Detailed Explanation of Rock Bolt Construction Steps: Make Your Project More Stable

Table of Contents

Rock bolt construction is a typical construction method in engineering construction, which can effectively improve the stability of engineering structures. This article will introduce you to the steps of rock bolt construction in detail to help you achieve the best stabilization effect.

Rock bolt construction mainly includes measuring and determining the drilling position, moving drilling equipment, adjusting the drilling angle, carrying out drilling construction, installing supporting rock bolts, and taking grouting reinforcement measures.

self drilling anchor bolt

Determine the drilling location

According to the relevant requirements of the design and planning, place fixed piles at the beginning and end of the rock bolt construction, measure and determine the position of other construction holes based on them, and require the position error to be controlled within ±50 mm, and reasonably adjust the density of the intermediate part based on the on-site situation. Take proper precautions to protect fixed piles, such as burying a warning sign, to prevent damage. Additionally, ensure that measurements and sampling are not conducted simultaneously with the construction process. In addition, the installation position of the rock bolt should be sampled according to the length of the equidistant slope and adjusted flexibly based on the site requirements.

Mobile drilling equipment

Before installing the drilling rig, it is necessary to set up the working surface of the rock bolt through earth excavation, measure the slope angle and other information, and determine the drilling position. Subsequently, install the drilling rig and adjust the equipment angle until the drill bit aligns with the drilling hole, ensuring the anchor hole is drilled accurately in place. Keep both the lateral error and vertical error controlled within ±50 mm. According to the drilling rig usage requirements and construction standards, the inclination error of the equipment is controlled within ±1.0°, and the azimuth error is controlled within ±2.0°. The angle between the rock bolt and the horizontal plane is 10~20°. The drilling rig should remain horizontal and stable throughout the entire process, and inspections should be done during drilling to avoid displacement problems.

self drilling anchor bolt

Drilling method

If the geological conditions in the project area are solid and dense, dry drilling can be employed. This method offers the advantages of lower costs and straightforward construction. Before drilling, it is essential to clear the soil, rock blocks, accumulated water, etc., to enhance the cohesion of the borehole’s inner wall. It ensures better engineering conditions for slope construction. It is important to note that construction personnel should control the drilling speed, avoiding excessive speed to prevent distortion of the hole channel or deformation of the hole diameter. This precaution is crucial to prevent any negative impact on subsequent construction activities.

Drilling process

During the drilling process, relevant personnel should make observation records, including changes in the drilling stratum, drilling speed and pressure, and fluctuations in the groundwater level. If abnormal issues such as collapsed holes and shrinkage holes are found, the operator should cease construction immediately, implement grouting reinforcement measures, and resume construction once the slurry has condensed.

Hole diameter and depth

To the design specifications, it is necessary to control the diameter and depth of the drill hole within the allowable error range. The hole diameter should be below 130 mm, and the rock bolt deflection should not exceed 3/100 of the rock bolt length. To ensure that the diameter of the rock bolt hole meets the construction standards, the actual diameter of the drill bit must exceed the design hole diameter, and the part where the actual depth exceeds the design depth must be more than 0.5 m.

self drilling anchor bolt

Rock bolt hole cleaning

Immediately shutting down the equipment when the drilling depth reaches the construction requirements may result in a sharp bottom of the hole, a smaller hole diameter, etc. Hence, construction workers should maintain a steady drilling state for 1 to 2 minutes when the drilling depth reaches the standard to avoid problems. To enhance adhesion between the cement mortar and the tunnel’s inner wall, we should use high-pressure ventilation equipment to carry out the removal work to prevent the retention of excess substances such as slag, rock dust, and water. Assess the rock mass condition at the hole location; if integrity and strength meet standards, use high-pressure water for flushing. Address water accumulation inside the rock bolt hole through grouting sealing, secondary drilling, and other appropriate measures.

Rock bolt hole inspection

To ensure the quality of subsequent construction, a thorough inspection of the rock bolt holes is necessary. The inspection encompasses drilling depth, diameter, and other indicators, with comparisons made against the design plan. Use standard drill pipe for inspection. The inspector must advance the drill bit steadily and slowly to prevent any impact on the accuracy of the inspection. If the drill pipe exhibits smooth movement without evident sediment or water accumulation, the inspection is considered qualified.

Installation of support rock bolts

self-drilling anchor bolt

According to the design requirements, select appropriate materials to make the rock bolt to ensure its strength and durability. When installing the rock bolt, the construction personnel should ensure its position is consistent with the drilled hole to avoid misalignment or distortion. Simultaneously, it is essential to guarantee that the insertion depth of the rock bolt meets the design requirements, ensuring the anchoring effect of the rock bolt.

Grouting pipe

Select grouting pipes with standard specifications and higher strength to serve as a fundamental assurance for grouting operations, reducing the likelihood of issues such as pipe blockage, breakage, or bursting. The rock bolt grouting employs a two-step process, with the first grouting using a 20 mm grouting pipe and the second grouting using a 15 mm grouting pipe.


Rock bolt construction is an effective method to improve the stability of engineering structures. Mastering the steps and key points of rock bolt construction and executing the construction by relevant regulations and requirements can effectively enhance the stability and safety of the project. At the same time, strengthening quality inspection and maintenance work is also an important measure to ensure the long-term stability of the project. In actual construction, it is necessary to take corresponding measures and methods according to specific conditions, continuously optimize construction technology and technical levels, and provide better technical support and services for project construction.

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