Miners employ several primary methods to support the roof and walls in soft-rock tunnels and rooms, focusing on rock reinforcement, surface support, and sometimes specialized floor stabilization techniques. The main objective of ground support is to mobilize and conserve the inherent strength of the rock mass, making it self-supporting (Australian Mining, n.d.).
Rock reinforcement is fundamental, commonly using rock bolts and cables. Rock bolts are installed in patterns and tightened, while yielding rock bolts are designed to control deformation in softer rock by reinforcing the broken rock mass (Australian Mining, n.d.).
Surface support techniques are often used with reinforcement to prevent smaller rock falls and create an integrated system (Australian Mining, n.d.).
These include:
- Meshing: Steel or non-metallic mesh is applied to contain loose fragments.
- Shotcreting: Spraying concrete onto rock surfaces provides immediate support and prevents weathering (ResearchGate, 2024).
- Strapping: Steel straps can extend bolt coverage but may leave areas between straps unsupported.
In challenging conditions, synergistic strategies like “anchor-shotcreting-grouting” combine high-strength anchors, prompt shotcreting, and high-pressure grouting to consolidate the rock mass (ResearchGate, 2024).
Specific mining methods also incorporate support:
- Room and Pillar Mining: Pillars of ore are left to support the roof. Proper pillar design is crucial.
- Longwall Mining: Self-advancing hydraulic roof supports are used, allowing the roof behind to collapse in a controlled manner (CDC, n.d.).
For floor heave in soft rock tunnels, a scheme of “floor grouting + floor anchors + sealing material” is employed to create an integrated support structure (MDPI, 2024).
The choice of support depends on rock mass behavior, mining depth, stresses, excavation life, and geological conditions like weak strata or discontinuities. Regular inspections are also vital (CDC, n.d.).
Why is combining reinforcement and surface support important in soft-rock mining? Share your thoughts!
References:
Australian Mining. (n.d.). Ground support design cycle: an approach to increase safety and efficiency. https://www.australianmining.com.au/ground-support-design-cycle-an-approach-to-increase-safety-and-efficiency/
CDC (Centers for Disease Control and Prevention). (n.d.). Mining: Ground Falls. https://www.cdc.gov/niosh/mining/topics/ground-falls.html
MDPI. (2024). A Novel Sealing Material for Floor Heave Control in Deep Soft Rock Tunnels: Mechanical Properties and Engineering Applications. Materials, 14(12), 4004. https://www.mdpi.com/2075-5309/14/12/4004
ResearchGate. (2024). Research on the comprehensive control technology of anchor- shotcreting- grouting for soft rock roadway: A case study. (https://www.researchgate.net/publication/385668918_Research_on_the_comprehensive_control_technology_of_anchor-_shotcreting-_grouting_for_soft_rock_roadway_A_case_study)
