In mineral resource extraction, especially when dealing with complex and variable geological conditions, ensuring the safety and stability of mining operations has always been a critical challenge in the mining industry. With advances in technology and in-depth engineering practices, a support method known as the split set rock bolt has gained prominence, especially for its exceptional performance in fractured zones. This type of rock bolt has become the preferred solution for many mining companies in addressing underground engineering support issues due to its wide adaptability to various rock types, the ability to promptly apply active prestress, and its efficient installation. This article explores the specific application of split set rock bolts in fractured zones, explains their working principles, advantages, and remarkable results in real projects, offering strong support for the safe production of mines.
Overview of Split Set Rock Bolts
Split set rock bolts were invented by Scott in Missouri, USA, in 1973. It is an efficient support method, which consists of high-strength metal plates rolled and pressed into long steel pipe-like rods with longitudinal slits along the whole length, relying on the friction between the pipe wall and the borehole wall to realize the anchoring effect. When the rock bolt is installed by external force into the borehole whose diameter is slightly smaller than its outer diameter, the elasticity of the steel pipe makes its outer wall closely fit the borehole wall, generating radial force distributed along the whole length. At the same time, a metal bearing plate at the outer end of the rock bolt immediately applies prestress, putting the surrounding rock into a triaxial stress state, thereby enhancing the stability and self-supporting ability of the rock mass.
Characteristics and Challenges of Fractured Zones
Fractured zones present one of the biggest challenges to underground engineering stability during mineral extraction. These areas often contain numerous joints and fractures, making the rock mass severely fragmented and highly unstable. Traditional support methods fail to achieve the desired support effect and may even result in support failure, leading to safety accidents.
Thus, choosing an efficient and reliable support method is critical for fractured zones. Due to its unique support mechanism and advantages, the split set rock bolt has become the ideal choice for support in these challenging areas.
Advantages of Split Set Rock Bolts in Fractured Zones
- Strong adaptability: split set rock bolts can be used in various rock types, whether in hard rock or soft soil, providing excellent support performance. This makes them particularly effective in fractured zones, where they can handle complex and variable geological conditions.
- Application of active prestress: by tightly integrating the metal bearing plate and the rock bolt, split set rock bolts can quickly apply prestress, tightly binding the supported rock mass into a stable structure. This active support method reduces rock movement and deformation, improving mine stability.
- High installation efficiency: the installation process of split set rock bolts is relatively simple and fast, requiring no complicated equipment or processes. It improves support efficiency, reduces labor costs, and shortens mine downtime, enhancing mining productivity.
- Excellent support effectiveness: split set rock bolts have been shown to achieve significant support results in fractured zones. They effectively control rock mass deformation and collapse, ensuring the safe operation of mines. Moreover, the even friction distribution between the rock bolt and the surrounding rock ensures a stable and reliable support structure.
Design and Application of Split Set Rock Bolt Support
In the design of split set rock bolts, we need to fully consider the geological conditions of the mining area, mining methods, support requirements, etc. Through the study of rock mass quality evaluation, rock bolt force analysis, and support parameter optimization, a reasonable support plan can be determined.
- Rock mass quality evaluation: the RMR (Rock Mass Rating) classification system is utilized to assess the rock mass’s quality in fractured zones, providing reliable and accurate references for support design.
- Rock bolt force analysis: by analyzing the forces acting on the rock bolt under tensile loads, the stress distribution and deformation characteristics of the rock bolt can be understood, providing a theoretical basis for support design.
- Optimization of support parameters: based on theoretical calculations and practical experience, optimal parameters for rock bolt length, outer diameter, wall thickness, and support spacing are determined to ensure the stability and reliability of the support structure.
In practical applications, we need to pay attention to the following points:
- Ensuring the proper match between the hole diameter and the rock bolt’s outer diameter to achieve uniform friction distribution.
- Applying sufficient prestress during rock bolt installation to ensure a tight fit between the bolt and the surrounding rock.
- Regularly inspecting and maintaining the support structure to identify and address potential safety hazards.
Stress Analysis of Split Set Rock Bolt Support
To assess the effectiveness of split set rock bolts in fractured areas, we examined their radial stresses and axial stresses.
- Radial stress analysis: once the split set rock bolt is in place, it generates radial force by pressing against the walls of the drilled hole. This force boosts the stability of the surrounding rock, subjecting it to a triaxial stress state. By using theoretical calculations, we can derive a formula for the radial stress of the rock bolt support, providing a theoretical basis for support design.
- Axial stress analysis: when subjected to tensile loads, the distribution of shear stress along the split set rock bolt follows a specific pattern. In cases where slippage occurs at the interface between the surrounding rock and the rock bolt, shear stress approximates the maximum static friction. Conversely, when no slippage occurs, shear stress decays approximately exponentially. By analyzing the shear stress distribution, we can derive a formula for the axial stress of the rock bolt, providing more precise data for support design.
Conclusion
The application of split set rock bolts in fractured zones demonstrates their advanced and practical nature as a modern support technology, playing an invaluable role in ensuring mine safety and improving mining efficiency. With scientific design calculations and reasonable support parameter settings, split set rock bolts can effectively control rock mass deformation and prevent block collapse, significantly enhancing the stability and safety of mining operations.
Successful applications of split set rock bolts in fractured zones have reduced the rate of secondary support and material consumption while significantly improving mining efficiency, bringing considerable economic benefits to mining enterprises. It is foreseeable that split set rock bolts will continue to play a unique role in future mine support projects, offering valuable insights and references for similar mines and promoting the sustainable and healthy development of the mining industry.
