Design and Stope Stability Analysis of Multiple Concurrent Excavated Veins in Underground Mine; Case Study of Hermyingyi Tin-Tungsten (W-Sn) Mine

The increasing demand for tin-tungsten (W-Sn) due to its versatile applications in various industries and its attractive high market price has created a motivation for mining companies to extract deep-seated tin-tungsten deposits in Myanmar at a fast pace to meet the world demands. At Hermyingyi (W-Sn) Deposit Mine, the feasibility of exploiting ore in multiple inclined veins simultaneously is being explored as a pilot project aimed at increasing W-Sn production. Thus, this study is aimed at the development of optimal design and guidelines for excavating multiple veins with stability certitude in weak rock mass based on the evaluations undertaken. The analyses were carried out using FLAC^3Dver. 5.0 and Phase² V 7.0 software. The results demonstrate that excavation of large stope dimensions with ≥ 5 m width in parallel multiple veins simultaneously is not recommendable as the stopes experience high potential stope failure, thus the development of stopes with width dimensions of ≤ 3 m in all the parallel multiple veins simultaneously in weak rock mass conditions is ideal. In terms of space intervals between parallel inclined veins, it is recommendable to undertake multiple vein excavations for gentle inclined veins in weak rock mass conditions only if the interval of the veins is emplaced at ≥ 14 and 10 m for steep dipping inclined veins with good rock mass conditions. The study also shows that the cut and fill method is a more favorable mining method for multiple veins excavation than the open stoping method.