Rock Bolting - Minova Global
Minova is a leading global brand and with over 135 years of experience, with this comes expertise in in developing leading edge bolting solutions and the know-how for design and application purposes as the industry innovator meeting the demands of tomorrow.
When an opening is created in rock, the surrounding strata invariably becomes instable, however this phenomena can be managed through the use of various support methods and reinforcement methods. In the case of support methods, structural elements are used such examples include steel arches, mesh and shotcrete. These method are termed passive as they rely on rock mass moving to create a resistance load.
Rock reinforcement includes methods that modify internal behaviors of the rock mass by installing structural elements. This type of reinforcement is seen as an active method of support and include examples such as point anchored bolts, friction bolts and fully encapsulated grouted bolts.
Rock bolts utilize the strength of the rock structure to be reinforced as support to the excavation made. Therefore the behaviors of the rock is fundamental to the selection of the bolts and the design pattern to be applied. The rock is the material under consideration and loads to be carried are represented by the rock stress field. There is a wide range of factors influencing design related to the rock being reinforced, life cycle of the excavation and the excavations methods. These inputs to design will determine the selection of the bolt including diameters, lengths and bolt design also in consideration is the grouting materials required and final bolting pattern.
Deformation of rock (rock shift into excavated space) causes tension in the installed bolt. The resulting tensile load is transmitted to passive zones in the rock (stable rock). Due this principle the fully grouted/bonded rock-bolts are preferred over point-anchored rock-bolts.
General considerations when searching for rock-bolts
- Capacity of bolt (tension - Yield / shear)
- Optimal length (extension of self-support rock arch)
- Optimal bolt grid / density of bolts
- Adequate service-life of bolt (temporary/permanent)
- Behavior of bolt under load (elongation/ creep)
- Technology of bolt installation
- Stabilizes the rock and extends natural rock-arch
- Actively prevents further loosening of the rock mass
- Reduces rock deformation caused by excavation
There are many rock bolt types and grouting technologies to select from driven by geological conditions and design requirements. Factors include:
- Rock type
- Structural features such as presence of laminations, breaks, fissures and fractures in the rock
- Strength and stiffness of the rock
- Presence of water
- Corrosive behavior of the rock
- Life expectancy of the excavated area
- Extraction height
- Installation equipment
- Access area
Our bolting solutions are widely used in the civil engineering, construction, tunneling and mining industries.