ABSTRACT
There are a series of technical challenges in deep mining for slightly inclined thin orebodies with a thickness of 0.8 to 1.8 m, which include small operating space, low production efficiency, high loss and dilution rate, and poor safety. A new mining method was proposed to resolve these issues. The new method is called ‘vertical strips with T-shape mining method and shallow-hole millisecond-delay blasting technology’. The T-shape mining with vertical strips can reasonably improve the stability of the roof exposed area, and significantly reduce the ore-dilution because of no footwall rock blasting. The stress wave super position of a millisecond-delay blasting mechanism could reduce blasting vibration. Simultaneous initiation of the multi-row holes could improve the mining efficiency and shorten the exposure time of the roof. In addition, this study presents a new method for blasthole-stemming by using ‘polyurethane expansion foam’ and ‘water-stem’ to reduce mining preparation time. The techniques were applied for an industrial test at Xiang-Xi Gold Mine (over 1000 m deep), China. Compared with the traditional technology, the blasting vibration of the new technology is reduced by 24.7%, the roof exposure time is reduced by 39.3%, the daily ore production is increased by 50%, and the explosive consumption is reduced by 13.3%. The results of the industrial test also show that the new quick blasthole-stemming method is much better than the traditional one in both stemming efficiency and stemming effect. It will reduce the blasting cost, improve the working conditions, and obtain a remarkable economic benefit.
