๐ Case Study
Coal Mine Longwall Gate Road Support Upgrade
Excessive roof sag and rib spalling compromising ventilation and haulage
๐๏ธ Project Overview
Black Diamond Coal, Australia โ High-stress gate road in 800 m deep seam
๐ฏ Challenge
Excessive roof sag and rib spalling compromising ventilation and haulage
๐ง Design Approach
Triple-row 2.4 m resin-grouted bolts + 150 mm steel-fibre shotcrete + hydraulic props at intersections
๐ Design Diagram
AI-generated project design illustration
๐ Key Calculations
Roof Sag Prediction (Radonovich)
ฮด = 0.02 ร ฯแตฅ ร hยฒ / E
Result: 128 mm
Predicted sag exceeded 100 mm threshold for intervention
Bolt Load Distribution Factor
K = (EโยทAโ)/(EแตฃยทAแตฃ)
Result: 4.3
Higher K improves load transfer to competent strata
๐ Results
Roof sag reduced to <35 mm; rib spalling frequency dropped 90%; ventilation resistance stabilized at 0.012 Nsยฒ/mโธ๐ก Lessons Learned
- โขResin bond length must exceed 1.2ร bolt embedment into competent layer
- โขSteel fibres increased shotcrete tensile strength by 3.8ร vs plain mix
- โขHydraulic props prevented intersection convergence cascade
โ Key Takeaways
- 1Resin bond length must exceed 1.2ร bolt embedment into competent layer
- 2Steel fibres increased shotcrete tensile strength by 3.8ร vs plain mix
- 3Hydraulic props prevented intersection convergence cascade