YuMing, L, Wang, H, Chen, X, Luan, T & Wang, H 2024, 'Design practice of PT iron mine transitioning to underground block caving from open pit mining', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 1511-1521.
(https://papers.acg.uwa.edu.au/p/2435_Q-05/)
Abstract: Situated in the rural area of Panzhihua City, Sichuan Province, China, PT iron mine is a late magmatic differentiation-type stratified iron-titanium deposit. The orebody strikes nearly east-west, with a length of about 700m and a width of about 400m at a dip angle of 40°. The hanging wall portion of the orebody features low-grade ore and its footwall portion features industrial ore, i.e, high-grade ore. Currently the mine is in production by means of open-pit mining. As the production goes on, a slope of up to 690m high will be formed on the southern wall at the end of the open pit mining. Then the mine will be transitioning to underground mining adopting block and panel caving method with a designed ore production capacity of 6 million tonnes per year. To ensure a successful application of block and panel caving, a series of rock mechanics researches have been conducted which include in-situ stress testing, physical and mechanical testing of rock, on-site geotechnical survey and cavabilty assessment of rock mass. The research results show that the industrial orebody is a poor rock mass with a RMR rating of 48 and a MRMR rating of 43 and the low-grade orebody is a good rock mass with a RMR rating of 59 and a MRMR rating of 57. To ensure a continuous caving propagation in the low-grade orebody and the hanging wall rock, preconditioning by hydraulic fracturing will be used to improve the cavability of rock mass. Based on the shape and dip angle of the orebody, the general mining development layout used in Tongkuangyu copper mine in China will be adopted, which has one main production level and several auxiliary production levels in every mining lift. The access development system consists of a service shaft, a ramp and a main shaft followed by a belt conveyor decline in the deep section. The mine construction is expected to begin in 2025.