In soft-rock mining, ensuring the stability of tunnels and rooms is paramount, achieved through various ground support methods. Rock reinforcement is a primary technique, aiming to make the rock mass self-supporting (Australian Mining, n.d.).
This commonly involves installing rock bolts and cables; rock bolts are tensioned into drilled holes, with yielding bolts specifically designed for deformable soft rock, while cables offer deeper reinforcement (Yang et al., 2024).
Surface support is often used with reinforcement to contain smaller rock fragments (Australian Mining, n.d.). Meshing, using steel or non-metallic materials, covers surfaces to hold loose rock (Australian Mining, n.d.). Shotcreting involves spraying concrete for immediate support and to prevent weathering. Steel strapping can also extend bolt coverage (Yang et al., 2024).
For challenging conditions, synergistic strategies like “anchor-shotcreting-grouting” combine high-strength anchors, shotcrete sealing, and high-pressure grouting to consolidate the rock mass (Yang et al., 2024).
Mining methods themselves incorporate support: room and pillar mining leaves ore pillars for roof support, requiring careful pillar design to prevent collapse (CDC, n.d.). Longwall mining uses self-advancing hydraulic roof supports, allowing controlled roof collapse behind the miner. Additionally, floor heave in soft rock tunnels is addressed with schemes like “floor grouting + floor anchors + sealing material” (Wang et al., 2024).
The selection of these systems depends on site-specific factors including rock mass behavior, mining depth, stress conditions, excavation lifespan, and geological features like weak strata or discontinuities (CDC, n.d.). Regular inspections are also critical for safety (MSHA, n.d.-b).
Why do you think soft-rock mines might need different support systems in different areas of the same mine? 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.
MSHA (Mine Safety and Health Administration). (n.d.-b). Module 11: Ground control. (https://arlweb.msha.gov/safetypro_in_a_box/IG%2040%20On%20the%20job%20training%20modues%20%20Sand%20Gravel%20and%20Crushed%20Stone/Module%2011%20Ground%20control.pdf))
Wang, Z., Liu, C., Ni, S., Wang, H., & Zhang, Z. (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
Yang, S., He, M., Wang, D., Liu, Z., & Jia, P. (2024). Research on the comprehensive control technology of anchor- shotcreting- grouting for soft rock roadway: A case study. ResearchGate.(https://www.researchgate.net/publication/385668918_Research_on_the_comprehensive_control_technology_of_anchor-_shotcreting-_grouting_for_soft_rock_roadway_A_case_study)
