Main parameters of spray spraying and grouting construction and related requirements

First, spray technology parameters

1. After the U steel scaffolding is good, the thickness of the bottom arch spray is 140mm. The height of the spray on the shed leg is not less than 500mm upwards.

2. The proportion of shotcrete is cement (P.O42.5R ordinary Portland cement): mixture (sand and stone) = 1:4 (weight ratio), the amount of quick-setting agent is 2.5~4 of cement weight %. The on-site construction ratio is cement: mixed sand = 2 bags: 1 hopper (0.25 m3).

3. The supply pressure of the sprayer is controlled at about 0.4 MPa, the water pressure is about 0.1 MPa higher than the wind pressure, and the water-cement ratio is 0.4-0.5.

4. The minimum angle of the arch is not less than 70o. The vertical distance between the spray head and the surface to be sprayed is preferably 0.8 to 1.0 m.

5. If the spray thickness is not enough, it should be re-injected in time. The interval between re-spraying should not exceed 2 hours.

6. When starting the machine, you must first open the wind, then the water supply, and then start the machine. Finally, when you stop the machine, you must stop the material first, then stop the machine, then turn off the water, and finally stop the wind. When the conveying pipe is blocked, it shall be dredged by tapping. If the high pressure wind is used, the wind pressure shall not exceed 0.4 MPa.

7. Spray quality: the spray should be even, without the phenomenon of “wearing skirts and bare feet”. After the shotcrete, the roadway wall should be straight and the arch should be smooth, and the unevenness is strictly prohibited. The thickness of the spray body should meet the design requirements.

8. After the spraying work, the spray layer must be continuously sprinkled for more than 28 days, sprinkle water once per shift within 7 days, and sprinkle water once a day after 7 days.

Second, grouting technical parameters

1. The length of grouting pipe is 2000mm, the depth of grouting hole is 2500mm, the spacing between rows is 1800×1800mm, the allowable error is ±100mm, and the grouting hole should be numbered. The grouting hole is set by YT-28 pneumatic rock drill . Angle of grouting hole: 30~45° under the two bottom angles, the other angle with the rock face is not less than 75°, and the grouting pipe is not more than 50mm.

2. P.O32.5R ordinary Portland cement is used for grouting. The slurry is stirred by a pneumatic stirring device. The water-cement ratio of the slurry is 1:0.6-0.8. The proportion must be strictly in accordance with the design requirements.

3. The final pressure of grouting is 3MPa. When grouting, the change of the roadway should be checked at any time. Overpressure grouting is strictly forbidden to prevent the support body from fracturing.

Third, scaffolding requirements

1. Scaffolding adopts standard seamless steel pipe with a diameter of not less than 40mm (one and a half) and a wall thickness of more than 3.5mm as the frame tube, and white and red phase paint (300mm spacing) before use. The width of the scaffolding frame is not less than 300mm, the thickness is not less than 50mm, and the length is determined according to the actual needs of the site.

2. When the scaffolding is erected, the bottom horizontal rods are arranged first, and the rods are erected to the two sides from the corners. The vertical and horizontal spacing of the vertical rods are controlled within 1.2m; the bottom horizontal rods are within 200mm from the ground; then a row is set up every 900mm upwards. The rod (such as the following, the height does not exceed 1500mm), the horizontal rod of the scaffold shall not be less than 2 rows, the horizontal rod shall be set on the inner side of the pole, and each horizontal rod shall use two horizontal diagonal rods to enhance the effect.

3. After the frame is set up, the scaffolding frame should be laid. When the frame is erected, the wire rope with a diameter of not less than 6mm must be tied tightly to ensure that the personnel will not be dangerous when operating on it. It is strictly forbidden to appear more than 200mm (deviation is ±50mm) The probe board of the inner) must be overlapped when the shelf is overlapped. In order to enhance the rigidity and stability of the scaffold, the scaffolding cross-bar extension can be used to tighten the surrounding roadway gang to play the role of reinforcement.

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