At present, the advancement of science and technology has constantly improved our requirements on tunnel construction ,and concrete shotcrete equipment has become the standard equipment for tunnel construction. What requirements should be paid attention to during tunnel construction? In fact, it is mainly to analyze the considerations for tunnel shotcrete from two aspects: safety and shotcrete quality.
Safety
1. ”Safety-oriented, prevention first ”
2. Must be equipped with a helmet when entering the construction site
3. Making safety operation rules and inform the construction staff
4. Workers only can be employed after passing safety test
5. Workplaces should have qualified safety protection facilities, and personnel on site should be equipped with labor protection supplies.
6. Temporary houses should be built above the flood level all year round, and safety precautions should be done according to meteorological, hydrological, and other conditions.
Shotcrete Quality
1. Strictly perform operations according to the requirements of the usual construction process.
2. The aggregate should use medium sand with acceptable quality，and the mud content should not be too large.
3. Spraying shall not be carried out when the wind is at level 4 or above； Spraying construction is strictly prohibited in heavy rain。
4. The base layer should be kept clean, release agent, and no oil stain before spraying.
5. When spraying, the concrete base layer should be watered in an appropriate amount to ensure effective and firm adhesion of the interface agent
6. The blasting slurry should cover all construction interfaces relatively evenly.
7. The second spraying treatment should be carried out on the uneven part , and it should be strictly in accordance with the precautions, so that the spray quality can be guaranteed, and the tunnel sprayer has the advantages of small working dust concentration ,less spray rebound,environmental protection , cost saving ,easy operation and convenient maintenance.
The following requirements should be checked before starting to use the shotcrete machine
1. Check that the safety valve is sensitive and reliable.
2. Check that the power cord has no cracking and the wiring is reliable
3. Check the pressure gauge pointer between the upper and lower limits, and adjust the limit value of the upper limit pressure according to the conveying distance.
Before starting the shotcrete machine, it should be connected to ventilation, water and electricity first. Open the intake valve and gradually reach the rated pressure. Then start the motor to run at no load. After confirming that everything is normal, the material can be put into operation. The installation of the pipeline should be correct,and the joint should be tightly sealed. When the pipeline passes through the road, it should be placed in the ground trough and covered with protection.
During the concrete spraying operation, it is strictly forbidden to stand in front of the nozzle. The operator should always stand within the concrete support surface that has been sprayed. If the suspension time exceeds one hour during operation ,the dry mix in the tank and conveying pipe should be sprayed out completely. When machine stops , stop the feeding first, and then turn off the motor and stop delivering compressed air.
After the spraying operation is completed, the dry mix in the tank and conveying pipe should be completely sprayed out, and the nozzle should be removed and cleaned, removing the concrete and debris adhering to the inside and outside of the fuselage ,cleaning the pipeline at the same time,and keep the seals in a relaxed state.
