(1) Rock bolts shall be prefabricated outside the tunnel according to design requirements; during construction, the drilling position and hole depth of rock bolts must be precise, and the rock bolts must be free of oil stains, rust, and impurities.
(2) For rock bolts longer than 5 m in larger caverns such as the underground powerhouse and traffic tunnels, three-boom drilling jumbos shall be used for hole drilling; for other rock bolts within 5 m in length, self-made work platforms equipped with YT-28 air-leg drills shall be used for hole drilling.
(3) The hole position, angle, depth, and diameter of rock bolt drilling shall strictly follow the design drawings; the deviation in hole position shall not exceed 10 cm, and the deviation in hole depth shall not exceed 5 cm; when the process of grouting first and then installing the rock bolt is adopted, the hole diameter shall be more than 15 mm larger than the rock bolt diameter. The hole direction of random reinforcement rock bolts shall be opposite to the dip direction of the possible sliding surface, and the intersection angle shall be greater than 45°.
(4) After drilling reaches the standard, use high-pressure air to remove rock cuttings from the hole, then use an MZ-1 grouting machine (for short rock bolts) or a 2SNS grouting pump (for long rock bolts) to inject the qualified prepared mortar into the hole, and then manually insert the prefabricated rod body into the anchor hole using the work platform. Under normal circumstances, rock bolts adopt the method of grouting first and then inserting the rod; for crown rock bolts with a length greater than or equal to 7 m, the method of using a self-contained grouting pipe, inserting the rod first and then grouting shall be adopted.
(5) The mix proportion of cement mortar for rock bolt grouting shall be determined through tests within the range required by the specifications. The test value range is: cement:sand = 1:1 to 1:2 (weight ratio), cement:water = 1:0.38 to 1:0.45. The cement mortar shall be mixed with a mortar mixer. Grouting shall be ensured to be full and dense, and the rod shall be inserted immediately after grouting. After the rock bolt is installed, the hole opening shall be fixed and sealed with a wedge, and disturbance shall be avoided within 72 h. After the rock bolt reaches the specified age, pull-out tests shall be carried out by sampling according to the specifications.