(1) Before wet shotcrete equipment spraying, the concrete wet sprayer and the feeding pipe must be lubricated with cement slurry. After the spraying, the residual concrete in the pipeline is washed with water.
(2) Strictly control the wind pressure of the working machine within the range of 0.15 to 0.2 MPa.
(3) Strictly control the water-cement ratio, with a layer of dull gloss on the surface of the freshly sprayed concrete.
(4) Treatment of seepage water section, when the water volume is not large, use compressed air to purge before spraying concrete, spray concrete batching and mixing materials are carried out according to normal construction procedures; when water volume is large, water is appropriately reduced when starting spraying The amount, the spray is from far to near, temporarily increase the amount of quick-setting agent (≯5%) and gradually close. After stopping the water, it must be closed with the shotcrete produced by the normal accelerator.
(5) During the wet mix shotcrete machine spraying process, the sprayer should always pay attention to observe the nozzle condition. Once the pipe is blocked, the assistant should immediately contact the driver, stop the machine, shut off the wind, and check whether the pipeline is unblocked.
(6) For the case where the local shotcrete is too thick, the protruding part of the concrete must be removed before the waterproof board is hung. Because it is possible to break the waterproof board in this case, it is more likely to form a point contact between the initial support and the secondary lining, causing local stress concentration and causing cracking of the secondary lining surface.
(7) After the wet mix shotcrete machine concrete is sprayed to the next cycle, the time should be determined by the test. Generally, it should be no less than 4 h. After the shot, the concrete should be inspected. If cracks occur, the interval between shots or the blasting parameters should be adjusted.
(8) After the wet shotcrete equipment concrete is condensed, the strength of the shotcrete needs to be tested. In the strength test, the cutting core method should be taken to approach the real situation of the shotcrete. If the sampled concrete cannot meet the design requirements, measures should be taken to remedy it in time.
(9) When wet shotcrete equipment spraying concrete, pay attention to observe the rock face from the arch waist to the vault, strengthen labor protection, and prevent the concrete and rock stone from falling and injuring under the impact of high-pressure shotcrete.
