September 2013 "Several Opinions on Further Strengthening the Quality and Safety Supervision of Tunnel Engineering" by the Ministry of Transport
1. the sprayed concrete should adopt the wet spraying process to ensure the strength, thickness and uniformity, and dry spraying is strictly prohibited.
2. Widely apply new machinery and equipment for tunnel construction. The construction unit shall proceed from the improvement of the quality assurance capability of the project, guide and encourage the construction unit to improve the level of tunnel construction equipment, improve the construction conditions, reduce labor intensity, and reduce human deviation. Active use of concrete spray equipment.
The mixed concrete is completely mixed in the mixing station, and pumped to the nozzle by the concrete pump of the manipulator. After the compressed air and the accelerator are added to the nozzle, the robot arm is remotely operated to spray.
