BHP Mitsubishi Alliance (BMA) Broadmeadow Mine, an underground coal mining operation, faced several geotechnical challenges. Specifically, the project team encountered a weathered zone extending 30 metres below the surface and needed to maintain a long-term unsupported diameter of at least 3.5 metres.
Additionally, issues like water hydrology and methane gas presence at the shaft site further complicated the situation. Furthermore, a robust concrete collar cap was essential to support the excavation of the shaft and fan. Therefore, the conditions demanded a sophisticated solution to ensure structural stability and safety.
To address these challenges, Master Drilling Australia (MDA) took a strategic approach, conducting a thorough geotechnical analysis of the weathered zone and deeper substrata. This analysis ensured a comprehensive understanding of the subterranean conditions.
Additionally, to guarantee structural integrity and manage water ingress, a hydrostatic steel liner was designed to span the entire length of the shaft. Moreover, piling and an integrated collar cap were engineered to provide critical support during the excavation stages and the mine’s lifespan.
The team also utilised live trending gas monitoring systems to mitigate methane risks, ensuring continuous surveillance and control of gas levels.
The Engineering, Procurement and Construction (EPC) model was designed through close collaboration with BMA , ensuring all stages of the project aligned with BMA’s vision and standards.
The hydrostatic steel liners were precisely manufactured and successfully installed, providing the necessary reinforcement for the shaft. The construction of the collar cap was accomplished without incident, further validating the design’s integrity.
Critically, managing methane levels during the excavation phase was well executed, showcasing BMA and MDA’s joint commitment to maintaining the highest standards of quality, safety, and occupational health.
Construction of guide wall
1.2m diameter secant piles to 35m depth
Cutback & construction of collar cap
Conventional drill pilot hole 114m
Back reaming of shaft to 3.5m dia
Supply & install steel liners 114m
