How to Prohibit Operation of Mining Anchor Bolts

Mining anchor bolts are a crucial component in coal mining, playing a vital role in ore body support. Therefore, understanding the characteristics and usage methods of anchor bolts is essential for maximizing their support function and ensuring ore body stability. Knowing the precautions for using anchor bolts is also crucial to prevent accidents.

Operating Steps for Mining Anchor Bolts:

(1) The tail section of the mining anchor bolt is the most stress-prone and vulnerable part of the bolt. Stress analysis of the threaded section revealed that the diameter change caused localized stress concentration of 2-3 times the normal value in the threaded area. Furthermore, improper spherical rotation between the bearing plate and the ball bearing pad led to self-locking between the two spherical surfaces, causing a rapid deterioration in the anchor bolt's stress and even breakage.

(2) When the installation angle of a mining anchor bolt is too large and the tensile stress reaches a certain value, long-term loading will cause the threaded section at the tail of the anchor bolt to bend and crack, or even break. When the applied preload torque is greater than 600 N·m, the combined stress on the anchor bolt is close to the yield stress of the material. Cracks first appear at the bending point, and then the cracks propagate, causing the anchor bolt to break before reaching the breaking tensile force.

(3) Tension-bending-torsion, tension-shear-torsion, and combined tension-bending-shear-torsion are common stress states during the installation of mining anchor bolts underground. The stress is greater closer to the fixed end, so the fixed end is the most unfavorable location.

(4) Optimization schemes such as vertical anchor bolt installation, redesign of the self-aligning ball pad, full-length preload anchor bolt anchoring, and adjustment of the anchor bolt preload torque to 400 N·m are implemented to reduce the impact of harmful forces on the bolt body.