Recovery of Level Pillar between Open-pit and Underground Mine by Using Underhand Heading Fill Method

The upper part of the Fujia deposit was mined out by open-pit, and the lower part is being mined underground. The level pillar between open-pit and underground mine had a thickness of 24 m, a length of 300 m and a maximum width of 35 m. As the level pillar contained about 5.2 million ton ore of high nickel grade, it was necessary to recover the level pillar. Because of special need of safety, underhand heading cut-and-fill stoping method was used. For the first two layers of heading, the cemented fill materials were a mix of water and high-aluminum-content cement with silicate gelling agent; and for other heading layers, total tailings was added into the fill mix in order to reduce the cement consumption. Finally, the level pillar was recovered successfully.