(1) The wet shotcrete machine and feeding pipe must be lubricated with cement slurry before spraying, and the residual concrete in the pipeline must be washed with water after wet mix shotcrete machine spraying.
(2) Strictly control the air pressure of the working machine in the range of 0.15-0.2 MPa.
(3) The water cement ratio should be strictly controlled, and the surface of the newly sprayed concrete should have a dark gloss.
(4) In the treatment of seepage area, when the amount of water is not large, compressed air is used to sweep before shotcrete, and the proportioning and mixing of shotcrete are carried out according to the normal construction procedure;wet mix shotcrete machine when the amount of water is large, the water consumption should be reduced appropriately at the beginning of shotcreting, and the amount of accelerator (5%) should be increased temporarily from far to near to close gradually. After water stopping, the output of normal accelerator must be followed closely. Shotcrete closure.
(5) During the injection process, the injector should always observe the nozzle situation. Once the pipe is blocked, the assistant should contact the operator immediately, stop the machine, turn off the wind and check whether the pipeline is smooth.
(6) When the local shotcrete is too thick, the protruding part of the concrete must be removed before hanging the waterproof board. Because this kind of situation may break the waterproof board, it is more likely to form point contact between the initial support and the secondary lining, resulting in local stress.
Concentration results in cracking of secondary lining surface.
(7) The firing time from wet shotcrete equipment to the next cycle should be determined by test, generally not less than 4 hours. After firing, concrete should be inspected. If cracks occur, the firing interval time or blasting parameters should be adjusted.
(8) The strength of shotcrete should be tested after the concrete has been set. In the process of strength testing, cutting and drilling core method should be adopted to sample in order to approach the real situation of shotcrete. If the sampled concrete can not meet the design requirements, it should be used.
(9) When wet shotcrete equipment shotcreting concrete, attention should be paid to the observation of the rock surface from the waist of arch to the top of arch, and labor protection should be strengthened to prevent the rock masses of concrete and rock surface from falling and injuring people under the impact of high-pressure shotcrete.
