What is self drilling anchor rod?

Ordinary mortar anchors and standard hollow grouting anchors exhibit similar construction efficiency in typical fractured zones. Self-drilling hollow grouting anchors, however, achieve approximately 10% to 20% higher efficiency due to their single-pass drilling and forming capability. In severely fractured zones, issues such as hole collapse, drill bit jamming, and insertion difficulties arise. resulting in low construction efficiency for both ordinary mortar anchors and ordinary hollow grouting anchors. Advance grouting and consolidation may be required before re-drilling. In particularly challenging sections, ordinary mortar anchors and ordinary hollow grouting anchors become unfeasible. Self-drilling hollow grouting anchors, however, avoid issues like hole collapse, drill jamming, and insertion difficulties. Their efficiency is 2 to 4 times that of the former two methods, offering a clear economic advantage.

Analyzing the cost per meter of anchor rods: Self-drilling hollow grouting anchor rods are approximately 15% more expensive than conventional hollow grouting anchor rods and about 60% more expensive than standard mortar anchor rods. Analyzing the cost per kilonewton of pullout resistance: In generally fractured rock mass areas, self-drilling hollow grouting bolts are about 15% higher than conventional hollow grouting bolts and about 30% higher than conventional mortar bolts. In severely fractured zones, they remain about 15% higher than conventional hollow grouting bolts but are about 10% lower than conventional mortar bolts. Therefore, based on cost per kilonewton of pullout resistance, self-drilling hollow grouting anchors demonstrate a significant economic advantage over conventional mortar anchors in severely fractured rock mass zones.

Self-drilling hollow grouting anchor rods offer exceptional versatility, particularly in weak rock formations. Combining drill rod and anchor rod into a single unit, the anchor can be directly driven into the rock mass. Its hollow core serves as a grouting channel, enabling grout injection from the interior outward. The continuous threading of the extra-long anchor rod reinforcement allows the self-drilling hollow grouting anchor rod to be cut and connected at any length, enabling the reinforcement of unstable rock in confined spaces. Simultaneously, the continuous threading provides significantly greater bond resistance than smooth steel pipes, exceeding that of conventional mortar anchor rods by 2–3 times.

In poor rock formations such as backfill zones, weathered rock, fractured rock, sand layers, clay layers, and gravel layers, no drilling is required, nor is casing needed for wall protection. The continuous international standard threading of the anchor rod, supplemented by connecting sleeves, facilitates simple, quick, and time-saving anchor body processing, drill bit installation, and anchor rod extension operations. After the anchor rod is drilled into position, hole cleaning and grouting can be performed immediately without the need to withdraw the drill rod or install the anchor rod. Compared to conventional hollow anchor rods and ordinary mortar anchor rods, the construction process is simplified, resulting in significant time savings and improved efficiency.