What precautions should be taken when using a shotcrete machine?

1. Shotcrete spraying with a shotcrete machine is generally carried out by two people. They must work closely together during the process, promptly addressing any problems. The sprayer must control the water-cement ratio to ensure the sprayed material does not appear white, does not run, and has a glossy surface.

2. When spraying, the spray angle and distance must be carefully controlled, and the nozzle must be perpendicular to the rock surface. The spraying sequence is generally from bottom to top and from back to front. First, fill in the recesses and level the surface, then follow the proper procedure to spray thoroughly in one go.

3. Before starting the shotcrete machine, remove any large pieces of gangue and debris from the machine to prevent pipe blockage. After stopping the feed, wait until all excess material in the chamber and pipe is completely blown out before stopping the machine. Clean the machine inside and out.

4. When the shotcrete machine is supplying air, be sure to secure the nozzle to prevent it from swinging and injuring anyone. When addressing a blocked pipe, do not use air or increase air pressure. Turn off the power and air supply, open the vent valve, and tap the blocked pipe. Then, close the vent valve and return the air and power to the pipe.

5. Pay attention to properly adjusting air and water pressure to minimize rebound and reduce dust concentration.

6. When spraying concrete in seepage sections of a tunnel, measures such as reducing the water supply, increasing the amount of accelerator, and inserting water pipes should be implemented.

7. Strengthen personal protection and strictly wear dust masks as required to reduce the risk of occupational diseases.