Self Drilling Hollow Bar:A Perfect Solution to Hole Collapsing When Supporting Loose & Broken Geology


In the realm of construction, encountering unfavorable geological conditions often poses a significant challenge for constructors. The need to reinforce building foundations in areas with loose and broken geology becomes particularly difficult. Traditional construction methods involving ordinary solid anchor rods struggle in such terrains due to the prevalent issue of hole collapsing, exacerbated by the influence of groundwater. However, a revolutionary solution has emerged – the self-drilling hollow bar. This construction material has proven to be a game-changer, streamlining the drilling, anchoring, and grouting processes into a single, efficient operation.

t thread self drilling hollow bar

Understanding the Components

The self-drilling hollow bar comprises several integral components, each contributing to its efficiency and effectiveness. The key elements include the drill bit, hollow anchor bar, coupler, plate, nut, and centralizer. Crafted from robust steel or alloy steel, these components ensure the durability and reliability of the self-drilling anchor system. The continuous threading on the hollow anchor bar plays a crucial role in securing the mortar's bonding to the hollow anchor bar, promoting stability in the construction process. The centralizer, strategically positioned in the middle of each hollow anchor bar, guarantees the straightness of the hole and maintains the axial force of the hollow anchor bar. The backing plate and nut serve to secure the hollow anchor bar's end and apply prestress. Drill bits are made from robust materials like 42CrMo, ensuring the drill bits can withstand drilling forces and effectively penetrate rock formations. Unlike traditional drill bits, these drill bits are disposable, eliminating the need for replacement and simplifying construction methods. This design allows for simultaneous drilling, grouting, and anchoring, eliminating the need for casings in the construction process.

self drilling hollow bar is drilling

Versatility in Geological Support

Self-drilling hollow anchor bars are exceptionally versatile, proving effective in a range of geological conditions. Specifically designed for pebble layer and boulder layer geology, these hollow anchor bars also exhibit proficiency in silty clay, sandy soil, miscellaneous fill, and strong weathered rock. Pressure grouting is performed while the hollow anchor bar is drilled, and this action provides an opportunity to reinforce the disturbed rock and soil around the borehole while expanding the diameter of the anchor solid.
In instances where water seepage poses a concern during drilling, the self-drilling hollow bar introduces another approach, which employs high-pressure wind to blow dry powder into the borehole creates a temporary barrier, mitigating the risk of hole collapse. This meticulous attention to detail in addressing specific geological challenges positions self-drilling hollow anchor bars as a versatile and reliable choice for construction projects across a multitude of terrains.

Streamlining Construction Processes

One of the standout features of self-drilling hollow anchor rods is their ability to revolutionize construction efficiency. Unlike conventional bolts that require additional casing pipes when drilling through challenging terrains, the self-drilling hollow bar eliminates the need for casings. This innovation allows for the injection of pure cement slurry, with a water-cement ratio of 0.45~0.6:1, during drilling to consolidate the hole wall and prevent collapse. The remarkable advantage lies in the integration of drilling, anchoring, and grouting into a single seamless process, simplifying construction and offering a practical alternative to the limitations of traditional methods.

Overcoming Limitations of Ordinary Bolts

When confronting weathered rock layers, gravel layers, clay, sand, or pebble soil, the usual recourse involves the inclusion of casing pipes during construction. However, self-drilling hollow anchor bars present a unique advantage by allowing the omission of casings. This opens up the possibility to inject pure cement slurry (non-clay layer) during drilling, fortifying the hole wall and mitigating the risk of collapse. The efficiency gains with self-drilling hollow anchor bars are particularly evident in the elimination of casings, showcasing their superiority over ordinary bolts in challenging geological conditions.

t thread self drilling hollow bars of Sinorock


In conclusion, the advent of self-drilling hollow anchor bars seamless integration of drilling, anchoring, and grouting in a single operation not only enhances construction efficiency but also addresses the persistent challenge of hole collapsing in loose and broken geology. As the construction industry continues to evolve, the self-drilling hollow anchor bars stands out as a beacon of innovation, offering a comprehensive solution to the complex geological intricacies that once hindered progress.
If you encounter problems during construction, please feel free to contact Sinorock at, our technical team will provide you with customized system solutions to help you solve problems.

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