1.General
Wan’anxi Water Diversion Project is located in Longyan City, Fujian Province. YREC is the EPC contractor. The total construction time is 48 months.
The Project is composed of the water intake structure, diversion tunnel, pipelines, etc. The water transfer line has a total length of about 34.45 km, crosses two rivers, and conveys gravity flow. The water diversion capacity is 202,500 t/d.

2.Challenges and Countermeasures
(1)Small tunnel diameter. The TBM diameter is 3.83 m, which is the smallest open-type TBM in China. Space constraints make the construction a very difficult process, especially for TBM operation and treatment of special strata.
YREC relies on its advantage in technology and management, and developed the mobile switching turnout to increase the mucking efficiency. Organization and management were also strengthened, analytical database established, and 36 optimizations of the TBM were conducted.

(2)Super hard rocks. The maximum burial depth of TBM tunnel is more than 900 m, the geological conditions of surrounding rocks are complex, and the rock hardness is up to 258 MPa, making tunneling a difficult job. YREC developed the high pressure hydraulic coupling rock breaking TBM, which is the first of its kind in the world. By adopting the “cutters + water jets” coupling mode, the construction progress was accelerated.

(3)Water inrush. More than 30 fracture zones were encountered within 6 km of TBM advancing. The maximum water inrush per hour in the tunnel reached 3,000 m3, indicating complex geological conditions. The contractor adopted comprehensive treatment measures to reduce the impact of water inrush, and the advancement rate was guaranteed.

3.Patents and Awards
The Project was awarded the Second National Innovation Prize. The “key technology of TBM high pressure hydraulic coupling rock breaking” was included in the 2021 Promotion List of Mature and Applicable Water Resources Scientific and Technological Achievements of the Ministry of Water Resources of China. The invention patent of “TBM cutter head” won the 22nd China Patent Excellence Prize.