Two-Step Sublevel Open Stoping with Backfilling Technology and Application for Low-Grade Orebody

Peiliang Xu ^1,2 Jun Wang ^1* Kepeng Hou ¹ Dengpan Qiao ¹ Tianyu Yang ¹

• ¹ Kunming University of Science and Technology, Kunming, China
• ² Datun tin mine of Yunnan Tin Industry Corporation Limited, Kunming, China

The Dahongshan copper mine contains three copper orebodies and four iron orebodies. These orebodies are gently dipping, ranging from thin to medium thickness, with moderately stable surrounding rock. The copper and iron orebodies occur in parallel interbedded layers, making them complex and difficult to mine. Based on the mining technical conditions of the ore bodies, a "copper and iron co-mining" model was proposed, and a two-step sublevel open stoping with backfilling mining technology was developed. To reasonably delineate the stope boundaries, an economic cut-off grade model for co-mining of copper and iron was established. To ensure the stability of the cemented backfill and provide safe mining conditions for the secondary stopes, while maintaining low backfilling costs, a strength model of the cemented backfill was constructed, and a layered precision backfilling technology was developed. To enhance the system's backfilling capacity and ensure a balance between mining and backfilling, the fundamental theory of continuous high-concentration steady-state sand discharge from vertical silos was established, and a multi-silo parallel continuous high-concentration steady-state sand discharge technology was developed. To ensure the stability of the retaining walls, shorten the construction time, and reduce construction costs, a strength and structural design model for the retaining walls was constructed, and a rapid construction technology using shotcrete retaining walls was developed. This technology achieves safe, efficient, and economical mining of gently dipping, multi-layered, thin to medium thickness, low-grade orebodies, effectively extending the mine's service life, with significant application results, economic benefits, and social benefits. The research results are of great significance for deepening mining theory research and have high application and promotion value for similar mines.