What is the mining sequence for the cemented backfill mining method?

(1) Block structure parameters

The block layout is determined comprehensively, taking into account the morphology of the ore body and mining efficiency. Blocks are generally arranged along the strike of the ore body; their height corresponds to that of the level, whilst their width is flexibly adjusted according to the thickness of the ore body. Inter-block pillars are installed as support structures, with headings excavated within them to serve as ventilation and access passages. Segmental rock-drilling drifts are constructed at appropriate intervals along the strike, whilst cutting shafts and cutting channels are laid out within the mining chambers to facilitate blasting and extraction. Ore chutes are installed at the base of the mining chambers to facilitate the collection, removal and transhipment of ore.

For thick and large ore bodies, the mining blocks are arranged perpendicular to the strike of the ore body; the length of the mining blocks is adjusted according to the thickness of the ore body, and the height of the segments is set reasonably in accordance with mining conditions.

(2) Stopping and Cutting

The main haulage drifts are laid out within the surrounding rock at the footwall of the vein, whilst the stopping and cutting works are situated within the ore body, close to the mining area, to facilitate construction operations. For ore bodies of considerable thickness, a double-row funnel ore discharge structure may be installed, with associated out-of-vein haulage drifts and loading drifts on the outer side of the mining chamber.

The expansion of the hoppers is carried out simultaneously with the cutting of the shafts, extending a certain distance beyond the current mining face, and is formed using medium-to-deep-hole blasting. The collapsed ore is transported out via the hoppers, the out-of-vein drifts and the loading drifts. Rock drilling operations may utilise pneumatic leg-type drilling equipment or drilling carriages, supported by local ventilation facilities to ensure adequate ventilation conditions at the working face and operational safety.

(3) Mining Process

Longwall mining follows the principle of top-down, section-by-section advancement, with the mining sequence proceeding from the centre of the longwall towards both sides. Medium-to-deep holes are drilled within the section-by-section drilling drifts, and optimal ore fragmentation is ensured through the design of appropriate blasting parameters. Using the cutting trench as the free blasting face, a micro-delay blasting technique is employed to initiate detonation in stages from the centre towards both sides, thereby minimising the disturbance to the surrounding rock caused by blasting vibrations and achieving uniform ore fragmentation.

Following blasting, the ore falls into the ore chute at the bottom and is transported out by shovelling equipment. Once mining in an individual chamber is complete, backfilling operations are carried out promptly, using appropriately proportioned tailings-based cemented backfill material to fill the goaf and maintain the stability of the surrounding rock in the mining area. This mining method achieves a high ore recovery rate.