced from 19-inch to 20-inch. Our cutters had excellent performance in full face weakly weathered granite, and the average wear life of edge cutters was 20-40 rings (average UCS 120-160MPa).
The service life of 20-inch cutters increased by 2-4 times, thus the results were less cutter change times, higher boring efficiency and a reduction in the cost on cutter consumption.
Management Department of China Railway Tunnel Stock Co., Ltd, Fuzhou Metro Line 5 Bid No. 1 Project
October 9, 2021