Abstract: A method for determining a physical similarity simulation material of a solid backfill body is provided. A compaction test is run on a gangue backfill body in a lab, to obtain a ?-? curve regarding the gangue backfill body in the compaction process. Backfill blocks are made by using a thin wood board, sponge, and a paper sheet in different proportions, and then an unconfined compression test is separately run on the backfill blocks used for physical similarity simulation, to obtain ?i-?i curves regarding the backfill blocks in the compression process. A sum of squared errors ?(?i??0)2 is introduced to separately calculate a sum of squared errors of the backfill block and that of the gangue backfill body, and accordingly an error between ?-? curves regarding the test block and the gangue backfill body is determined. Finally, a backfill block for which the sum of squared errors is less than 0.5 is determined as a physical similarity simulation material of the gangue backfill body.

Abstract: A method for recovering room-mining coal pillars by solid filling in synergy with artificial pillars. Solid materials and cementing materials on the ground are conveyed through a feeding well and a pipeline to a room-and-pillar goaf, a plurality of artificial pillars is cast at an interval in a coal room area, and gangue is cast to fill other regions of the coal room using a gangue casting machine. Under joint support by the artificial pillars and the coal room filler, coal pillars are recovered using a continuous coal mining machine, artificial pillars are cast in the original coal pillar area after recovery, and gangue is cast to fill the original coal pillar area using the gangue casting machine. A system for recovering room-mining coal pillars by solid filling in synergy with artificial pillars mainly includes a material conveying system, a joint support system, and a coal pillar recovery system.

Abstract: A method for determining a physical similarity simulation material of a solid backfill body is provided. A compaction test is run on a gangue backfill body in a lab, to obtain a ?-? curve regarding the gangue backfill body in the compaction process. Backfill blocks are made by using a thin wood board, sponge, and a paper sheet in different proportions, and then an unconfined compression test is separately run on the backfill blocks used for physical similarity simulation, to obtain ?i-?i curves regarding the backfill blocks in the compression process. A sum of squared errors ?(?i??0)2 is introduced to separately calculate a sum of squared errors of the backfill block and that of the gangue backfill body, and accordingly an error between ?-? curves regarding the test block and the gangue backfill body is determined. Finally, a backfill block for which the sum of squared errors is less than 0.5 is determined as a physical similarity simulation material of the gangue backfill body.

Abstract: A method for recovering room-mining coal pillars by solid filling in synergy with artificial pillars. Solid materials and cementing materials on the ground are conveyed through a feeding well and a pipeline to a room-and-pillar goaf, a plurality of artificial pillars is cast at an interval in a coal room area, and gangue is cast to fill other regions of the coal room using a gangue casting machine. Under joint support by the artificial pillars and the coal room filler, coal pillars are recovered using a continuous coal mining machine, artificial pillars are cast in the original coal pillar area after recovery, and gangue is cast to fill the original coal pillar area using the gangue casting machine. A system for recovering room-mining coal pillars by solid filling in synergy with artificial pillars mainly includes a material conveying system, a joint support system, and a coal pillar recovery system.