CRCHI slurry pressure shield machine (SPB) tunneled under the Songhua River and finished the mission with prominent speed and high safety, which marked successful breakthrough of the first under-river tunnel in Harbin, China. This shield machine drove a tunnel of 2911.9 meters for the section between Shimao Avenue Station and Ice-snow World Station. The section is the longest part among the Harbin metro lines under construction and has highest latitude among all Chinese under-construction lines.
The SPB was launched on July 15th , 2017. Major difficulties in the project were that:
1. as the SPB drove in the geology with high contents of quartz for a long distance, it would have serious wear on cutterhead, cutters, slurry pipes and pumps;
2. as the river has a width of 410m, there would be a high risk in cutter changing at the river bottom;
3. as the SPB drove in a high water pressure environment for a long distance, there were high requirements on reliability of machine, especially on main drive, tail skin, articulation and sealing system;
4. when the SPB drove in clay and mudstone, it would be easy to form mud cakes in the cutterhead and have clogs at pump’s mouth;
5. there was high requirement on settlement control as the SPB tunneled under the river.
The SPB needed to tunnel under the flood land of the Songhua River which has high contents of underground water and clay, which was very dangerous and difficult. It is the first time for the construction unit to do in this technically demanding environment with high and strong water pressure and shallow overburden in China’s under-river construction history. To meet the requirements of construction and produce the SPB adapted to working environment, CRCHI R&D persons specifically designed this machine, adopted large pieces of wear-resistant alloy blocks for the cutterhead, used the slurry circulation system with big flow and arranged washing points to effectively flush the center of the cutterhead and the panel for preventing the formation of mud cakes. Besides, the SPB was equipped with hydraulic-driven motors with large torque and high rotation speed, stirrers of large power and the automatic pressure maintaining system, which accurately controlled ground settlement, prevented mud from settling and ensured tunneling efficiency.
Since the machine was launched in July of 2017, it has helped the customer to create many construction records in China with its optimal designs, good quality and excellent technical services of CRCHI.