Method for recovering room-mining coal pillars by solid filling in synergy with artificial pillars

A method for recovering room-mining coal pillars by solid filling in synergy with artificial pillars, comprising the following steps:

• a. under a joint support to overlying strata by a filler in synergy with artificial pillars, recovering room-mining coal pillars using a continuous coal mining machine:
• firstly, conveying solid materials and cementing materials on a ground level through a feeding well and a conveying pipeline to a room-and-pillar goaf;
• b. casting a plurality of artificial pillars at an interval in the room-and-pillar goaf among the room-mining coal pillars, filling areas with a filling material among the cast artificial pillars, and tamping and reinforcing a combined structure of the cast artificial pillars and the filling material, to form a coal room filler;
• c. under the joint support by the cast artificial pillars and the coal room filler, recovering the room-mining coal pillars one-by-one in a joint support area using the continuous coal mining machine till all the room-mining coal pillars are recovered;
• wherein the recovery process of a single room-mining coal pillar comprises the following steps:
• a1. firstly constructing square pillar grooves having sides of 4 m long at an interval in the room-and-pillar goaf on one side of the room-mining coal pillar, and building retaining walls in the constructed square pillar grooves, wherein the retaining walls in each of the square pillar grooves contact a roof and are configured to define a sealed space;
• b1. constructing artificial pillars by injecting slurry into the constructed square pillar grooves, and when a height of the slurry for casting the artificial pillars reaches a position that is 50 mm below the roof, increasing a concentration of the slurry and performing roof-contacted filling on the artificial pillars;
• c1. after casting of the artificial pillars, casting the filling material to fill the room-and-pillar goaf using a gangue casting machine, and also, tamping and reinforcing the combined structure using a bulldozer, wherein the filling material comprises gangue;
• d1. repeating Steps a1 to c1 to complete filling of the room-and-pillar goaf on the other side of the room-mining coal pillar;
• e1. after a strength of the artificial pillars and the coal room filler reaches a strength of an ambient rock structure, recovering the room-mining coal pillar using the continuous coal mining machine in a horizontal recovery manner by firstly forming a cross-shaped recovered space;
• f1. casting artificial pillars in the area of the recovered room-mining coal pillar, and casting gangue to fill the area of the recovered room-mining coal pillar using the gangue casting machine.